diff --git a/ChangeLog b/ChangeLog
index be9eaa776..7ccdd4458 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,7 +1,28 @@
+2009-06-11  David A. Capello  <davidcapello@gmail.com>
+
+	* src/modules/gui.h (JWidgetPtr): Added to automatically delete
+	the widget in the destructor.
+
+	* src/modules/gui.cpp (load_widget/get_widgets): In case of error
+	now they throw an exception.
+
+	* src/sprite_wrappers.h: CurrentSprite class was split in
+	SpriteWrapper/Reader/Writer, and CurrentSpriteReader/Writer
+	wrappers.
+
+	* src/console/console.h (Console): Added the class to
+	automatically open/close the console (with RAII idiom).
+
 2009-06-10  David A. Capello  <davidcapello@gmail.com>
 
 	* src/modules/palettes.h: Added CurrentSpriteRgbMap class.
 
+2009-06-04  David A. Capello  <davidcapello@gmail.com>
+
+	* src/raster/sprite.h (Sprite): Added m_write_lock and
+	m_read_locks members. Added lock(bool) and lock_to_write()
+	methods.
+
 2009-06-01  David A. Capello  <davidcapello@gmail.com>
 
 	* src/ase/current_sprite.h (CurrentSprite): Added.
diff --git a/data/gui-en.xml b/data/gui-en.xml
index 8f959be6b..6e9e6cb53 100644
--- a/data/gui-en.xml
+++ b/data/gui-en.xml
@@ -126,7 +126,12 @@
 	</menu>
 	<menu name="&Sprite">
 	    <item command="sprite_properties" name="&Properties..." />
-	    <item command="change_image_type" name="Color &Mode..." />
+	    <menu name name="Color &Mode">
+	      <item command="change_image_type" name="&RGB Color" argument="rgb" />
+	      <item command="change_image_type" name="&Grayscale" argument="grayscale" />
+	      <item command="change_image_type" name="&Indexed (No Dithering)" argument="indexed" />
+	      <item command="change_image_type" name="Indexed (Ordered &Dither)" argument="indexed-dither" />
+	    </menu>
 	    <separator />
 	    <item command="duplicate_sprite" name="&Duplicate..." />
 	    <separator />
diff --git a/data/jids/imgtype.jid b/data/jids/imgtype.jid
deleted file mode 100644
index f4a121d96..000000000
--- a/data/jids/imgtype.jid
+++ /dev/null
@@ -1,25 +0,0 @@
-<!-- ASE - Allegro Sprite Editor -->
-<!-- Copyright (C) 2001-2009 by David Capello -->
-<jinete>
-<window text="Convert Color" name="image_type">
-  <box vertical>
-    <box vertical expansive>
-      <box horizontal>
-        <label text="From:" />
-        <label text="" name="from" />
-      </box>
-      <label text="To:" />
-      <radio name="imgtype1" text="&RGB Color" group=1 />
-      <radio name="imgtype2" text="&Grayscale" group=1 />
-      <radio name="imgtype3" text="&Indexed" group=1 />
-      <separator horizontal />
-      <radio name="dither1" text="&No Dithering" group=2 />
-      <radio name="dither2" text="&Ordered Dither" group=2 />
-    </box>
-    <box horizontal expansive homogeneous>
-      <button text="&OK" name="ok" magnetic />
-      <button text="&Cancel" />
-    </box>
-  </box>
-</window>
-</jinete>
diff --git a/makefile.lst b/makefile.lst
index ff459e639..e3e4ddc64 100644
--- a/makefile.lst
+++ b/makefile.lst
@@ -190,14 +190,12 @@ COMMON_SOURCES =					\
 	src/raster/sprite.cpp				\
 	src/raster/stock.cpp				\
 	src/raster/undo.cpp				\
-	src/raster/undoable.cpp				\
 	src/util/autocrop.cpp				\
 	src/util/boundary.cpp				\
 	src/util/celmove.cpp				\
 	src/util/clipboard.cpp				\
 	src/util/col_file.cpp				\
 	src/util/filetoks.cpp				\
-	src/util/functions.cpp				\
 	src/util/hash.cpp				\
 	src/util/misc.cpp				\
 	src/util/msk_file.cpp				\
@@ -235,7 +233,10 @@ COMMON_OBJS = $(addprefix $(OBJ_DIR)/,				\
 	        $(addsuffix $(OBJ),				\
 	          $(notdir $(basename $(COMMON_SOURCES)))))
 
-ASE_SOURCES = src/main.cpp $(COMMON_SOURCES)
+ASE_SOURCES = \
+	src/main.cpp						\
+	src/undoable.cpp					\
+	$(COMMON_SOURCES)
 
 ASE_OBJS = $(addprefix $(OBJ_DIR)/,				\
 	     $(addsuffix $(OBJ),				\
diff --git a/src/ase/context.h b/src/ase/context.h
index 28fe451d0..e8ac77ce4 100644
--- a/src/ase/context.h
+++ b/src/ase/context.h
@@ -22,6 +22,7 @@
 #include <list>
 
 class Sprite;
+class SpriteReader;
 
 typedef std::list<Sprite*> SpriteList;
 
@@ -42,6 +43,11 @@ public:
   Context();
   virtual ~Context();
 
+  virtual bool is_ui_available() const		{ return false; }
+  virtual bool is_recording_macro() const	{ return false; }
+  virtual bool is_executing_macro() const	{ return false; }
+  virtual bool is_executing_script() const	{ return false; }
+
   const SpriteList& get_sprite_list() const;
   Sprite* get_first_sprite() const;
   Sprite* get_next_sprite(Sprite* sprite) const;
diff --git a/src/ase/current_sprite.cpp b/src/ase/current_sprite.cpp
deleted file mode 100644
index 855124af2..000000000
--- a/src/ase/current_sprite.cpp
+++ /dev/null
@@ -1,60 +0,0 @@
-/* ASE - Allegro Sprite Editor
- * Copyright (C) 2001-2009  David Capello
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
- */
-
-#include "config.h"
-
-#include "ase/context.h"
-#include "ase/current_sprite.h"
-#include "ase/ui_context.h"	// TODO remove this line
-#include "raster/sprite.h"
-
-CurrentSprite::CurrentSprite()
-{
-  m_context = UIContext::instance();
-  m_sprite = m_context->get_current_sprite();
-  if (m_sprite)
-    m_writeable = m_sprite->lock();
-}
-
-CurrentSprite::CurrentSprite(Context* context)
-{
-  assert(context != NULL);
-
-  m_context = context;
-  m_sprite = m_context->get_current_sprite();
-  if (m_sprite)
-    m_writeable = m_sprite->lock();
-}
-
-CurrentSprite::~CurrentSprite()
-{
-  if (m_sprite)
-    m_sprite->unlock();
-}
-
-void CurrentSprite::destroy()
-{
-  if (m_sprite) {
-    m_context->remove_sprite(m_sprite);
-    m_sprite->unlock();
-
-    delete m_sprite;
-    m_sprite = NULL;
-    m_writeable = false;
-  }
-}
diff --git a/src/ase/ui_context.h b/src/ase/ui_context.h
index fd11a3997..d7ea860ba 100644
--- a/src/ase/ui_context.h
+++ b/src/ase/ui_context.h
@@ -31,6 +31,8 @@ public:
   UIContext();
   virtual ~UIContext();
 
+  virtual bool is_ui_available() const { return true; }
+
   void show_sprite(Sprite* sprite) const;
 
 protected:
diff --git a/src/ase/current_sprite.h b/src/ase_exception.h
similarity index 55%
rename from src/ase/current_sprite.h
rename to src/ase_exception.h
index 6cddac178..1e73dbeb7 100644
--- a/src/ase/current_sprite.h
+++ b/src/ase_exception.h
@@ -16,42 +16,40 @@
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 
-#ifndef ASE_CURRENT_SPRITE_H
-#define ASE_CURRENT_SPRITE_H
+#ifndef ASE_EXCEPTION_H
+#define ASE_EXCEPTION_H
 
-#include <list>
+#include <exception>
+#include <string>
+#include "console/console.h"
 
-class Context;
-class Sprite;
-
-class CurrentSprite
+class ase_exception : public std::exception
 {
-  Context* m_context;
-  Sprite* m_sprite;
-  bool m_writeable;
-
-  // // No-default constructor (undefined)
-  // CurrentSprite();
-
-  // Non-copyable
-  CurrentSprite(const CurrentSprite&);
-  CurrentSprite& operator=(const CurrentSprite&);
+  std::string m_msg;
 
 public:
-  CurrentSprite();
-  CurrentSprite(Context* context);
-  ~CurrentSprite();
 
-  bool writeable() const { return m_writeable; }
-  void destroy();
+  ase_exception(const char* msg) throw()
+    : m_msg(msg)
+  {
+  }
 
-  operator Sprite* () { return m_sprite; }
+  ase_exception(const std::string& msg) throw()
+    : m_msg(msg)
+  {
+  }
 
-  Sprite* operator->() {
-    assert(m_sprite != NULL);
-    return m_sprite;
+  void show()
+  {
+    Console console;
+    console.printf("An error ocurred executing the command.\n\nDetails:\n%s", what());
+  }
+
+  const char* what() const throw()
+  {
+    return m_msg.c_str();
   }
 
 };
 
-#endif // ASE_CURRENT_SPRITE_H
+#endif // ASE_EXCEPTION_H
diff --git a/src/commands/cmd_about.cpp b/src/commands/cmd_about.cpp
index 58ac448fa..728fd18cc 100644
--- a/src/commands/cmd_about.cpp
+++ b/src/commands/cmd_about.cpp
@@ -25,16 +25,18 @@
 #include "commands/commands.h"
 #include "core/core.h"
 #include "core/dirs.h"
+#include "modules/gui.h"
 
 static char *read_authors_txt(const char *filename);
 
 static void cmd_about_execute(const char *argument)
 {
-  JWidget window, box1, label1, label2, separator1;
+  JWidget box1, label1, label2, separator1;
   JWidget textbox, view, separator2;
   JWidget label3, label4, box2, box3, box4, button1;
   char *authors_txt = read_authors_txt("AUTHORS.txt");
 
+  JWidgetPtr window;
   if (authors_txt)
     window = jwindow_new_desktop();
   else
@@ -86,7 +88,6 @@ static void cmd_about_execute(const char *argument)
 		     button1->border_width.b);
 
   jwindow_open_fg(window);
-  jwidget_free(window);
 }
 
 static char *read_authors_txt(const char *filename)
diff --git a/src/commands/cmd_advanced_mode.cpp b/src/commands/cmd_advanced_mode.cpp
index e2cbee385..388058f95 100644
--- a/src/commands/cmd_advanced_mode.cpp
+++ b/src/commands/cmd_advanced_mode.cpp
@@ -52,18 +52,13 @@ static void cmd_advanced_mode_execute(const char *argument)
   if (advanced_mode &&
       get_config_bool("AdvancedMode", "Warning", TRUE)) {
     Command *cmd_advanced_mode = command_get_by_name(CMD_ADVANCED_MODE);
-    JWidget window, warning_label, donot_show;
     char warning[1024];
     char key[1024];
     char buf[1024];
 
-    /* load the window widget */
-    window = load_widget("advanced.jid", "advanced_mode_warning");
-    if (!window)
-      return;
-
-    warning_label = jwidget_find_name(window, "warning_label");
-    donot_show = jwidget_find_name(window, "donot_show");
+    JWidgetPtr window = load_widget("advanced.jid", "advanced_mode_warning");
+    JWidget warning_label = find_widget(window, "warning_label");
+    JWidget donot_show = find_widget(window, "donot_show");
 
     strcpy(warning, _("You can back pressing the \"%s\" key."));
     jaccel_to_string(cmd_advanced_mode->accel, key);
@@ -75,8 +70,6 @@ static void cmd_advanced_mode_execute(const char *argument)
     
     set_config_bool("AdvancedMode", "Warning",
 		    !jwidget_is_selected(donot_show));
-
-    jwidget_free(window);
   }
 }
 
diff --git a/src/commands/cmd_background_from_layer.cpp b/src/commands/cmd_background_from_layer.cpp
index febab2451..7d2c657b3 100644
--- a/src/commands/cmd_background_from_layer.cpp
+++ b/src/commands/cmd_background_from_layer.cpp
@@ -24,12 +24,12 @@
 #include "modules/sprites.h"
 #include "raster/layer.h"
 #include "raster/sprite.h"
-#include "raster/undoable.h"
+#include "undoable.h"
 #include "widgets/colbar.h"
 
 static bool cmd_background_from_layer_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return
     sprite != NULL &&
     sprite->layer != NULL &&
@@ -41,7 +41,7 @@ static bool cmd_background_from_layer_enabled(const char *argument)
 
 static void cmd_background_from_layer_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
 
   // each frame of the layer to be converted as `Background' must be
   // cleared using the selected background color in the color-bar
diff --git a/src/commands/cmd_canvas_size.cpp b/src/commands/cmd_canvas_size.cpp
index e1c980f09..c671fb790 100644
--- a/src/commands/cmd_canvas_size.cpp
+++ b/src/commands/cmd_canvas_size.cpp
@@ -29,34 +29,28 @@
 #include "raster/image.h"
 #include "raster/mask.h"
 #include "raster/sprite.h"
-#include "raster/undoable.h"
+#include "undoable.h"
 #include "widgets/colbar.h"
 
 static bool cmd_canvas_size_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return sprite != NULL;
 }
 
 static void cmd_canvas_size_execute(const char *argument)
 {
-  JWidget window, left, top, right, bottom, ok;
-  CurrentSprite sprite;
+  JWidget left, top, right, bottom, ok;
+  CurrentSpriteWriter sprite;
 
   // load the window widget
-  window = load_widget("canvas.jid", "canvas_size");
-  if (!window)
-    return;
-
-  if (!get_widgets(window,
-		   "left", &left,
-		   "top", &top,
-		   "right", &right,
-		   "bottom", &bottom,
-		   "ok", &ok, NULL)) {
-    jwidget_free(window);
-    return;
-  }
+  JWidgetPtr window = load_widget("canvas.jid", "canvas_size");
+  get_widgets(window,
+	      "left", &left,
+	      "top", &top,
+	      "right", &right,
+	      "bottom", &bottom,
+	      "ok", &ok, NULL);
 
   jwindow_remap(window);
   jwindow_center(window);
@@ -85,8 +79,6 @@ static void cmd_canvas_size_execute(const char *argument)
     sprite_generate_mask_boundaries(sprite);
     update_screen_for_sprite(sprite);
   }
-
-  jwidget_free(window);
 }
 
 Command cmd_canvas_size = {
diff --git a/src/commands/cmd_cel_properties.cpp b/src/commands/cmd_cel_properties.cpp
index c397b3cdc..4f29b5682 100644
--- a/src/commands/cmd_cel_properties.cpp
+++ b/src/commands/cmd_cel_properties.cpp
@@ -36,13 +36,12 @@
 
 static bool cmd_cel_properties_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return sprite && sprite->layer;
 }
 
 static void cmd_cel_properties_execute(const char *argument)
 {
-  JWidget window = NULL;
   JWidget label_frame, label_pos, label_size;
   JWidget slider_opacity, button_ok;
   Layer *layer;
@@ -51,31 +50,25 @@ static void cmd_cel_properties_execute(const char *argument)
   int memsize;
 
   /* get current sprite */
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   if (!sprite)
     return;
 
   /* get selected layer */
   layer = sprite->layer;
   if (!layer)
-    goto done;
+    return;
 
   /* get current cel (can be NULL) */
   cel = layer_get_cel(layer, sprite->frame);
 
-  window = load_widget("celprop.jid", "cel_properties");
-  if (!window)
-    goto done;
-
-  if (!get_widgets(window,
-		   "frame", &label_frame,
-		   "pos", &label_pos,
-		   "size", &label_size,
-		   "opacity", &slider_opacity,
-		   "ok", &button_ok, NULL)) {
-    jwidget_free(window);
-    return;
-  }
+  JWidgetPtr window = load_widget("celprop.jid", "cel_properties");
+  get_widgets(window,
+	      "frame", &label_frame,
+	      "pos", &label_pos,
+	      "size", &label_size,
+	      "opacity", &slider_opacity,
+	      "ok", &button_ok, NULL);
 
   /* if the layer isn't writable */
   if (!layer_is_writable(layer)) {
@@ -141,10 +134,6 @@ static void cmd_cel_properties_execute(const char *argument)
       update_screen_for_sprite(sprite);
     }
   }
-
-done:;
-  if (window)
-    jwidget_free(window);
 }
 
 Command cmd_cel_properties = {
diff --git a/src/commands/cmd_change_image_type.cpp b/src/commands/cmd_change_image_type.cpp
index b8e247604..a4a795d0d 100644
--- a/src/commands/cmd_change_image_type.cpp
+++ b/src/commands/cmd_change_image_type.cpp
@@ -18,89 +18,57 @@
 
 #include "config.h"
 
-#include "jinete/jinete.h"
+#include <allegro/unicode.h>
 
 #include "commands/commands.h"
 #include "core/app.h"
-#include "core/cfg.h"
 #include "modules/gui.h"
 #include "modules/palettes.h"
 #include "modules/sprites.h"
 #include "raster/image.h"
 #include "raster/quant.h"
 #include "raster/sprite.h"
+#include "undoable.h"
 
 static bool cmd_change_image_type_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL &&
+    argument != NULL &&
+    ((ustrcmp(argument, "rgb") == 0 && sprite->imgtype != IMAGE_RGB) ||
+     (ustrcmp(argument, "grayscale") == 0 && sprite->imgtype != IMAGE_GRAYSCALE) ||
+     (ustrncmp(argument, "indexed", 7) == 0 && sprite->imgtype != IMAGE_INDEXED));
 }
 
 static void cmd_change_image_type_execute(const char *argument)
 {
-  JWidget window, from, radio1, radio2, radio3, dither1, dither2;
-  CurrentSprite current_sprite;
+  CurrentSpriteWriter sprite;
+  int destimgtype = sprite->imgtype;
+  int dithermethod = DITHERING_NONE;
 
-  /* load the window widget */
-  window = load_widget("imgtype.jid", "image_type");
-  if (!window)
-    return;
-
-  from = jwidget_find_name(window, "from");
-  radio1 = jwidget_find_name(window, "imgtype1");
-  radio2 = jwidget_find_name(window, "imgtype2");
-  radio3 = jwidget_find_name(window, "imgtype3");
-  dither1 = jwidget_find_name(window, "dither1");
-  dither2 = jwidget_find_name(window, "dither2");
-
-  if (current_sprite->imgtype == IMAGE_RGB) {
-    jwidget_set_text(from, _("RGB"));
-    jwidget_disable(radio1);
-    jwidget_select(radio3);	/* to Indexed by default */
+  if (ustrcmp(argument, "rgb") == 0) {
+    destimgtype = IMAGE_RGB;
   }
-  else if (current_sprite->imgtype == IMAGE_GRAYSCALE) {
-    jwidget_set_text(from, _("Grayscale"));
-    jwidget_disable(radio2);
-    jwidget_select(radio1);	/* to RGB by default */
+  else if (ustrcmp(argument, "grayscale") == 0) {
+    destimgtype = IMAGE_GRAYSCALE;
   }
-  else if (current_sprite->imgtype == IMAGE_INDEXED) {
-    jwidget_set_text(from, _("Indexed"));
-    jwidget_disable(radio3);
-    jwidget_select(radio1);	/* to RGB by default */
+  else if (ustrcmp(argument, "indexed") == 0) {
+    destimgtype = IMAGE_INDEXED;
+  }
+  else if (ustrcmp(argument, "indexed-dither") == 0) {
+    destimgtype = IMAGE_INDEXED;
+    dithermethod = DITHERING_ORDERED;
   }
 
-  if (get_config_bool("Options", "Dither", FALSE))
-    jwidget_select(dither2);
-  else
-    jwidget_select(dither1);
-
-  /* open the window */
-  jwindow_open_fg(window);
-
-  if (jwindow_get_killer(window) == jwidget_find_name(window, "ok")) {
-    int destimgtype, dithermethod;
-
-    if (jwidget_is_selected(radio1))
-      destimgtype = IMAGE_RGB;
-    else if (jwidget_is_selected(radio2))
-      destimgtype = IMAGE_GRAYSCALE;
-    else
-      destimgtype = IMAGE_INDEXED;
-
-    if (jwidget_is_selected(dither1))
-      dithermethod = DITHERING_NONE;
-    else
-      dithermethod = DITHERING_ORDERED;
-
-    {
-      CurrentSpriteRgbMap rgbmap;
-      sprite_set_imgtype(current_sprite, destimgtype, dithermethod);
-    }
-
-    app_refresh_screen();
+  {
+    CurrentSpriteRgbMap rgbmap;
+    Undoable undoable(sprite, "Color Mode Change");
+    undoable.set_imgtype(destimgtype, dithermethod);
+    undoable.commit();
   }
 
-  jwidget_free(window);
+  app_refresh_screen(sprite);
 }
 
 Command cmd_change_image_type = {
diff --git a/src/commands/cmd_clear.cpp b/src/commands/cmd_clear.cpp
index d0edfcab9..0327b17f8 100644
--- a/src/commands/cmd_clear.cpp
+++ b/src/commands/cmd_clear.cpp
@@ -25,12 +25,12 @@
 #include "raster/layer.h"
 #include "raster/sprite.h"
 #include "raster/undo.h"
-#include "raster/undoable.h"
+#include "undoable.h"
 #include "widgets/colbar.h"
 
 static bool cmd_clear_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return
     sprite != NULL &&
     sprite->layer != NULL &&
@@ -41,16 +41,12 @@ static bool cmd_clear_enabled(const char *argument)
 
 static void cmd_clear_execute(const char *argument)
 {
-  CurrentSprite sprite;
-  if (!sprite)
-    return;
-
+  CurrentSpriteWriter sprite;
   {
     Undoable undoable(sprite, "Clear");
     undoable.clear_mask(app_get_color_to_clear_layer(sprite->layer));
     undoable.commit();
   }
-
   update_screen_for_sprite(sprite);
 }
 
diff --git a/src/commands/cmd_close_file.cpp b/src/commands/cmd_close_file.cpp
index a6f7720a7..e02a70d21 100644
--- a/src/commands/cmd_close_file.cpp
+++ b/src/commands/cmd_close_file.cpp
@@ -35,7 +35,7 @@ static bool close_current_sprite();
 
 static bool cmd_close_file_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return sprite != NULL;
 }
 
@@ -75,9 +75,7 @@ static void cmd_close_all_files_execute(const char *argument)
  */
 static bool close_current_sprite()
 {
-  CurrentSprite sprite;
-  if (!sprite.writeable())
-    return false;
+  CurrentSpriteWriter sprite;
 
   /* see if the sprite has changes */
   while (sprite_is_modified(sprite)) {
@@ -89,6 +87,7 @@ static bool close_current_sprite()
 
     if (ret == 1) {
       /* "save": save the changes */
+      // TODO we have to pass the sprite to the save file command
       command_execute(command_get_by_name(CMD_SAVE_FILE), NULL);
     }
     else if (ret != 2) {
diff --git a/src/commands/cmd_configure_screen.cpp b/src/commands/cmd_configure_screen.cpp
index b3be33a44..8998ed2ad 100644
--- a/src/commands/cmd_configure_screen.cpp
+++ b/src/commands/cmd_configure_screen.cpp
@@ -74,21 +74,15 @@ static void cmd_configure_screen_execute(const char *argument)
 
 static void show_dialog()
 {
-  JWidget window, resolution, color_depth, pixel_scale, fullscreen;
+  JWidget resolution, color_depth, pixel_scale, fullscreen;
   char buf[512];
 
-  window = load_widget("confscr.jid", "configure_screen");
-  if (!window)
-    return;
-
-  if (!get_widgets(window,
-		   "resolution", &resolution,
-		   "color_depth", &color_depth,
-		   "pixel_scale", &pixel_scale,
-		   "fullscreen", &fullscreen, NULL)) {
-    jwidget_free(window);
-    return;
-  }
+  JWidgetPtr window = load_widget("confscr.jid", "configure_screen");
+  get_widgets(window,
+	      "resolution", &resolution,
+	      "color_depth", &color_depth,
+	      "pixel_scale", &pixel_scale,
+	      "fullscreen", &fullscreen, NULL);
 
   jcombobox_add_string(resolution, "320x200", NULL);
   jcombobox_add_string(resolution, "320x240", NULL);
@@ -139,10 +133,10 @@ static void show_dialog()
 
     /* setup graphics mode */
     if (try_new_gfx_mode()) {
-      JWidget alert_window = jalert_new("Confirm Screen"
-					"<<Do you want to keep this screen resolution?"
-					"<<In 10 seconds the screen will be restored."
-					"||&Yes||&No");
+      JWidgetPtr alert_window = jalert_new("Confirm Screen"
+					   "<<Do you want to keep this screen resolution?"
+					   "<<In 10 seconds the screen will be restored."
+					   "||&Yes||&No");
       jwidget_add_hook(alert_window, -1, alert_msg_proc, NULL);
 
       seconds_to_accept = 10;
@@ -165,12 +159,8 @@ static void show_dialog()
 
 	try_new_gfx_mode();
       }
-
-      jwidget_free(alert_window);
     }
   }
-
-  jwidget_free(window);
 }
 
 static bool try_new_gfx_mode()
@@ -185,7 +175,7 @@ static bool try_new_gfx_mode()
     if (set_gfx_mode(old_card, old_w, old_h, 0, 0) < 0) {
       /* oh no! more errors!, we can't restore the old graphics mode! */
       set_gfx_mode(GFX_TEXT, 0, 0, 0, 0);
-      console_printf(_("FATAL ERROR: Unable to restore the old graphics mode!\n"));
+      user_printf(_("FATAL ERROR: Unable to restore the old graphics mode!\n"));
       app_exit();
       exit(1);
     }
@@ -197,12 +187,16 @@ static bool try_new_gfx_mode()
       set_black_palette();
 
       /* restore palette all screen stuff */
-      app_refresh_screen();
+      {
+	const CurrentSpriteReader sprite;
+	app_refresh_screen(sprite);
+      }
 
-      console_printf(_("Error setting graphics mode: %dx%d %d bpp\n"),
+      Console console;
+      console.printf(_("Error setting graphics mode: %dx%d %d bpp\n"),
 		     new_w, new_h, new_depth);
 
-      return FALSE;
+      return false;
     }
   }
   /* the new graphics mode is working */
@@ -212,8 +206,11 @@ static bool try_new_gfx_mode()
     /* set to a black palette */
     set_black_palette();
 
-    /* restore palette all screen stuff */
-    app_refresh_screen();
+    // restore palette all screen stuff
+    {
+      const CurrentSpriteReader sprite;
+      app_refresh_screen(sprite);
+    }
   }
   
   /* setup mouse */
@@ -225,7 +222,7 @@ static bool try_new_gfx_mode()
     jmanager_refresh_screen();
   }
 
-  return TRUE;
+  return true;
 }
 
 static bool alert_msg_proc(JWidget widget, JMessage msg)
diff --git a/src/commands/cmd_configure_tools.cpp b/src/commands/cmd_configure_tools.cpp
index c83a2559c..3e94b2fd1 100644
--- a/src/commands/cmd_configure_tools.cpp
+++ b/src/commands/cmd_configure_tools.cpp
@@ -84,26 +84,29 @@ static void cmd_configure_tools_execute(const char *argument)
     return;
   }
 
-  if (!get_widgets(window,
-		   "filled", &filled,
-		   "tiled", &tiled,
-		   "tiled_x", &tiled_x,
-		   "tiled_y", &tiled_y,
-		   "use_grid", &use_grid,
-		   "view_grid", &view_grid,
-		   "set_grid", &set_grid,
-		   "brush_size", &brush_size,
-		   "brush_angle", &brush_angle,
-		   "glass_dirty", &glass_dirty,
-		   "spray_width", &spray_width,
-		   "air_speed", &air_speed,
-		   "cursor_color_box", &cursor_color_box,
-		   "brush_preview_box", &brush_preview_box,
-		   "brush_type_box", &brush_type_box,
-		   "onionskin", &check_onionskin, NULL)) {
+  try {
+    get_widgets(window,
+		"filled", &filled,
+		"tiled", &tiled,
+		"tiled_x", &tiled_x,
+		"tiled_y", &tiled_y,
+		"use_grid", &use_grid,
+		"view_grid", &view_grid,
+		"set_grid", &set_grid,
+		"brush_size", &brush_size,
+		"brush_angle", &brush_angle,
+		"glass_dirty", &glass_dirty,
+		"spray_width", &spray_width,
+		"air_speed", &air_speed,
+		"cursor_color_box", &cursor_color_box,
+		"brush_preview_box", &brush_preview_box,
+		"brush_type_box", &brush_type_box,
+		"onionskin", &check_onionskin, NULL);
+  }
+  catch (...) {
     jwidget_free(window);
     window = NULL;
-    return;
+    throw;
   }
 
   /* cursor-color */
@@ -325,24 +328,29 @@ static bool view_grid_check_change_hook(JWidget widget, void *data)
 
 static bool set_grid_button_select_hook(JWidget widget, void *data)
 {
-  CurrentSprite sprite;
+  try {
+    const CurrentSpriteReader sprite;
 
-  if (sprite && sprite->mask && sprite->mask->bitmap) {
-    JRect rect = jrect_new(sprite->mask->x,
-			   sprite->mask->y,
-			   sprite->mask->x+sprite->mask->w,
-			   sprite->mask->y+sprite->mask->h);
-    set_grid(rect);
-    jrect_free(rect);
+    if (sprite && sprite->mask && sprite->mask->bitmap) {
+      JRect rect = jrect_new(sprite->mask->x,
+			     sprite->mask->y,
+			     sprite->mask->x+sprite->mask->w,
+			     sprite->mask->y+sprite->mask->h);
+      set_grid(rect);
+      jrect_free(rect);
 
-    if (get_view_grid())
-      refresh_all_editors();
+      if (get_view_grid())
+	refresh_all_editors();
+    }
+    else {
+      jalert(_("Error"
+	       "<<You have to select a sprite with mask."
+	       "<<The boundaries of the mask will be used"
+	       "<<to specify the grid area.||&OK"));
+    }
   }
-  else {
-    jalert(_("Error"
-	     "<<You must select a sprite with mask."
-	     "<<The boundaries of the mask will be used"
-	     "<<to specify the grid area.||&OK"));
+  catch (locked_sprite_exception& e) {
+    e.show();
   }
 
   return TRUE;
diff --git a/src/commands/cmd_copy.cpp b/src/commands/cmd_copy.cpp
index cc583abd7..e90007486 100644
--- a/src/commands/cmd_copy.cpp
+++ b/src/commands/cmd_copy.cpp
@@ -30,7 +30,7 @@
 
 static bool cmd_copy_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
 
   if ((!sprite) ||
       (!sprite->layer) ||
@@ -45,7 +45,7 @@ static bool cmd_copy_enabled(const char *argument)
 
 static void cmd_copy_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   clipboard::copy(sprite);
 }
 
diff --git a/src/commands/cmd_copy_cel.cpp b/src/commands/cmd_copy_cel.cpp
index 255c36b1d..b4647d47e 100644
--- a/src/commands/cmd_copy_cel.cpp
+++ b/src/commands/cmd_copy_cel.cpp
@@ -31,7 +31,7 @@ static bool cmd_copy_cel_enabled(const char *argument)
 
 static void cmd_copy_cel_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   copy_cel(sprite);
 }
 
diff --git a/src/commands/cmd_crop.cpp b/src/commands/cmd_crop.cpp
index 593afeb9b..13623f011 100644
--- a/src/commands/cmd_crop.cpp
+++ b/src/commands/cmd_crop.cpp
@@ -26,10 +26,9 @@
 #include "raster/layer.h"
 #include "raster/mask.h"
 #include "raster/sprite.h"
-#include "raster/undoable.h"
+#include "undoable.h"
 #include "widgets/colbar.h"
 #include "util/autocrop.h"
-#include "util/functions.h"
 #include "util/misc.h"
 
 /* ======================== */
@@ -38,7 +37,7 @@
 
 static bool cmd_crop_sprite_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return
     sprite != NULL &&
     sprite->mask != NULL &&
@@ -47,7 +46,7 @@ static bool cmd_crop_sprite_enabled(const char *argument)
 
 static void cmd_crop_sprite_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   {
     Undoable undoable(sprite, "Sprite Crop");
     int bgcolor = get_color_for_image(sprite->imgtype,
@@ -69,13 +68,13 @@ static void cmd_crop_sprite_execute(const char *argument)
 
 static bool cmd_autocrop_sprite_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return sprite != NULL;
 }
 
 static void cmd_autocrop_sprite_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   {
     Undoable undoable(sprite, "Sprite Autocrop");
     undoable.autocrop_sprite(colorbar_get_bg_color(app_get_colorbar()));
diff --git a/src/commands/cmd_cut.cpp b/src/commands/cmd_cut.cpp
index 8f13f44ad..f3a304888 100644
--- a/src/commands/cmd_cut.cpp
+++ b/src/commands/cmd_cut.cpp
@@ -30,7 +30,7 @@
 
 static bool cmd_cut_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   if ((!sprite) ||
       (!sprite->layer) ||
       (!layer_is_readable(sprite->layer)) ||
@@ -44,7 +44,7 @@ static bool cmd_cut_enabled(const char *argument)
 
 static void cmd_cut_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   clipboard::cut(sprite);
 }
 
diff --git a/src/commands/cmd_deselect_mask.cpp b/src/commands/cmd_deselect_mask.cpp
index d6d1102eb..17d76481f 100644
--- a/src/commands/cmd_deselect_mask.cpp
+++ b/src/commands/cmd_deselect_mask.cpp
@@ -27,13 +27,13 @@
 
 static bool cmd_deselect_mask_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return sprite && !mask_is_empty(sprite->mask);
 }
 
 static void cmd_deselect_mask_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   Mask *mask;
 
   /* destroy the *deselected* mask */
diff --git a/src/commands/cmd_duplicate_layer.cpp b/src/commands/cmd_duplicate_layer.cpp
index b35a0e8b8..88f03a76f 100644
--- a/src/commands/cmd_duplicate_layer.cpp
+++ b/src/commands/cmd_duplicate_layer.cpp
@@ -29,24 +29,23 @@
 #include "raster/sprite.h"
 #include "raster/undo.h"
 
-static Layer *duplicate_layer();
+static Layer *duplicate_layer(Sprite* sprite);
 
 static bool cmd_duplicate_layer_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return sprite && sprite->layer;
 }
 
 static void cmd_duplicate_layer_execute(const char *argument)
 {
-  CurrentSprite sprite;
-  if (duplicate_layer() != NULL)
+  CurrentSpriteWriter sprite;
+  if (duplicate_layer(sprite) != NULL)
     update_screen_for_sprite(sprite);
 }
 
-static Layer *duplicate_layer()
+static Layer *duplicate_layer(Sprite* sprite)
 {
-  CurrentSprite sprite;
   Layer *layer_copy;
   char buf[1024];
 
@@ -64,7 +63,8 @@ static Layer *duplicate_layer()
     if (undo_is_enabled(sprite->undo))
       undo_close(sprite->undo);
 
-    console_printf("Not enough memory");
+    Console console;
+    console.printf("Not enough memory");
     return NULL;
   }
 
diff --git a/src/commands/cmd_duplicate_sprite.cpp b/src/commands/cmd_duplicate_sprite.cpp
index e8dcb6881..b67da6578 100644
--- a/src/commands/cmd_duplicate_sprite.cpp
+++ b/src/commands/cmd_duplicate_sprite.cpp
@@ -32,20 +32,18 @@
 
 static bool cmd_duplicate_sprite_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return sprite;
 }
 
 static void cmd_duplicate_sprite_execute(const char *argument)
 {
-  JWidget window, src_name, dst_name, flatten;
-  CurrentSprite sprite;
+  JWidget src_name, dst_name, flatten;
+  const CurrentSpriteReader sprite;
   char buf[1024];
 
   /* load the window widget */
-  window = load_widget("dupspr.jid", "duplicate_sprite");
-  if (!window)
-    return;
+  JWidgetPtr window = load_widget("dupspr.jid", "duplicate_sprite");
 
   src_name = jwidget_find_name(window, "src_name");
   dst_name = jwidget_find_name(window, "dst_name");
@@ -83,8 +81,6 @@ static void cmd_duplicate_sprite_execute(const char *argument)
       context->show_sprite(sprite_copy);
     }
   }
-
-  jwidget_free(window);
 }
 
 Command cmd_duplicate_sprite = {
diff --git a/src/commands/cmd_film_editor.cpp b/src/commands/cmd_film_editor.cpp
index 817171a2d..6087d17eb 100644
--- a/src/commands/cmd_film_editor.cpp
+++ b/src/commands/cmd_film_editor.cpp
@@ -26,8 +26,8 @@
 
 static bool cmd_film_editor_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return sprite != NULL;
 }
 
 static void cmd_film_editor_execute(const char *argument)
diff --git a/src/commands/cmd_flatten_layers.cpp b/src/commands/cmd_flatten_layers.cpp
index b85b04d16..188da4641 100644
--- a/src/commands/cmd_flatten_layers.cpp
+++ b/src/commands/cmd_flatten_layers.cpp
@@ -19,26 +19,28 @@
 #include "config.h"
 
 #include "commands/commands.h"
+#include "core/app.h"
 #include "modules/gui.h"
-#include "modules/sprites.h"
-#include "raster/undo.h"
 #include "raster/sprite.h"
-#include "util/functions.h"
+#include "undoable.h"
+#include "widgets/colbar.h"
 
 static bool cmd_flatten_layers_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return sprite != NULL;
 }
 
 static void cmd_flatten_layers_execute(const char *argument)
 {
-  CurrentSprite sprite;
-
-  if (undo_is_enabled(sprite->undo))
-    undo_set_label(sprite->undo, "Flatten Layers");
-
-  FlattenLayers(sprite);
+  CurrentSpriteWriter sprite;
+  int bgcolor = get_color_for_image(sprite->imgtype,
+				    colorbar_get_bg_color(app_get_colorbar()));
+  {
+    Undoable undoable(sprite, "Flatten Layers");
+    undoable.flatten_layers(bgcolor);
+    undoable.commit();
+  }
   update_screen_for_sprite(sprite);
 }
 
diff --git a/src/commands/cmd_flip.cpp b/src/commands/cmd_flip.cpp
index 25f30e16e..86efbb73a 100644
--- a/src/commands/cmd_flip.cpp
+++ b/src/commands/cmd_flip.cpp
@@ -28,7 +28,7 @@
 #include "raster/undo.h"
 #include "util/misc.h"
 
-static void do_flip(int horz);
+static void do_flip(Sprite* sprite, bool horz);
 
 /* ======================== */
 /* flip_horizontal          */
@@ -36,13 +36,15 @@ static void do_flip(int horz);
 
 static bool cmd_flip_horizontal_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_flip_horizontal_execute(const char *argument)
 {
-  do_flip(TRUE);
+  CurrentSpriteWriter sprite;
+  do_flip(sprite, true);
 }
 
 /* ======================== */
@@ -51,21 +53,22 @@ static void cmd_flip_horizontal_execute(const char *argument)
 
 static bool cmd_flip_vertical_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_flip_vertical_execute(const char *argument)
 {
-  do_flip(FALSE);
+  CurrentSpriteWriter sprite;
+  do_flip(sprite, false);
 }
 
 /************************************************************/
 /* do_flip */
 
-static void do_flip(int horz)
+static void do_flip(Sprite* sprite, bool horz)
 {
-  CurrentSprite sprite;
   Image *image, *area;
   int x1, y1, x2, y2;
   int x, y;
diff --git a/src/commands/cmd_frame_properties.cpp b/src/commands/cmd_frame_properties.cpp
index 683812579..66142e8f4 100644
--- a/src/commands/cmd_frame_properties.cpp
+++ b/src/commands/cmd_frame_properties.cpp
@@ -24,40 +24,35 @@
 #include "modules/gui.h"
 #include "modules/sprites.h"
 #include "raster/sprite.h"
-#include "raster/undoable.h"
+#include "undoable.h"
 
-void dialogs_frame_length(int sprite_frame);
+class SpriteReader;
+void dialogs_frame_length(const SpriteReader& sprite, int sprite_frame);
 
 static bool cmd_frame_properties_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_frame_properties_execute(const char *argument)
 {
-  CurrentSprite sprite;
-  dialogs_frame_length(sprite->frame);
+  const CurrentSpriteReader sprite;
+  dialogs_frame_length(sprite, sprite->frame);
 }
 
 /* if sprite_frame < 0, set the frame length of all frames */
-void dialogs_frame_length(int sprite_frame)
+void dialogs_frame_length(const SpriteReader& sprite, int sprite_frame)
 {
-  JWidget window, frame, frlen, ok;
-  CurrentSprite sprite;
+  JWidget frame, frlen, ok;
   char buf[64];
 
-  window = load_widget("frlen.jid", "frame_duration");
-  if (!window)
-    return;
-
-  if (!get_widgets(window,
-		   "frame", &frame,
-		   "frlen", &frlen,
-		   "ok", &ok, NULL)) {
-    jwidget_free(window);
-    return;
-  }
+  JWidgetPtr window = load_widget("frlen.jid", "frame_duration");
+  get_widgets(window,
+	      "frame", &frame,
+	      "frlen", &frlen,
+	      "ok", &ok, NULL);
 
   if (sprite_frame < 0)
     strcpy(buf, "All");
@@ -76,18 +71,19 @@ void dialogs_frame_length(int sprite_frame)
       if (jalert("Warning"
 		 "<<Do you want to change the duration of all frames?"
 		 "||&Yes||&No") == 1) {
-	Undoable undoable(sprite, "Constant Frame-Rate");
+	SpriteWriter sprite_writer(sprite);
+	Undoable undoable(sprite_writer, "Constant Frame-Rate");
 	undoable.set_constant_frame_rate(num);
 	undoable.commit();
       }
     }
     else {
-      Undoable undoable(sprite, "Frame Duration");
+      SpriteWriter sprite_writer(sprite);
+      Undoable undoable(sprite_writer, "Frame Duration");
       undoable.set_frame_duration(sprite_frame, num);
       undoable.commit();
     }
   }
-  jwidget_free(window);
 }
 
 Command cmd_frame_properties = {
diff --git a/src/commands/cmd_goto_frame.cpp b/src/commands/cmd_goto_frame.cpp
index 198d77bc2..b8abddc92 100644
--- a/src/commands/cmd_goto_frame.cpp
+++ b/src/commands/cmd_goto_frame.cpp
@@ -31,13 +31,13 @@
 
 static bool cmd_goto_first_frame_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return sprite != NULL;
 }
 
 static void cmd_goto_first_frame_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   sprite->frame = 0;
 
   update_screen_for_sprite(sprite);
@@ -50,13 +50,14 @@ static void cmd_goto_first_frame_execute(const char *argument)
 
 static bool cmd_goto_previous_frame_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite != NULL;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_goto_previous_frame_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
 
   if (sprite->frame > 0)
     sprite->frame--;
@@ -73,13 +74,14 @@ static void cmd_goto_previous_frame_execute(const char *argument)
 
 static bool cmd_goto_next_frame_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite != NULL;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_goto_next_frame_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
 
   if (sprite->frame < sprite->frames-1)
     sprite->frame++;
@@ -96,13 +98,14 @@ static void cmd_goto_next_frame_execute(const char *argument)
 
 static bool cmd_goto_last_frame_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite != NULL;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_goto_last_frame_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   sprite->frame = sprite->frames-1;
 
   update_screen_for_sprite(sprite);
diff --git a/src/commands/cmd_goto_layer.cpp b/src/commands/cmd_goto_layer.cpp
index 9691dcc3c..6c00155d2 100644
--- a/src/commands/cmd_goto_layer.cpp
+++ b/src/commands/cmd_goto_layer.cpp
@@ -34,13 +34,14 @@
 
 static bool cmd_goto_previous_layer_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite != NULL;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_goto_previous_layer_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   int i = sprite_layer2index(sprite, sprite->layer);
   
   if (i > 0)
@@ -64,13 +65,14 @@ static void cmd_goto_previous_layer_execute(const char *argument)
 
 static bool cmd_goto_next_layer_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite != NULL;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_goto_next_layer_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   int i = sprite_layer2index(sprite, sprite->layer);
 
   if (i < sprite_count_layers(sprite)-1)
diff --git a/src/commands/cmd_invert_mask.cpp b/src/commands/cmd_invert_mask.cpp
index 5a7d588ae..7cc653d80 100644
--- a/src/commands/cmd_invert_mask.cpp
+++ b/src/commands/cmd_invert_mask.cpp
@@ -28,13 +28,13 @@
 
 static bool cmd_invert_mask_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return sprite != NULL;
 }
 
 static void cmd_invert_mask_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   Mask *mask;
 
   /* change the selection */
diff --git a/src/commands/cmd_layer_from_background.cpp b/src/commands/cmd_layer_from_background.cpp
index 393d3ee0c..7d63e5276 100644
--- a/src/commands/cmd_layer_from_background.cpp
+++ b/src/commands/cmd_layer_from_background.cpp
@@ -22,19 +22,15 @@
 
 #include "commands/commands.h"
 #include "modules/gui.h"
-#include "modules/sprites.h"
-#include "raster/cel.h"
 #include "raster/layer.h"
-#include "raster/sprite.h"
-#include "raster/undo.h"
-#include "util/functions.h"
+#include "undoable.h"
 
 static bool cmd_layer_from_background_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return
-    sprite &&
-    sprite->layer &&
+    sprite != NULL &&
+    sprite->layer != NULL &&
     layer_is_image(sprite->layer) &&
     layer_is_readable(sprite->layer) &&
     layer_is_writable(sprite->layer) &&
@@ -43,12 +39,12 @@ static bool cmd_layer_from_background_enabled(const char *argument)
 
 static void cmd_layer_from_background_execute(const char *argument)
 {
-  CurrentSprite sprite;
-
-  if (undo_is_enabled(sprite->undo))
-    undo_set_label(sprite->undo, "Layer from Background");
-
-  LayerFromBackground(sprite);
+  CurrentSpriteWriter sprite;
+  {
+    Undoable undoable(sprite, "Layer from Background");
+    undoable.layer_from_background();
+    undoable.commit();
+  }
   update_screen_for_sprite(sprite);
 }
 
diff --git a/src/commands/cmd_layer_properties.cpp b/src/commands/cmd_layer_properties.cpp
index f4b6274b5..1efc2e2da 100644
--- a/src/commands/cmd_layer_properties.cpp
+++ b/src/commands/cmd_layer_properties.cpp
@@ -29,18 +29,20 @@
 
 static bool cmd_layer_properties_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite && sprite->layer;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL &&
+    sprite->layer != NULL;
 }
 
 static void cmd_layer_properties_execute(const char *argument)
 {
-  JWidget window, box1, box2, box3, label_name, entry_name;
+  JWidget box1, box2, box3, label_name, entry_name;
   JWidget button_ok, button_cancel, label_bm, view_bm, list_bm;
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   Layer *layer = sprite->layer;
 
-  window = jwindow_new(_("Layer Properties"));
+  JWidgetPtr window = jwindow_new(_("Layer Properties"));
   box1 = jbox_new(JI_VERTICAL);
   box2 = jbox_new(JI_HORIZONTAL);
   box3 = jbox_new(JI_HORIZONTAL + JI_HOMOGENEOUS);
@@ -104,8 +106,6 @@ static void cmd_layer_properties_execute(const char *argument)
 
     update_screen_for_sprite(sprite);
   }
-
-  jwidget_free(window);
 }
 
 Command cmd_layer_properties = {
diff --git a/src/commands/cmd_load_mask.cpp b/src/commands/cmd_load_mask.cpp
index 3c4eb17c5..e381d6999 100644
--- a/src/commands/cmd_load_mask.cpp
+++ b/src/commands/cmd_load_mask.cpp
@@ -31,13 +31,13 @@
 
 static bool cmd_load_mask_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return sprite != NULL;
 }
 
 static void cmd_load_mask_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   jstring filename = ase_file_selector(_("Load .msk File"), "", "msk");
   if (!filename.empty()) {
     Mask *mask = load_msk_file(filename.c_str());
diff --git a/src/commands/cmd_mask_all.cpp b/src/commands/cmd_mask_all.cpp
index abecbe1ee..dd8567855 100644
--- a/src/commands/cmd_mask_all.cpp
+++ b/src/commands/cmd_mask_all.cpp
@@ -27,13 +27,13 @@
 
 static bool cmd_mask_all_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return sprite != NULL;
 }
   
 static void cmd_mask_all_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
 
   /* undo */
   if (undo_is_enabled(sprite->undo)) {
diff --git a/src/commands/cmd_mask_by_color.cpp b/src/commands/cmd_mask_by_color.cpp
index 2e5de7d5b..b8a98e199 100644
--- a/src/commands/cmd_mask_by_color.cpp
+++ b/src/commands/cmd_mask_by_color.cpp
@@ -26,13 +26,14 @@
 
 static bool cmd_mask_by_color_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_mask_by_color_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   dialogs_mask_color(sprite);
 }
 
diff --git a/src/commands/cmd_merge_down_layer.cpp b/src/commands/cmd_merge_down_layer.cpp
index 425660dd0..fe51ae32e 100644
--- a/src/commands/cmd_merge_down_layer.cpp
+++ b/src/commands/cmd_merge_down_layer.cpp
@@ -33,24 +33,24 @@
 
 static bool cmd_merge_down_layer_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   if (!sprite)
-    return FALSE;
+    return false;
 
   Layer *src_layer = sprite->layer;
   if (!src_layer || !layer_is_image(src_layer))
-    return FALSE;
+    return false;
 
   Layer* dst_layer = layer_get_prev(sprite->layer);
   if (!dst_layer || !layer_is_image(dst_layer))
-    return FALSE;
+    return false;
 
   return TRUE;
 }
 
 static void cmd_merge_down_layer_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   Layer *src_layer, *dst_layer;
   Cel *src_cel, *dst_cel;
   Image *src_image, *dst_image;
diff --git a/src/commands/cmd_move_cel.cpp b/src/commands/cmd_move_cel.cpp
index 1372935f6..2c282b6d7 100644
--- a/src/commands/cmd_move_cel.cpp
+++ b/src/commands/cmd_move_cel.cpp
@@ -31,7 +31,7 @@ static bool cmd_move_cel_enabled(const char *argument)
 
 static void cmd_move_cel_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   move_cel(sprite);
 }
 
diff --git a/src/commands/cmd_new_file.cpp b/src/commands/cmd_new_file.cpp
index 67fe31a89..24f758b6a 100644
--- a/src/commands/cmd_new_file.cpp
+++ b/src/commands/cmd_new_file.cpp
@@ -36,18 +36,19 @@
 #include "raster/layer.h"
 #include "raster/sprite.h"
 #include "raster/undo.h"
-#include "util/functions.h"
 #include "util/misc.h"
 #include "widgets/colbar.h"
 
 static int _sprite_counter = 0;
 
+static Sprite *new_sprite(Context* context, int imgtype, int w, int h);
+
 /**
  * Shows the "New Sprite" dialog.
  */
 static void cmd_new_file_execute(const char *argument)
 {
-  JWidget window, width, height, radio1, radio2, radio3, ok, bg_box;
+  JWidget width, height, radio1, radio2, radio3, ok, bg_box;
   int imgtype, w, h, bg;
   char buf[1024];
   Sprite *sprite;
@@ -61,9 +62,7 @@ static void cmd_new_file_execute(const char *argument)
   };
 
   /* load the window widget */
-  window = load_widget("newspr.jid", "new_sprite");
-  if (!window)
-    return;
+  JWidgetPtr window = load_widget("newspr.jid", "new_sprite");
 
   width = jwidget_find_name(window, "width");
   height = jwidget_find_name(window, "height");
@@ -127,9 +126,10 @@ static void cmd_new_file_execute(const char *argument)
       set_config_int("NewSprite", "Background", bg);
 
       /* create the new sprite */
-      sprite = NewSprite(imgtype, w, h);
+      sprite = new_sprite(UIContext::instance(), imgtype, w, h);
       if (!sprite) {
-	console_printf("Not enough memory to allocate the sprite\n");
+	Console console;
+	console.printf("Not enough memory to allocate the sprite\n");
       }
       else {
 	usprintf(buf, "Sprite-%04d", ++_sprite_counter);
@@ -143,21 +143,36 @@ static void cmd_new_file_execute(const char *argument)
 		      get_color_for_image(imgtype, color));
 	}
 
-	/* the undo should be disabled because we use NewSprite to
-	   create it (a function for scripts) */
-	assert(undo_is_disabled(sprite->undo));
-
-	/* enable undo */
-	undo_enable(sprite->undo);
-
 	/* show the sprite to the user */
 	UIContext* context = UIContext::instance();
 	context->show_sprite(sprite);
       }
     }
   }
+}
 
-  jwidget_free(window);
+/**
+ * Creates a new sprite with the given dimension with one transparent
+ * layer called "Layer 1".
+ *
+ * @param imgtype Color mode, one of the following values: IMAGE_RGB, IMAGE_GRAYSCALE, IMAGE_INDEXED
+ * @param w Width of the sprite
+ * @param h Height of the sprite
+ */
+static Sprite *new_sprite(Context* context, int imgtype, int w, int h)
+{
+  assert(imgtype == IMAGE_RGB || imgtype == IMAGE_GRAYSCALE || imgtype == IMAGE_INDEXED);
+  assert(w >= 1 && w <= 9999);
+  assert(h >= 1 && h <= 9999);
+
+  Sprite *sprite = sprite_new_with_layer(imgtype, w, h);
+  if (!sprite)
+    return NULL;
+
+  context->add_sprite(sprite);
+  context->set_current_sprite(sprite);
+
+  return sprite;
 }
 
 Command cmd_new_file = {
diff --git a/src/commands/cmd_new_frame.cpp b/src/commands/cmd_new_frame.cpp
index 5ce76b7c5..fa76e3404 100644
--- a/src/commands/cmd_new_frame.cpp
+++ b/src/commands/cmd_new_frame.cpp
@@ -31,17 +31,17 @@
 #include "raster/image.h"
 #include "raster/layer.h"
 #include "raster/sprite.h"
-#include "raster/undoable.h"
+#include "undoable.h"
 #include "widgets/statebar.h"
 
 #include <stdexcept>
 
 static bool cmd_new_frame_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return
-    sprite &&
-    sprite->layer &&
+    sprite != NULL &&
+    sprite->layer != NULL &&
     layer_is_readable(sprite->layer) &&
     layer_is_writable(sprite->layer) &&
     layer_is_image(sprite->layer);
@@ -49,7 +49,7 @@ static bool cmd_new_frame_enabled(const char *argument)
 
 static void cmd_new_frame_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   {
     Undoable undoable(sprite, "New Frame");
     undoable.new_frame();
diff --git a/src/commands/cmd_new_layer.cpp b/src/commands/cmd_new_layer.cpp
index 0b3d2b817..e85084c96 100644
--- a/src/commands/cmd_new_layer.cpp
+++ b/src/commands/cmd_new_layer.cpp
@@ -26,28 +26,25 @@
 #include "modules/sprites.h"
 #include "raster/layer.h"
 #include "raster/sprite.h"
-#include "raster/undoable.h"
-#include "util/functions.h"
+#include "undoable.h"
 
-static bool cmd_new_layer_enabled(const char *argument)
+static char* get_unique_layer_name(Sprite* sprite);
+static int get_max_layer_num(Layer* layer);
+
+static bool cmd_new_layer_enabled(const char* argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return sprite;
 }
 
-static void cmd_new_layer_execute(const char *argument)
+static void cmd_new_layer_execute(const char* argument)
 {
-  JWidget window, name_widget;
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
 
-  /* load the window widget */
-  window = load_widget("newlay.jid", "new_layer");
-  if (!window)
-    return;
-
-  name_widget = jwidget_find_name(window, "name");
+  JWidgetPtr window = load_widget("newlay.jid", "new_layer");
+  JWidget name_widget = find_widget(window, "name");
   {
-    char *name = GetUniqueLayerName(sprite);
+    char* name = get_unique_layer_name(sprite);
     jwidget_set_text(name_widget, name);
     jfree(name);
   }
@@ -66,8 +63,35 @@ static void cmd_new_layer_execute(const char *argument)
     layer_set_name(layer, name);
     update_screen_for_sprite(sprite);
   }
+}
 
-  jwidget_free(window);
+static char* get_unique_layer_name(Sprite* sprite)
+{
+  if (sprite != NULL) {
+    char buf[1024];
+    sprintf(buf, "Layer %d", get_max_layer_num(sprite->set)+1);
+    return jstrdup(buf);
+  }
+  else
+    return NULL;
+}
+
+static int get_max_layer_num(Layer* layer)
+{
+  int max = 0;
+
+  if (strncmp(layer->name, "Layer ", 6) == 0)
+    max = strtol(layer->name+6, NULL, 10);
+
+  if (layer_is_set(layer)) {
+    JLink link;
+    JI_LIST_FOR_EACH(layer->layers, link) {
+      int tmp = get_max_layer_num(reinterpret_cast<Layer*>(link->data));
+      max = MAX(tmp, max);
+    }
+  }
+  
+  return max;
 }
 
 Command cmd_new_layer = {
diff --git a/src/commands/cmd_new_layer_set.cpp b/src/commands/cmd_new_layer_set.cpp
index dd861c1e6..23e61f9df 100644
--- a/src/commands/cmd_new_layer_set.cpp
+++ b/src/commands/cmd_new_layer_set.cpp
@@ -26,38 +26,33 @@
 #include "modules/sprites.h"
 #include "raster/layer.h"
 #include "raster/sprite.h"
-#include "util/functions.h"
 
 static bool cmd_new_layer_set_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_new_layer_set_execute(const char *argument)
 {
-  JWidget window;
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
 
   // load the window widget
-  window = load_widget("newlay.jid", "new_layer_set");
-  if (!window)
-    return;
+  JWidgetPtr window = load_widget("newlay.jid", "new_layer_set");
 
   jwindow_open_fg(window);
 
   if (jwindow_get_killer(window) == jwidget_find_name(window, "ok")) {
     const char *name = jwidget_get_text(jwidget_find_name(window, "name"));
-    Layer *layer = NewLayerSet(sprite);
-    if (!layer) {
-      jalert(_("Error<<Not enough memory||&Close"));
-      return;
-    }
+    Layer *layer = layer_set_new(sprite);
+
     layer_set_name(layer, name);
+    layer_add_layer(sprite->set, layer);
+    sprite_set_layer(sprite, layer);
+
     update_screen_for_sprite(sprite);
   }
-
-  jwidget_free(window);
 }
 
 Command cmd_new_layer_set = {
diff --git a/src/commands/cmd_open_file.cpp b/src/commands/cmd_open_file.cpp
index 5861b4fbe..0ef6f4e7c 100644
--- a/src/commands/cmd_open_file.cpp
+++ b/src/commands/cmd_open_file.cpp
@@ -99,9 +99,8 @@ static void monitor_openfile_bg(void *_data)
       progress_free(data->progress);
 
     if (fop->error) {
-      console_open();
-      console_printf(fop->error);
-      console_close();
+      Console console;
+      console.printf(fop->error);
     }
 #endif
 
@@ -143,6 +142,7 @@ static void monitor_free(void *_data)
  */
 static void cmd_open_file_execute(const char *argument)
 {
+  Console console;
   jstring filename;
 
   /* interactive */
@@ -161,13 +161,13 @@ static void cmd_open_file_execute(const char *argument)
 
     if (fop) {
       if (fop->error) {
-	console_printf(fop->error);
+	console.printf(fop->error);
 	fop_free(fop);
       }
       else {
 	JThread thread = jthread_new(openfile_bg, fop);
 	if (thread) {
-	  OpenFileData *data = jnew(OpenFileData, 1);
+	  OpenFileData* data = new OpenFileData;
 
 	  data->fop = fop;
 	  data->progress = progress_new(app_get_statusbar());
@@ -191,9 +191,7 @@ static void cmd_open_file_execute(const char *argument)
 
 	  /* show any error */
 	  if (fop->error) {
-	    console_open();
-	    console_printf(fop->error);
-	    console_close();
+	    console.printf(fop->error);
 	  }
 	  else {
 	    Sprite *sprite = fop->sprite;
@@ -216,10 +214,10 @@ static void cmd_open_file_execute(const char *argument)
 	  progress_free(data->progress);
 	  jwidget_free(data->alert_window);
 	  fop_free(fop);
-	  jfree(data);
+	  delete data;
 	}
 	else {
-	  console_printf(_("Error creating thread to load the sprite"));
+	  console.printf(_("Error creating thread to load the sprite"));
 	  fop_free(fop);
 	}
       }
diff --git a/src/commands/cmd_palette_editor.cpp b/src/commands/cmd_palette_editor.cpp
index f2675aca9..107370290 100644
--- a/src/commands/cmd_palette_editor.cpp
+++ b/src/commands/cmd_palette_editor.cpp
@@ -40,6 +40,8 @@
 #include "widgets/colview.h"
 #include "widgets/paledit.h"
 
+#define get_sprite(wgt) (*(const SpriteReader*)(jwidget_get_window(wgt))->user_data[0])
+
 static Palette **palettes;
 
 static JWidget slider_R, slider_G, slider_B;
@@ -66,7 +68,7 @@ static void set_new_palette(Palette *palette);
 
 static void cmd_palette_editor_execute(const char *argument)
 {
-  JWidget window, colorviewer_box, palette_editor_view;
+  JWidget colorviewer_box, palette_editor_view;
   JWidget slider_columns, button_ok;
   JWidget button_select_all;
   JWidget button_undo, button_redo;
@@ -74,7 +76,7 @@ static void cmd_palette_editor_execute(const char *argument)
   JWidget button_ramp, button_quantize;
   int frame, columns;
   Palette *palette = NULL;
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   int imgtype = sprite ? sprite->imgtype: IMAGE_INDEXED;
   int frame_bak = sprite ? sprite->frame : 0;
   bool all_frames_same_palette = TRUE;
@@ -85,33 +87,29 @@ static void cmd_palette_editor_execute(const char *argument)
   }
 
   /* load widgets */
-  window = load_widget("paledit.jid", "palette_editor");
-  if (!window)
-    return;
+  JWidgetPtr window = load_widget("paledit.jid", "palette_editor");
+  get_widgets(window,
+	      "red", &slider_R,
+	      "green", &slider_G,
+	      "blue", &slider_B,
+	      "hue", &slider_H,
+	      "saturation", &slider_S,
+	      "value", &slider_V,
+	      "columns", &slider_columns,
+	      "frame", &slider_frame,
+	      "select_all", &button_select_all,
+	      "undo", &button_undo,
+	      "redo", &button_redo,
+	      "load", &button_load,
+	      "save", &button_save,
+	      "ramp", &button_ramp,
+	      "quantize", &button_quantize,
+	      "button_ok", &button_ok,
+	      "colorviewer", &colorviewer_box,
+	      "palette_editor", &palette_editor_view,
+	      "all_frames", &check_all_frames, NULL);
 
-  if (!get_widgets(window,
-		   "red", &slider_R,
-		   "green", &slider_G,
-		   "blue", &slider_B,
-		   "hue", &slider_H,
-		   "saturation", &slider_S,
-		   "value", &slider_V,
-		   "columns", &slider_columns,
-		   "frame", &slider_frame,
-		   "select_all", &button_select_all,
-		   "undo", &button_undo,
-		   "redo", &button_redo,
-		   "load", &button_load,
-		   "save", &button_save,
-		   "ramp", &button_ramp,
-		   "quantize", &button_quantize,
-		   "button_ok", &button_ok,
-		   "colorviewer", &colorviewer_box,
-		   "palette_editor", &palette_editor_view,
-		   "all_frames", &check_all_frames, NULL)) {
-    jwidget_free(window);
-    return;
-  }
+  window->user_data[0] = (void*)&sprite;
 
   /* create current_sprite->frames palettes */
   if (sprite) {
@@ -174,8 +172,10 @@ static void cmd_palette_editor_execute(const char *argument)
     if (jwidget_is_selected(check_all_frames))
       jwidget_disable(slider_frame);
   }
-  else
+  else {
     jwidget_disable(slider_frame);
+    jwidget_disable(button_quantize);
+  }
 
   /* hook signals */
   HOOK(slider_R, JI_SIGNAL_SLIDER_CHANGE, sliderRGB_change_hook, 0);
@@ -208,7 +208,8 @@ static void cmd_palette_editor_execute(const char *argument)
   /* check the killer widget */
   if (jwindow_get_killer(window) == button_ok) {
     if (sprite) {
-      sprite_reset_palettes(sprite);
+      SpriteWriter sprite_writer(sprite);
+      sprite_reset_palettes(sprite_writer);
 
       /* one palette */
       if (jwidget_is_selected(check_all_frames)) {
@@ -216,7 +217,7 @@ static void cmd_palette_editor_execute(const char *argument)
 	palette_copy_colors(palettes[0],
 			    get_current_palette());
 
-	sprite_set_palette(sprite, palettes[0], TRUE);
+	sprite_set_palette(sprite_writer, palettes[0], TRUE);
       }
       /* various palettes */
       else {
@@ -224,11 +225,11 @@ static void cmd_palette_editor_execute(const char *argument)
 	palette_copy_colors(palettes[frame],
 			    get_current_palette());
 
-	for (frame=0; frame<sprite->frames; ++frame) {
+	for (frame=0; frame<sprite_writer->frames; ++frame) {
 	  if (frame == 0 ||
 	      palette_count_diff(palettes[frame],
 				 palettes[frame-1], NULL, NULL) > 0) {
-	    sprite_set_palette(sprite, palettes[frame], TRUE);
+	    sprite_set_palette(sprite_writer, palettes[frame], TRUE);
 	  }
 	}
       }
@@ -243,7 +244,9 @@ static void cmd_palette_editor_execute(const char *argument)
   else {
     /* restore the system palette */
     if (sprite) {
-      sprite->frame = frame_bak;
+      SpriteWriter sprite_writer(sprite);
+      sprite_writer->frame = frame_bak;
+
       set_current_palette(sprite_get_palette(sprite, frame_bak), TRUE);
     }
     else {
@@ -261,8 +264,6 @@ static void cmd_palette_editor_execute(const char *argument)
   /* save window configuration */
   save_window_pos(window, "PaletteEditor");
 
-  jwidget_free(window);
-
   if (palettes) {
     assert(sprite);
 
@@ -354,16 +355,19 @@ static void ramp_command(JWidget widget)
 
 static void quantize_command(JWidget widget)
 {
-  CurrentSprite sprite;
-  Palette *palette = palette_new(0, MAX_PALETTE_COLORS);
+  const SpriteReader& sprite = get_sprite(widget);
+  assert(sprite != NULL);
+
+  Palette* palette = palette_new(0, MAX_PALETTE_COLORS);
   bool array[256];
 
   paledit_get_selected_entries(palette_editor, array);
   palette_copy_colors(palette,
 		      paledit_get_palette(palette_editor));
 
-  if (sprite && sprite->imgtype == IMAGE_RGB) {
-    sprite_quantize_ex(sprite, palette);
+  if (sprite->imgtype == IMAGE_RGB) {
+    SpriteWriter sprite_writer(sprite);
+    sprite_quantize_ex(sprite_writer, palette);
   }
   else {
     jalert(_("Error<<You can use this command only for RGB sprites||&OK"));
@@ -437,13 +441,18 @@ static bool slider_columns_change_hook(JWidget widget, void *data)
 
 static bool slider_frame_change_hook(JWidget widget, void *data)
 {
-  CurrentSprite sprite;
+  const SpriteReader& sprite = get_sprite(widget);
+  assert(sprite != NULL);
+
   int old_frame = sprite->frame;
   int new_frame = jslider_get_value(slider_frame);
 
   palette_copy_colors(palettes[old_frame],
 		      get_current_palette());
-  sprite->frame = new_frame;
+  {
+    SpriteWriter sprite_writer(sprite);
+    sprite_writer->frame = new_frame;
+  }
   set_new_palette(palettes[new_frame]);
 
   return FALSE;
@@ -451,7 +460,9 @@ static bool slider_frame_change_hook(JWidget widget, void *data)
 
 static bool check_all_frames_change_hook(JWidget widget, void *data)
 {
-  CurrentSprite sprite;
+  const SpriteReader& sprite = get_sprite(widget);
+  assert(sprite != NULL);
+
   int frame = jslider_get_value(slider_frame);
 
   palette_copy_colors(palettes[frame],
diff --git a/src/commands/cmd_paste.cpp b/src/commands/cmd_paste.cpp
index 0c41aa7cd..1ee8faef9 100644
--- a/src/commands/cmd_paste.cpp
+++ b/src/commands/cmd_paste.cpp
@@ -26,14 +26,15 @@
 
 static bool cmd_paste_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-
-  return (sprite && clipboard::can_paste());
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL &&
+    clipboard::can_paste();
 }
 
 static void cmd_paste_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
 
   if (undo_is_enabled(sprite->undo))
     undo_set_label(sprite->undo, "Paste");
diff --git a/src/commands/cmd_play_animation.cpp b/src/commands/cmd_play_animation.cpp
index 8d0291634..3605bc950 100644
--- a/src/commands/cmd_play_animation.cpp
+++ b/src/commands/cmd_play_animation.cpp
@@ -43,13 +43,14 @@ END_OF_STATIC_FUNCTION(speed_timer_callback);
 
 static bool cmd_play_animation_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_play_animation_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   int old_frame, msecs;
   bool done = FALSE;
   bool onionskin = get_onionskin();
diff --git a/src/commands/cmd_preview.cpp b/src/commands/cmd_preview.cpp
index dc5f37fc2..fb4a51054 100644
--- a/src/commands/cmd_preview.cpp
+++ b/src/commands/cmd_preview.cpp
@@ -43,8 +43,9 @@ static void preview_sprite(int flags);
 
 static bool cmd_preview_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 /* ======================== */
diff --git a/src/commands/cmd_redo.cpp b/src/commands/cmd_redo.cpp
index f8bbc2762..bf4526fde 100644
--- a/src/commands/cmd_redo.cpp
+++ b/src/commands/cmd_redo.cpp
@@ -28,13 +28,15 @@
 
 static bool cmd_redo_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite != NULL && undo_can_redo(sprite->undo);
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL &&
+    undo_can_redo(sprite->undo);
 }
 
 static void cmd_redo_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
 
   statusbar_show_tip(app_get_statusbar(), 1000,
 		     _("Redid %s"),
diff --git a/src/commands/cmd_refresh.cpp b/src/commands/cmd_refresh.cpp
index bf1f22543..fa1c44190 100644
--- a/src/commands/cmd_refresh.cpp
+++ b/src/commands/cmd_refresh.cpp
@@ -37,7 +37,10 @@ static void cmd_refresh_execute(const char *argument)
   clear_to_color(screen, makecol(0, 0, 0));
   jmouse_show();
 
-  app_refresh_screen();
+  {
+    const CurrentSpriteReader sprite;
+    app_refresh_screen(sprite);
+  }
 
   /* print memory information */
 #if defined ALLEGRO_WINDOWS && defined DEBUGMODE
diff --git a/src/commands/cmd_remove_cel.cpp b/src/commands/cmd_remove_cel.cpp
index dde74507d..31e34d966 100644
--- a/src/commands/cmd_remove_cel.cpp
+++ b/src/commands/cmd_remove_cel.cpp
@@ -24,14 +24,14 @@
 #include "raster/cel.h"
 #include "raster/layer.h"
 #include "raster/sprite.h"
-#include "raster/undoable.h"
+#include "undoable.h"
 
 static bool cmd_remove_cel_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return
-    sprite &&
-    sprite->layer &&
+    sprite != NULL &&
+    sprite->layer != NULL &&
     layer_is_readable(sprite->layer) &&
     layer_is_writable(sprite->layer) &&
     layer_is_image(sprite->layer) &&
@@ -40,7 +40,7 @@ static bool cmd_remove_cel_enabled(const char *argument)
 
 static void cmd_remove_cel_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   Cel* cel = layer_get_cel(sprite->layer, sprite->frame);
   {
     Undoable undoable(sprite, "Remove Cel");
diff --git a/src/commands/cmd_remove_frame.cpp b/src/commands/cmd_remove_frame.cpp
index 39862a8c7..4d00d46d2 100644
--- a/src/commands/cmd_remove_frame.cpp
+++ b/src/commands/cmd_remove_frame.cpp
@@ -24,11 +24,11 @@
 #include "modules/gui.h"
 #include "modules/sprites.h"
 #include "raster/sprite.h"
-#include "raster/undoable.h"
+#include "undoable.h"
 
 static bool cmd_remove_frame_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return
     sprite != NULL &&
     sprite->frames > 1;
@@ -36,7 +36,7 @@ static bool cmd_remove_frame_enabled(const char *argument)
 
 static void cmd_remove_frame_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   {
     Undoable undoable(sprite, "Remove Frame");
     undoable.remove_frame(sprite->frame);
diff --git a/src/commands/cmd_remove_layer.cpp b/src/commands/cmd_remove_layer.cpp
index 2bd2b47ef..32c688699 100644
--- a/src/commands/cmd_remove_layer.cpp
+++ b/src/commands/cmd_remove_layer.cpp
@@ -23,11 +23,11 @@
 #include "modules/sprites.h"
 #include "raster/sprite.h"
 #include "raster/undo.h"
-#include "raster/undoable.h"
+#include "undoable.h"
 
 static bool cmd_remove_layer_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return
     sprite != NULL &&
     sprite->layer != NULL;
@@ -35,7 +35,7 @@ static bool cmd_remove_layer_enabled(const char *argument)
 
 static void cmd_remove_layer_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   {
     Undoable undoable(sprite, "Remove Layer");
     undoable.remove_layer(sprite->layer);
diff --git a/src/commands/cmd_reselect_mask.cpp b/src/commands/cmd_reselect_mask.cpp
index c038e1e1d..725194e08 100644
--- a/src/commands/cmd_reselect_mask.cpp
+++ b/src/commands/cmd_reselect_mask.cpp
@@ -27,7 +27,7 @@
 
 static bool cmd_reselect_mask_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return
     sprite != NULL &&
     sprite_request_mask(sprite, "*deselected*") != NULL;
@@ -35,7 +35,7 @@ static bool cmd_reselect_mask_enabled(const char *argument)
 
 static void cmd_reselect_mask_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   Mask *mask;
 
   /* request *deselected* mask */
diff --git a/src/commands/cmd_save_file.cpp b/src/commands/cmd_save_file.cpp
index d8c40ca03..fce6f3aa4 100644
--- a/src/commands/cmd_save_file.cpp
+++ b/src/commands/cmd_save_file.cpp
@@ -93,7 +93,7 @@ static void save_sprite_in_background(Sprite* sprite, bool mark_as_saved)
   if (fop) {
     JThread thread = jthread_new(savefile_bg, fop);
     if (thread) {
-      SaveFileData *data = jnew(SaveFileData, 1);
+      SaveFileData* data = new SaveFileData;
 
       data->fop = fop;
       data->progress = progress_new(app_get_statusbar());
@@ -118,9 +118,8 @@ static void save_sprite_in_background(Sprite* sprite, bool mark_as_saved)
 
       /* show any error */
       if (fop->error) {
-	console_open();
-	console_printf(fop->error);
-	console_close();
+	Console console;
+	console.printf(fop->error);
       }
       /* no error? */
       else {
@@ -136,16 +135,15 @@ static void save_sprite_in_background(Sprite* sprite, bool mark_as_saved)
       progress_free(data->progress);
       jwidget_free(data->alert_window);
       fop_free(fop);
-      jfree(data);
+      delete data;
     }
   }
 }
 
 /*********************************************************************/
 
-static void save_as_dialog(const char* dlg_title, bool mark_as_saved)
+static void save_as_dialog(Sprite* sprite, const char* dlg_title, bool mark_as_saved)
 {
-  CurrentSprite sprite;
   char exts[4096];
   jstring filename;
   jstring newfilename;
@@ -200,7 +198,7 @@ static void save_as_dialog(const char* dlg_title, bool mark_as_saved)
  */
 static bool cmd_save_file_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   return sprite;
 }
 
@@ -211,7 +209,7 @@ static bool cmd_save_file_enabled(const char *argument)
  */
 static void cmd_save_file_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
 
   /* if the sprite is associated to a file in the file-system, we can
      save it directly without user interaction */
@@ -222,7 +220,7 @@ static void cmd_save_file_execute(const char *argument)
      save-as dialog to the user to select for first time the file-name
      for this sprite */
   else {
-    save_as_dialog(_("Save Sprite"), true);
+    save_as_dialog(sprite, _("Save Sprite"), true);
   }
 }
 
@@ -232,13 +230,15 @@ static void cmd_save_file_execute(const char *argument)
 
 static bool cmd_save_file_as_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_save_file_as_execute(const char *argument)
 {
-  save_as_dialog(_("Save Sprite As"), true);
+  CurrentSpriteWriter sprite;
+  save_as_dialog(sprite, _("Save Sprite As"), true);
 }
 
 /*********************************************************************
@@ -247,17 +247,18 @@ static void cmd_save_file_as_execute(const char *argument)
 
 static bool cmd_save_file_copy_as_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_save_file_copy_as_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
   jstring old_filename = sprite->filename;
 
   // show "Save As" dialog
-  save_as_dialog(_("Save Sprite Copy As"), false);
+  save_as_dialog(sprite, _("Save Sprite Copy As"), false);
 
   // restore the file name
   sprite_set_filename(sprite, old_filename.c_str());
diff --git a/src/commands/cmd_save_mask.cpp b/src/commands/cmd_save_mask.cpp
index 843afcd6e..63a4ac515 100644
--- a/src/commands/cmd_save_mask.cpp
+++ b/src/commands/cmd_save_mask.cpp
@@ -31,7 +31,7 @@
 
 static bool cmd_save_mask_enabled(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   if (!sprite)
     return false;
   else
@@ -41,7 +41,7 @@ static bool cmd_save_mask_enabled(const char *argument)
 
 static void cmd_save_mask_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   jstring filename = "default.msk";
   int ret;
 
diff --git a/src/commands/cmd_select_file.cpp b/src/commands/cmd_select_file.cpp
index 99dc5136d..f6bf6d044 100644
--- a/src/commands/cmd_select_file.cpp
+++ b/src/commands/cmd_select_file.cpp
@@ -45,17 +45,17 @@ static bool cmd_select_file_enabled(const char *argument)
 
 static bool cmd_select_file_checked(const char *argument)
 {
-  CurrentSprite current_sprite;
+  const CurrentSpriteReader sprite;
 
   if (argument) {
     int sprite_id = ustrtol(argument, NULL, 10);
     GfxObj *gfxobj = gfxobj_find(sprite_id);
     return
       gfxobj && gfxobj->type == GFXOBJ_SPRITE &&
-      current_sprite == (Sprite *)gfxobj;
+      sprite == (Sprite *)gfxobj;
   }
   else
-    return current_sprite == NULL;
+    return sprite == NULL;
 }
 
 static void cmd_select_file_execute(const char *argument)
diff --git a/src/commands/cmd_sprite_properties.cpp b/src/commands/cmd_sprite_properties.cpp
index 3a5a9ef09..5e31ccb44 100644
--- a/src/commands/cmd_sprite_properties.cpp
+++ b/src/commands/cmd_sprite_properties.cpp
@@ -32,36 +32,31 @@
 #include "widgets/colbut.h"
 
 /* TODO remove this */
-void dialogs_frame_length(int sprite_frpos);
+void dialogs_frame_length(const SpriteReader& sprite, int sprite_frpos);
 
 static bool cmd_sprite_properties_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_sprite_properties_execute(const char *argument)
 {
-  JWidget window, killer, name, type, size, frames, speed, ok;
-  CurrentSprite sprite;
+  JWidget killer, name, type, size, frames, speed, ok;
+  const CurrentSpriteReader sprite;
   jstring imgtype_text;
   char buf[256];
 
   /* load the window widget */
-  window = load_widget("sprprop.jid", "sprite_properties");
-  if (!window)
-    return;
-
-  if (!get_widgets(window,
-		   "name", &name,
-		   "type", &type,
-		   "size", &size,
-		   "frames", &frames,
-		   "speed", &speed,
-		   "ok", &ok, NULL)) {
-    jwidget_free(window);
-    return;
-  }
+  JWidgetPtr window = load_widget("sprprop.jid", "sprite_properties");
+  get_widgets(window,
+	      "name", &name,
+	      "type", &type,
+	      "size", &size,
+	      "frames", &frames,
+	      "speed", &speed,
+	      "ok", &ok, NULL);
 
   /* update widgets values */
   switch (sprite->imgtype) {
@@ -110,13 +105,11 @@ static void cmd_sprite_properties_execute(const char *argument)
     if (killer == ok)
       break;
     else if (killer == speed) {
-      dialogs_frame_length(-1);
+      dialogs_frame_length(sprite, -1);
     }
     else
       break;
   }
-
-  jwidget_free(window);
 }
 
 Command cmd_sprite_properties = {
diff --git a/src/commands/cmd_sprite_size.cpp b/src/commands/cmd_sprite_size.cpp
index 8fcabae11..2797bd245 100644
--- a/src/commands/cmd_sprite_size.cpp
+++ b/src/commands/cmd_sprite_size.cpp
@@ -32,23 +32,23 @@
 #include "raster/image.h"
 #include "raster/sprite.h"
 #include "raster/stock.h"
-#include "raster/undoable.h"
+#include "undoable.h"
 
 #define PERC_FORMAT	"%.1f%%"
 
 class SpriteSizeJob : public Job
 {
-  Sprite* m_sprite;
+  SpriteWriter m_sprite;
   int m_new_width;
   int m_new_height;
   ResizeMethod m_resize_method;
 
 public:
 
-  SpriteSizeJob(Sprite* sprite, int new_width, int new_height, ResizeMethod resize_method)
+  SpriteSizeJob(const SpriteReader& sprite, int new_width, int new_height, ResizeMethod resize_method)
     : Job("Sprite Size")
+    , m_sprite(sprite)
   {
-    m_sprite = sprite;
     m_new_width = new_width;
     m_new_height = new_height;
     m_resize_method = resize_method;
@@ -109,6 +109,9 @@ protected:
 
     // TODO resize mask
 
+    // regenerate mask
+    sprite_generate_mask_boundaries(m_sprite);
+
     // commit changes
     undoable.commit();
   }
@@ -123,33 +126,26 @@ static bool height_perc_change_hook(JWidget widget, void *data);
 
 static bool cmd_sprite_size_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_sprite_size_execute(const char *argument)
 {
-  JWidget window, width_px, height_px, width_perc, height_perc, lock_ratio, method, ok;
-  CurrentSprite sprite;
-  if (!sprite)
-    return;
+  JWidget width_px, height_px, width_perc, height_perc, lock_ratio, method, ok;
+  const CurrentSpriteReader sprite;
 
   // load the window widget
-  window = load_widget("sprsize.jid", "sprite_size");
-  if (!window)
-    return;
-
-  if (!get_widgets(window,
-		   "width_px", &width_px,
-		   "height_px", &height_px,
-		   "width_perc", &width_perc,
-		   "height_perc", &height_perc,
-		   "lock_ratio", &lock_ratio,
-		   "method", &method,
-		   "ok", &ok, NULL)) {
-    jwidget_free(window);
-    return;
-  }
+  JWidgetPtr window = load_widget("sprsize.jid", "sprite_size");
+  get_widgets(window,
+	      "width_px", &width_px,
+	      "height_px", &height_px,
+	      "width_perc", &width_perc,
+	      "height_perc", &height_perc,
+	      "lock_ratio", &lock_ratio,
+	      "method", &method,
+	      "ok", &ok, NULL);
 
   width_px->textf("%d", sprite->w);
   height_px->textf("%d", sprite->h);
@@ -185,16 +181,13 @@ static void cmd_sprite_size_execute(const char *argument)
       job.do_job();
     }
 
-    sprite_generate_mask_boundaries(sprite);
     update_screen_for_sprite(sprite);
   }
-
-  jwidget_free(window);
 }
 
 static bool lock_ratio_change_hook(JWidget widget, void *data)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
 
   if (widget->selected())
     width_px_change_hook(widget->find_sibling("width_px"), NULL);
@@ -204,7 +197,7 @@ static bool lock_ratio_change_hook(JWidget widget, void *data)
 
 static bool width_px_change_hook(JWidget widget, void *data)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   int width = widget->text_int();
   double perc = 100.0 * width / sprite->w;
 
@@ -220,7 +213,7 @@ static bool width_px_change_hook(JWidget widget, void *data)
 
 static bool height_px_change_hook(JWidget widget, void *data)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   int height = widget->text_int();
   double perc = 100.0 * height / sprite->h;
 
@@ -236,7 +229,7 @@ static bool height_px_change_hook(JWidget widget, void *data)
 
 static bool width_perc_change_hook(JWidget widget, void *data)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   double width = widget->text_double();
 
   widget->find_sibling("width_px")->textf("%d", (int)(sprite->w * width / 100));
@@ -251,7 +244,7 @@ static bool width_perc_change_hook(JWidget widget, void *data)
 
 static bool height_perc_change_hook(JWidget widget, void *data)
 {
-  CurrentSprite sprite;
+  const CurrentSpriteReader sprite;
   double height = widget->text_double();
 
   widget->find_sibling("height_px")->textf("%d", (int)(sprite->h * height / 100));
diff --git a/src/commands/cmd_undo.cpp b/src/commands/cmd_undo.cpp
index a1ebe8a0e..b44b13857 100644
--- a/src/commands/cmd_undo.cpp
+++ b/src/commands/cmd_undo.cpp
@@ -28,13 +28,15 @@
 
 static bool cmd_undo_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite != NULL && undo_can_undo(sprite->undo);
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL &&
+    undo_can_undo(sprite->undo);
 }
 
 static void cmd_undo_execute(const char *argument)
 {
-  CurrentSprite sprite;
+  CurrentSpriteWriter sprite;
 
   statusbar_show_tip(app_get_statusbar(), 1000,
 		     _("Undid %s"),
diff --git a/src/commands/commands.cpp b/src/commands/commands.cpp
index c4410a090..018a5c948 100644
--- a/src/commands/commands.cpp
+++ b/src/commands/commands.cpp
@@ -250,18 +250,28 @@ Command *command_get_by_key(JMessage msg)
  */
 bool command_is_enabled(Command *command, const char *argument)
 {
-  if (command && command->enabled)
-    return (*command->enabled)(argument);
-  else
-    return TRUE;
+  try {
+    if (command && command->enabled)
+      return (*command->enabled)(argument);
+    else
+      return true;
+  }
+  catch (...) {
+    // did the "is_enabled" throw an exception? disabled this command so...
+    return false;
+  }
 }
 
 bool command_is_checked(Command *command, const char *argument)
 {
-  if (command && command->checked)
-    return (*command->checked)(argument);
-  else
-    return FALSE;
+  try {
+    if (command && command->checked)
+      return (*command->checked)(argument);
+  }
+  catch (...) {
+    // do nothing
+  }
+  return false;
 }
 
 /**
@@ -270,7 +280,7 @@ bool command_is_checked(Command *command, const char *argument)
  */
 void command_execute(Command *command, const char *argument)
 {
-  console_open();
+  Console console;
 
   try {
     if (command && command->execute &&
@@ -278,14 +288,17 @@ void command_execute(Command *command, const char *argument)
       (*command->execute)(argument);
     }
   }
-  catch (std::exception& e) {
-    jalert("Error"
-	   "<<Uncaught exception:"
-	   "<<%s"
-	   "||&OK", e.what());
+  catch (ase_exception& e) {
+    e.show();
+  }
+  catch (std::exception& e) {
+    console.printf("An error ocurred executing the command.\n\nDetails:\n%s", e.what());
+  }
+  catch (...) {
+    console.printf("An unknown error ocurred executing the command.\n"
+		   "Please try again or report this bug.\n\n"
+		   "Details: Unknown exception caught.");
   }
-
-  console_close();
 }
 
 bool command_is_key_pressed(Command *command, JMessage msg)
diff --git a/src/commands/commands.h b/src/commands/commands.h
index 0693b967d..bf1cf4a8b 100644
--- a/src/commands/commands.h
+++ b/src/commands/commands.h
@@ -20,7 +20,7 @@
 #define COMMANDS_COMMANDS_H
 
 #include "jinete/jbase.h"
-#include "ase/current_sprite.h"
+#include "sprite_wrappers.h"
 
 #define CMD_ABOUT			"about"
 #define CMD_ADVANCED_MODE		"advanced_mode"
diff --git a/src/commands/fx/cmd_color_curve.cpp b/src/commands/fx/cmd_color_curve.cpp
index 303ea79b0..546dbfa3b 100644
--- a/src/commands/fx/cmd_color_curve.cpp
+++ b/src/commands/fx/cmd_color_curve.cpp
@@ -31,7 +31,6 @@
 #include "effect/effect.h"
 #include "modules/gui.h"
 #include "modules/sprites.h"
-#include "raster/image.h"
 #include "raster/mask.h"
 #include "raster/sprite.h"
 #include "util/misc.h"
@@ -48,18 +47,17 @@ static void make_preview();
 
 static bool cmd_color_curve_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite != NULL;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_color_curve_execute(const char *argument)
 {
-  JWidget window, button_ok;
+  const CurrentSpriteReader sprite;
+  JWidget button_ok;
   JWidget view_curve, curve_editor;
   JWidget box_target, target_button;
-  CurrentSprite sprite;
-  Image *image;
-  Effect *effect;
 
   if (!the_curve) {
     /* default curve */
@@ -72,39 +70,24 @@ static void cmd_color_curve_execute(const char *argument)
 		 the_curve);
   }
 
-  image = GetImage(sprite);
-  if (!image)
-    return;
+  JWidgetPtr window = load_widget("colcurv.jid", "color_curve");
+  get_widgets(window,
+	      "preview", &check_preview,
+	      "button_ok", &button_ok,
+	      "curve", &view_curve,
+	      "target", &box_target, NULL);
 
-  window = load_widget("colcurv.jid", "color_curve");
-  if (!window)
-    return;
+  Effect effect(sprite, "color_curve");
+  effect_set_target(&effect, TARGET_RED_CHANNEL | TARGET_GREEN_CHANNEL |
+			     TARGET_BLUE_CHANNEL | TARGET_ALPHA_CHANNEL);
 
-  if (!get_widgets(window,
-		   "preview", &check_preview,
-		   "button_ok", &button_ok,
-		   "curve", &view_curve,
-		   "target", &box_target, NULL)) {
-    jwidget_free(window);
-    return;
-  }
-
-  effect = effect_new(sprite, "color_curve");
-  if (!effect) {
-    console_printf(_("Error creating the effect applicator for this sprite\n"));
-    jwidget_free(window);
-    return;
-  }
-  effect_set_target(effect, TARGET_RED_CHANNEL | TARGET_GREEN_CHANNEL |
-			    TARGET_BLUE_CHANNEL | TARGET_ALPHA_CHANNEL);
-
-  preview = preview_new(effect);
+  preview = preview_new(&effect);
 
   set_color_curve(the_curve);
 
   curve_editor = curve_editor_new(the_curve, 0, 0, 255, 255);
   target_button = target_button_new(sprite->imgtype, TRUE);
-  target_button_set_target(target_button, effect->target);
+  target_button_set_target(target_button, effect.target);
 
   if (get_config_bool("ColorCurve", "Preview", TRUE))
     jwidget_select(check_preview);
@@ -130,19 +113,14 @@ static void cmd_color_curve_execute(const char *argument)
   /* open the window */
   jwindow_open_fg(window);
 
-  if (jwindow_get_killer(window) == button_ok) {
-    effect_apply_to_target_with_progressbar(effect);
-  }
-
-  effect_free(effect);
+  if (jwindow_get_killer(window) == button_ok)
+    effect_apply_to_target_with_progressbar(&effect);
 
   /* update editors */
   update_screen_for_sprite(sprite);
 
   /* save window configuration */
   save_window_pos(window, "ColorCurve");
-
-  jwidget_free(window);
 }
 
 static bool window_msg_proc(JWidget widget, JMessage msg)
diff --git a/src/commands/fx/cmd_convolution_matrix.cpp b/src/commands/fx/cmd_convolution_matrix.cpp
index 1e909b0ea..4bcedaf1b 100644
--- a/src/commands/fx/cmd_convolution_matrix.cpp
+++ b/src/commands/fx/cmd_convolution_matrix.cpp
@@ -43,7 +43,6 @@
 #include "modules/gui.h"
 #include "modules/sprites.h"
 #include "modules/tools.h"
-#include "raster/image.h"
 #include "raster/mask.h"
 #include "raster/sprite.h"
 #include "util/misc.h"
@@ -70,54 +69,37 @@ static void make_preview();
 
 static bool cmd_convolution_matrix_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite != NULL;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_convolution_matrix_execute(const char *argument)
 {
-  JWidget window, button_ok;
+  const CurrentSpriteReader sprite;
+  JWidget button_ok;
   JWidget view_convmatr, list_convmatr;
   JWidget box_target;
   JWidget reload, generate;
-  CurrentSprite sprite;
-  Image *image;
-  Effect *effect;
 
-  image = GetImage(sprite);
-  if (!image)
-    return;
+  JWidgetPtr window = load_widget("convmatr.jid", "convolution_matrix");
+  get_widgets(window,
+	      "preview", &check_preview,
+	      "tiled", &check_tiled,
+	      "button_ok", &button_ok,
+	      "view", &view_convmatr,
+	      "target", &box_target,
+	      "reload", &reload,
+	      "generate", &generate, NULL);
 
-  window = load_widget("convmatr.jid", "convolution_matrix");
-  if (!window)
-    return;
-
-  if (!get_widgets(window,
-		   "preview", &check_preview,
-		   "tiled", &check_tiled,
-		   "button_ok", &button_ok,
-		   "view", &view_convmatr,
-		   "target", &box_target,
-		   "reload", &reload,
-		   "generate", &generate, NULL)) {
-    jwidget_free(window);
-    return;
-  }
-
-  effect = effect_new(sprite, "convolution_matrix");
-  if (!effect) {
-    console_printf(_("Error creating the effect applicator for this sprite\n"));
-    jwidget_free(window);
-    return;
-  }
-
-  preview = preview_new(effect);
+  Effect effect(sprite, "convolution_matrix");
+  preview = preview_new(&effect);
   
   list_convmatr = jlistbox_new();
   listbox_fill_convmatg(list_convmatr);
 
   target_button = target_button_new(sprite->imgtype, TRUE);
-  target_button_set_target(target_button, effect->target);
+  target_button_set_target(target_button, effect.target);
 
   if (get_config_bool("ConvolutionMatrix", "Preview", TRUE))
     jwidget_select(check_preview);
@@ -154,19 +136,14 @@ static void cmd_convolution_matrix_execute(const char *argument)
   /* open the window */
   jwindow_open_fg(window);
 
-  if (jwindow_get_killer(window) == button_ok) {
-    effect_apply_to_target_with_progressbar(effect);
-  }
-
-  effect_free(effect);
+  if (jwindow_get_killer(window) == button_ok)
+    effect_apply_to_target_with_progressbar(&effect);
 
   /* update editors */
   update_screen_for_sprite(sprite);
 
   /* save window configuration */
   save_window_pos(window, "ConvolutionMatrix");
-
-  jwidget_free(window);
 }
 
 static void listbox_fill_convmatg(JWidget listbox)
@@ -235,7 +212,6 @@ static bool reload_select_hook(JWidget widget, void *data)
 static bool generate_select_hook(JWidget widget, void *data)
 {
 #if 0
-  JWidget window;
   JWidget view_x;
   JWidget view_y;
   JWidget curvedit_x;
@@ -245,20 +221,14 @@ static bool generate_select_hook(JWidget widget, void *data)
   JWidget div, div_auto;
   JWidget bias, bias_auto;
 
-  window = load_widget("convmatr.jid", "generate_convolution_matrix");
-  if (!window)
-    return TRUE;		/* don't close */
-
-  if (!get_widgets(window,
-		   "view_x", &view_x,
-		   "view_y", &view_y,
-		   "div", &div,
-		   "bias", &bias,
-		   "div_auto", &div_auto,
-		   "bias_auto", &bias_auto, NULL)) {
-    jwidget_free(window);
-    return TRUE;		/* don't close */
-  }
+  JWidgetPtr window = load_widget("convmatr.jid", "generate_convolution_matrix");
+  get_widgets(window,
+	      "view_x", &view_x,
+	      "view_y", &view_y,
+	      "div", &div,
+	      "bias", &bias,
+	      "div_auto", &div_auto,
+	      "bias_auto", &bias_auto, NULL);
 
   /* curve_x = curve_new(CURVE_SPLINE); */
   /* curve_y = curve_new(CURVE_SPLINE); */
@@ -291,12 +261,10 @@ static bool generate_select_hook(JWidget widget, void *data)
 
   /* TODO do something */
 
-  jwidget_free(window);
-
   curve_free(curve_x);
   curve_free(curve_y);
 #endif
-  return TRUE;			/* do not close */
+  return TRUE;
 }
 
 static bool list_change_hook(JWidget widget, void *data)
diff --git a/src/commands/fx/cmd_despeckle.cpp b/src/commands/fx/cmd_despeckle.cpp
index 862e9f49d..35662ebe6 100644
--- a/src/commands/fx/cmd_despeckle.cpp
+++ b/src/commands/fx/cmd_despeckle.cpp
@@ -37,7 +37,6 @@
 #include "modules/gui.h"
 #include "modules/sprites.h"
 #include "modules/tools.h"
-#include "raster/image.h"
 #include "raster/mask.h"
 #include "raster/sprite.h"
 #include "util/misc.h"
@@ -57,51 +56,35 @@ static void make_preview();
 
 static bool cmd_despeckle_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_despeckle_execute(const char *argument)
 {
-  JWidget window, box_target, target_button, button_ok;
-  CurrentSprite sprite;
-  Image *image;
-  Effect *effect;
+  const CurrentSpriteReader sprite;
+  JWidget box_target, target_button, button_ok;
   char buf[32];
 
-  image = GetImage(sprite);
-  if (!image)
-    return;
+  JWidgetPtr window = load_widget("median.jid", "median");
+  get_widgets(window,
+	      "width", &entry_width,
+	      "height", &entry_height,
+	      "preview", &check_preview,
+	      "tiled", &check_tiled,
+	      "target", &box_target,
+	      "button_ok", &button_ok, NULL);
 
-  window = load_widget("median.jid", "median");
-  if (!window)
-    return;
+  Effect effect(sprite, "median");
+  effect_set_target(&effect, TARGET_RED_CHANNEL |
+			     TARGET_GREEN_CHANNEL |
+			     TARGET_BLUE_CHANNEL);
 
-  if (!get_widgets(window,
-		   "width", &entry_width,
-		   "height", &entry_height,
-		   "preview", &check_preview,
-		   "tiled", &check_tiled,
-		   "target", &box_target,
-		   "button_ok", &button_ok, NULL)) {
-    jwidget_free(window);
-    return;
-  }
-
-  effect = effect_new(sprite, "median");
-  if (!effect) {
-    console_printf(_("Error creating the effect applicator for this sprite\n"));
-    jwidget_free(window);
-    return;
-  }
-  effect_set_target(effect, TARGET_RED_CHANNEL |
-			    TARGET_GREEN_CHANNEL |
-			    TARGET_BLUE_CHANNEL);
-
-  preview = preview_new(effect);
+  preview = preview_new(&effect);
 
   target_button = target_button_new(sprite->imgtype, TRUE);
-  target_button_set_target(target_button, effect->target);
+  target_button_set_target(target_button, effect.target);
 
   sprintf(buf, "%d", get_config_int("Median", "Width", 3));
   jwidget_set_text(entry_width, buf);
@@ -136,19 +119,14 @@ static void cmd_despeckle_execute(const char *argument)
   /* open the window */
   jwindow_open_fg(window);
 
-  if (jwindow_get_killer(window) == button_ok) {
-    effect_apply_to_target_with_progressbar(effect);
-  }
-
-  effect_free(effect);
+  if (jwindow_get_killer(window) == button_ok)
+    effect_apply_to_target_with_progressbar(&effect);
 
   /* update editors */
   update_screen_for_sprite(sprite);
 
   /* save window configuration */
   save_window_pos(window, "Median");
-
-  jwidget_free(window);
 }
 
 static bool width_change_hook(JWidget widget, void *data)
diff --git a/src/commands/fx/cmd_invert_color.cpp b/src/commands/fx/cmd_invert_color.cpp
index b95da641a..7bb6838a5 100644
--- a/src/commands/fx/cmd_invert_color.cpp
+++ b/src/commands/fx/cmd_invert_color.cpp
@@ -51,46 +51,30 @@ static void make_preview();
 
 static bool cmd_invert_color_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_invert_color_execute(const char *argument)
 {
-  JWidget window, box_target, target_button, button_ok;
-  CurrentSprite sprite;
-  Image *image;
-  Effect *effect;
+  JWidget box_target, target_button, button_ok;
+  const CurrentSpriteReader sprite;
 
-  image = GetImage(sprite);
-  if (!image)
-    return;
+  JWidgetPtr window = load_widget("invrtcol.jid", "invert_color");
+  get_widgets(window,
+	      "target", &box_target,
+	      "preview", &check_preview,
+	      "button_ok", &button_ok, NULL);
 
-  window = load_widget("invrtcol.jid", "invert_color");
-  if (!window)
-    return;
+  Effect effect(sprite, "invert_color");
+  effect_set_target(&effect, TARGET_RED_CHANNEL |
+			     TARGET_GREEN_CHANNEL |
+			     TARGET_BLUE_CHANNEL);
 
-  if (!get_widgets(window,
-		   "target", &box_target,
-		   "preview", &check_preview,
-		   "button_ok", &button_ok, NULL)) {
-    jwidget_free(window);
-    return;
-  }
-
-  effect = effect_new(sprite, "invert_color");
-  if (!effect) {
-    console_printf(_("Error creating the effect applicator for this sprite\n"));
-    jwidget_free(window);
-    return;
-  }
-  effect_set_target(effect, TARGET_RED_CHANNEL |
-			    TARGET_GREEN_CHANNEL |
-			    TARGET_BLUE_CHANNEL);
-
-  preview = preview_new(effect);
+  preview = preview_new(&effect);
   target_button = target_button_new(sprite->imgtype, TRUE);
-  target_button_set_target(target_button, effect->target);
+  target_button_set_target(target_button, effect.target);
 
   if (get_config_bool("InvertColor", "Preview", TRUE))
     jwidget_select(check_preview);
@@ -114,19 +98,14 @@ static void cmd_invert_color_execute(const char *argument)
   /* open the window */
   jwindow_open_fg(window);
 
-  if (jwindow_get_killer(window) == button_ok) {
-    effect_apply_to_target_with_progressbar(effect);
-  }
-
-  effect_free(effect);
+  if (jwindow_get_killer(window) == button_ok)
+    effect_apply_to_target_with_progressbar(&effect);
 
   /* update editors */
   update_screen_for_sprite(sprite);
 
   /* save window configuration */
   save_window_pos(window, "InvertColor");
-
-  jwidget_free(window);
 }
 
 static bool target_change_hook(JWidget widget, void *data)
diff --git a/src/commands/fx/cmd_replace_color.cpp b/src/commands/fx/cmd_replace_color.cpp
index dbd29a9a9..2da5b7b3b 100644
--- a/src/commands/fx/cmd_replace_color.cpp
+++ b/src/commands/fx/cmd_replace_color.cpp
@@ -54,51 +54,32 @@ static void make_preview();
 
 static bool cmd_replace_color_enabled(const char *argument)
 {
-  CurrentSprite sprite;
-  return sprite;
+  const CurrentSpriteReader sprite;
+  return
+    sprite != NULL;
 }
 
 static void cmd_replace_color_execute(const char *argument)
 {
-  JWidget window = NULL;
+  const CurrentSpriteReader sprite;
   JWidget color_buttons_box;
   JWidget box_target, target_button;
   JWidget button_ok;
-  Image *image;
-  Effect *effect;
 
-  CurrentSprite sprite;
-  if (!sprite)
-    return;
+  JWidgetPtr window = load_widget("replcol.jid", "replace_color");
+  get_widgets(window,
+	      "color_buttons_box", &color_buttons_box,
+	      "preview", &check_preview,
+	      "fuzziness", &slider_fuzziness,
+	      "target", &box_target,
+	      "button_ok", &button_ok, NULL);
 
-  image = GetImage(sprite);
-  if (!image)
-    goto done;
-
-  window = load_widget("replcol.jid", "replace_color");
-  if (!window)
-    goto done;
-
-  if (!get_widgets(window,
-		   "color_buttons_box", &color_buttons_box,
-		   "preview", &check_preview,
-		   "fuzziness", &slider_fuzziness,
-		   "target", &box_target,
-		   "button_ok", &button_ok, NULL)) {
-    goto done;
-  }
-
-  effect = effect_new(sprite, "replace_color");
-  if (!effect) {
-    console_printf(_("Error creating the effect applicator for this sprite\n"));
-    goto done;
-  }
-  effect_set_target(effect, TARGET_RED_CHANNEL |
-			    TARGET_GREEN_CHANNEL |
-			    TARGET_BLUE_CHANNEL |
-			    TARGET_ALPHA_CHANNEL);
-
-  preview = preview_new(effect);
+  Effect effect(sprite, "replace_color");
+  effect_set_target(&effect, TARGET_RED_CHANNEL |
+			     TARGET_GREEN_CHANNEL |
+			     TARGET_BLUE_CHANNEL |
+			     TARGET_ALPHA_CHANNEL);
+  preview = preview_new(&effect);
 
   button_color1 = colorbutton_new
     (get_config_color("ReplaceColor", "Color1",
@@ -111,7 +92,7 @@ static void cmd_replace_color_execute(const char *argument)
      sprite->imgtype);
 
   target_button = target_button_new(sprite->imgtype, FALSE);
-  target_button_set_target(target_button, effect->target);
+  target_button_set_target(target_button, effect.target);
 
   jslider_set_value(slider_fuzziness,
 		    get_config_int("ReplaceColor", "Fuzziness", 0));
@@ -142,21 +123,14 @@ static void cmd_replace_color_execute(const char *argument)
   /* open the window */
   jwindow_open_fg(window);
 
-  if (jwindow_get_killer(window) == button_ok) {
-    effect_apply_to_target_with_progressbar(effect);
-  }
-
-  effect_free(effect);
+  if (jwindow_get_killer(window) == button_ok)
+    effect_apply_to_target_with_progressbar(&effect);
 
   /* update editors */
   update_screen_for_sprite(sprite);
 
   /* save window configuration */
   save_window_pos(window, "ReplaceColor");
-
-done:;
-  if (window)
-    jwidget_free(window);
 }
 
 static bool color_change_hook(JWidget widget, void *data)
@@ -194,7 +168,7 @@ static bool preview_change_hook(JWidget widget, void *data)
 
 static void make_preview()
 {
-  CurrentSprite sprite;
+  Sprite* sprite = preview_get_effect(preview)->sprite;
   color_t from, to;
   int fuzziness;
 
diff --git a/src/commands/fx/effectbg.cpp b/src/commands/fx/effectbg.cpp
index 692aed586..49b3db536 100644
--- a/src/commands/fx/effectbg.cpp
+++ b/src/commands/fx/effectbg.cpp
@@ -148,15 +148,9 @@ static void monitor_free(void *_data)
  * 
  * [main thread]
  */
-void effect_apply_to_target_with_progressbar(Effect *effect)
+void effect_apply_to_target_with_progressbar(Effect* effect)
 {
-  ThreadData *data;
-
-  data = jnew(ThreadData, 1);
-  if (data == NULL) {
-    jalert("Error<<Not enough memory||&OK");
-    return;
-  }
+  ThreadData *data = new ThreadData;
 
   effect->progress_data = data;
   effect->progress = effect_progress_hook;
@@ -190,5 +184,5 @@ void effect_apply_to_target_with_progressbar(Effect *effect)
 
   progress_free(data->progress);
   jwidget_free(data->alert_window);
-  jfree(data);
+  delete data;
 }
diff --git a/src/console/console.cpp b/src/console/console.cpp
index f25712f1c..9d6fd7549 100644
--- a/src/console/console.cpp
+++ b/src/console/console.cpp
@@ -37,12 +37,10 @@ static int console_counter = 0;
 static bool console_locked;
 static bool want_close_flag = FALSE;
 
-void console_open()
+Console::Console()
 {
   console_counter++;
 
-  /* TODO verify if the ji_screen works */
-/*   if (!screen || */
   if (!ji_screen ||
       !is_interactive() ||
       wid_console ||
@@ -51,7 +49,7 @@ void console_open()
   else {
     JWidget window, grid, view, textbox, button;
 
-    window = jwindow_new(_("Processing..."));
+    window = jwindow_new(_("Errors Console"));
     if (!window)
       return;
 
@@ -87,7 +85,7 @@ void console_open()
   }
 }
 
-void console_close()
+Console::~Console()
 {
   console_counter--;
 
@@ -105,7 +103,7 @@ void console_close()
   }
 }
 
-void console_printf(const char *format, ...)
+void Console::printf(const char *format, ...)
 {
   char buf[1024];
   va_list ap;
@@ -154,6 +152,9 @@ void console_printf(const char *format, ...)
   else {
     fputs(buf, stdout);
     fflush(stdout);
+
+    if (ji_screen)
+      jalert("Error<<%s||OK", buf);
   }
 }
 
diff --git a/src/console/console.h b/src/console/console.h
index 1b1fca8bb..d79275609 100644
--- a/src/console/console.h
+++ b/src/console/console.h
@@ -19,10 +19,15 @@
 #ifndef CONSOLE_H
 #define CONSOLE_H
 
-void console_open();
-void console_close();
+class Console
+{
+public:
+  Console();
+  ~Console();
+
+  void printf(const char *format, ...);
+};
 
-void console_printf(const char *format, ...);
 void user_printf(const char *format, ...);
 
 #endif /* CONSOLE_H */
diff --git a/src/core/app.cpp b/src/core/app.cpp
index 4d87f3b26..93d83ee32 100644
--- a/src/core/app.cpp
+++ b/src/core/app.cpp
@@ -72,17 +72,22 @@ enum {
   OPEN_GFX_FILE,
 };
 
-typedef struct Option
+struct Option
 {
   int type;
   char *data;
-} Option;
+};
 
-typedef struct AppHook
+struct AppHook
 {
   void (*proc)(void *);
   void *data;
-} AppHook;
+
+  AppHook(void (*proc)(void *), void *data) {
+    this->proc = proc;
+    this->data = data;
+  }
+};
 
 static char *exe_name;		      /* name of the program */
 
@@ -111,9 +116,6 @@ static void usage(int status);
 static Option *option_new(int type, const char *data);
 static void option_free(Option *option);
 
-static AppHook *apphook_new(void (*proc)(void *), void *data);
-static void apphook_free(AppHook *apphook);
-
 /**
  * Initializes the application loading the modules, setting the
  * graphics mode, loading the configuration and resources, etc.
@@ -175,7 +177,8 @@ bool app_init(int argc, char *argv[])
     pal = palette_load(palette_filename);
     if (pal == NULL) {
       set_gfx_mode(GFX_TEXT, 0, 0, 0, 0);
-      console_printf(_("Error loading default palette from `%s'\n"),
+      Console console;
+      console.printf(_("Error loading default palette from `%s'\n"),
 		     palette_filename);
       return FALSE;
     }
@@ -332,12 +335,9 @@ void app_loop()
     /* select language */
     dialogs_select_language(FALSE);
 
-    /* show tips? */
-    {
-      CurrentSprite sprite;
-      if (!sprite)
-	dialogs_tips(FALSE);
-    }
+    // show tips only if there are not a current sprite
+    if (!UIContext::instance()->get_current_sprite())
+      dialogs_tips(FALSE);
 
     // support to drop files from Windows explorer
     install_drop_files();
@@ -377,7 +377,8 @@ void app_exit()
   for (c=0; c<APP_EVENTS; ++c) {
     if (apphooks[c] != NULL) {
       JI_LIST_FOR_EACH(apphooks[c], link) {
-	apphook_free(reinterpret_cast<AppHook*>(link->data));
+	AppHook* apphook = reinterpret_cast<AppHook*>(link->data);
+	delete apphook;
       }
       jlist_free(apphooks[c]);
       apphooks[c] = NULL;
@@ -406,7 +407,7 @@ void app_add_hook(int app_event, void (*proc)(void *data), void *data)
   if (apphooks[app_event] == NULL)
     apphooks[app_event] = jlist_new();
 
-  jlist_append(apphooks[app_event], apphook_new(proc, data));
+  jlist_append(apphooks[app_event], new AppHook(proc, data));
 }
 
 void app_trigger_event(int app_event)
@@ -427,19 +428,17 @@ void app_trigger_event(int app_event)
 /**
  * Updates palette and redraw the screen.
  */
-void app_refresh_screen()
+void app_refresh_screen(const Sprite* sprite)
 {
-  if (ase_mode & MODE_GUI) {
-    CurrentSprite sprite;
+  assert(screen != NULL);
 
-    /* update the color palette */
-    set_current_palette(sprite != NULL ?
-			sprite_get_palette(sprite, sprite->frame): NULL,
-			FALSE);
+  if (sprite)
+    set_current_palette(sprite_get_palette(sprite, sprite->frame), false);
+  else
+    set_current_palette(NULL, false);
 
-    /* redraw the screen */
-    jmanager_refresh_screen();
-  }
+  // redraw the screen
+  jmanager_refresh_screen();
 }
 
 /**
@@ -514,8 +513,11 @@ bool app_realloc_recent_list()
 
 int app_get_current_image_type()
 {
-  CurrentSprite sprite;
-  if (sprite)
+  Context* context = UIContext::instance();
+  assert(context != NULL);
+
+  Sprite* sprite = context->get_current_sprite();
+  if (sprite != NULL)
     return sprite->imgtype;
   else if (screen != NULL && bitmap_color_depth(screen) == 8)
     return IMAGE_INDEXED;
@@ -589,6 +591,7 @@ static void tabsbar_select_callback(JWidget tabs, void *data, int button)
  */
 static int check_args(int argc, char *argv[])
 {
+  Console console;
   int i, n, len;
   char *arg;
 
@@ -643,7 +646,7 @@ static int check_args(int argc, char *argv[])
 	  }
 	}
         else {
-	  console_printf(_("%s: option \"res\" requires an argument\n"), exe_name);
+	  console.printf(_("%s: option \"res\" requires an argument\n"), exe_name);
           usage(1);
 	}
       }
@@ -659,7 +662,7 @@ static int check_args(int argc, char *argv[])
       else if (strncmp(arg+n, "version", len) == 0) {
         ase_mode |= MODE_BATCH;
 
-        console_printf("ase %s\n", VERSION);
+        console.printf("ase %s\n", VERSION);
       }
       /* invalid argument */
       else {
@@ -679,21 +682,23 @@ static int check_args(int argc, char *argv[])
  */
 static void usage(int status)
 {
+  Console console;
+
   /* show options */
   if (!status) {
     /* copyright */
-    console_printf
+    console.printf
       ("ase %s -- allegro-sprite-editor, %s\n"
        COPYRIGHT "\n\n",
        VERSION, _("The Ultimate Sprites Factory"));
 
     /* usage */
-    console_printf
+    console.printf
       ("%s\n  %s [%s] [%s]...\n\n",
        _("Usage:"), exe_name, _("OPTION"), _("FILE"));
 
     /* options */
-    console_printf
+    console.printf
       ("%s:\n"
        "  -palette GFX-FILE        %s\n"
        "  -resolution WxH[xBPP]    %s\n"
@@ -709,24 +714,20 @@ static void usage(int status)
        _("Output version information and exit"));
 
     /* web-site */
-    console_printf
+    console.printf
       ("%s: %s\n%s\n\n  %s\n\n",
        _("Find more information in the ASE's official web site at:"), WEBSITE);
   }
   /* how to show options */
   else {
-    console_printf(_("Try \"%s --help\" for more information.\n"), exe_name);
+    console.printf(_("Try \"%s --help\" for more information.\n"), exe_name);
   }
   exit(status);
 }
 
 static Option *option_new(int type, const char *data)
 {
-  Option *option;
-
-  option = jnew(Option, 1);
-  if (!option)
-    return NULL;
+  Option *option = new Option;
 
   option->type = type;
   option->data = jstrdup(data);
@@ -737,22 +738,5 @@ static Option *option_new(int type, const char *data)
 static void option_free(Option* option)
 {
   jfree(option->data);
-  jfree(option);
-}
-
-static AppHook *apphook_new(void (*proc)(void*), void* data)
-{
-  AppHook* apphook = jnew(AppHook, 1);
-  if (!apphook)
-    return NULL;
-
-  apphook->proc = proc;
-  apphook->data = data;
-
-  return apphook;
-}
-
-static void apphook_free(AppHook *apphook)
-{
-  jfree(apphook);
+  delete option;
 }
diff --git a/src/core/app.h b/src/core/app.h
index 6d09778ef..755f82223 100644
--- a/src/core/app.h
+++ b/src/core/app.h
@@ -38,7 +38,7 @@ void app_exit();
 void app_add_hook(int app_event, void (*proc)(void *data), void *data);
 void app_trigger_event(int app_event);
 
-void app_refresh_screen();
+void app_refresh_screen(const Sprite* sprite);
 
 void app_realloc_sprite_list();
 bool app_realloc_recent_list();
diff --git a/src/dialogs/aniedit.cpp b/src/dialogs/aniedit.cpp
index 228dd0a82..27d8dfd86 100644
--- a/src/dialogs/aniedit.cpp
+++ b/src/dialogs/aniedit.cpp
@@ -34,9 +34,8 @@
 #include "modules/rootmenu.h"
 #include "modules/sprites.h"
 #include "raster/raster.h"
-#include "raster/undoable.h"
+#include "undoable.h"
 #include "util/celmove.h"
-#include "util/functions.h"
 #include "util/thmbnail.h"
 
 /*
@@ -98,9 +97,8 @@ enum {
 
 typedef struct AniEditor
 {
-  Sprite* sprite;
+  const Sprite* sprite;
   int state;
-  Layer* selected_layer;
   Layer** layers;
   int nlayers;
   int scroll_x;
@@ -122,7 +120,7 @@ typedef struct AniEditor
 
 static JWidget current_anieditor = NULL;
 
-static JWidget anieditor_new(Sprite* sprite);
+static JWidget anieditor_new(const Sprite* sprite);
 static int anieditor_type();
 static AniEditor* anieditor_data(JWidget widget);
 static bool anieditor_msg_proc(JWidget widget, JMessage msg);
@@ -163,7 +161,7 @@ bool animation_editor_is_movingcel()
  */
 void switch_between_animation_and_sprite_editor()
 {
-  CurrentSprite sprite;
+  const Sprite* sprite = UIContext::instance()->get_current_sprite();
   JWidget window;
   JWidget anieditor;
   int layer;
@@ -198,10 +196,10 @@ void switch_between_animation_and_sprite_editor()
    The Animation Editor
  *********************************************************************/
 
-static JWidget anieditor_new(Sprite* sprite)
+static JWidget anieditor_new(const Sprite* sprite)
 {
   JWidget widget = jwidget_new(anieditor_type());
-  AniEditor* anieditor = jnew0(AniEditor, 1);
+  AniEditor* anieditor = new AniEditor;
 
   anieditor->sprite = sprite;
   anieditor->state = STATE_STANDBY;
@@ -245,7 +243,7 @@ static bool anieditor_msg_proc(JWidget widget, JMessage msg)
     case JM_DESTROY:
       if (anieditor->layers)
 	jfree(anieditor->layers);
-      jfree(anieditor);
+      delete anieditor;
       break;
 
     case JM_REQSIZE:
@@ -325,18 +323,26 @@ static bool anieditor_msg_proc(JWidget widget, JMessage msg)
 	  /* do nothing */
 	  break;
 	case PART_HEADER_FRAME:
-	  anieditor->sprite->frame = anieditor->clk_frame;
+	  {
+	    const SpriteReader sprite((Sprite*)anieditor->sprite);
+	    SpriteWriter sprite_writer(sprite);
+	    sprite_writer->frame = anieditor->clk_frame;
+	  }
 	  jwidget_dirty(widget); /* TODO replace this by redrawing old current frame and new current frame */
 	  jwidget_hard_capture_mouse(widget);
 	  anieditor->state = STATE_MOVING_FRAME;
 	  break;
 	case PART_LAYER: {
-	  int old_layer = anieditor_get_layer_index(widget, anieditor->sprite->layer);
+	  const SpriteReader sprite((Sprite*)anieditor->sprite);
+	  int old_layer = anieditor_get_layer_index(widget, sprite->layer);
 	  int frame = anieditor->sprite->frame;
 
 	  /* did the user select another layer? */
 	  if (old_layer != anieditor->clk_layer) {
-	    anieditor->sprite->layer = anieditor->layers[anieditor->clk_layer];
+	    {
+	      SpriteWriter sprite_writer(sprite);
+	      sprite_writer->layer = anieditor->layers[anieditor->clk_layer];
+	    }
 
 	    jmouse_hide();
 	    /* redraw the old & new selected cel */
@@ -348,9 +354,7 @@ static bool anieditor_msg_proc(JWidget widget, JMessage msg)
 	  }
 
 	  /* change the scroll to show the new selected cel */
-	  anieditor_show_cel(widget,
-			     anieditor->clk_layer,
-			     anieditor->sprite->frame);
+	  anieditor_show_cel(widget, anieditor->clk_layer, sprite->frame);
 	  jwidget_hard_capture_mouse(widget);
 	  anieditor->state = STATE_MOVING_LAYER;
 	  break;
@@ -362,14 +366,18 @@ static bool anieditor_msg_proc(JWidget widget, JMessage msg)
 	  jwidget_hard_capture_mouse(widget);
 	  break;
 	case PART_CEL: {
-	  int old_layer = anieditor_get_layer_index(widget, anieditor->sprite->layer);
-	  int old_frame = anieditor->sprite->frame;
+	  const SpriteReader sprite((Sprite*)anieditor->sprite);
+	  int old_layer = anieditor_get_layer_index(widget, sprite->layer);
+	  int old_frame = sprite->frame;
 
 	  /* select the new clicked-part */
 	  if (old_layer != anieditor->clk_layer ||
 	      old_frame != anieditor->clk_frame) {
-	    anieditor->sprite->layer = anieditor->layers[anieditor->clk_layer];
-	    anieditor->sprite->frame = anieditor->clk_frame;
+	    {
+	      SpriteWriter sprite_writer(sprite);
+	      sprite_writer->layer = anieditor->layers[anieditor->clk_layer];
+	      sprite_writer->frame = anieditor->clk_frame;
+	    }
 
 	    jmouse_hide();
 	    /* redraw the old & new selected layer */
@@ -385,9 +393,7 @@ static bool anieditor_msg_proc(JWidget widget, JMessage msg)
 	  }
 
 	  /* change the scroll to show the new selected cel */
-	  anieditor_show_cel(widget,
-			     anieditor->clk_layer,
-			     anieditor->sprite->frame);
+	  anieditor_show_cel(widget, anieditor->clk_layer, sprite->frame);
 
 	  /* capture the mouse (to move the cel) */
 	  jwidget_hard_capture_mouse(widget);
@@ -533,11 +539,14 @@ static bool anieditor_msg_proc(JWidget widget, JMessage msg)
 	      if (anieditor->clk_frame == anieditor->hot_frame)
 		command_execute(command_get_by_name(CMD_FRAME_PROPERTIES), NULL);
 	      else {
+		const SpriteReader sprite((Sprite*)anieditor->sprite);
+
 		if (anieditor->hot_frame >= 0 &&
-		    anieditor->hot_frame < anieditor->sprite->frames &&
+		    anieditor->hot_frame < sprite->frames &&
 		    anieditor->hot_frame != anieditor->clk_frame+1) {
 		  {
-		    Undoable undoable(anieditor->sprite, "Move Frame");
+		    SpriteWriter sprite_writer(sprite);
+		    Undoable undoable(sprite_writer, "Move Frame");
 		    undoable.move_frame_before(anieditor->clk_frame, anieditor->hot_frame);
 		    undoable.commit();
 		  }
@@ -568,15 +577,20 @@ static bool anieditor_msg_proc(JWidget widget, JMessage msg)
 		  anieditor->hot_layer != anieditor->clk_layer+1) {
 		if (!layer_is_background(anieditor->layers[anieditor->clk_layer])) {
 		  // move the clicked-layer after the hot-layer
-		  {
-		    Undoable undoable(anieditor->sprite, "Move Layer");
+		  try {
+		    const SpriteReader sprite((Sprite*)anieditor->sprite);
+		    SpriteWriter sprite_writer(sprite);
+		    Undoable undoable(sprite_writer, "Move Layer");
 		    undoable.move_layer_after(anieditor->layers[anieditor->clk_layer],
 					      anieditor->layers[anieditor->hot_layer]);
 		    undoable.commit();
-		  }
 
-		  /* select the new layer */
-		  anieditor->sprite->layer = anieditor->layers[anieditor->clk_layer];
+		    /* select the new layer */
+		    sprite_writer->layer = anieditor->layers[anieditor->clk_layer];
+		  }
+		  catch (locked_sprite_exception& e) {
+		    e.show();
+		  }
 
 		  jwidget_dirty(widget);
 		  anieditor_regenerate_layers(widget);
@@ -639,7 +653,11 @@ static bool anieditor_msg_proc(JWidget widget, JMessage msg)
 	    /* move the cel */
 	    else if (msg->mouse.left) {
 	      if (movement) {
-		move_cel(anieditor->sprite);
+		{
+		  const SpriteReader sprite((Sprite*)anieditor->sprite);
+		  SpriteWriter sprite_writer(sprite);
+		  move_cel(sprite_writer);
+		}
 
 		destroy_thumbnails();
 		anieditor_regenerate_layers(widget);
@@ -668,7 +686,6 @@ static bool anieditor_msg_proc(JWidget widget, JMessage msg)
 
     case JM_KEYPRESSED: {
       Command *command = command_get_by_key(msg);
-      Sprite *sprite = anieditor->sprite;
 
       /* close animation editor */
       if ((command && (strcmp(command->name, CMD_FILM_EDITOR) == 0)) ||
@@ -679,8 +696,10 @@ static bool anieditor_msg_proc(JWidget widget, JMessage msg)
 
       /* undo */
       if (command && strcmp(command->name, CMD_UNDO) == 0) {
+	const SpriteReader sprite((Sprite*)anieditor->sprite);
 	if (undo_can_undo(sprite->undo)) {
-	  undo_do_undo(sprite->undo);
+	  SpriteWriter sprite_writer(sprite);
+	  undo_do_undo(sprite_writer->undo);
 
 	  destroy_thumbnails();
 	  anieditor_regenerate_layers(widget);
@@ -692,8 +711,10 @@ static bool anieditor_msg_proc(JWidget widget, JMessage msg)
 
       /* redo */
       if (command && strcmp(command->name, CMD_REDO) == 0) {
+	const SpriteReader sprite((Sprite*)anieditor->sprite);
 	if (undo_can_redo(sprite->undo)) {
-	  undo_do_redo(sprite->undo);
+	  SpriteWriter sprite_writer(sprite);
+	  undo_do_redo(sprite_writer->undo);
 
 	  destroy_thumbnails();
 	  anieditor_regenerate_layers(widget);
diff --git a/src/dialogs/drawtext.cpp b/src/dialogs/drawtext.cpp
index f666694a2..05486626b 100644
--- a/src/dialogs/drawtext.cpp
+++ b/src/dialogs/drawtext.cpp
@@ -50,8 +50,9 @@ static void update_button_text();
 
 void dialogs_draw_text(Sprite* sprite)
 {
+#if 0
   Image *image, *dest_image;
-  JWidget window, button_ok, color_box, color_but;
+  JWidget button_ok, color_box, color_but;
   JWidget entry_size, entry_text;
   char buf[256];
 
@@ -62,9 +63,7 @@ void dialogs_draw_text(Sprite* sprite)
   if (!dest_image)
     return;
 
-  window = load_widget("drawtext.jid", "drawtext_window");
-  if (!window)
-    return;
+  JWidgetPtr window = load_widget("drawtext.jid", "drawtext_window");
 
   if (!get_widgets(window,
 		   "font", &font_button,
@@ -72,7 +71,6 @@ void dialogs_draw_text(Sprite* sprite)
 		   "size", &entry_size,
 		   "color_box", &color_box,
 		   "ok", &button_ok, NULL)) {
-    jwidget_free(window);
     return;
   }
 
@@ -147,8 +145,7 @@ void dialogs_draw_text(Sprite* sprite)
       destroy_font(f);
     }
   }
-
-  jwidget_free(window);
+#endif
 }
 
 Image *RenderText(Sprite* sprite, const char *fontname, int size, int color, const char *text)
@@ -270,8 +267,10 @@ static FONT *my_load_font(const char *filename)
   dirs_free(dirs);
 
   /* error loading font */
-  if (!f)
-    console_printf(_("Error loading font.\n"));
+  if (!f) {
+    Console console;
+    console.printf(_("Error loading font.\n"));
+  }
 
   return f;
 }
diff --git a/src/dialogs/options.cpp b/src/dialogs/options.cpp
index 3900d3ce9..2584645a0 100644
--- a/src/dialogs/options.cpp
+++ b/src/dialogs/options.cpp
@@ -45,7 +45,7 @@ static bool slider_mouse_hook(JWidget widget, void *data);
 /* shows option dialog */
 void dialogs_options()
 {
-  JWidget window, check_smooth, check_dither;
+  JWidget check_smooth, check_dither;
   JWidget button_ok;
   JWidget move_click2, draw_click2, killer;
   JWidget undo_size_limit;
@@ -60,23 +60,17 @@ void dialogs_options()
   old_y = y;
 
   /* load the window widget */
-  window = load_widget("options.jid", "options");
-  if (!window)
-    return;
-
-  if (!get_widgets(window,
-		   "mouse_x", &slider_x,
-		   "mouse_y", &slider_y,
-		   "lock_axis", &check_lockmouse,
-		   "smooth", &check_smooth,
-		   "dither", &check_dither,
-		   "move_click2", &move_click2,
-		   "draw_click2", &draw_click2,
-		   "undo_size_limit", &undo_size_limit,
-		   "button_ok", &button_ok, NULL)) {
-    jwidget_free(window);
-    return;
-  }
+  JWidgetPtr window = load_widget("options.jid", "options");
+  get_widgets(window,
+	      "mouse_x", &slider_x,
+	      "mouse_y", &slider_y,
+	      "lock_axis", &check_lockmouse,
+	      "smooth", &check_smooth,
+	      "dither", &check_dither,
+	      "move_click2", &move_click2,
+	      "draw_click2", &draw_click2,
+	      "undo_size_limit", &undo_size_limit,
+	      "button_ok", &button_ok, NULL);
 
   jslider_set_value(slider_x, x);
   jslider_set_value(slider_y, y);
@@ -129,8 +123,6 @@ void dialogs_options()
 
     set_mouse_speed(8-old_x, 8-old_y);
   }
-
-  jwidget_free(window);
 }
 
 static bool slider_mouse_hook(JWidget widget, void *data)
diff --git a/src/dialogs/tips.cpp b/src/dialogs/tips.cpp
index 2f2c6749e..783b674a6 100644
--- a/src/dialogs/tips.cpp
+++ b/src/dialogs/tips.cpp
@@ -272,7 +272,8 @@ static int tips_count_pages()
 
   f = tips_open_file();
   if (!f) {
-    console_printf("Error loading tips files\n");
+    Console console;
+    console.printf("Error loading tips files\n");
     return 0;
   }
 
@@ -283,8 +284,10 @@ static int tips_count_pages()
 
   fclose(f);
 
-  if (!page)
-    console_printf("No pages tips file\n");
+  if (!page) {
+    Console console;
+    console.printf("No pages tips file\n");
+  }
 
   return page;
 }
diff --git a/src/effect/effect.cpp b/src/effect/effect.cpp
index e4c0c163a..e86924d03 100644
--- a/src/effect/effect.cpp
+++ b/src/effect/effect.cpp
@@ -69,9 +69,9 @@ static EffectData effects_data[] = {
 };
 
 static EffectData *get_effect_data(const char *name);
-static int effect_init(Effect *effect, Layer *layer, Image *image, int offset_x, int offset_y);
+static void effect_init(Effect *effect, Layer *layer, Image *image, int offset_x, int offset_y);
 static void effect_apply_to_image(Effect *effect, ImageRef *p, int x, int y);
-static int effect_update_mask(Effect *effect, Mask *mask, Image *image);
+static bool effect_update_mask(Effect *effect, Mask *mask, Image *image);
 
 int init_module_effect()
 {
@@ -84,68 +84,55 @@ void exit_module_effect()
   exit_convolution_matrix();
 }
 
-Effect *effect_new(Sprite *sprite, const char *name)
+Effect::Effect(const SpriteReader& sprite, const char* name)
 {
   int offset_x, offset_y;
-  EffectData *effect_data;
-  Effect *effect;
-  Image *image;
+  EffectData* effect_data;
+  Image* image;
   void (*apply)(Effect*);
 
   effect_data = get_effect_data(name);
-  if (!effect_data)
-    return NULL;
 
   apply = NULL;
   switch (sprite->imgtype) {
     case IMAGE_RGB:       apply = effect_data->apply_4; break;
     case IMAGE_GRAYSCALE: apply = effect_data->apply_2; break;
     case IMAGE_INDEXED:   apply = effect_data->apply_1; break;
+    default:
+      throw invalid_imgtype_exception();
   }
-  if (!apply)
-    return NULL;
 
-  effect = jnew(Effect, 1);
-  if (!effect)
-    return NULL;
-
-  effect->sprite = sprite;
-  effect->src = NULL;
-  effect->dst = NULL;
-  effect->row = 0;
-  effect->offset_x = 0;
-  effect->offset_y = 0;
-  effect->mask = NULL;
-  effect->preview_mask = NULL;
-  effect->mask_address = NULL;
-  effect->effect_data = effect_data;
-  effect->apply = apply;
-  effect->_target = TARGET_ALL_CHANNELS;
-  effect->target = TARGET_ALL_CHANNELS;
-  effect->progress_data = NULL;
-  effect->progress = NULL;
-  effect->is_cancelled = NULL;
+  this->sprite = sprite;
+  this->src = NULL;
+  this->dst = NULL;
+  this->row = 0;
+  this->offset_x = 0;
+  this->offset_y = 0;
+  this->mask = NULL;
+  this->preview_mask = NULL;
+  this->mask_address = NULL;
+  this->effect_data = effect_data;
+  this->apply = apply;
+  this->_target = TARGET_ALL_CHANNELS;
+  this->target = TARGET_ALL_CHANNELS;
+  this->progress_data = NULL;
+  this->progress = NULL;
+  this->is_cancelled = NULL;
 
   image = GetImage2(sprite, &offset_x, &offset_y, NULL);
-  if (image) {
-    if (!effect_init(effect, sprite->layer, image, offset_x, offset_y)) {
-      effect_free(effect);
-      return NULL;
-    }
-  }
+  if (image == NULL)
+    throw no_image_exception();
 
-  return effect;
+  effect_init(this, sprite->layer, image, offset_x, offset_y);
 }
 
-void effect_free(Effect *effect)
+Effect::~Effect()
 {
-  if (effect->preview_mask)
-    mask_free(effect->preview_mask);
+  if (this->preview_mask)
+    mask_free(this->preview_mask);
 
-  if (effect->dst)
-    image_free(effect->dst);
-
-  jfree(effect);
+  if (this->dst)
+    image_free(this->dst);
 }
 
 void effect_set_target(Effect *effect, int target)
@@ -363,17 +350,17 @@ static EffectData *get_effect_data(const char *name)
       return effects_data+c;
   }
 
-  return NULL;
+  throw invalid_effect_exception(name);
 }
 
-static int effect_init(Effect *effect, Layer *layer, Image *image,
-		       int offset_x, int offset_y)
+static void effect_init(Effect *effect, Layer *layer, Image *image,
+			int offset_x, int offset_y)
 {
   effect->offset_x = offset_x;
   effect->offset_y = offset_y;
 
   if (!effect_update_mask(effect, effect->sprite->mask, image))
-    return FALSE;
+    throw invalid_area_exception();
 
   if (effect->preview_mask) {
     mask_free(effect->preview_mask);
@@ -397,17 +384,15 @@ static int effect_init(Effect *effect, Layer *layer, Image *image,
   /* the alpha channel of the background layer can't be modified */
   if (layer_is_background(layer))
     effect->target &= ~TARGET_ALPHA_CHANNEL;
-  
-  return TRUE;
 }
 
 static void effect_apply_to_image(Effect *effect, ImageRef *p, int x, int y)
 {
-  if (effect_init(effect, p->layer, p->image, x, y))
-    effect_apply(effect);
+  effect_init(effect, p->layer, p->image, x, y);
+  effect_apply(effect);
 }
 
-static int effect_update_mask(Effect *effect, Mask *mask, Image *image)
+static bool effect_update_mask(Effect *effect, Mask *mask, Image *image)
 {
   int x, y, w, h;
 
@@ -445,13 +430,13 @@ static int effect_update_mask(Effect *effect, Mask *mask, Image *image)
     effect->y = 0;
     effect->w = 0;
     effect->h = 0;
-    return FALSE;
+    return false;
   }
   else {
     effect->x = x;
     effect->y = y;
     effect->w = w;
     effect->h = h;
-    return TRUE;
+    return true;
   }
 }
diff --git a/src/effect/effect.h b/src/effect/effect.h
index a2f8f0466..1dde8d5a1 100644
--- a/src/effect/effect.h
+++ b/src/effect/effect.h
@@ -20,6 +20,8 @@
 #define EFFECT_H
 
 #include <stdlib.h>
+#include <cstring>
+#include "sprite_wrappers.h"
 #include "jinete/jbase.h"
 
 class Image;
@@ -42,14 +44,41 @@ class Sprite;
    TARGET_ALPHA_CHANNEL		|	\
    TARGET_GRAY_CHANNEL		)
 
-int init_module_effect();
-void exit_module_effect();
+
+class invalid_effect_exception : public ase_exception
+{
+public:
+  invalid_effect_exception(const char* effect_name) throw()
+    : ase_exception(std::string("Invalid effect specified: ") + effect_name) { }
+};
+
+class invalid_imgtype_exception : public ase_exception
+{
+public:
+  invalid_imgtype_exception() throw()
+  : ase_exception("Invalid image type specified.") { }
+};
+
+class invalid_area_exception : public ase_exception
+{
+public:
+  invalid_area_exception() throw()
+  : ase_exception("The current mask/area to apply the effect is completelly invalid.") { }
+};
+
+class no_image_exception : public ase_exception
+{
+public:
+  no_image_exception() throw()
+  : ase_exception("There are not an active image to apply the effect.\n"
+		  "Please select a layer/cel with an image and try again.") { }
+};
 
 struct EffectData;
 
 struct Effect
 {
-  Sprite* sprite;
+  SpriteWriter sprite;
   Image* src;
   Image* dst;
   int row;
@@ -68,10 +97,13 @@ struct Effect
   void *progress_data;
   void (*progress)(void *data, float progress);
   bool (*is_cancelled)(void *data);
+
+  Effect(const SpriteReader& sprite, const char* name);
+  ~Effect();
 };
 
-Effect* effect_new(Sprite* sprite, const char* name);
-void effect_free(Effect* effect);
+int init_module_effect();
+void exit_module_effect();
 
 void effect_set_target(Effect* effect, int target);
 
diff --git a/src/file/file.cpp b/src/file/file.cpp
index df0b8c990..72252f0e4 100644
--- a/src/file/file.cpp
+++ b/src/file/file.cpp
@@ -112,8 +112,10 @@ Sprite *sprite_load(const char *filename)
   fop_operate(fop);
   fop_done(fop);
 
-  if (fop->error)
-    console_printf(fop->error);
+  if (fop->error) {
+    Console console;
+    console.printf(fop->error);
+  }
 
   sprite = fop->sprite;
   fop_free(fop);
@@ -132,8 +134,10 @@ int sprite_save(Sprite *sprite)
   fop_operate(fop);
   fop_done(fop);
 
-  if (fop->error)
-    console_printf(fop->error);
+  if (fop->error) {
+    Console console;
+    console.printf(fop->error);
+  }
 
   ret = (fop->error == NULL) ? 0: -1;
   fop_free(fop);
diff --git a/src/file/jpeg_format.cpp b/src/file/jpeg_format.cpp
index 3b0ca1ed0..af6589300 100644
--- a/src/file/jpeg_format.cpp
+++ b/src/file/jpeg_format.cpp
@@ -350,44 +350,41 @@ static bool save_JPEG(FileOp *fop)
  */
 static FormatOptions *get_options_JPEG(FileOp *fop)
 {
-  JWidget window, slider_quality, ok;
   JpegOptions *jpeg_options = jpeg_options_new();
+  try {
+    /* configuration parameters */
+    jpeg_options->quality = get_config_float("JPEG", "Quality", 1.0f);
 
-  /* configuration parameters */
-  jpeg_options->quality = get_config_float("JPEG", "Quality", 1.0f);
+    /* interactive mode */
+    if (!is_interactive())
+      return (FormatOptions*)jpeg_options;
+
+    /* widgets */
+    JWidgetPtr window = load_widget("jpeg_options.jid", "jpeg_options");
+    JWidget slider_quality, ok;
+    get_widgets(window,
+		"quality", &slider_quality,
+		"ok", &ok, NULL);
+
+    jslider_set_value(slider_quality, jpeg_options->quality * 10.0f);
+
+    jwindow_open_fg(window);
+
+    if (jwindow_get_killer(window) == ok) {
+      jpeg_options->quality = jslider_get_value(slider_quality) / 10.0f;
+      set_config_float("JPEG", "Quality", jpeg_options->quality);
+    }
+    else {
+      format_options_free((FormatOptions *)jpeg_options);
+      jpeg_options = NULL;
+    }
 
-  /* interactive mode */
-  if (!is_interactive())
     return (FormatOptions *)jpeg_options;
-
-  /* widgets */
-  window = load_widget("jpeg_options.jid", "jpeg_options");
-  if (!window) {
+  }
+  catch (ase_exception& e) {
     format_options_free((FormatOptions *)jpeg_options);
+
+    e.show();
     return NULL;
   }
-
-  if (!get_widgets(window,
-		   "quality", &slider_quality,
-		   "ok", &ok, NULL)) {
-    jwidget_free(window);
-    format_options_free((FormatOptions *)jpeg_options);
-    return NULL;
-  }
-
-  jslider_set_value(slider_quality, jpeg_options->quality * 10.0f);
-
-  jwindow_open_fg(window);
-
-  if (jwindow_get_killer(window) == ok) {
-    jpeg_options->quality = jslider_get_value(slider_quality) / 10.0f;
-    set_config_float("JPEG", "Quality", jpeg_options->quality);
-  }
-  else {
-    format_options_free((FormatOptions *)jpeg_options);
-    jpeg_options = NULL;
-  }
-
-  jwidget_free(window);
-  return (FormatOptions *)jpeg_options;
 }
diff --git a/src/main.cpp b/src/main.cpp
index 42dbf5028..e70f86da3 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -28,18 +28,33 @@ const char ase_ident[] =
     "$ASE: " VERSION " " COPYRIGHT " $\n"
     "$Website: " WEBSITE " $\n";
 
-/***********************************************************************
-			     Main Routine
- ***********************************************************************/
+//////////////////////////////////////////////////////////////////////
+// Basic classes for some RAII
+
+class Allegro {
+public:
+  Allegro() { allegro_init(); }
+  ~Allegro() { allegro_exit(); }
+};
+
+class MemLeaks {
+public:
+#if defined MEMLEAK
+  MemLeaks() { jmemleak_init(); }
+  ~MemLeaks() { jmemleak_exit(); }
+#endif
+};
+
+//////////////////////////////////////////////////////////////////////
+//			       Main Routine
+//////////////////////////////////////////////////////////////////////
 
 int main(int argc, char *argv[])
 {
-  allegro_init();
-  set_uformat(U_ASCII);
+  Allegro allegro;
+  MemLeaks memleaks;
 
-#if defined MEMLEAK
-  jmemleak_init();
-#endif
+  set_uformat(U_ASCII);
 
   // initialises the application
   if (!app_init(argc, argv))
@@ -47,12 +62,6 @@ int main(int argc, char *argv[])
 
   app_loop();
   app_exit();
-
-#if defined  MEMLEAK
-  jmemleak_exit();
-#endif
-
-  allegro_exit();
   return 0;
 }
 
diff --git a/src/modules/editors.cpp b/src/modules/editors.cpp
index c40832796..62cd9cf8b 100644
--- a/src/modules/editors.cpp
+++ b/src/modules/editors.cpp
@@ -20,7 +20,7 @@
 
 #include "jinete/jinete.h"
 
-#include "ase/current_sprite.h"
+#include "sprite_wrappers.h"
 #include "ase/ui_context.h"
 #include "core/app.h"
 #include "modules/editors.h"
@@ -82,7 +82,7 @@ void refresh_all_editors()
     jwidget_dirty(reinterpret_cast<JWidget>(link->data));
 }
 
-void update_editors_with_sprite(Sprite *sprite)
+void update_editors_with_sprite(const Sprite *sprite)
 {
   JWidget widget;
   JLink link;
@@ -95,7 +95,7 @@ void update_editors_with_sprite(Sprite *sprite)
   }
 }
 
-void editors_draw_sprite(Sprite *sprite, int x1, int y1, int x2, int y2)
+void editors_draw_sprite(const Sprite *sprite, int x1, int y1, int x2, int y2)
 {
   JWidget widget;
   JLink link;
@@ -110,7 +110,7 @@ void editors_draw_sprite(Sprite *sprite, int x1, int y1, int x2, int y2)
 
 /* TODO improve this (with JRegion or something, and without
    recursivity) */
-void editors_draw_sprite_tiled(Sprite *sprite, int x1, int y1, int x2, int y2)
+void editors_draw_sprite_tiled(const Sprite *sprite, int x1, int y1, int x2, int y2)
 {
   int cx1, cy1, cx2, cy2;	/* cel rectangle */
   int lx1, ly1, lx2, ly2;	/* limited rectangle to the cel rectangle */
@@ -174,45 +174,27 @@ void editors_draw_sprite_tiled(Sprite *sprite, int x1, int y1, int x2, int y2)
   }
 }
 
-void editors_hide_sprite(Sprite *sprite)
+void editors_hide_sprite(const Sprite *sprite)
 {
-  CurrentSprite current_sprite;
-  JWidget widget;
-  int refresh;
+  UIContext* context = UIContext::instance();
+  bool refresh = (context->get_current_sprite() == sprite) ? true: false;
+
   JLink link;
-
-  refresh = (current_sprite == sprite) ? TRUE: FALSE;
-
   JI_LIST_FOR_EACH(editors, link) {
-    widget = reinterpret_cast<JWidget>(link->data);
+    JWidget widget = reinterpret_cast<JWidget>(link->data);
 
     if (sprite == editor_get_sprite(widget))
       editor_set_sprite(widget, get_more_reliable_sprite());
   }
 
   if (refresh) {
-    UIContext* context = UIContext::instance();
-    context->set_current_sprite(editor_get_sprite(current_editor));
+    Sprite* sprite = editor_get_sprite(current_editor);
 
-    app_refresh_screen();
+    context->set_current_sprite(sprite);
+    app_refresh_screen(sprite);
   }
 }
 
-void replace_sprite_in_editors(Sprite *old_sprite, Sprite *new_sprite)
-{
-  JWidget widget;
-  JLink link;
-
-  JI_LIST_FOR_EACH(editors, link) {
-    widget = reinterpret_cast<JWidget>(link->data);
-
-    if (old_sprite == editor_get_sprite(widget))
-      editor_set_sprite(widget, new_sprite);
-  }
-
-  app_refresh_screen();
-}
-
 void set_current_editor(JWidget editor)
 {
   if (current_editor != editor) {
@@ -224,9 +206,10 @@ void set_current_editor(JWidget editor)
     jwidget_dirty(jwidget_get_view(current_editor));
 
     UIContext* context = UIContext::instance();
-    context->set_current_sprite(editor_get_sprite(current_editor));
+    Sprite* sprite = editor_get_sprite(current_editor);
+    context->set_current_sprite(sprite);
 
-    app_refresh_screen();
+    app_refresh_screen(sprite);
     app_realloc_sprite_list();
   }
 }
@@ -244,7 +227,7 @@ void set_sprite_in_current_editor(Sprite *sprite)
 
     jwidget_dirty(jwidget_get_view(current_editor));
 
-    app_refresh_screen();
+    app_refresh_screen(sprite);
     app_realloc_sprite_list();
   }
 }
diff --git a/src/modules/editors.h b/src/modules/editors.h
index 288091c5b..9e5f41c20 100644
--- a/src/modules/editors.h
+++ b/src/modules/editors.h
@@ -35,11 +35,10 @@ void remove_editor(JWidget editor);
 void set_current_editor(JWidget editor);
 
 void refresh_all_editors();
-void update_editors_with_sprite(Sprite* sprite);
-void editors_draw_sprite(Sprite* sprite, int x1, int y1, int x2, int y2);
-void editors_draw_sprite_tiled(Sprite* sprite, int x1, int y1, int x2, int y2);
-void editors_hide_sprite(Sprite* sprite);
-void replace_sprite_in_editors(Sprite* old_sprite, Sprite* new_sprite);
+void update_editors_with_sprite(const Sprite* sprite);
+void editors_draw_sprite(const Sprite* sprite, int x1, int y1, int x2, int y2);
+void editors_draw_sprite_tiled(const Sprite* sprite, int x1, int y1, int x2, int y2);
+void editors_hide_sprite(const Sprite* sprite);
 
 void set_sprite_in_current_editor(Sprite* sprite);
 void set_sprite_in_more_reliable_editor(Sprite* sprite);
diff --git a/src/modules/gui.cpp b/src/modules/gui.cpp
index 00d1929f7..e99996464 100644
--- a/src/modules/gui.cpp
+++ b/src/modules/gui.cpp
@@ -368,7 +368,7 @@ void set_screen_scaling(int scaling)
   screen_scaling = scaling;
 }
 
-void update_screen_for_sprite(Sprite *sprite)
+void update_screen_for_sprite(const Sprite* sprite)
 {
   if (!(ase_mode & MODE_GUI))
     return;
@@ -412,7 +412,9 @@ void gui_feedback()
 
   if (next_idle_flags & REFRESH_FULL_SCREEN) {
     next_idle_flags ^= REFRESH_FULL_SCREEN;
-    update_screen_for_sprite(UIContext::instance()->get_current_sprite());
+
+    const CurrentSpriteReader sprite;
+    update_screen_for_sprite(sprite);
   }
 
   /* record file if is necessary */
@@ -549,7 +551,7 @@ JWidget load_widget(const char *filename, const char *name)
   JWidget widget;
   DIRS *it, *dirs;
   char buf[512];
-  bool found = FALSE;
+  bool found = false;
 
   dirs = dirs_new();
 
@@ -561,25 +563,32 @@ JWidget load_widget(const char *filename, const char *name)
   for (it=dirs; it; it=it->next) {
     if (exists(it->path)) {
       ustrcpy(buf, it->path);
-      found = TRUE;
+      found = true;
       break;
     }
   }
 
   dirs_free(dirs);
 
-  if (!found) {
-    console_printf(_("File not found: \"%s\"\n"), filename);
-    return NULL;
-  }
+  if (!found)
+    throw widget_file_not_found(filename);
 
   widget = ji_load_widget(buf, name);
   if (!widget)
-    console_printf(_("Error loading widget: \"%s\"\n"), name);
+    throw widget_not_found(name);
 
   return widget;
 }
 
+JWidget find_widget(JWidget widget, const char *name)
+{
+  JWidget child = jwidget_find_name(widget, name);
+  if (!child)
+    throw widget_not_found(name);
+
+  return child;
+}
+
 void schedule_rebuild_recent_list()
 {
   next_idle_flags |= REBUILD_RECENT_LIST;
@@ -653,7 +662,7 @@ void hook_signal(JWidget widget,
  * }
  * @endcode
  */
-bool get_widgets(JWidget window, ...)
+void get_widgets(JWidget window, ...)
 {
   JWidget *widget;
   char *name;
@@ -666,14 +675,10 @@ bool get_widgets(JWidget window, ...)
       break;
 
     *widget = jwidget_find_name(window, name);
-    if (!*widget) {
-      console_printf(_("Widget %s not found.\n"), name);
-      return FALSE;
-    }
+    if (!*widget)
+      throw widget_not_found(name);
   }
   va_end(ap);
-
-  return TRUE;
 }
 
 /**********************************************************************/
diff --git a/src/modules/gui.h b/src/modules/gui.h
index 6998660bb..47580a9aa 100644
--- a/src/modules/gui.h
+++ b/src/modules/gui.h
@@ -19,8 +19,34 @@
 #ifndef MODULES_GUI_H
 #define MODULES_GUI_H
 
+#include <cassert>
+#include <string>
+#include "ase_exception.h"
 #include "jinete/jbase.h"
 
+//////////////////////////////////////////////////////////////////////
+
+class widget_file_not_found : public ase_exception
+{
+public:
+  widget_file_not_found(const char* file_name) throw()
+    : ase_exception(std::string("Cannot load file: ") + file_name
+		    + "\nPlease reinstall " PACKAGE) { }
+};
+
+/**
+ * Exception thrown by find_widget() if a widget is not found.
+ */
+class widget_not_found : public ase_exception
+{
+public:
+  widget_not_found(const char* widget_name) throw()
+  : ase_exception("A data file is corrupted.\nPlease reinstall " PACKAGE
+		  "\n\nDetails: Widget not found: " + std::string(widget_name)) { }
+};
+
+//////////////////////////////////////////////////////////////////////
+
 #define HOOK(widget, signal, signal_handler, data)			\
   hook_signal((widget), (signal), (signal_handler), (void *)(data))
 
@@ -35,7 +61,7 @@ int guiscale();
 int get_screen_scaling();
 void set_screen_scaling(int scaling);
 
-void update_screen_for_sprite(Sprite* sprite);
+void update_screen_for_sprite(const Sprite* sprite);
 
 void gui_run();
 void gui_feedback();
@@ -47,6 +73,7 @@ void load_window_pos(JWidget window, const char *section);
 void save_window_pos(JWidget window, const char *section);
 
 JWidget load_widget(const char *filename, const char *name);
+JWidget find_widget(JWidget widget, const char *name);
 
 void schedule_rebuild_recent_list();
 
@@ -55,7 +82,7 @@ void hook_signal(JWidget widget,
 		 bool (*signal_handler)(JWidget widget, void *data),
 		 void *data);
 
-bool get_widgets(JWidget window, ...);
+void get_widgets(JWidget window, ...);
 
 void add_gfxicon_to_button(JWidget button, int gfx_id, int icon_align);
 void set_gfxicon_in_button(JWidget button, int gfx_id);
@@ -71,4 +98,49 @@ Monitor* add_gui_monitor(void (*proc)(void*),
 			 void (*free)(void*), void* data);
 void remove_gui_monitor(Monitor* monitor);
 
+//////////////////////////////////////////////////////////////////////
+// Smart JWidget pointer
+
+class JWidgetPtr
+{
+  JWidget m_widget;
+
+  // TODO make this class copyable and count references (so this is
+  //      really "smart" pointer)...
+  JWidgetPtr(const JWidgetPtr&);
+  JWidgetPtr& operator=(const JWidgetPtr&);
+
+public:
+  JWidgetPtr() {
+    m_widget = NULL;
+  }
+
+  JWidgetPtr(JWidget widget) {
+    m_widget = widget;
+  }
+
+  ~JWidgetPtr() {
+    delete m_widget;
+  }
+
+  JWidgetPtr& operator=(JWidget widget) {
+    if (m_widget)
+      delete m_widget;
+
+    m_widget = widget;
+    return *this;
+  }
+
+  operator JWidget() {
+    return m_widget;
+  }
+
+  JWidget operator->() {
+    assert(m_widget != NULL);
+    return m_widget;
+  }
+
+};
+
+
 #endif /* MODULES_GUI_H */
diff --git a/src/modules/palettes.cpp b/src/modules/palettes.cpp
index 77f12eff7..caef32e26 100644
--- a/src/modules/palettes.cpp
+++ b/src/modules/palettes.cpp
@@ -120,10 +120,10 @@ void set_default_palette(Palette *palette)
  * @param palette If "palette" is NULL will be used the default one
  * (ase_default_palette)
  */
-bool set_current_palette(Palette *_palette, int forced)
+bool set_current_palette(Palette *_palette, bool forced)
 {
   Palette *palette = _palette ? _palette: ase_default_palette;
-  bool ret = FALSE;
+  bool ret = false;
 
   /* have changes */
   if (forced ||
@@ -245,7 +245,7 @@ void set_current_color(int index, int r, int g, int b)
   }
 }
 
-/**********************************************************************/
+//////////////////////////////////////////////////////////////////////
 
 CurrentSpriteRgbMap::CurrentSpriteRgbMap()
 {
@@ -257,7 +257,7 @@ CurrentSpriteRgbMap::~CurrentSpriteRgbMap()
   rgb_map = my_rgb_map;
 
   if (regen_my_rgb_map) {
-    regen_my_rgb_map = FALSE;
+    regen_my_rgb_map = false;
     create_rgb_table(my_rgb_map, _current_palette, NULL);
   }
 }
diff --git a/src/modules/palettes.h b/src/modules/palettes.h
index d96030217..2686dcf0e 100644
--- a/src/modules/palettes.h
+++ b/src/modules/palettes.h
@@ -35,7 +35,7 @@ Palette* get_default_palette();
 Palette* get_current_palette();
 
 void set_default_palette(Palette* palette);
-bool set_current_palette(Palette* palette, int forced);
+bool set_current_palette(Palette* palette, bool forced);
 void set_black_palette();
 void set_current_color(int index, int r, int g, int b);
 
diff --git a/src/modules/rootmenu.cpp b/src/modules/rootmenu.cpp
index f7d8a0fd8..3adf4d0a2 100644
--- a/src/modules/rootmenu.cpp
+++ b/src/modules/rootmenu.cpp
@@ -318,7 +318,7 @@ static JWidget convert_xmlelem_to_menuitem(JXmlElem elem)
   menuitem = menuitem_new(jxmlelem_get_attr(elem, "name"),
 			  command_get_by_name(jxmlelem_get_attr(elem,
 								"command")),
-			  NULL);
+			  jxmlelem_get_attr(elem, "argument"));
   if (!menuitem)
     return 0;
 
diff --git a/src/modules/tools.cpp b/src/modules/tools.cpp
index 222b42e77..4059eaa31 100644
--- a/src/modules/tools.cpp
+++ b/src/modules/tools.cpp
@@ -710,14 +710,8 @@ static void tool_rectangle_draw_trace(int x1, int y1, int x2, int y2, ToolData *
   }
 
   if (filled_mode) {
-    int bak_color;
-    bak_color = data->color;
-    data->color = data->other_color;
-
     for (c=y1; c<=y2; c++)
       do_ink_hline(x1, c, x2, data);
-
-    data->color = bak_color;
   }
 
   for (c=x1; c<=x2; c++) do_ink_brush(c, y1, data);
@@ -746,14 +740,8 @@ static Tool tool_rectangle =
 static void tool_ellipse_draw_trace(int x1, int y1, int x2, int y2, ToolData *data)
 {
   if (filled_mode) {
-    int bak_color;
-    bak_color = data->color;
-    data->color = data->other_color;
-
     algo_ellipsefill(x1, y1, x2, y2, data,
 		     (AlgoHLine)do_ink_hline);
-
-    data->color = bak_color;
   }
 
   algo_ellipse(x1, y1, x2, y2, data,
diff --git a/src/raster/gfxobj.cpp b/src/raster/gfxobj.cpp
index 29b130c97..767b3011f 100644
--- a/src/raster/gfxobj.cpp
+++ b/src/raster/gfxobj.cpp
@@ -71,7 +71,9 @@ GfxObj::~GfxObj()
 {
   // we have to remove this object from the map
   jmutex_lock(objects_mutex);
-  erase_gfxobj(this);
+  {
+    erase_gfxobj(this);
+  }
   jmutex_unlock(objects_mutex);
 }
 
@@ -114,9 +116,11 @@ void _gfxobj_set_id(GfxObj* gfxobj, gfxobj_id id)
   assert(gfxobj_find(id) == NULL);
 
   jmutex_lock(objects_mutex);
-  erase_gfxobj(gfxobj);		// remove the object
-  gfxobj->id = id;		// change the ID
-  insert_gfxobj(gfxobj);	// insert the object again in the map
+  {
+    erase_gfxobj(gfxobj);	// remove the object
+    gfxobj->id = id;		// change the ID
+    insert_gfxobj(gfxobj);	// insert the object again in the map
+  }
   jmutex_unlock(objects_mutex);
 }
 
diff --git a/src/raster/image.cpp b/src/raster/image.cpp
index d11989a97..3ef183417 100644
--- a/src/raster/image.cpp
+++ b/src/raster/image.cpp
@@ -327,135 +327,6 @@ void image_to_allegro(const Image* image, BITMAP *bmp, int x, int y)
   image->to_allegro(bmp, x, y);
 }
 
-void image_convert(const Image* src, Image* dst)
-{
-  int c, x, y, w, h;
-  float hue, s, v;
-
-  if ((src->w != dst->w) || (src->h != dst->h))
-    return;
-  else if (src->imgtype == dst->imgtype) {
-    image_copy(dst, src, 0, 0);
-    return;
-  }
-
-  w = dst->w;
-  h = dst->h;
-
-  switch (src->imgtype) {
-
-    case IMAGE_RGB:
-      switch (dst->imgtype) {
-
-	/* RGB -> Grayscale */
-	case IMAGE_GRAYSCALE:
-	  for (y=0; y<h; y++) {
-	    for (x=0; x<w; x++) {
-	      c = image_getpixel_fast<RgbTraits>(src, x, y);
-	      rgb_to_hsv(_rgba_getr(c),
-			 _rgba_getg(c),
-			 _rgba_getb(c), &hue, &s, &v);
-	      v = v * 255.0f;
-	      image_putpixel_fast<GrayscaleTraits>(dst, x, y,
-						   _graya((int)MID(0, v, 255),
-							  _rgba_geta(c)));
-	    }
-	  }
-	  break;
-
-	/* RGB -> Indexed */
-	case IMAGE_INDEXED:
-	  for (y=0; y<h; y++) {
-	    for (x=0; x<w; x++) {
-	      c = image_getpixel_fast<RgbTraits>(src, x, y);
-	      if  (!_rgba_geta (c))
-		image_putpixel_fast<IndexedTraits>(dst, x, y, 0);
-	      else
-		image_putpixel_fast<IndexedTraits>(dst, x, y,
-						   makecol8(_rgba_getr(c),
-							    _rgba_getg(c),
-							    _rgba_getb(c)));
-	    }
-	  }
-	  break;
-      }
-      break;
-
-    case IMAGE_GRAYSCALE:
-      switch (dst->imgtype) {
-
-	/* Grayscale -> RGB */
-	case IMAGE_RGB:
-	  for (y=0; y<h; y++) {
-	    for (x=0; x<w; x++) {
-	      c = image_getpixel_fast<GrayscaleTraits>(src, x, y);
-	      image_putpixel_fast<RgbTraits>(dst, x, y,
-					     _rgba(_graya_getv(c),
-						   _graya_getv(c),
-						   _graya_getv(c),
-						   _graya_geta(c)));
-	    }
-	  }
-	  break;
-
-	/* Grayscale -> Indexed */
-	case IMAGE_INDEXED:
-	  for (y=0; y<h; y++) {
-	    for (x=0; x<w; x++) {
-	      c = image_getpixel_fast<GrayscaleTraits>(src, x, y);
-	      if  (!_graya_geta(c))
-		image_putpixel_fast<IndexedTraits>(dst, x, y, 0);
-	      else
-		image_putpixel_fast<IndexedTraits>(dst, x, y,
-						   makecol8(_graya_getv(c),
-							    _graya_getv(c),
-							    _graya_getv(c)));
-	    }
-	  }
-	  break;
-      }
-      break;
-
-    case IMAGE_INDEXED:
-      switch (dst->imgtype) {
-
-	/* Indexed -> RGB */
-	case IMAGE_RGB:
-	  for (y=0; y<h; y++) {
-	    for (x=0; x<w; x++) {
-	      c = image_getpixel_fast<IndexedTraits>(src, x, y);
-	      if (!c)
-		image_putpixel_fast<RgbTraits>(dst, x, y, 0);
-	      else
-		image_putpixel_fast<RgbTraits>(dst, x, y,
-					       _rgba(getr8(c),
-						     getg8(c),
-						     getb8(c), 255));
-	    }
-	  }
-	  break;
-
-	/* Indexed -> Grayscale */
-	case IMAGE_GRAYSCALE:
-	  for (y=0; y<h; y++) {
-	    for (x=0; x<w; x++) {
-	      c = image_getpixel_fast<GrayscaleTraits>(src, x, y);
-	      if (!c)
-		image_putpixel_fast<GrayscaleTraits>(dst, x, y, 0);
-	      else {
-		rgb_to_hsv(getr8(c), getg8(c), getb8(c), &hue, &s, &v);
-		v = v * 255.0f;
-		image_putpixel_fast<GrayscaleTraits>(dst, x, y,
-						     _graya((int)MID(0, v, 255), 255));
-	      }
-	    }
-	  }
-	  break;
-      }
-      break;
-  }
-}
-
 void image_resize(const Image* src, Image* dst, ResizeMethod method, Palette* pal, RGB_MAP* rgb_map)
 {
   switch (method) {
diff --git a/src/raster/image.h b/src/raster/image.h
index 6378288ca..dc74ae81f 100644
--- a/src/raster/image.h
+++ b/src/raster/image.h
@@ -88,7 +88,6 @@ void image_ellipsefill(Image* image, int x1, int y1, int x2, int y2, int color);
 
 void image_to_allegro(const Image* image, BITMAP* bmp, int x, int y);
 
-void image_convert(const Image* src, Image* dst);
 void image_resize(const Image* src, Image* dst, ResizeMethod method, Palette* palette, RGB_MAP* rgb_map);
 int image_count_diff(const Image* i1, const Image* i2);
 bool image_shrink_rect(Image *image, int *x1, int *y1, int *x2, int *y2, int refpixel);
diff --git a/src/raster/quant.cpp b/src/raster/quant.cpp
index 1b8c61205..7cea09cec 100644
--- a/src/raster/quant.cpp
+++ b/src/raster/quant.cpp
@@ -28,20 +28,22 @@ Image *image_set_imgtype(Image *image, int imgtype,
 			 RGB_MAP *rgb_map,
 			 Palette *palette)
 {
-  ase_uint32 *rgb_address;
-  ase_uint16 *gray_address;
-  ase_uint8 *idx_address;
-  int i, c, r, g, b, size;
+  ase_uint32* rgb_address;
+  ase_uint16* gray_address;
+  ase_uint8* idx_address;
+  ase_uint32 c;
+  int i, r, g, b, size;
   Image *new_image;
 
-  /* no convertion */
+  // no convertion
   if (image->imgtype == imgtype)
     return NULL;
-  /* RGB -> Indexed with ordered dithering */
+  // RGB -> Indexed with ordered dithering
   else if (image->imgtype == IMAGE_RGB &&
 	   imgtype == IMAGE_INDEXED &&
-	   dithering_method == DITHERING_ORDERED)
+	   dithering_method == DITHERING_ORDERED) {
     return image_rgb_to_indexed(image, 0, 0, rgb_map, palette);
+  }
 
   new_image = image_new(imgtype, image->w, image->h);
   if (!new_image)
@@ -52,24 +54,24 @@ Image *image_set_imgtype(Image *image, int imgtype,
   switch (image->imgtype) {
 
     case IMAGE_RGB:
-      rgb_address = (ase_uint32 *)image->dat;
+      rgb_address = (ase_uint32*)image->dat;
 
       switch (new_image->imgtype) {
-	/* RGB -> Grayscale */
+	// RGB -> Grayscale
 	case IMAGE_GRAYSCALE:
-	  gray_address = (ase_uint16 *)new_image->dat;
+	  gray_address = (ase_uint16*)new_image->dat;
 	  for (i=0; i<size; i++) {
 	    c = *rgb_address;
-	    r = _rgba_getr (c);
-	    g = _rgba_getg (c);
-	    b = _rgba_getb (c);
-	    rgb_to_hsv_int (&r, &g, &b);
-	    *gray_address = _graya (b, _rgba_geta (c));
+	    r = _rgba_getr(c);
+	    g = _rgba_getg(c);
+	    b = _rgba_getb(c);
+	    rgb_to_hsv_int(&r, &g, &b);
+	    *gray_address = _graya(b, _rgba_geta(c));
 	    rgb_address++;
 	    gray_address++;
 	  }
 	  break;
-        /* RGB -> Indexed */
+	// RGB -> Indexed
 	case IMAGE_INDEXED:
 	  idx_address = new_image->dat;
 	  for (i=0; i<size; i++) {
@@ -89,12 +91,12 @@ Image *image_set_imgtype(Image *image, int imgtype,
       break;
 
     case IMAGE_GRAYSCALE:
-      gray_address = (ase_uint16 *)image->dat;
+      gray_address = (ase_uint16*)image->dat;
 
       switch (new_image->imgtype) {
-	/* Grayscale -> RGB */
+	// Grayscale -> RGB
 	case IMAGE_RGB:
-	  rgb_address = (ase_uint32 *)new_image->dat;
+	  rgb_address = (ase_uint32*)new_image->dat;
 	  for (i=0; i<size; i++) {
 	    c = *gray_address;
 	    g = _graya_getv(c);
@@ -103,7 +105,7 @@ Image *image_set_imgtype(Image *image, int imgtype,
 	    rgb_address++;
 	  }
 	  break;
-	/* Grayscale -> Indexed */
+	// Grayscale -> Indexed
 	case IMAGE_INDEXED:
 	  idx_address = new_image->dat;
 	  for (i=0; i<size; i++) {
@@ -123,9 +125,9 @@ Image *image_set_imgtype(Image *image, int imgtype,
       idx_address = image->dat;
 
       switch (new_image->imgtype) {
-	/* Indexed -> RGB */
+	// Indexed -> RGB
 	case IMAGE_RGB:
-	  rgb_address = (ase_uint32 *)new_image->dat;
+	  rgb_address = (ase_uint32*)new_image->dat;
 	  for (i=0; i<size; i++) {
 	    c = *idx_address;
 	    if (c == 0)
@@ -138,9 +140,9 @@ Image *image_set_imgtype(Image *image, int imgtype,
 	    rgb_address++;
 	  }
 	  break;
-	/* Indexed -> Grayscale */
+	// Indexed -> Grayscale
 	case IMAGE_GRAYSCALE:
-	  gray_address = (ase_uint16 *)new_image->dat;
+	  gray_address = (ase_uint16*)new_image->dat;
 	  for (i=0; i<size; i++) {
 	    c = *idx_address;
 	    if (c == 0)
diff --git a/src/raster/sprite.cpp b/src/raster/sprite.cpp
index 32cd6e8a6..9d5a592eb 100644
--- a/src/raster/sprite.cpp
+++ b/src/raster/sprite.cpp
@@ -91,7 +91,8 @@ Sprite::Sprite(int imgtype, int w, int h)
   sprite_set_speed(this, 100);
 
   /* multiple access */
-  m_locked = 0;
+  m_write_lock = false;
+  m_read_locks = 0;
   m_mutex = jmutex_new();
 
   /* file format options */
@@ -314,26 +315,82 @@ bool sprite_need_alpha(const Sprite* sprite)
 }
 
 /**
- * Lock the sprite to write or read it.
+ * Lock the sprite to read or write it.
  *
- * @return true if the sprite can be written (because this is the first lock).
+ * @return true if the sprite can be accessed in the desired mode.
  */
-bool Sprite::lock()
+bool Sprite::lock(bool write)
 {
   ScopedLock hold(m_mutex);
 
-  if (++m_locked == 1)
+  // read-only
+  if (!write) {
+    // If no body is writting the sprite...
+    if (!m_write_lock) {
+      // We can read it
+      ++m_read_locks;
+      return true;
+    }
+  }
+  // read and write
+  else {
+    // If no body is reading and writting...
+    if (m_read_locks == 0 && !m_write_lock) {
+      // We can start writting the sprite...
+      m_write_lock = true;
+      return true;
+    }
+  }
+
+  return false;
+}
+
+/**
+ * If you have locked the sprite to read, using this method
+ * you can raise your access level to write it.
+ */
+bool Sprite::lock_to_write()
+{
+  ScopedLock hold(m_mutex);
+
+  // this only is possible if there are just one reader
+  if (m_read_locks == 1) {
+    assert(!m_write_lock);
+    m_read_locks = 0;
+    m_write_lock = true;
     return true;
+  }
   else
     return false;
 }
 
+/**
+ * If you have locked the sprite to write, using this method
+ * you can your access level to only read it.
+ */
+void Sprite::unlock_to_read()
+{
+  ScopedLock hold(m_mutex);
+  assert(m_read_locks == 0);
+  assert(m_write_lock);
+
+  m_write_lock = false;
+  m_read_locks = 1;
+}
+
 void Sprite::unlock()
 {
   ScopedLock hold(m_mutex);
 
-  --m_locked;
-  assert(m_locked >= 0);
+  if (m_write_lock) {
+    m_write_lock = false;
+  }
+  else if (m_read_locks > 0) {
+    --m_read_locks;
+  }
+  else {
+    assert(false);
+  }
 }
 
 Palette* sprite_get_palette(const Sprite* sprite, int frame)
@@ -362,9 +419,10 @@ Palette* sprite_get_palette(const Sprite* sprite, int frame)
 void sprite_set_palette(Sprite* sprite, Palette* pal, bool truncate)
 {
   assert(sprite != NULL);
+  assert(pal != NULL);
 
   if (!truncate) {
-    Palette* sprite_pal = sprite_get_palette(sprite, sprite->frame);
+    Palette* sprite_pal = sprite_get_palette(sprite, pal->frame);
     palette_copy_colors(sprite_pal, pal);
   }
   else {
@@ -402,6 +460,18 @@ void sprite_reset_palettes(Sprite* sprite)
   }
 }
 
+void sprite_delete_palette(Sprite* sprite, Palette* pal)
+{
+  assert(sprite != NULL);
+  assert(pal != NULL);
+
+  JLink link = jlist_find(sprite->palettes, pal);
+  assert(link != NULL);
+
+  palette_free(pal);
+  jlist_delete_link(sprite->palettes, link);
+}
+
 /**
  * Changes the sprite's filename
  */
@@ -504,76 +574,6 @@ void sprite_set_frame(Sprite* sprite, int frame)
   sprite->frame = frame;
 }
 
-/**
- * @warning: it uses the current Allegro "rgb_map"
- */
-void sprite_set_imgtype(Sprite* sprite, int imgtype, int dithering_method)
-{
-  Image *old_image;
-  Image *new_image;
-  int c;
-
-  /* nothing to do */
-  if (sprite->imgtype == imgtype)
-    return;
-
-  /* if the undo is enabled, open a "big" group */
-  if (undo_is_enabled(sprite->undo)) {
-    undo_set_label(sprite->undo, "Color Mode Change");
-    undo_open(sprite->undo);
-  }
-
-  /* change imgtype of the stock of images */
-  if (undo_is_enabled(sprite->undo))
-    undo_int(sprite->undo, (GfxObj *)sprite->stock, &sprite->stock->imgtype);
-
-  sprite->stock->imgtype = imgtype;
-
-  for (c=0; c<sprite->stock->nimage; c++) {
-    old_image = stock_get_image(sprite->stock, c);
-    if (!old_image)
-      continue;
-
-    new_image = image_set_imgtype(old_image, imgtype, dithering_method,
-				  rgb_map,
-				  /* TODO check this out */
-				  sprite_get_palette(sprite,
-						     sprite->frame));
-    if (!new_image)
-      return;		/* TODO error handling: not enough memory!
-			   we should undo all work done */
-
-    if (undo_is_enabled(sprite->undo))
-      undo_replace_image(sprite->undo, sprite->stock, c);
-
-    image_free(old_image);
-    stock_replace_image(sprite->stock, c, new_image);
-  }
-
-  /* change "sprite.imgtype" field */
-  if (undo_is_enabled(sprite->undo))
-    undo_int(sprite->undo, (GfxObj *)sprite, &sprite->imgtype);
-
-  sprite->imgtype = imgtype;
-
-#if 0				/* TODO */
-  /* change "sprite.palette" */
-  if (imgtype == IMAGE_GRAYSCALE) {
-    int c;
-    undo_data(sprite->undo, (GfxObj *)sprite,
-	      &sprite->palette, sizeof(PALETTE));
-    for (c=0; c<256; c++) {
-      sprite->palette[c].r = c >> 2;
-      sprite->palette[c].g = c >> 2;
-      sprite->palette[c].b = c >> 2;
-    }
-  }
-#endif
-
-  if (undo_is_enabled(sprite->undo))
-    undo_close(sprite->undo);
-}
-
 Layer *sprite_get_background_layer(const Sprite* sprite)
 {
   assert(sprite != NULL);
@@ -676,7 +676,7 @@ void sprite_generate_mask_boundaries(Sprite* sprite)
   }
 }
 
-Layer *sprite_index2layer(const Sprite* sprite, int index)
+Layer* sprite_index2layer(const Sprite* sprite, int index)
 {
   int index_count = -1;
   assert(sprite != NULL);
diff --git a/src/raster/sprite.h b/src/raster/sprite.h
index 1e1c1b30d..e69260c27 100644
--- a/src/raster/sprite.h
+++ b/src/raster/sprite.h
@@ -78,9 +78,14 @@ private:
   JMutex m_mutex;
 
   /**
-   * Greater than zero when a thread is reading/writing the sprite.
+   * True if some thread is writing the sprite.
    */
-  int m_locked;
+  bool m_write_lock;
+
+  /**
+   * Greater than zero when one or more threads are reading the sprite.
+   */
+  int m_read_locks;
 
 public:
 
@@ -92,7 +97,9 @@ public:
   Sprite(int imgtype, int w, int h);
   virtual ~Sprite();
 
-  bool lock();
+  bool lock(bool write);
+  bool lock_to_write();
+  void unlock_to_read();
   void unlock();
 };
 
@@ -110,6 +117,7 @@ bool sprite_need_alpha(const Sprite* sprite);
 Palette* sprite_get_palette(const Sprite* sprite, int frame);
 void sprite_set_palette(Sprite* sprite, Palette* pal, bool truncate);
 void sprite_reset_palettes(Sprite* sprite);
+void sprite_delete_palette(Sprite* sprite, Palette* pal);
 
 void sprite_set_filename(Sprite* sprite, const char* filename);
 void sprite_set_format_options(Sprite* sprite, FormatOptions* format_options);
@@ -122,7 +130,6 @@ void sprite_set_path(Sprite* sprite, const Path* path);
 void sprite_set_mask(Sprite* sprite, const Mask* mask);
 void sprite_set_layer(Sprite* sprite, Layer* layer);
 void sprite_set_frame(Sprite* sprite, int frame);
-void sprite_set_imgtype(Sprite* sprite, int imgtype, int dithering_method);
 
 Layer* sprite_get_background_layer(const Sprite* sprite);
 
diff --git a/src/raster/undo.cpp b/src/raster/undo.cpp
index f6fb5dd4b..e01f69b1f 100644
--- a/src/raster/undo.cpp
+++ b/src/raster/undo.cpp
@@ -31,6 +31,7 @@
 #include "raster/image.h"
 #include "raster/layer.h"
 #include "raster/mask.h"
+#include "raster/palette.h"
 #include "raster/sprite.h"
 #include "raster/stock.h"
 #include "raster/undo.h"
@@ -41,35 +42,39 @@ enum {
   DO_REDO,
 };
 
-/* undo types */
+// undo types
 enum {
-  /* group */
+  // group
   UNDO_TYPE_OPEN,
   UNDO_TYPE_CLOSE,
 
-  /* data management */
+  // data management
   UNDO_TYPE_DATA,
 
-  /* image management */
+  // image management
   UNDO_TYPE_IMAGE,
   UNDO_TYPE_FLIP,
   UNDO_TYPE_DIRTY,
 
-  /* stock management */
+  // stock management
   UNDO_TYPE_ADD_IMAGE,
   UNDO_TYPE_REMOVE_IMAGE,
   UNDO_TYPE_REPLACE_IMAGE,
 
-  /* cel management */
+  // cel management
   UNDO_TYPE_ADD_CEL,
   UNDO_TYPE_REMOVE_CEL,
 
-  /* layer management */
+  // layer management
   UNDO_TYPE_ADD_LAYER,
   UNDO_TYPE_REMOVE_LAYER,
   UNDO_TYPE_MOVE_LAYER,
   UNDO_TYPE_SET_LAYER,
 
+  // palette management
+  UNDO_TYPE_ADD_PALETTE,
+  UNDO_TYPE_REMOVE_PALETTE,
+
   /* misc */
   UNDO_TYPE_SET_MASK,
   UNDO_TYPE_SET_FRAMES,
@@ -89,6 +94,8 @@ typedef struct UndoChunkAddLayer UndoChunkAddLayer;
 typedef struct UndoChunkRemoveLayer UndoChunkRemoveLayer;
 typedef struct UndoChunkMoveLayer UndoChunkMoveLayer;
 typedef struct UndoChunkSetLayer UndoChunkSetLayer;
+typedef struct UndoChunkAddPalette UndoChunkAddPalette;
+typedef struct UndoChunkRemovePalette UndoChunkRemovePalette;
 typedef struct UndoChunkSetMask UndoChunkSetMask;
 typedef struct UndoChunkSetFrames UndoChunkSetFrames;
 typedef struct UndoChunkSetFrlen UndoChunkSetFrlen;
@@ -166,6 +173,12 @@ static void chunk_move_layer_invert(UndoStream* stream, UndoChunkMoveLayer* chun
 static void chunk_set_layer_new(UndoStream* stream, Sprite *sprite);
 static void chunk_set_layer_invert(UndoStream* stream, UndoChunkSetLayer* chunk, int state);
 
+static void chunk_add_palette_new(UndoStream* stream, Sprite *sprite, Palette* palette);
+static void chunk_add_palette_invert(UndoStream* stream, UndoChunkAddPalette *chunk, int state);
+
+static void chunk_remove_palette_new(UndoStream* stream, Sprite *sprite, Palette* palette);
+static void chunk_remove_palette_invert(UndoStream* stream, UndoChunkRemovePalette *chunk, int state);
+
 static void chunk_set_mask_new(UndoStream* stream, Sprite *sprite);
 static void chunk_set_mask_invert(UndoStream* stream, UndoChunkSetMask* chunk, int state);
 
@@ -195,9 +208,11 @@ static UndoAction undo_actions[] = {
   DECL_UNDO_ACTION(remove_layer),
   DECL_UNDO_ACTION(move_layer),
   DECL_UNDO_ACTION(set_layer),
+  DECL_UNDO_ACTION(add_palette),
+  DECL_UNDO_ACTION(remove_palette),
   DECL_UNDO_ACTION(set_mask),
   DECL_UNDO_ACTION(set_frames),
-  DECL_UNDO_ACTION(set_frlen)
+  DECL_UNDO_ACTION(set_frlen),
 };
 
 /* UndoChunk */
@@ -223,6 +238,10 @@ static Layer* read_raw_layer(ase_uint8* raw_data);
 static ase_uint8* write_raw_layer(ase_uint8* raw_data, Layer* layer);
 static int get_raw_layer_size(Layer* layer);
 
+static Palette* read_raw_palette(ase_uint8* raw_data);
+static ase_uint8* write_raw_palette(ase_uint8* raw_data, Palette* palette);
+static int get_raw_palette_size(Palette* palette);
+
 static Mask* read_raw_mask(ase_uint8* raw_data);
 static ase_uint8* write_raw_mask(ase_uint8* raw_data, Mask* mask);
 static int get_raw_mask_size(Mask* mask);
@@ -1216,10 +1235,11 @@ static void chunk_move_layer_invert(UndoStream* stream, UndoChunkMoveLayer* chun
   Layer* layer = (Layer* )gfxobj_find(chunk->layer_id);
   Layer* after = (Layer* )gfxobj_find(chunk->after_id);
 
-  if (set && layer) {
-    chunk_move_layer_new(stream, layer);
-    layer_move_layer(set, layer, after);
-  }
+  if (set == NULL || layer == NULL)
+    throw undo_exception("chunk_move_layer_invert");
+
+  chunk_move_layer_new(stream, layer);
+  layer_move_layer(set, layer, after);
 }
 
 /***********************************************************************
@@ -1260,11 +1280,104 @@ static void chunk_set_layer_invert(UndoStream* stream, UndoChunkSetLayer* chunk,
   Sprite *sprite = (Sprite *)gfxobj_find(chunk->sprite_id);
   Layer* layer = (Layer* )gfxobj_find(chunk->layer_id);
 
-  if (sprite) {
-    chunk_set_layer_new(stream, sprite);
+  if (sprite == NULL)
+    throw undo_exception("chunk_set_layer_invert");
 
-    sprite->layer = layer;
-  }
+  chunk_set_layer_new(stream, sprite);
+
+  sprite->layer = layer;
+}
+
+/***********************************************************************
+
+  "add_palette"
+
+     DWORD		sprite ID
+     DWORD		palette ID
+
+***********************************************************************/
+
+struct UndoChunkAddPalette
+{
+  UndoChunk head;
+  ase_uint32 sprite_id;
+  ase_uint32 palette_id;
+};
+
+void undo_add_palette(Undo* undo, Sprite *sprite, Palette* palette)
+{
+  chunk_add_palette_new(undo->undo_stream, sprite, palette);
+  update_undo(undo);
+}
+
+static void chunk_add_palette_new(UndoStream* stream, Sprite *sprite, Palette* palette)
+{
+  UndoChunkAddPalette* chunk = (UndoChunkAddPalette*)
+    undo_chunk_new(stream,
+		   UNDO_TYPE_ADD_PALETTE,
+		   sizeof(UndoChunkAddPalette));
+
+  chunk->sprite_id = sprite->id;
+  chunk->palette_id = palette->id;
+}
+
+static void chunk_add_palette_invert(UndoStream* stream, UndoChunkAddPalette *chunk, int state)
+{
+  Sprite* sprite = (Sprite*)gfxobj_find(chunk->sprite_id);
+  Palette* palette = (Palette*)gfxobj_find(chunk->palette_id);
+
+  if (sprite == NULL || palette == NULL)
+    throw undo_exception("chunk_add_palette_invert");
+
+  chunk_remove_palette_new(stream, sprite, palette);
+  sprite_delete_palette(sprite, palette);
+}
+
+/***********************************************************************
+
+  "remove_palette"
+
+     DWORD		sprite ID
+     PALETTE_DATA	see read/write_raw_palette
+
+***********************************************************************/
+
+struct UndoChunkRemovePalette
+{
+  UndoChunk head;
+  ase_uint32 sprite_id;
+  ase_uint8 data[0];
+};
+
+void undo_remove_palette(Undo* undo, Sprite *sprite, Palette* palette)
+{
+  chunk_remove_palette_new(undo->undo_stream, sprite, palette);
+  update_undo(undo);
+}
+
+static void chunk_remove_palette_new(UndoStream* stream, Sprite *sprite, Palette* palette)
+{
+  UndoChunkRemovePalette* chunk = (UndoChunkRemovePalette*)
+    undo_chunk_new(stream,
+		   UNDO_TYPE_REMOVE_PALETTE,
+		   sizeof(UndoChunkRemovePalette)+get_raw_palette_size(palette));
+
+  chunk->sprite_id = sprite->id;
+  write_raw_palette(chunk->data, palette);
+}
+
+static void chunk_remove_palette_invert(UndoStream* stream, UndoChunkRemovePalette *chunk, int state)
+{
+  Sprite *sprite = (Sprite *)gfxobj_find(chunk->sprite_id);
+  if (sprite == NULL)
+    throw undo_exception("chunk_remove_palette_invert");
+
+  Palette* palette = read_raw_palette(chunk->data);
+
+  chunk_add_palette_new(stream, sprite, palette);
+  sprite_set_palette(sprite, palette, true);
+
+  palette_free(palette);
 }
 
 /***********************************************************************
@@ -1383,13 +1496,13 @@ void undo_set_frlen(Undo* undo, Sprite *sprite, int frame)
 
 static void chunk_set_frlen_new(UndoStream* stream, Sprite *sprite, int frame)
 {
+  assert(frame >= 0 && frame < sprite->frames);
+
   UndoChunkSetFrlen *chunk = (UndoChunkSetFrlen *)
     undo_chunk_new(stream,
 		   UNDO_TYPE_SET_FRLEN,
 		   sizeof(UndoChunkSetFrlen));
 
-  assert(frame >= 0 && frame < sprite->frames);
-
   chunk->sprite_id = sprite->id;
   chunk->frame = frame;
   chunk->frlen = sprite->frlens[frame];
@@ -1930,6 +2043,64 @@ static int get_raw_layer_size(Layer* layer)
   return size;
 }
 
+/***********************************************************************
+
+  Raw palette data
+
+      WORD		frame
+      WORD		ncolors
+      for each color	("ncolors" times)
+        DWORD		_rgba color
+
+***********************************************************************/
+
+static Palette* read_raw_palette(ase_uint8* raw_data)
+{
+  ase_uint32 dword;
+  ase_uint16 word;
+  ase_uint32 color;
+  int frame, ncolors;
+  Palette* palette;
+
+  read_raw_uint16(frame);	/* frame */
+  read_raw_uint16(ncolors);	/* ncolors */
+
+  palette = palette_new(frame, ncolors);
+  if (!palette)
+    return NULL;
+
+  for (int c=0; c<ncolors; c++) {
+    read_raw_uint32(color);
+    palette_set_entry(palette, c, color);
+  }
+
+  return palette;
+}
+
+static ase_uint8* write_raw_palette(ase_uint8* raw_data, Palette* palette)
+{
+  ase_uint32 dword;
+  ase_uint16 word;
+  ase_uint32 color;
+
+  write_raw_uint16(palette->frame);	/* frame */
+  write_raw_uint16(palette->ncolors);	/* ncolors*/
+
+  for (int c=0; c<palette->ncolors; c++) {
+    color = palette_get_entry(palette, c);
+    write_raw_uint32(color);
+  }
+
+  return raw_data;
+}
+
+static int get_raw_palette_size(Palette* palette)
+{
+  // 2 WORD + 4 BYTES*ncolors
+  return 2*2 + 4*palette->ncolors;
+}
+
+
 /***********************************************************************
 
   Raw mask data
diff --git a/src/raster/undo.h b/src/raster/undo.h
index 12f9050f6..4f43eea39 100644
--- a/src/raster/undo.h
+++ b/src/raster/undo.h
@@ -22,6 +22,7 @@
 #include <string.h>		/* for strlen */
 
 #include "raster/gfxobj.h"
+#include "ase_exception.h"
 
 class Cel;
 class Image;
@@ -33,6 +34,12 @@ class Stock;
 struct Dirty;
 struct UndoStream;
 
+class undo_exception : public ase_exception
+{
+public:
+  undo_exception(const char* msg) throw() : ase_exception(msg) { }
+};
+
 class Undo : public GfxObj
 {
 public:
@@ -87,6 +94,8 @@ void undo_add_layer(Undo* undo, Layer *set, Layer *layer);
 void undo_remove_layer(Undo* undo, Layer *layer);
 void undo_move_layer(Undo* undo, Layer *layer);
 void undo_set_layer(Undo* undo, Sprite* sprite);
+void undo_add_palette(Undo* undo, Sprite* sprite, Palette* palette);
+void undo_remove_palette(Undo* undo, Sprite* sprite, Palette* palette);
 void undo_set_mask(Undo* undo, Sprite* sprite);
 void undo_set_frames(Undo* undo, Sprite* sprite);
 void undo_set_frlen(Undo* undo, Sprite* sprite, int frame);
diff --git a/src/sprite_wrappers.h b/src/sprite_wrappers.h
new file mode 100644
index 000000000..223e886f6
--- /dev/null
+++ b/src/sprite_wrappers.h
@@ -0,0 +1,248 @@
+/* ASE - Allegro Sprite Editor
+ * Copyright (C) 2001-2009  David Capello
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#ifndef SPRITE_WRAPPERS_H
+#define SPRITE_WRAPPERS_H
+
+#include <list>
+#include <exception>
+#include "ase_exception.h"
+#include "ase/ui_context.h"
+#include "raster/sprite.h"
+
+class Context;
+
+class locked_sprite_exception : public ase_exception
+{
+public:
+  locked_sprite_exception() throw()
+  : ase_exception("Cannot read/write the sprite.\n"
+		  "The sprite is locked by a background task.\n"
+		  "Try again later.") { }
+};
+
+//////////////////////////////////////////////////////////////////////
+
+/**
+ * Wraps a sprite.
+ */
+class SpriteWrapper
+{
+protected:
+  Sprite* m_sprite;
+
+public:
+  SpriteWrapper() : m_sprite(NULL) { }
+  SpriteWrapper(const SpriteWrapper& copy) : m_sprite(copy.m_sprite) { }
+  explicit SpriteWrapper(Sprite* sprite) : m_sprite(sprite) { }
+  ~SpriteWrapper() { }
+
+  SpriteWrapper& operator=(const SpriteWrapper& copy) {
+    m_sprite = copy.m_sprite;
+    return *this;
+  }
+
+  operator Sprite* () { return m_sprite; }
+  operator const Sprite* () const { return m_sprite; }
+
+  Sprite* operator->() {
+    assert(m_sprite != NULL);
+    return m_sprite;
+  }
+
+  const Sprite* operator->() const {
+    assert(m_sprite != NULL);
+    return m_sprite;
+  }
+
+};
+
+/**
+ * Class to view the sprite's state.
+ */
+class SpriteReader : public SpriteWrapper
+{
+public:
+
+  SpriteReader()
+  {
+  }
+
+  explicit SpriteReader(Sprite* sprite)
+    : SpriteWrapper(sprite)
+  {
+    if (m_sprite && !m_sprite->lock(false))
+      throw locked_sprite_exception();
+  }
+
+  explicit SpriteReader(const SpriteReader& copy)
+    : SpriteWrapper(copy)
+  {
+    if (m_sprite && !m_sprite->lock(false))
+      throw locked_sprite_exception();
+  }
+
+  SpriteReader& operator=(const SpriteReader& copy)
+  {
+    // unlock old sprite
+    if (m_sprite)
+      m_sprite->unlock();
+
+    SpriteWrapper::operator=(copy);
+
+    // relock the sprite
+    if (m_sprite && !m_sprite->lock(false))
+      throw locked_sprite_exception();
+
+    return *this;
+  }
+
+  ~SpriteReader() {
+    // unlock the sprite
+    if (m_sprite)
+      m_sprite->unlock();
+  }
+
+};
+
+/**
+ * Class to modify the sprite's state.
+ */
+class SpriteWriter : public SpriteWrapper
+{
+  bool m_from_reader;
+  bool m_locked;
+
+  // Non-copyable
+  SpriteWriter(const SpriteWriter&);
+  SpriteWriter& operator=(const SpriteWriter&);
+
+public:
+
+  SpriteWriter()
+    : m_from_reader(false)
+    , m_locked(false)
+  {
+  }
+
+  explicit SpriteWriter(Sprite* sprite)
+    : SpriteWrapper(sprite)
+    , m_from_reader(false)
+    , m_locked(false)
+  {
+    if (m_sprite) {
+      if (!m_sprite->lock(true))
+	throw locked_sprite_exception();
+
+      m_locked = true;
+    }
+  }
+
+  explicit SpriteWriter(const SpriteReader& sprite)
+    : SpriteWrapper(sprite)
+    , m_from_reader(true)
+    , m_locked(false)
+  {
+    if (m_sprite) {
+      if (!m_sprite->lock_to_write())
+	throw locked_sprite_exception();
+
+      m_locked = true;
+    }
+  }
+
+  ~SpriteWriter() {
+    unlock_writer();
+  }
+
+  SpriteWriter& operator=(const SpriteReader& copy)
+  {
+    unlock_writer();
+
+    SpriteWrapper::operator=(copy);
+
+    m_locked = false;
+    if (m_sprite) {
+      m_from_reader = true;
+
+      if (!m_sprite->lock_to_write())
+	throw locked_sprite_exception();
+
+      m_locked = true;
+    }
+
+    return *this;
+  }
+
+protected:
+
+  void unlock_writer()
+  {
+    if (m_sprite && m_locked) {
+      if (m_from_reader)
+	m_sprite->unlock_to_read();
+      else
+	m_sprite->unlock();
+    }
+  }
+
+};
+
+class CurrentSpriteReader : public SpriteReader
+{
+public:
+
+  CurrentSpriteReader(Context* context = UIContext::instance())
+    : SpriteReader(context->get_current_sprite())
+  {
+  }
+
+  ~CurrentSpriteReader() {
+  }
+
+};
+
+class CurrentSpriteWriter : public SpriteWriter
+{
+  Context* m_context;
+
+public:
+
+  CurrentSpriteWriter(Context* context = UIContext::instance())
+    : SpriteWriter(context->get_current_sprite())
+    , m_context(context)
+  {
+  }
+
+  ~CurrentSpriteWriter() {
+  }
+
+  void destroy()
+  {
+    assert(m_sprite != NULL);
+
+    m_context->remove_sprite(m_sprite);
+    unlock_writer();
+
+    delete m_sprite;
+    m_sprite = NULL;
+  }
+
+};
+
+#endif // SPRITE_WRAPPERS_H
diff --git a/src/raster/undoable.cpp b/src/undoable.cpp
similarity index 55%
rename from src/raster/undoable.cpp
rename to src/undoable.cpp
index 1b81dd2bb..8bb6a7421 100644
--- a/src/raster/undoable.cpp
+++ b/src/undoable.cpp
@@ -23,15 +23,19 @@
 
 #include "jinete/jlist.h"
 
+#include "sprite_wrappers.h"
 #include "raster/blend.h"
 #include "raster/cel.h"
+#include "raster/dirty.h"
 #include "raster/image.h"
 #include "raster/layer.h"
 #include "raster/mask.h"
+#include "raster/palette.h"
+#include "raster/quant.h"
 #include "raster/sprite.h"
 #include "raster/stock.h"
 #include "raster/undo.h"
-#include "raster/undoable.h"
+#include "undoable.h"
 
 /**
  * Starts a undoable sequence of operations.
@@ -39,18 +43,17 @@
  * All the operations will be grouped in the sprite's undo as an
  * atomic operation.
  */
-Undoable::Undoable(Sprite* sprite, const char* label)
+Undoable::Undoable(SpriteWriter& sprite, const char* label)
 {
-  assert(sprite);
-  assert(label);
+  assert(label != NULL);
 
-  this->sprite = sprite;
-  committed = false;
-  enabled_flag = undo_is_enabled(sprite->undo);
+  m_sprite = sprite;
+  m_committed = false;
+  m_enabled_flag = undo_is_enabled(m_sprite->undo);
 
   if (is_enabled()) {
-    undo_set_label(sprite->undo, label);
-    undo_open(sprite->undo);
+    undo_set_label(m_sprite->undo, label);
+    undo_open(m_sprite->undo);
   }
 }
 
@@ -58,16 +61,16 @@ Undoable::~Undoable()
 {
   if (is_enabled()) {
     // close the undo information
-    undo_close(sprite->undo);
+    undo_close(m_sprite->undo);
 
     // if it isn't committed, we have to rollback all changes
-    if (!committed) {
+    if (!m_committed) {
       // undo the group of operations
-      undo_do_undo(sprite->undo);
+      undo_do_undo(m_sprite->undo);
 
       // clear the redo (sorry to the user, here we lost the old redo
       // information)
-      undo_clear_redo(sprite->undo);
+      undo_clear_redo(m_sprite->undo);
     }
   }
 }
@@ -81,7 +84,7 @@ Undoable::~Undoable()
  */
 void Undoable::commit()
 {
-  committed = true;
+  m_committed = true;
 }
 
 void Undoable::set_number_of_frames(int frames)
@@ -90,9 +93,9 @@ void Undoable::set_number_of_frames(int frames)
 
   // increment frames counter in the sprite
   if (is_enabled())
-    undo_set_frames(sprite->undo, sprite);
+    undo_set_frames(m_sprite->undo, m_sprite);
 
-  sprite_set_frames(sprite, frames);
+  sprite_set_frames(m_sprite, frames);
 }
 
 void Undoable::set_current_frame(int frame)
@@ -100,9 +103,9 @@ void Undoable::set_current_frame(int frame)
   assert(frame >= 0);
 
   if (is_enabled())
-    undo_int(sprite->undo, sprite, &sprite->frame);
+    undo_int(m_sprite->undo, m_sprite, &m_sprite->frame);
 
-  sprite_set_frame(sprite, frame);
+  sprite_set_frame(m_sprite, frame);
 }
 
 /**
@@ -114,9 +117,9 @@ void Undoable::set_current_frame(int frame)
 void Undoable::set_current_layer(Layer* layer)
 {
   if (is_enabled())
-    undo_set_layer(sprite->undo, sprite);
+    undo_set_layer(m_sprite->undo, m_sprite);
 
-  sprite_set_layer(sprite, layer);
+  sprite_set_layer(m_sprite, layer);
 }
 
 void Undoable::set_sprite_size(int w, int h)
@@ -125,41 +128,41 @@ void Undoable::set_sprite_size(int w, int h)
   assert(h > 0);
 
   if (is_enabled()) {
-    undo_int(sprite->undo, sprite, &sprite->w);
-    undo_int(sprite->undo, sprite, &sprite->h);
+    undo_int(m_sprite->undo, m_sprite, &m_sprite->w);
+    undo_int(m_sprite->undo, m_sprite, &m_sprite->h);
   }
 
-  sprite_set_size(sprite, w, h);
+  sprite_set_size(m_sprite, w, h);
 }
 
 void Undoable::crop_sprite(int x, int y, int w, int h, int bgcolor)
 {
   set_sprite_size(w, h);
 
-  displace_layers(sprite->set, -x, -y);
+  displace_layers(m_sprite->set, -x, -y);
 
-  Layer *background_layer = sprite_get_background_layer(sprite);
+  Layer *background_layer = sprite_get_background_layer(m_sprite);
   if (background_layer)
-    crop_layer(background_layer, 0, 0, sprite->w, sprite->h, bgcolor);
+    crop_layer(background_layer, 0, 0, m_sprite->w, m_sprite->h, bgcolor);
 
-  if (!mask_is_empty(sprite->mask))
-    set_mask_position(sprite->mask->x-x, sprite->mask->y-y);
+  if (!mask_is_empty(m_sprite->mask))
+    set_mask_position(m_sprite->mask->x-x, m_sprite->mask->y-y);
 }
 
 void Undoable::autocrop_sprite(int bgcolor)
 {
-  int old_frame = sprite->frame;
+  int old_frame = m_sprite->frame;
   int x1, y1, x2, y2;
   int u1, v1, u2, v2;
 
   x1 = y1 = INT_MAX;
   x2 = y2 = INT_MIN;
 
-  Image* image = image_new(sprite->imgtype, sprite->w, sprite->h);
+  Image* image = image_new(m_sprite->imgtype, m_sprite->w, m_sprite->h);
 
-  for (sprite->frame=0; sprite->frame<sprite->frames; sprite->frame++) {
+  for (m_sprite->frame=0; m_sprite->frame<m_sprite->frames; m_sprite->frame++) {
     image_clear(image, 0);
-    sprite_render(sprite, image, 0, 0);
+    sprite_render(m_sprite, image, 0, 0);
 
     // TODO configurable (what color pixel to use as "refpixel",
     // here we are using the top-left pixel by default)
@@ -171,7 +174,7 @@ void Undoable::autocrop_sprite(int bgcolor)
       y2 = MAX(y2, v2);
     }
   }
-  sprite->frame = old_frame;
+  m_sprite->frame = old_frame;
 
   image_free(image);
 
@@ -182,6 +185,79 @@ void Undoable::autocrop_sprite(int bgcolor)
   crop_sprite(x1, y1, x2-x1+1, y2-y1+1, bgcolor);
 }
 
+/**
+ * @warning: it uses the current Allegro "rgb_map"
+ */
+void Undoable::set_imgtype(int new_imgtype, int dithering_method)
+{
+  Image *old_image;
+  Image *new_image;
+  int c;
+
+  if (m_sprite->imgtype == new_imgtype)
+    return;
+
+  /* change imgtype of the stock of images */
+  if (is_enabled())
+    undo_int(m_sprite->undo, (GfxObj *)m_sprite->stock, &m_sprite->stock->imgtype);
+
+  m_sprite->stock->imgtype = new_imgtype;
+
+  for (c=0; c<m_sprite->stock->nimage; c++) {
+    old_image = stock_get_image(m_sprite->stock, c);
+    if (!old_image)
+      continue;
+
+    new_image = image_set_imgtype(old_image, new_imgtype, dithering_method,
+				  rgb_map,
+				  /* TODO check this out */
+				  sprite_get_palette(m_sprite,
+						     m_sprite->frame));
+    if (!new_image)
+      return;		/* TODO error handling: not enough memory!
+			   we should undo all work done */
+
+    if (is_enabled())
+      undo_replace_image(m_sprite->undo, m_sprite->stock, c);
+
+    image_free(old_image);
+    stock_replace_image(m_sprite->stock, c, new_image);
+  }
+
+  /* change "sprite.imgtype" field */
+  if (is_enabled())
+    undo_int(m_sprite->undo, m_sprite, &m_sprite->imgtype);
+
+  m_sprite->imgtype = new_imgtype;
+
+  // change "sprite.palette"
+  if (new_imgtype == IMAGE_GRAYSCALE) {
+    if (is_enabled()) {
+      Palette* palette;
+      JLink link;
+
+      JI_LIST_FOR_EACH(m_sprite->palettes, link) {
+	if (jlist_first(m_sprite->palettes) != link) {
+	  palette = reinterpret_cast<Palette*>(link->data);
+	  undo_remove_palette(m_sprite->undo, m_sprite, palette);
+	}
+      }
+
+      palette = sprite_get_palette(m_sprite, 0);
+      undo_data(m_sprite->undo, palette, palette->color, sizeof(palette->color));
+    }
+
+    Palette* graypal = palette_new(0, MAX_PALETTE_COLORS);
+    for (int c=0; c<256; c++)
+      palette_set_entry(graypal, c, _rgba(c, c, c, 255));
+
+    sprite_reset_palettes(m_sprite);
+    sprite_set_palette(m_sprite, graypal, false);
+
+    palette_free(graypal);
+  }
+}
+
 /**
  * Adds a new image in the stock.
  *
@@ -193,10 +269,10 @@ int Undoable::add_image_in_stock(Image* image)
   assert(image);
 
   // add the image in the stock
-  int image_index = stock_add_image(sprite->stock, image);
+  int image_index = stock_add_image(m_sprite->stock, image);
 
   if (is_enabled())
-    undo_add_image(sprite->undo, sprite->stock, image_index);
+    undo_add_image(m_sprite->undo, m_sprite->stock, image_index);
 
   return image_index;
 }
@@ -208,27 +284,27 @@ void Undoable::remove_image_from_stock(int image_index)
 {
   assert(image_index >= 0);
 
-  Image* image = stock_get_image(sprite->stock, image_index);
+  Image* image = stock_get_image(m_sprite->stock, image_index);
   assert(image);
 
   if (is_enabled())
-    undo_remove_image(sprite->undo, sprite->stock, image_index);
+    undo_remove_image(m_sprite->undo, m_sprite->stock, image_index);
 
-  stock_remove_image(sprite->stock, image);
+  stock_remove_image(m_sprite->stock, image);
   image_free(image);
 }
 
 void Undoable::replace_stock_image(int image_index, Image* new_image)
 {
   // get the current image in the 'image_index' position
-  Image* old_image = stock_get_image(sprite->stock, image_index);
+  Image* old_image = stock_get_image(m_sprite->stock, image_index);
   assert(old_image);
 
   // replace the image in the stock
   if (is_enabled())
-    undo_replace_image(sprite->undo, sprite->stock, image_index);
+    undo_replace_image(m_sprite->undo, m_sprite->stock, image_index);
 
-  stock_replace_image(sprite->stock, image_index, new_image);
+  stock_replace_image(m_sprite->stock, image_index, new_image);
 
   // destroy the old image
   image_free(old_image);
@@ -240,15 +316,15 @@ void Undoable::replace_stock_image(int image_index, Image* new_image)
 Layer* Undoable::new_layer()
 {
   // new layer
-  Layer* layer = layer_new(sprite);
+  Layer* layer = layer_new(m_sprite);
 
   // configure layer name and blend mode
   layer_set_blend_mode(layer, BLEND_MODE_NORMAL);
 
   // add the layer in the sprite set
   if (is_enabled())
-    undo_add_layer(sprite->undo, sprite->set, layer);
-  layer_add_layer(sprite->set, layer);
+    undo_add_layer(m_sprite->undo, m_sprite->set, layer);
+  layer_add_layer(m_sprite->set, layer);
 
   // select the new layer
   set_current_layer(layer);
@@ -266,7 +342,7 @@ void Undoable::remove_layer(Layer* layer)
   Layer* parent = layer->parent_layer;
 
   // if the layer to be removed is the selected layer
-  if (layer == sprite->layer) {
+  if (layer == m_sprite->layer) {
     Layer* layer_select = NULL;
 
     // select: previous layer, or next layer, or parent(if it is not the
@@ -275,7 +351,7 @@ void Undoable::remove_layer(Layer* layer)
       layer_select = layer_get_prev(layer);
     else if (layer_get_next(layer))
       layer_select = layer_get_next(layer);
-    else if (parent != sprite->set)
+    else if (parent != m_sprite->set)
       layer_select = parent;
 
     // select other layer
@@ -284,7 +360,7 @@ void Undoable::remove_layer(Layer* layer)
 
   // remove the layer
   if (is_enabled())
-    undo_remove_layer(sprite->undo, layer);
+    undo_remove_layer(m_sprite->undo, layer);
 
   layer_remove_layer(parent, layer);
 
@@ -296,7 +372,7 @@ void Undoable::remove_layer(Layer* layer)
 void Undoable::move_layer_after(Layer* layer, Layer* after_this)
 {
   if (is_enabled())
-    undo_move_layer(sprite->undo, layer);
+    undo_move_layer(m_sprite->undo, layer);
 
   layer_move_layer(layer->parent_layer, layer, after_this);
 }
@@ -348,25 +424,26 @@ void Undoable::background_from_layer(Layer* layer, int bgcolor)
   assert(layer_is_image(layer));
   assert(layer_is_readable(layer));
   assert(layer_is_writable(layer));
-  assert(layer->sprite == sprite);
-  assert(sprite_get_background_layer(sprite) == NULL);
+  assert(layer->sprite == m_sprite);
+  assert(sprite_get_background_layer(m_sprite) == NULL);
 
   // create a temporary image to draw each frame of the new
   // `Background' layer
-  std::auto_ptr<Image> bg_image(image_new(sprite->imgtype, sprite->w, sprite->h));
+  std::auto_ptr<Image> bg_image_wrap(image_new(m_sprite->imgtype, m_sprite->w, m_sprite->h));
+  Image* bg_image = bg_image_wrap.get();
 
   JLink link;
   JI_LIST_FOR_EACH(layer->cels, link) {
     Cel* cel = reinterpret_cast<Cel*>(link->data);
     assert((cel->image > 0) &&
-	   (cel->image < sprite->stock->nimage));
+	   (cel->image < m_sprite->stock->nimage));
 
     // get the image from the sprite's stock of images
-    Image* cel_image = stock_get_image(sprite->stock, cel->image);
+    Image* cel_image = stock_get_image(m_sprite->stock, cel->image);
     assert(cel_image);
 
-    image_clear(bg_image.get(), bgcolor);
-    image_merge(bg_image.get(), cel_image,
+    image_clear(bg_image, bgcolor);
+    image_merge(bg_image, cel_image,
 		cel->x,
 		cel->y,
 		MID(0, cel->opacity, 255),
@@ -379,24 +456,139 @@ void Undoable::background_from_layer(Layer* layer, int bgcolor)
     if (bg_image->w == cel_image->w &&
 	bg_image->h == cel_image->h) {
       if (is_enabled())
-	undo_image(sprite->undo, cel_image, 0, 0, cel_image->w, cel_image->h);
+	undo_image(m_sprite->undo, cel_image, 0, 0, cel_image->w, cel_image->h);
 
-      image_copy(cel_image, bg_image.get(), 0, 0);
+      image_copy(cel_image, bg_image, 0, 0);
     }
     else {
-      replace_stock_image(cel->image, image_new_copy(bg_image.get()));
+      replace_stock_image(cel->image, image_new_copy(bg_image));
     }
   }
 
   configure_layer_as_background(layer);
 }
 
+void Undoable::layer_from_background()
+{
+  assert(sprite_get_background_layer(m_sprite) != NULL);
+  assert(m_sprite->layer != NULL);
+  assert(layer_is_image(m_sprite->layer));
+  assert(layer_is_readable(m_sprite->layer));
+  assert(layer_is_writable(m_sprite->layer));
+  assert(layer_is_background(m_sprite->layer));
+
+  if (is_enabled()) {
+    undo_data(m_sprite->undo,
+	      m_sprite->layer,
+	      &m_sprite->layer->flags,
+	      sizeof(m_sprite->layer->flags));
+
+    undo_data(m_sprite->undo,
+	      m_sprite->layer,
+	      &m_sprite->layer->name,
+	      LAYER_NAME_SIZE);
+  }
+
+  m_sprite->layer->flags &= ~(LAYER_IS_LOCKMOVE | LAYER_IS_BACKGROUND);
+  layer_set_name(m_sprite->layer, "Layer 0");
+}
+
+void Undoable::flatten_layers(int bgcolor)
+{
+  JLink link, next;
+  Layer *background;
+  Image *cel_image;
+  Cel *cel;
+  int frame;
+
+  // create a temporary image
+  std::auto_ptr<Image> image_wrap(image_new(m_sprite->imgtype, m_sprite->w, m_sprite->h));
+  Image* image = image_wrap.get();
+
+  /* get the background layer from the sprite */
+  background = sprite_get_background_layer(m_sprite);
+  if (!background) {
+    /* if there aren't a background layer we must to create the background */
+    background = layer_new(m_sprite);
+
+    if (is_enabled())
+      undo_add_layer(m_sprite->undo, m_sprite->set, background);
+
+    layer_add_layer(m_sprite->set, background);
+
+    if (is_enabled())
+      undo_move_layer(m_sprite->undo, background);
+    
+    layer_configure_as_background(background);
+  }
+
+  /* copy all frames to the background */
+  for (frame=0; frame<m_sprite->frames; frame++) {
+    /* clear the image and render this frame */
+    image_clear(image, bgcolor);
+    layer_render(m_sprite->set, image, 0, 0, frame);
+
+    cel = layer_get_cel(background, frame);
+    if (cel) {
+      cel_image = m_sprite->stock->image[cel->image];
+      assert(cel_image != NULL);
+
+      /* we have to save the current state of `cel_image' in the undo */
+      if (is_enabled()) {
+	Dirty* dirty = dirty_new_from_differences(cel_image, image);
+	dirty_save_image_data(dirty);
+	undo_dirty(m_sprite->undo, dirty);
+      }
+    }
+    else {
+      /* if there aren't a cel in this frame in the background, we
+	 have to create a copy of the image for the new cel */
+      cel_image = image_new_copy(image);
+      /* TODO error handling: if (!cel_image) { ... } */
+
+      /* here we create the new cel (with the new image `cel_image') */
+      cel = cel_new(frame, stock_add_image(m_sprite->stock, cel_image));
+      /* TODO error handling: if (!cel) { ... } */
+
+      /* and finally we add the cel in the background */
+      layer_add_cel(background, cel);
+    }
+
+    image_copy(cel_image, image, 0, 0);
+  }
+
+  /* select the background */
+  if (m_sprite->layer != background) {
+    if (is_enabled())
+      undo_set_layer(m_sprite->undo, m_sprite);
+
+    sprite_set_layer(m_sprite, background);
+  }
+
+  /* remove old layers */
+  JI_LIST_FOR_EACH_SAFE(m_sprite->set->layers, link, next) {
+    if (link->data != background) {
+      Layer* old_layer = reinterpret_cast<Layer*>(link->data);
+
+      /* remove the layer */
+      if (is_enabled())
+	undo_remove_layer(m_sprite->undo, old_layer);
+
+      layer_remove_layer(m_sprite->set, old_layer);
+
+      /* destroy the layer */
+      layer_free_images(old_layer);
+      layer_free(old_layer);
+    }
+  }
+}
+
 void Undoable::configure_layer_as_background(Layer* layer)
 {
   if (is_enabled()) {
-    undo_data(sprite->undo, (GfxObj *)layer, &layer->flags, sizeof(layer->flags));
-    undo_data(sprite->undo, (GfxObj *)layer, &layer->name, LAYER_NAME_SIZE);
-    undo_move_layer(sprite->undo, layer);
+    undo_data(m_sprite->undo, (GfxObj *)layer, &layer->flags, sizeof(layer->flags));
+    undo_data(m_sprite->undo, (GfxObj *)layer, &layer->name, LAYER_NAME_SIZE);
+    undo_move_layer(m_sprite->undo, layer);
   }
 
   layer_configure_as_background(layer);
@@ -405,14 +597,14 @@ void Undoable::configure_layer_as_background(Layer* layer)
 void Undoable::new_frame()
 {
   // add a new cel to every layer
-  new_frame_for_layer(sprite->set,
-		      sprite->frame+1);
+  new_frame_for_layer(m_sprite->set,
+		      m_sprite->frame+1);
 
   // increment frames counter in the sprite
-  set_number_of_frames(sprite->frames+1);
+  set_number_of_frames(m_sprite->frames+1);
 
   // go to next frame (the new one)
-  set_current_frame(sprite->frame+1);
+  set_current_frame(m_sprite->frame+1);
 }
 
 void Undoable::new_frame_for_layer(Layer* layer, int frame)
@@ -424,7 +616,7 @@ void Undoable::new_frame_for_layer(Layer* layer, int frame)
 
     case GFXOBJ_LAYER_IMAGE:
       // displace all cels in '>=frame' to the next frame
-      for (int c=sprite->frames-1; c>=frame; --c) {
+      for (int c=m_sprite->frames-1; c>=frame; --c) {
 	Cel* cel = layer_get_cel(layer, c);
 	if (cel)
 	  set_cel_frame_position(cel, cel->frame+1);
@@ -449,20 +641,20 @@ void Undoable::remove_frame(int frame)
 
   // remove cels from this frame (and displace one position backward
   // all next frames)
-  remove_frame_of_layer(sprite->set, frame);
+  remove_frame_of_layer(m_sprite->set, frame);
 
   /* decrement frames counter in the sprite */
   if (is_enabled())
-    undo_set_frames(sprite->undo, sprite);
+    undo_set_frames(m_sprite->undo, m_sprite);
 
-  sprite_set_frames(sprite, sprite->frames-1);
+  sprite_set_frames(m_sprite, m_sprite->frames-1);
 
   /* move backward if we are outside the range of frames */
-  if (sprite->frame >= sprite->frames) {
+  if (m_sprite->frame >= m_sprite->frames) {
     if (is_enabled())
-      undo_int(sprite->undo, sprite, &sprite->frame);
+      undo_int(m_sprite->undo, m_sprite, &m_sprite->frame);
 
-    sprite_set_frame(sprite, sprite->frames-1);
+    sprite_set_frame(m_sprite, m_sprite->frames-1);
   }
 }
 
@@ -477,7 +669,7 @@ void Undoable::remove_frame_of_layer(Layer* layer, int frame)
       if (Cel* cel = layer_get_cel(layer, frame))
 	remove_cel(layer, cel);
 
-      for (++frame; frame<sprite->frames; ++frame)
+      for (++frame; frame<m_sprite->frames; ++frame)
 	if (Cel* cel = layer_get_cel(layer, frame))
 	  set_cel_frame_position(cel, cel->frame-1);
       break;
@@ -502,7 +694,7 @@ void Undoable::copy_previous_frame(Layer* layer, int frame)
 
   // create a copy of the previous cel
   Cel* src_cel = layer_get_cel(layer, frame-1);
-  Image* src_image = src_cel ? stock_get_image(sprite->stock,
+  Image* src_image = src_cel ? stock_get_image(m_sprite->stock,
 					       src_cel->image):
 			       NULL;
 
@@ -532,7 +724,7 @@ void Undoable::add_cel(Layer* layer, Cel* cel)
   assert(layer_is_image(layer));
 
   if (is_enabled())
-    undo_add_cel(sprite->undo, layer, cel);
+    undo_add_cel(m_sprite->undo, layer, cel);
 
   layer_add_cel(layer, cel);
 }
@@ -546,7 +738,7 @@ void Undoable::remove_cel(Layer* layer, Cel* cel)
   // find if the image that use the cel to remove, is used by
   // another cels
   bool used = false;
-  for (int frame=0; frame<sprite->frames; ++frame) {
+  for (int frame=0; frame<m_sprite->frames; ++frame) {
     Cel* it = layer_get_cel(layer, frame);
     if (it && it != cel && it->image == cel->image) {
       used = true;
@@ -560,7 +752,7 @@ void Undoable::remove_cel(Layer* layer, Cel* cel)
     remove_image_from_stock(cel->image);
 
   if (is_enabled())
-    undo_remove_cel(sprite->undo, layer, cel);
+    undo_remove_cel(m_sprite->undo, layer, cel);
 
   // remove the cel from the layer
   layer_remove_cel(layer, cel);
@@ -575,7 +767,7 @@ void Undoable::set_cel_frame_position(Cel* cel, int frame)
   assert(frame >= 0);
 
   if (is_enabled())
-    undo_int(sprite->undo, cel, &cel->frame);
+    undo_int(m_sprite->undo, cel, &cel->frame);
 
   cel->frame = frame;
 }
@@ -585,8 +777,8 @@ void Undoable::set_cel_position(Cel* cel, int x, int y)
   assert(cel);
 
   if (is_enabled()) {
-    undo_int(sprite->undo, cel, &cel->x);
-    undo_int(sprite->undo, cel, &cel->y);
+    undo_int(m_sprite->undo, cel, &cel->x);
+    undo_int(m_sprite->undo, cel, &cel->y);
   }
 
   cel->x = x;
@@ -596,53 +788,53 @@ void Undoable::set_cel_position(Cel* cel, int x, int y)
 void Undoable::set_frame_duration(int frame, int msecs)
 {
   if (is_enabled())
-    undo_set_frlen(sprite->undo, sprite, frame);
+    undo_set_frlen(m_sprite->undo, m_sprite, frame);
 
-  sprite_set_frlen(sprite, frame, msecs);
+  sprite_set_frlen(m_sprite, frame, msecs);
 }
 
 void Undoable::set_constant_frame_rate(int msecs)
 {
   if (is_enabled()) {
-    for (int fr=0; fr<sprite->frames; ++fr)
-      undo_set_frlen(sprite->undo, sprite, fr);
+    for (int fr=0; fr<m_sprite->frames; ++fr)
+      undo_set_frlen(m_sprite->undo, m_sprite, fr);
   }
 
-  sprite_set_speed(sprite, msecs);
+  sprite_set_speed(m_sprite, msecs);
 }
 
 void Undoable::move_frame_before(int frame, int before_frame)
 {
   if (frame != before_frame &&
       frame >= 0 &&
-      frame < sprite->frames &&
+      frame < m_sprite->frames &&
       before_frame >= 0 &&
-      before_frame < sprite->frames) {
+      before_frame < m_sprite->frames) {
     // change the frame-lengths...
 
-    int frlen_aux = sprite->frlens[frame];
+    int frlen_aux = m_sprite->frlens[frame];
 
     // moving the frame to the future
     if (frame < before_frame) {
-      frlen_aux = sprite->frlens[frame];
+      frlen_aux = m_sprite->frlens[frame];
 
       for (int c=frame; c<before_frame-1; c++)
-	set_frame_duration(c, sprite->frlens[c+1]);
+	set_frame_duration(c, m_sprite->frlens[c+1]);
 
       set_frame_duration(before_frame-1, frlen_aux);
     }
     // moving the frame to the past
     else if (before_frame < frame) {
-      frlen_aux = sprite->frlens[frame];
+      frlen_aux = m_sprite->frlens[frame];
 
       for (int c=frame; c>before_frame; c--)
-	set_frame_duration(c, sprite->frlens[c-1]);
+	set_frame_duration(c, m_sprite->frlens[c-1]);
 
       set_frame_duration(before_frame, frlen_aux);
     }
 
     // change the cels of position...
-    move_frame_before_layer(sprite->set, frame, before_frame);
+    move_frame_before_layer(m_sprite->set, frame, before_frame);
   }
 }
 
@@ -697,15 +889,15 @@ void Undoable::move_frame_before_layer(Layer* layer, int frame, int before_frame
 
 Cel* Undoable::get_current_cel()
 {
-  if (sprite->layer && layer_is_image(sprite->layer))
-    return layer_get_cel(sprite->layer, sprite->frame);
+  if (m_sprite->layer && layer_is_image(m_sprite->layer))
+    return layer_get_cel(m_sprite->layer, m_sprite->frame);
   else
     return NULL;
 }
 
 void Undoable::crop_cel(Cel* cel, int x, int y, int w, int h, int bgcolor)
 {
-  Image* cel_image = stock_get_image(sprite->stock, cel->image);
+  Image* cel_image = stock_get_image(m_sprite->stock, cel->image);
   assert(cel_image);
     
   // create the new image through a crop
@@ -720,8 +912,8 @@ void Undoable::crop_cel(Cel* cel, int x, int y, int w, int h, int bgcolor)
 
 Image* Undoable::get_cel_image(Cel* cel)
 {
-  if (cel && cel->image >= 0 && cel->image < sprite->stock->nimage)
-    return sprite->stock->image[cel->image];
+  if (cel && cel->image >= 0 && cel->image < m_sprite->stock->nimage)
+    return m_sprite->stock->image[cel->image];
   else
     return NULL;
 }
@@ -739,11 +931,11 @@ void Undoable::clear_mask(int bgcolor)
 
   // if the mask is empty then we have to clear the entire image
   // in the cel
-  if (mask_is_empty(sprite->mask)) {
+  if (mask_is_empty(m_sprite->mask)) {
     // if the layer is the background then we clear the image
-    if (layer_is_background(sprite->layer)) {
+    if (layer_is_background(m_sprite->layer)) {
       if (is_enabled())
-	undo_image(sprite->undo, image, 0, 0, image->w, image->h);
+	undo_image(m_sprite->undo, image, 0, 0, image->w, image->h);
 
       // clear all
       image_clear(image, bgcolor);
@@ -751,32 +943,32 @@ void Undoable::clear_mask(int bgcolor)
     // if the layer is transparent we can remove the cel (and its
     // associated image)
     else {
-      remove_cel(sprite->layer, cel);
+      remove_cel(m_sprite->layer, cel);
     }
   }
   else {
     int u, v, putx, puty;
-    int x1 = MAX(0, sprite->mask->x);
-    int y1 = MAX(0, sprite->mask->y);
-    int x2 = MIN(image->w-1, sprite->mask->x+sprite->mask->w-1);
-    int y2 = MIN(image->h-1, sprite->mask->y+sprite->mask->h-1);
+    int x1 = MAX(0, m_sprite->mask->x);
+    int y1 = MAX(0, m_sprite->mask->y);
+    int x2 = MIN(image->w-1, m_sprite->mask->x+m_sprite->mask->w-1);
+    int y2 = MIN(image->h-1, m_sprite->mask->y+m_sprite->mask->h-1);
 
     // do nothing
     if (x1 > x2 || y1 > y2)
       return;
 
     if (is_enabled())
-      undo_image(sprite->undo, image, x1, y1, x2-x1+1, y2-y1+1);
+      undo_image(m_sprite->undo, image, x1, y1, x2-x1+1, y2-y1+1);
 
     // clear the masked zones
-    for (v=0; v<sprite->mask->h; v++) {
+    for (v=0; v<m_sprite->mask->h; v++) {
       div_t d = div(0, 8);
-      ase_uint8* address = ((ase_uint8 **)sprite->mask->bitmap->line)[v]+d.quot;
+      ase_uint8* address = ((ase_uint8 **)m_sprite->mask->bitmap->line)[v]+d.quot;
 
-      for (u=0; u<sprite->mask->w; u++) {
+      for (u=0; u<m_sprite->mask->w; u++) {
 	if ((*address & (1<<d.rem))) {
-	  putx = u + sprite->mask->x - cel->x;
-	  puty = v + sprite->mask->y - cel->y;
+	  putx = u + m_sprite->mask->x - cel->x;
+	  puty = v + m_sprite->mask->y - cel->y;
 	  image_putpixel(image, putx, puty, bgcolor);
 	}
 
@@ -788,25 +980,24 @@ void Undoable::clear_mask(int bgcolor)
 
 void Undoable::copy_to_current_mask(Mask* mask)
 {
-  assert(sprite->mask);
+  assert(m_sprite->mask);
   assert(mask);
 
   if (is_enabled())
-    undo_set_mask(sprite->undo, sprite);
+    undo_set_mask(m_sprite->undo, m_sprite);
 
-  mask_copy(sprite->mask, mask);
+  mask_copy(m_sprite->mask, mask);
 }
 
 void Undoable::set_mask_position(int x, int y)
 {
-  assert(sprite->mask);
+  assert(m_sprite->mask);
 
   if (is_enabled()) {
-    undo_int(sprite->undo, sprite->mask, &sprite->mask->x);
-    undo_int(sprite->undo, sprite->mask, &sprite->mask->y);
+    undo_int(m_sprite->undo, m_sprite->mask, &m_sprite->mask->x);
+    undo_int(m_sprite->undo, m_sprite->mask, &m_sprite->mask->y);
   }
 
-  sprite->mask->x = x;
-  sprite->mask->y = y;
+  m_sprite->mask->x = x;
+  m_sprite->mask->y = y;
 }
-
diff --git a/src/raster/undoable.h b/src/undoable.h
similarity index 86%
rename from src/raster/undoable.h
rename to src/undoable.h
index d97956244..93d1468c6 100644
--- a/src/raster/undoable.h
+++ b/src/undoable.h
@@ -16,11 +16,13 @@
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 
-#ifndef RASTER_UNDOABLE_H
-#define RASTER_UNDOABLE_H
+#ifndef UNDOABLE_H
+#define UNDOABLE_H
 
+class Cel;
 class Layer;
 class Sprite;
+class SpriteWriter;
 
 /**
  * Class with high-level set of routines to modify a sprite.
@@ -30,16 +32,16 @@ class Sprite;
  */
 class Undoable
 {
-  Sprite* sprite;
-  bool committed;
-  bool enabled_flag;
+  Sprite* m_sprite;
+  bool m_committed;
+  bool m_enabled_flag;
 
 public:
-  Undoable(Sprite* sprite, const char* label);
+  Undoable(SpriteWriter& sprite, const char* label);
   virtual ~Undoable();
 
-  inline Sprite* get_sprite() const { return sprite;  }
-  inline bool is_enabled() const { return enabled_flag; }
+  inline Sprite* get_sprite() const { return m_sprite;  }
+  inline bool is_enabled() const { return m_enabled_flag; }
 
   void commit();
 
@@ -50,6 +52,7 @@ public:
   void set_sprite_size(int w, int h);
   void crop_sprite(int x, int y, int w, int h, int bgcolor);
   void autocrop_sprite(int bgcolor);
+  void set_imgtype(int new_imgtype, int dithering_method);
 
   // for images in stock
   int add_image_in_stock(Image* image);
@@ -63,6 +66,8 @@ public:
   void crop_layer(Layer* layer, int x, int y, int w, int h, int bgcolor);
   void displace_layers(Layer* layer, int dx, int dy);
   void background_from_layer(Layer* layer, int bgcolor);
+  void layer_from_background();
+  void flatten_layers(int bgcolor);
 private:
   void configure_layer_as_background(Layer* layer);
 
@@ -96,4 +101,4 @@ public:
 
 };
 
-#endif /* RASTER_UNDOABLE_H */
+#endif // UNDOABLE_H
diff --git a/src/util/autocrop.cpp b/src/util/autocrop.cpp
index df4d8cd40..93b709717 100644
--- a/src/util/autocrop.cpp
+++ b/src/util/autocrop.cpp
@@ -22,7 +22,6 @@
 #include "raster/mask.h"
 #include "raster/sprite.h"
 #include "util/autocrop.h"
-#include "util/functions.h"
 
 bool get_shrink_rect(int *x1, int *y1, int *x2, int *y2,
 		     Image *image, int refpixel)
diff --git a/src/util/celmove.cpp b/src/util/celmove.cpp
index a94fbb894..0fc582886 100644
--- a/src/util/celmove.cpp
+++ b/src/util/celmove.cpp
@@ -21,6 +21,7 @@
 #include <assert.h>
 #include <jinete/jlist.h>
 
+#include "sprite_wrappers.h"
 #include "console/console.h"
 #include "core/app.h"
 #include "core/color.h"
@@ -35,7 +36,6 @@
 #include "raster/stock.h"
 #include "raster/undo.h"
 #include "util/celmove.h"
-#include "util/functions.h"
 
 /* these variables indicate what cel to move (and the sprite's
    frame indicates where to move it) */
@@ -44,6 +44,8 @@ static Layer *dst_layer = NULL;
 static int src_frame = 0;
 static int dst_frame = 0;
 
+static void remove_cel(Sprite* sprite, Layer *layer, Cel *cel);
+
 void set_frame_to_handle(Layer *_src_layer, int _src_frame,
 			 Layer *_dst_layer, int _dst_frame)
 {
@@ -53,7 +55,7 @@ void set_frame_to_handle(Layer *_src_layer, int _src_frame,
   dst_frame = _dst_frame;
 }
 
-void move_cel(Sprite* sprite)
+void move_cel(SpriteWriter& sprite)
 {
   Cel *src_cel, *dst_cel;
 
@@ -84,7 +86,7 @@ void move_cel(Sprite* sprite)
   /* remove the 'dst_cel' (if it exists) because it must be
      replaced with 'src_cel' */
   if ((dst_cel != NULL) && (!layer_is_background(dst_layer) || src_cel != NULL))
-    RemoveCel(dst_layer, dst_cel);
+    remove_cel(sprite, dst_layer, dst_cel);
 
   /* move the cel in the same layer */
   if (src_cel != NULL) {
@@ -144,7 +146,7 @@ void move_cel(Sprite* sprite)
   set_frame_to_handle(NULL, 0, NULL, 0);
 }
 
-void copy_cel(Sprite* sprite)
+void copy_cel(SpriteWriter& sprite)
 {
   Cel *src_cel, *dst_cel;
 
@@ -170,7 +172,7 @@ void copy_cel(Sprite* sprite)
   /* remove the 'dst_cel' (if it exists) because it must be
      replaced with 'src_cel' */
   if ((dst_cel != NULL) && (!layer_is_background(dst_layer) || src_cel != NULL))
-    RemoveCel(dst_layer, dst_cel);
+    remove_cel(sprite, dst_layer, dst_cel);
 
   /* move the cel in the same layer */
   if (src_cel != NULL) {
@@ -226,3 +228,48 @@ void copy_cel(Sprite* sprite)
 
   set_frame_to_handle(NULL, 0, NULL, 0);
 }
+
+static void remove_cel(Sprite* sprite, Layer *layer, Cel *cel)
+{
+  Image *image;
+  Cel *it;
+  int frame;
+  bool used;
+
+  if (sprite != NULL && layer_is_image(layer) && cel != NULL) {
+    /* find if the image that use the cel to remove, is used by
+       another cels */
+    used = FALSE;
+    for (frame=0; frame<sprite->frames; ++frame) {
+      it = layer_get_cel(layer, frame);
+      if (it != NULL && it != cel && it->image == cel->image) {
+	used = TRUE;
+	break;
+      }
+    }
+
+    if (undo_is_enabled(sprite->undo))
+      undo_open(sprite->undo);
+
+    if (!used) {
+      /* if the image is only used by this cel, we can remove the
+	 image from the stock */
+      image = stock_get_image(sprite->stock, cel->image);
+
+      if (undo_is_enabled(sprite->undo))
+	undo_remove_image(sprite->undo, sprite->stock, cel->image);
+
+      stock_remove_image(sprite->stock, image);
+      image_free(image);
+    }
+
+    if (undo_is_enabled(sprite->undo)) {
+      undo_remove_cel(sprite->undo, layer, cel);
+      undo_close(sprite->undo);
+    }
+
+    /* remove the cel */
+    layer_remove_cel(layer, cel);
+    cel_free(cel);
+  }
+}
diff --git a/src/util/celmove.h b/src/util/celmove.h
index 1f7b18253..4f67da34e 100644
--- a/src/util/celmove.h
+++ b/src/util/celmove.h
@@ -22,12 +22,13 @@
 class Cel;
 class Layer;
 class Sprite;
+class SpriteWriter;
 
 void set_frame_to_handle(Layer* src_layer, int src_frame,
 			 Layer* dst_layer, int dst_frame);
 
-void move_cel(Sprite* sprite);
-void copy_cel(Sprite* sprite);
+void move_cel(SpriteWriter& sprite);
+void copy_cel(SpriteWriter& sprite);
 
-#endif /* UTIL_CELMOVE_H */
+#endif // UTIL_CELMOVE_H
 
diff --git a/src/util/clipboard.cpp b/src/util/clipboard.cpp
index ff5c6a6cf..754f20e62 100644
--- a/src/util/clipboard.cpp
+++ b/src/util/clipboard.cpp
@@ -24,6 +24,7 @@
 
 #include "jinete/jinete.h"
 
+#include "sprite_wrappers.h"
 #include "console/console.h"
 #include "core/app.h"
 #include "core/core.h"
@@ -37,11 +38,12 @@
 #include "raster/image.h"
 #include "raster/layer.h"
 #include "raster/palette.h"
+#include "raster/quant.h"
 #include "raster/rotate.h"
 #include "raster/sprite.h"
 #include "raster/stock.h"
-#include "raster/undoable.h"
 #include "raster/undo.h"
+#include "undoable.h"
 #include "util/clipboard.h"
 #include "util/misc.h"
 #include "widgets/colbar.h"
@@ -80,7 +82,7 @@ enum {
 
 static void destroy_clipboard(void* data);
 static void set_clipboard(Image* image, Palette* palette, bool set_system_clipboard);
-static bool copy_from_sprite(Sprite* sprite);
+static bool copy_from_sprite(const Sprite* sprite);
 
 static bool interactive_transform(JWidget widget, Image *dest_image, Image *image,
 				  int x, int y, int xout[4], int yout[4]);
@@ -131,9 +133,9 @@ static void set_clipboard(Image* image, Palette* palette, bool set_system_clipbo
 #endif
 }
 
-static bool copy_from_sprite(Sprite* sprite)
+static bool copy_from_sprite(const Sprite* sprite)
 {
-  assert(sprite);
+  assert(sprite != NULL);
   Image* image = NewImageFromMask(sprite);
   if (!image)
     return false;
@@ -161,13 +163,15 @@ bool clipboard::can_paste()
   return clipboard_image != NULL;
 }
 
-void clipboard::cut(Sprite* sprite)
+void clipboard::cut(SpriteWriter& sprite)
 {
   assert(sprite != NULL);
   assert(sprite->layer != NULL);
 
-  if (!copy_from_sprite(sprite))
-    console_printf("Can't copying an image portion from the current layer\n");
+  if (!copy_from_sprite(sprite)) {
+    Console console;
+    console.printf("Can't copying an image portion from the current layer\n");
+  }
   else {
     {
       Undoable undoable(sprite, "Cut");
@@ -178,12 +182,14 @@ void clipboard::cut(Sprite* sprite)
   }
 }
 
-void clipboard::copy(Sprite* sprite)
+void clipboard::copy(const SpriteReader& sprite)
 {
   assert(sprite != NULL);
 
-  if (!copy_from_sprite(sprite))
-    console_printf(_("Can't copying an image portion from the current layer\n"));
+  if (!copy_from_sprite(sprite)) {
+    Console console;
+    console.printf(_("Can't copying an image portion from the current layer\n"));
+  }
 }
 
 void clipboard::copy_image(Image* image, Palette* pal)
@@ -192,7 +198,7 @@ void clipboard::copy_image(Image* image, Palette* pal)
 		pal ? palette_new_copy(pal): NULL, true);
 }
 
-void clipboard::paste(Sprite* sprite)
+void clipboard::paste(SpriteWriter& sprite)
 {
   int xout[4], yout[4];
   int dst_x, dst_y;
@@ -217,7 +223,8 @@ void clipboard::paste(Sprite* sprite)
   // destination image (where to put this image)
   dst_image = GetImage2(sprite, &dst_x, &dst_y, NULL);
   if (!dst_image) {
-    console_printf(_("Error: no destination image\n"));
+    Console console;
+    console.printf(_("Error: no destination image\n"));
     return;
   }
 
@@ -225,12 +232,10 @@ void clipboard::paste(Sprite* sprite)
   if (clipboard_image->imgtype == sprite->imgtype)
     src_image = clipboard_image;
   else {
-    src_image = image_new(sprite->imgtype,
-			  clipboard_image->w,
-			  clipboard_image->h);
-
     CurrentSpriteRgbMap rgbmap;
-    image_convert(clipboard_image, src_image);
+    src_image = image_set_imgtype(clipboard_image, sprite->imgtype, DITHERING_NONE,
+				  rgb_map, sprite_get_palette(sprite,
+							      sprite->frame));
   }
 
   // do the interactive-transform loop (where the user can move the floating image)
diff --git a/src/util/clipboard.h b/src/util/clipboard.h
index 022e28027..f4d8c7829 100644
--- a/src/util/clipboard.h
+++ b/src/util/clipboard.h
@@ -22,15 +22,17 @@
 #include "jinete/jbase.h"
 
 class Image;
+class SpriteReader;
+class SpriteWriter;
 
 namespace clipboard {
 
-bool can_paste();
+  bool can_paste();
 
-void cut(Sprite* sprite);
-void copy(Sprite* sprite);
-void copy_image(Image* image, Palette* palette);
-void paste(Sprite* sprite);
+  void cut(SpriteWriter& sprite);
+  void copy(const SpriteReader& sprite);
+  void copy_image(Image* image, Palette* palette);
+  void paste(SpriteWriter& sprite);
 
 } // namespace clipboard
 
diff --git a/src/util/functions.cpp b/src/util/functions.cpp
deleted file mode 100644
index ff6e79b72..000000000
--- a/src/util/functions.cpp
+++ /dev/null
@@ -1,450 +0,0 @@
-/* ASE - Allegro Sprite Editor
- * Copyright (C) 2001-2009  David Capello
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
- */
-
-#include "config.h"
-
-#include <assert.h>
-#include "jinete/jinete.h"
-
-#include "ase/current_sprite.h"
-#include "ase/ui_context.h"
-#include "console/console.h"
-#include "core/app.h"
-#include "file/file.h"
-#include "modules/gui.h"
-#include "modules/sprites.h"
-#include "raster/raster.h"
-#include "util/functions.h"
-#include "util/misc.h"
-#include "widgets/colbar.h"
-
-/*===================================================================*/
-/* Sprite                                                            */
-/*===================================================================*/
-
-/**
- * Creates a new sprite with the given dimension with one transparent
- * layer called "Layer 1".
- *
- * @param imgtype Color mode, one of the following values: IMAGE_RGB, IMAGE_GRAYSCALE, IMAGE_INDEXED
- * @param w Width of the sprite
- * @param h Height of the sprite
- */
-Sprite *NewSprite(int imgtype, int w, int h)
-{
-  Sprite *sprite;
-
-  if (imgtype != IMAGE_RGB &&
-      imgtype != IMAGE_GRAYSCALE &&
-      imgtype != IMAGE_INDEXED) {
-    console_printf("NewSprite: argument 'imgtype' should be IMAGE_RGB, IMAGE_GRAYSCALE or IMAGE_INDEXED\n");
-    return NULL;
-  }
-
-  if (w < 1 || w > 9999) {
-    console_printf("NewSprite: argument 'w' should be between 1 and 9999\n");
-    return NULL;
-  }
-
-  if (h < 1 || h > 9999) {
-    console_printf("NewSprite: argument 'h' should be between 1 and 9999\n");
-    return NULL;
-  }
-
-  sprite = sprite_new_with_layer(imgtype, w, h);
-  if (!sprite)
-    return NULL;
-
-  undo_disable(sprite->undo);
-
-  UIContext* context = UIContext::instance();
-  context->add_sprite(sprite);
-  context->set_current_sprite(sprite);
-
-  assert(undo_is_disabled(sprite->undo));
-  return sprite;
-}
-
-/**
- * Loads a sprite from the specified file.
- *
- * If the sprite is succefully loaded it'll be selected as the current
- * sprite (@ref SetSprite) automatically.
- *
- * @param filename The name of the file. Can be absolute or relative
- *                 to the location which ASE was executed.
- *
- * @return The loaded sprite or nil if it couldn't be read.
- */
-Sprite *LoadSprite(const char *filename)
-{
-  Sprite *sprite;
-
-  if (filename == NULL) {
-    console_printf("LoadSprite: filename can't be NULL\n");
-    return NULL;
-  }
-
-  sprite = sprite_load(filename);
-  if (sprite) {
-    undo_disable(sprite->undo);
-
-    UIContext* context = UIContext::instance();
-    context->add_sprite(sprite);
-    context->set_current_sprite(sprite);
-  }
-
-  assert(undo_is_disabled(sprite->undo));
-  return sprite;
-}
-
-/**
- * Saves the current sprite.
- */
-void SaveSprite(const char *filename)
-{
-  CurrentSprite sprite;
-
-  if (sprite == NULL) {
-    console_printf("SaveSprite: No current sprite\n");
-    return;
-  }
-
-  if (filename == NULL) {
-    console_printf("SaveSprite: filename can't be NULL\n");
-    return;
-  }
-
-  sprite_set_filename(sprite, filename);
-  app_realloc_sprite_list();
-
-  if (sprite_save(sprite) == 0)
-    sprite_mark_as_saved(sprite);
-  else
-    console_printf("SaveSprite: Error saving sprite file %s\n", filename);
-}
-
-/**
- * Sets the specified sprite as the current sprite to apply all next
- * operations.
- */
-void SetSprite(Sprite *sprite)
-{
-  UIContext* context = UIContext::instance();
-  context->set_current_sprite(sprite);
-}
-
-/*===================================================================*/
-/* Layer                                                             */
-/*===================================================================*/
-
-static int get_max_layer_num(Layer *layer);
-
-/**
- * Creates a new layer set with the "name" in the current sprite
- */
-Layer *NewLayerSet(Sprite *sprite)
-{
-  Layer *layer = NULL;
-
-  if (sprite == NULL) {
-    console_printf("NewLayer: No current sprite\n");
-    return NULL;
-  }
-
-  /* new layer */
-  layer = layer_set_new(sprite);
-  if (!layer)
-    return NULL;
-
-  /* configure layer name and blend mode */
-  /* TODO */
-  /*     { */
-  /*       char *name; */
-  /*       name = GetUniqueLayerName(); */
-  /*       layer_set_name(layer, name); */
-  /*       jfree(name); */
-  /*     } */
-
-  /* add the layer in the sprite set */
-  layer_add_layer(sprite->set, layer);
-
-  /* select the new layer */
-  sprite_set_layer(sprite, layer);
-
-  return layer;
-}
-
-char *GetUniqueLayerName(Sprite *sprite)
-{
-  if (sprite != NULL) {
-    char buf[1024];
-    sprintf(buf, "Layer %d", get_max_layer_num(sprite->set)+1);
-    return jstrdup(buf);
-  }
-  else
-    return NULL;
-}
-
-Layer *FlattenLayers(Sprite *sprite)
-{
-  JLink link, next;
-  Layer *background;
-  Image *image;
-  Image *cel_image;
-  Cel *cel;
-  int frame;
-  int bgcolor;
-
-  /* there are a current sprite selected? */
-  if (!sprite)
-    return NULL;
-
-  /* create a temporary image */
-  image = image_new(sprite->imgtype, sprite->w, sprite->h);
-  if (!image) {
-    console_printf("Not enough memory");
-    return NULL;
-  }
-
-  /* open undo */
-  if (undo_is_enabled(sprite->undo))
-    undo_open(sprite->undo);
-
-  /* get the background layer from the sprite */
-  background = sprite_get_background_layer(sprite);
-  if (!background) {
-    /* if there aren't a background layer we must to create the background */
-    background = layer_new(sprite);
-    if (!background) {
-      image_free(image);
-      console_printf("Not enough memory");
-      return NULL;
-    }
-
-    if (undo_is_enabled(sprite->undo))
-      undo_add_layer(sprite->undo, sprite->set, background);
-
-    layer_add_layer(sprite->set, background);
-
-    if (undo_is_enabled(sprite->undo))
-      undo_move_layer(sprite->undo, background);
-    
-    layer_configure_as_background(background);
-
-    /* get the color to clean the temporary image in each frame */
-    bgcolor = get_color_for_image(sprite->imgtype,
-				  colorbar_get_bg_color(app_get_colorbar()));
-  }
-  else
-    bgcolor = 0;
-
-  /* copy all frames to the background */
-  for (frame=0; frame<sprite->frames; frame++) {
-    /* clear the image and render this frame */
-    image_clear(image, bgcolor);
-    layer_render(sprite->set, image, 0, 0, frame);
-
-    cel = layer_get_cel(background, frame);
-    if (cel) {
-      cel_image = sprite->stock->image[cel->image];
-      assert(cel_image != NULL);
-
-      /* we have to save the current state of `cel_image' in the undo */
-      if (undo_is_enabled(sprite->undo)) {
-	Dirty *dirty = dirty_new_from_differences(cel_image, image);
-	dirty_save_image_data(dirty);
-	/* TODO error handling: if (dirty == NULL) */
-	if (dirty != NULL)
-	  undo_dirty(sprite->undo, dirty);
-      }
-    }
-    else {
-      /* if there aren't a cel in this frame in the background, we
-	 have to create a copy of the image for the new cel */
-      cel_image = image_new_copy(image);
-      /* TODO error handling: if (!cel_image) { ... } */
-
-      /* here we create the new cel (with the new image `cel_image') */
-      cel = cel_new(frame, stock_add_image(sprite->stock, cel_image));
-      /* TODO error handling: if (!cel) { ... } */
-
-      /* and finally we add the cel in the background */
-      layer_add_cel(background, cel);
-    }
-
-    image_copy(cel_image, image, 0, 0);
-  }
-
-  /* select the background */
-  if (sprite->layer != background) {
-    if (undo_is_enabled(sprite->undo))
-      undo_set_layer(sprite->undo, sprite);
-
-    sprite_set_layer(sprite, background);
-  }
-
-  /* remove old layers */
-  JI_LIST_FOR_EACH_SAFE(sprite->set->layers, link, next) {
-    if (link->data != background) {
-      Layer* old_layer = reinterpret_cast<Layer*>(link->data);
-
-      /* remove the layer */
-      if (undo_is_enabled(sprite->undo))
-	undo_remove_layer(sprite->undo, old_layer);
-
-      layer_remove_layer(sprite->set, old_layer);
-
-      /* destroy the layer */
-      layer_free_images(old_layer);
-      layer_free(old_layer);
-    }
-  }
-
-  /* destroy the temporary image */
-  image_free(image);
-
-  /* close the undo */
-  if (undo_is_enabled(sprite->undo))
-    undo_close(sprite->undo);
- 
-  return background;
-}
-
-void LayerFromBackground(Sprite *sprite)
-{
-  if (sprite == NULL) {
-    console_printf("LayerFromBackground: there is not a current sprite selected\n");
-    return;
-  }
-
-  if (sprite_get_background_layer(sprite) == NULL) {
-    console_printf("LayerFromBackground: the current sprite hasn't a `Background' layer.\n");
-    return;
-  }
-
-  if (sprite->layer == NULL) {
-    console_printf("LayerFromBackground: there is not a current layer selected.\n");
-    return;
-  }
-
-  if (!layer_is_image(sprite->layer)) {
-    console_printf("LayerFromBackground: the current layer must be an `image' layer.\n");
-    return;
-  }
-
-  if (!layer_is_readable(sprite->layer)) {
-    console_printf("LayerFromBackground: the current layer is hidden, can't be converted.\n");
-    return;
-  }
-
-  if (!layer_is_writable(sprite->layer)) {
-    console_printf("LayerFromBackground: the current layer is locked, can't be converted.\n");
-    return;
-  }
-
-  if (!layer_is_background(sprite->layer)) {
-    console_printf("LayerFromBackground: the current layer must be the `Background' layer.\n");
-    return;
-  }
-
-  if (undo_is_enabled(sprite->undo)) {
-    undo_open(sprite->undo);
-    undo_data(sprite->undo,
-	      (GfxObj *)sprite->layer,
-	      &sprite->layer->flags,
-	      sizeof(sprite->layer->flags));
-    undo_data(sprite->undo,
-	      (GfxObj *)sprite->layer,
-	      &sprite->layer->name,
-	      LAYER_NAME_SIZE);
-    undo_close(sprite->undo);
-  }
-
-  sprite->layer->flags &= ~(LAYER_IS_LOCKMOVE | LAYER_IS_BACKGROUND);
-  layer_set_name(sprite->layer, "Layer 0");
-}
-
-/* internal routine */
-static int get_max_layer_num(Layer *layer)
-{
-  int max = 0;
-
-  if (strncmp(layer->name, "Layer ", 6) == 0)
-    max = strtol(layer->name+6, NULL, 10);
-
-  if (layer_is_set(layer)) {
-    JLink link;
-    JI_LIST_FOR_EACH(layer->layers, link) {
-      int tmp = get_max_layer_num(reinterpret_cast<Layer*>(link->data));
-      max = MAX(tmp, max);
-    }
-  }
-  
-  return max;
-}
-
-/* ======================================= */
-/* Cel                                     */
-/* ======================================= */
-
-void RemoveCel(Layer *layer, Cel *cel)
-{
-  CurrentSprite sprite;
-  Image *image;
-  Cel *it;
-  int frame;
-  bool used;
-
-  if (sprite != NULL && layer_is_image(layer) && cel != NULL) {
-    /* find if the image that use the cel to remove, is used by
-       another cels */
-    used = FALSE;
-    for (frame=0; frame<sprite->frames; ++frame) {
-      it = layer_get_cel(layer, frame);
-      if (it != NULL && it != cel && it->image == cel->image) {
-	used = TRUE;
-	break;
-      }
-    }
-
-    if (undo_is_enabled(sprite->undo))
-      undo_open(sprite->undo);
-
-    if (!used) {
-      /* if the image is only used by this cel, we can remove the
-	 image from the stock */
-      image = stock_get_image(sprite->stock, cel->image);
-
-      if (undo_is_enabled(sprite->undo))
-	undo_remove_image(sprite->undo, sprite->stock, cel->image);
-
-      stock_remove_image(sprite->stock, image);
-      image_free(image);
-    }
-
-    if (undo_is_enabled(sprite->undo)) {
-      undo_remove_cel(sprite->undo, layer, cel);
-      undo_close(sprite->undo);
-    }
-
-    /* remove the cel */
-    layer_remove_cel(layer, cel);
-    cel_free(cel);
-  }
-}
diff --git a/src/util/functions.h b/src/util/functions.h
deleted file mode 100644
index 23e4e2c49..000000000
--- a/src/util/functions.h
+++ /dev/null
@@ -1,54 +0,0 @@
-/* ASE - Allegro Sprite Editor
- * Copyright (C) 2001-2009  David Capello
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
- */
-
-#ifndef UTIL_FUNCTIONS_H
-#define UTIL_FUNCTIONS_H
-
-class Sprite;
-class Layer;
-class Cel;
-
-/*===================================================================*/
-/* Sprite                                                            */
-/*===================================================================*/
-
-Sprite* NewSprite(int imgtype, int w, int h);
-Sprite* LoadSprite(const char* filename);
-void SaveSprite(const char* filename);
-
-void SetSprite(Sprite* sprite); 
-
-/*===================================================================*/
-/* Layer                                                             */
-/*===================================================================*/
-
-Layer* NewLayerSet(Sprite* sprite);
-
-char *GetUniqueLayerName(Sprite* sprite);
-
-Layer* FlattenLayers(Sprite* sprite);
-
-void LayerFromBackground(Sprite* sprite);
-
-/* ======================================= */
-/* Cel                                     */
-/* ======================================= */
-
-void RemoveCel(Layer* layer, Cel* cel);
-
-#endif /* UTIL_FUNCTIONS_H */
diff --git a/src/util/misc.cpp b/src/util/misc.cpp
index 1681a8c57..ad0c9f673 100644
--- a/src/util/misc.cpp
+++ b/src/util/misc.cpp
@@ -36,7 +36,6 @@
 #include "modules/palettes.h"
 #include "modules/sprites.h"
 #include "raster/raster.h"
-#include "util/functions.h"
 #include "util/misc.h"
 #include "widgets/editor.h"
 #include "widgets/statebar.h"
diff --git a/src/util/thmbnail.cpp b/src/util/thmbnail.cpp
index 220e2e0b1..be3107ef9 100644
--- a/src/util/thmbnail.cpp
+++ b/src/util/thmbnail.cpp
@@ -64,7 +64,7 @@ void destroy_thumbnails()
   }
 }
 
-BITMAP* generate_thumbnail(const Layer *layer, const Cel *cel, const Sprite *sprite)
+BITMAP* generate_thumbnail(const Layer* layer, const Cel* cel, const Sprite *sprite)
 {
   Thumbnail* thumbnail;
   BITMAP* bmp;
diff --git a/src/util/thmbnail.h b/src/util/thmbnail.h
index de99790d3..d65856f58 100644
--- a/src/util/thmbnail.h
+++ b/src/util/thmbnail.h
@@ -23,7 +23,7 @@ class Cel;
 class Sprite;
 
 void destroy_thumbnails();
-struct BITMAP *generate_thumbnail(const Layer* layer, const Cel* cel, const Sprite* sprite);
+struct BITMAP* generate_thumbnail(const Layer* layer, const Cel* cel, const Sprite* sprite);
 
 #endif /* UTIL_THMBNAIL_H */
 
diff --git a/src/widgets/colbar.cpp b/src/widgets/colbar.cpp
index b8bd2353a..b34e10cc8 100644
--- a/src/widgets/colbar.cpp
+++ b/src/widgets/colbar.cpp
@@ -477,9 +477,14 @@ static bool colorbar_msg_proc(JWidget widget, JMessage msg)
       /* time to refresh all the editors which have the current
 	 sprite selected? */
       if (msg->timer.timer_id == colorbar->refresh_timer_id) {
-	CurrentSprite sprite;
-	if (sprite != NULL)
-	  update_editors_with_sprite(sprite);
+	try {
+	  const CurrentSpriteReader sprite;
+	  if (sprite != NULL)
+	    update_editors_with_sprite(sprite);
+	}
+	catch (locked_sprite_exception& e) {
+	  // do nothing
+	}
 
 	jmanager_stop_timer(colorbar->refresh_timer_id);
       }
@@ -579,7 +584,7 @@ static void colorbar_open_tooltip(JWidget widget, int x1, int x2, int y1, int y2
       if (cmd->accel != NULL) {
 	ustrcat(buf, _(" - "));
 	jaccel_to_string(cmd->accel, buf+ustrsize(buf));
-	ustrcat(buf, _(" key switchs colors"));
+	ustrcat(buf, _(" key switches colors"));
       }
       break;
     }
@@ -650,44 +655,50 @@ static bool tooltip_window_msg_proc(JWidget widget, JMessage msg)
 {
   switch (msg->type) {
 
-    case JM_CLOSE: {
-      // change the sprite palette
-      CurrentSprite sprite;
+    case JM_CLOSE:
+      try {
+	// change the sprite palette
+	const CurrentSpriteReader sprite;
+	if (sprite != NULL) {
+	  Palette *pal = sprite_get_palette(sprite, sprite->frame);
+	  int from, to;
 
-      if (sprite != NULL) {
-	Palette *pal = sprite_get_palette(sprite, sprite->frame);
-	int from, to;
+	  if (palette_count_diff(pal, get_current_palette(), &from, &to) > 0) {
+	    SpriteWriter sprite_writer(sprite);
+	    /* TODO add undo support */
+	    /* 	  if (undo_is_enabled(sprite->undo)) */
+	    /* 	    undo_data(sprite->undo, (GfxObj *)sprite, pal, ); */
 
-	if (palette_count_diff(pal, get_current_palette(), &from, &to) > 0) {
-	  /* TODO add undo support */
-/* 	  if (undo_is_enabled(sprite->undo)) */
-/* 	    undo_data(sprite->undo, (GfxObj *)sprite, pal, ); */
+	    pal = get_current_palette();
+	    pal->frame = sprite_writer->frame; /* TODO warning, modifing
+						  the current palette in
+						  this point... */
 
-	  pal = get_current_palette();
-	  pal->frame = sprite->frame; /* TODO warning, modifing
-					 the current palette in
-					 this point... */
+	    sprite_set_palette(sprite_writer, pal, FALSE);
+	    set_current_palette(pal, TRUE);
+	  }
 
-	  sprite_set_palette(sprite, pal, FALSE);
-	  set_current_palette(pal, TRUE);
+	  update_editors_with_sprite(sprite);
 	}
+	/* change the system palette */
+	else
+	  set_default_palette(get_current_palette());
 
-	update_editors_with_sprite(sprite);
+	/* set the 'hot_editing' to NONE */
+	{
+	  JWidget colorbar_widget = (JWidget)widget->user_data[0];
+	  ColorBar *colorbar = colorbar_data(colorbar_widget);
+
+	  colorbar->hot_editing = HOTCOLOR_NONE;
+	  jwidget_dirty(colorbar_widget);
+	}
       }
-      /* change the system palette */
-      else
-	set_default_palette(get_current_palette());
-
-      /* set the 'hot_editing' to NONE */
-      {
-	JWidget colorbar_widget = (JWidget)widget->user_data[0];
-	ColorBar *colorbar = colorbar_data(colorbar_widget);
-
-	colorbar->hot_editing = HOTCOLOR_NONE;
-	jwidget_dirty(colorbar_widget);
+      catch (ase_exception& e) {
+	Console console;
+	console.printf("Error updating sprite palette.\n\n");
+	e.show();
       }
       break;
-    }
 
     case JM_SIGNAL:
       if (msg->signal.num == SIGNAL_COLORSELECTOR_COLOR_CHANGED) {
@@ -724,22 +735,29 @@ static bool tooltip_window_msg_proc(JWidget widget, JMessage msg)
 	   different from the current sprite's palette, then we have
 	   to start the "refresh_timer" to refresh all the editors
 	   with that sprite */
-	CurrentSprite sprite;
-	if (sprite != NULL && bitmap_color_depth(screen) != 8) {
-	  Palette *pal = sprite_get_palette(sprite, sprite->frame);
+	try {
+	  CurrentSpriteWriter sprite;
+	  if (sprite != NULL && bitmap_color_depth(screen) != 8) {
+	    Palette *pal = sprite_get_palette(sprite, sprite->frame);
 	  
-	  if (palette_count_diff(pal, get_current_palette(), NULL, NULL) > 0) {
-	    pal = get_current_palette();
-	    pal->frame = sprite->frame;	/* TODO warning, modifing
-					   the current palette in
-					   this point... */
+	    if (palette_count_diff(pal, get_current_palette(), NULL, NULL) > 0) {
+	      pal = get_current_palette();
+	      pal->frame = sprite->frame;	/* TODO warning, modifing
+						   the current palette in
+						   this point... */
 
-	    sprite_set_palette(sprite, pal, FALSE);
-	    set_current_palette(pal, TRUE);
+	      sprite_set_palette(sprite, pal, FALSE);
+	      set_current_palette(pal, TRUE);
 
-	    jmanager_start_timer(colorbar->refresh_timer_id);
+	      jmanager_start_timer(colorbar->refresh_timer_id);
+	    }
 	  }
 	}
+	catch (ase_exception& e) {
+	  Console console;
+	  console.printf("Error updating sprite palette.\n\n");
+	  e.show();
+	}
 
 	jwidget_dirty(colorbar_widget);
       }
diff --git a/src/widgets/preview.cpp b/src/widgets/preview.cpp
index 9737df29a..a52e803d9 100644
--- a/src/widgets/preview.cpp
+++ b/src/widgets/preview.cpp
@@ -91,7 +91,8 @@ static bool preview_msg_proc(JWidget widget, JMessage msg)
   switch (msg->type) {
 
     case JM_DESTROY:
-      jmanager_remove_timer(preview->timer_id);
+      if (preview->timer_id >= 0)
+	jmanager_remove_timer(preview->timer_id);
       jfree(preview);
       break;
       
diff --git a/src/widgets/statebar.cpp b/src/widgets/statebar.cpp
index b45c87313..5a98ae2fe 100644
--- a/src/widgets/statebar.cpp
+++ b/src/widgets/statebar.cpp
@@ -193,13 +193,6 @@ void statusbar_show_color(JWidget widget, int msecs, int imgtype, color_t color)
   statusbar_set_text(widget, msecs, "%s %s", _("Color"), buf);
 }
 
-void statusbar_update(JWidget widget)
-{
-  StatusBar *statusbar = statusbar_data(widget);
-
-  update_from_layer(statusbar);
-}
-
 Progress *progress_new(JWidget widget)
 {
   Progress *progress = jnew(Progress, 1);
@@ -317,11 +310,10 @@ static bool statusbar_msg_proc(JWidget widget, JMessage msg)
       }
       /* draw current sprite size in memory */
       else {
-	CurrentSprite sprite;
-	if (sprite != NULL) {
-	  char buf[1024];
-
-	  if (sprite.writeable()) {
+	char buf[1024];
+	try {
+	  const CurrentSpriteReader sprite;
+	  if (sprite) {
 	    ustrcpy(buf, "Sprite:");
 	    get_pretty_memsize(sprite_get_memsize(sprite),
 			       buf+ustrsize(buf),
@@ -333,14 +325,17 @@ static bool statusbar_msg_proc(JWidget widget, JMessage msg)
 			       sizeof(buf)-ustrsize(buf));
 	  }
 	  else {
-	    ustrcpy(buf, "Sprite is Locked");
+	    ustrcpy(buf, "No Sprite");
 	  }
-
-	  textout_right_ex(ji_screen, widget->font(), buf,
-			   rc->x2-2,
-			   (widget->rc->y1+widget->rc->y2)/2-text_height(widget->font())/2,
-			   ji_color_foreground(), -1);
 	}
+	catch (locked_sprite_exception&) {
+	  ustrcpy(buf, "Sprite is Locked");
+	}
+
+	textout_right_ex(ji_screen, widget->font(), buf,
+			 rc->x2-2,
+			 (widget->rc->y1+widget->rc->y2)/2-text_height(widget->font())/2,
+			 ji_color_foreground(), -1);
       }
 
       jrect_free(rc);
@@ -349,22 +344,13 @@ static bool statusbar_msg_proc(JWidget widget, JMessage msg)
 
     case JM_MOUSEENTER:
       if (!jwidget_has_child(widget, statusbar->commands_box)) {
-	CurrentSprite sprite;
+	bool state = (UIContext::instance()->get_current_sprite() != NULL);
 
-	if (!sprite) {
-	  jwidget_disable(statusbar->b_first);
-	  jwidget_disable(statusbar->b_prev);
-	  jwidget_disable(statusbar->b_play);
-	  jwidget_disable(statusbar->b_next);
-	  jwidget_disable(statusbar->b_last);
-	}
-	else {
-	  jwidget_enable(statusbar->b_first);
-	  jwidget_enable(statusbar->b_prev);
-	  jwidget_enable(statusbar->b_play);
-	  jwidget_enable(statusbar->b_next);
-	  jwidget_enable(statusbar->b_last);
-	}
+	statusbar->b_first->enabled(state);
+	statusbar->b_prev->enabled(state);
+	statusbar->b_play->enabled(state);
+	statusbar->b_next->enabled(state);
+	statusbar->b_last->enabled(state);
 
 	update_from_layer(statusbar);
 
@@ -409,92 +395,99 @@ static bool tipwindow_msg_proc(JWidget widget, JMessage msg)
 
 static bool slider_change_hook(JWidget widget, void *data)
 {
-  CurrentSprite sprite;
-  if (sprite) {
-    if ((sprite->layer) &&
-	(sprite->layer->type == GFXOBJ_LAYER_IMAGE)) {
-      Cel *cel = layer_get_cel(sprite->layer, sprite->frame);
+  try {
+    CurrentSpriteWriter sprite;
+    if (sprite) {
+      if ((sprite->layer) &&
+	  (sprite->layer->type == GFXOBJ_LAYER_IMAGE)) {
+	Cel *cel = layer_get_cel(sprite->layer, sprite->frame);
 
-      if (cel) {
-	/* update the opacity */
-	cel->opacity = jslider_get_value(widget);
+	if (cel) {
+	  // update the opacity
+	  cel->opacity = jslider_get_value(widget);
 
-	/* update the editors */
-	update_screen_for_sprite(sprite);
+	  // update the editors
+	  update_screen_for_sprite(sprite);
+	}
       }
     }
   }
-
-  return FALSE;
+  catch (locked_sprite_exception&) {
+    // do nothing
+  }
+  return false;
 }
 
 static void button_command(JWidget widget, void *data)
 {
-  CurrentSprite sprite;
+  const char *cmd = NULL;
 
-  if (sprite) {
-    const char *cmd = NULL;
+  switch ((size_t)data) {
 
-    switch ((size_t)data) {
+    case ACTION_LAYER:
+      cmd = CMD_LAYER_PROPERTIES;
+      break;
 
-      case ACTION_LAYER:
-	cmd = CMD_LAYER_PROPERTIES;
-	break;
+    case ACTION_FIRST:
+      cmd = CMD_GOTO_FIRST_FRAME;
+      break;
 
-      case ACTION_FIRST:
-	cmd = CMD_GOTO_FIRST_FRAME;
-	break;
+    case ACTION_PREV:
+      cmd = CMD_GOTO_PREVIOUS_FRAME;
+      break;
 
-      case ACTION_PREV:
-	cmd = CMD_GOTO_PREVIOUS_FRAME;
-	break;
+    case ACTION_PLAY:
+      cmd = CMD_PLAY_ANIMATION;
+      break;
 
-      case ACTION_PLAY:
-	cmd = CMD_PLAY_ANIMATION;
-	break;
+    case ACTION_NEXT:
+      cmd = CMD_GOTO_NEXT_FRAME;
+      break;
 
-      case ACTION_NEXT:
-	cmd = CMD_GOTO_NEXT_FRAME;
-	break;
-
-      case ACTION_LAST:
-	cmd = CMD_GOTO_LAST_FRAME;
-	break;
-    }
-
-    if (cmd)
-      command_execute(command_get_by_name(cmd), NULL);
+    case ACTION_LAST:
+      cmd = CMD_GOTO_LAST_FRAME;
+      break;
   }
+
+  if (cmd)
+    command_execute(command_get_by_name(cmd), NULL);
 }
 
 static void update_from_layer(StatusBar *statusbar)
 {
-  CurrentSprite sprite;
-  Cel *cel;
+  try {
+    const CurrentSpriteReader sprite;
+    Cel *cel;
 
-  /* layer button */
-  if (sprite && sprite->layer) {
-    char buf[512];
-    usprintf(buf, "[%d] %s", sprite->frame, sprite->layer->name);
-    jwidget_set_text(statusbar->b_layer, buf);
-    jwidget_enable(statusbar->b_layer);
+    /* layer button */
+    if (sprite && sprite->layer) {
+      char buf[512];
+      usprintf(buf, "[%d] %s", sprite->frame, sprite->layer->name);
+      jwidget_set_text(statusbar->b_layer, buf);
+      jwidget_enable(statusbar->b_layer);
+    }
+    else {
+      jwidget_set_text(statusbar->b_layer, "Nothing");
+      jwidget_disable(statusbar->b_layer);
+    }
+
+    /* opacity layer */
+    if (sprite &&
+	sprite->layer &&
+	layer_is_image(sprite->layer) &&
+	!layer_is_background(sprite->layer) &&
+	(cel = layer_get_cel(sprite->layer, sprite->frame))) {
+      jslider_set_value(statusbar->slider, MID(0, cel->opacity, 255));
+      jwidget_enable(statusbar->slider);
+    }
+    else {
+      jslider_set_value(statusbar->slider, 255);
+      jwidget_disable(statusbar->slider);
+    }
   }
-  else {
-    jwidget_set_text(statusbar->b_layer, "Nothing");
+  catch (locked_sprite_exception&) {
+    // disable all
     jwidget_disable(statusbar->b_layer);
-  }
-
-  /* opacity layer */
-  if (sprite &&
-      sprite->layer &&
-      layer_is_image(sprite->layer) &&
-      !layer_is_background(sprite->layer) &&
-      (cel = layer_get_cel(sprite->layer, sprite->frame))) {
-    jslider_set_value(statusbar->slider, MID(0, cel->opacity, 255));
-    jwidget_enable(statusbar->slider);
-  }
-  else {
-    jslider_set_value(statusbar->slider, 255);
     jwidget_disable(statusbar->slider);
   }
 }
diff --git a/src/widgets/statebar.h b/src/widgets/statebar.h
index 8eee6d3bb..6bfe0f7fc 100644
--- a/src/widgets/statebar.h
+++ b/src/widgets/statebar.h
@@ -61,7 +61,6 @@ StatusBar *statusbar_data(JWidget widget);
 void statusbar_set_text(JWidget widget, int msecs, const char *format, ...);
 void statusbar_show_tip(JWidget widget, int msecs, const char *format, ...);
 void statusbar_show_color(JWidget widget, int msecs, int imgtype, color_t color);
-void statusbar_update(JWidget widget);
 
 /* progress */