diff --git a/src/app/cmd.h b/src/app/cmd.h
index 4a6fc8f95..575226d43 100644
--- a/src/app/cmd.h
+++ b/src/app/cmd.h
@@ -20,6 +20,7 @@
 #define APP_CMD_H_INCLUDED
 #pragma once
 
+#include "base/disable_copying.h"
 #include "doc/sprite_position.h"
 #include "undo/undo_command.h"
 
@@ -55,6 +56,8 @@ namespace app {
     enum class State { NotExecuted, Executed, Undone, Redone };
     State m_state;
 #endif
+
+    DISABLE_COPYING(Cmd);
   };
 
 } // namespace app
diff --git a/src/app/cmd/add_palette.h b/src/app/cmd/add_palette.h
index c3c710471..ab9ee85cf 100644
--- a/src/app/cmd/add_palette.h
+++ b/src/app/cmd/add_palette.h
@@ -51,7 +51,6 @@ namespace cmd {
     }
 
   private:
-    frame_t m_frame;
     std::stringstream m_stream;
   };
 
diff --git a/src/app/cmd/copy_frame.h b/src/app/cmd/copy_frame.h
index 54716af2c..83941c9c9 100644
--- a/src/app/cmd/copy_frame.h
+++ b/src/app/cmd/copy_frame.h
@@ -43,7 +43,6 @@ namespace cmd {
   private:
     frame_t m_fromFrame;
     frame_t m_newFrame;
-    bool m_firstTime;
   };
 
 } // namespace cmd
diff --git a/src/app/cmd/copy_region.cpp b/src/app/cmd/copy_region.cpp
index 812e5c108..8c8d4ae2c 100644
--- a/src/app/cmd/copy_region.cpp
+++ b/src/app/cmd/copy_region.cpp
@@ -89,7 +89,9 @@ void CopyRegion::swap()
     }
   }
 
-  std::swap(m_stream, tmp);
+  // TODO use m_stream.swap(tmp) when clang and gcc support it
+  m_stream.str(tmp.str());
+  m_stream.clear();
 }
 
 } // namespace cmd
diff --git a/src/app/cmd/object_io.h b/src/app/cmd/object_io.h
index 4806606ec..8ad3f57a2 100644
--- a/src/app/cmd/object_io.h
+++ b/src/app/cmd/object_io.h
@@ -22,6 +22,7 @@
 
 #include "base/serialization.h"
 #include "base/unique_ptr.h"
+#include "doc/object_id.h"
 #include "doc/subobjects_io.h"
 
 namespace doc {
diff --git a/src/app/cmd/replace_image.h b/src/app/cmd/replace_image.h
index 0fcb8fe76..b62e45e01 100644
--- a/src/app/cmd/replace_image.h
+++ b/src/app/cmd/replace_image.h
@@ -45,13 +45,13 @@ namespace cmd {
     }
 
   private:
+    ObjectId m_oldImageId;
+    ObjectId m_newImageId;
+
     // Reference used only to keep the copy of the new image from the
     // ReplaceImage() ctor until the ReplaceImage::onExecute() call.
     // Then the reference is not used anymore.
     ImageRef m_newImage;
-
-    ObjectId m_oldImageId;
-    ObjectId m_newImageId;
     ImageRef m_copy;
   };
 
diff --git a/src/app/cmd/set_cel_frame.h b/src/app/cmd/set_cel_frame.h
index a479b2a7d..5317a2b39 100644
--- a/src/app/cmd/set_cel_frame.h
+++ b/src/app/cmd/set_cel_frame.h
@@ -17,7 +17,7 @@
  */
 
 #ifndef APP_CMD_SET_CEL_FRAME_H_INCLUDED
-#define APP_CMD_SET_CEL_FRAME_CEL_H_INCLUDED
+#define APP_CMD_SET_CEL_FRAME_H_INCLUDED
 #pragma once
 
 #include "app/cmd.h"
diff --git a/src/app/commands/cmd_mask_content.cpp b/src/app/commands/cmd_mask_content.cpp
index dd58400c5..a73fbb796 100644
--- a/src/app/commands/cmd_mask_content.cpp
+++ b/src/app/commands/cmd_mask_content.cpp
@@ -65,8 +65,6 @@ void MaskContentCommand::onExecute(Context* context)
 {
   ContextWriter writer(context);
   Document* document(writer.document());
-  Sprite* sprite(writer.sprite());
-  Layer* layer = writer.layer();
   Cel* cel = writer.cel(); // Get current cel (can be NULL)
   if (!cel)
     return;
diff --git a/src/app/commands/cmd_preview.cpp b/src/app/commands/cmd_preview.cpp
index cba217571..0bfda7931 100644
--- a/src/app/commands/cmd_preview.cpp
+++ b/src/app/commands/cmd_preview.cpp
@@ -61,10 +61,10 @@ public:
     , m_doc(editor->document())
     , m_sprite(editor->sprite())
     , m_pal(m_sprite->palette(editor->frame()))
+    , m_zoom(editor->zoom())
     , m_index_bg_color(-1)
     , m_doublebuf(Image::create(IMAGE_RGB, ui::display_w(), ui::display_h()))
-    , m_doublesur(she::instance()->createRgbaSurface(ui::display_w(), ui::display_h()))
-    , m_zoom(editor->zoom()) {
+    , m_doublesur(she::instance()->createRgbaSurface(ui::display_w(), ui::display_h())) {
     // Do not use DocumentWriter (do not lock the document) because we
     // will call other sub-commands (e.g. previous frame, next frame,
     // etc.).
diff --git a/src/app/document_range_ops.cpp b/src/app/document_range_ops.cpp
index 974ad6232..345722278 100644
--- a/src/app/document_range_ops.cpp
+++ b/src/app/document_range_ops.cpp
@@ -40,6 +40,12 @@ static DocumentRange drop_range_op(
   Document* doc, Op op, const DocumentRange& from,
   DocumentRangePlace place, const DocumentRange& to)
 {
+  if (place != kDocumentRangeBefore &&
+      place != kDocumentRangeAfter) {
+    ASSERT(false);
+    throw std::invalid_argument("Invalid 'place' argument");
+  }
+
   Sprite* sprite = doc->sprite();
 
   // Check noop/trivial/do nothing cases, i.e., move a range to the same place.
@@ -83,6 +89,9 @@ static DocumentRange drop_range_op(
   switch (op) {
     case Move: undoLabel = "Move Range"; break;
     case Copy: undoLabel = "Copy Range"; break;
+    default:
+      ASSERT(false);
+      throw std::invalid_argument("Invalid 'op' argument");
   }
   DocumentRange resultRange;
 
diff --git a/src/app/transaction.cpp b/src/app/transaction.cpp
index 482f2843f..a8c108cf3 100644
--- a/src/app/transaction.cpp
+++ b/src/app/transaction.cpp
@@ -34,7 +34,6 @@ using namespace doc;
 
 Transaction::Transaction(Context* ctx, const std::string& label, Modification modification)
   : m_ctx(ctx)
-  , m_modification(modification)
   , m_cmds(NULL)
 {
   DocumentLocation location = m_ctx->activeLocation();
diff --git a/src/app/transaction.h b/src/app/transaction.h
index 7e645ec8a..75bcaca8f 100644
--- a/src/app/transaction.h
+++ b/src/app/transaction.h
@@ -73,7 +73,6 @@ namespace app {
     Context* m_ctx;
     DocumentUndo* m_undo;
     CmdTransaction* m_cmds;
-    Modification m_modification;
   };
 
 } // namespace app
diff --git a/src/doc/object.cpp b/src/doc/object.cpp
index 7bd44dc7c..4466dbe81 100644
--- a/src/doc/object.cpp
+++ b/src/doc/object.cpp
@@ -13,13 +13,14 @@
 #include "base/mutex.h"
 #include "base/scoped_lock.h"
 
-#include <unordered_map>
+#include <map>
 
 namespace doc {
 
 static base::mutex mutex;
 static ObjectId newId = 0;
-static std::unordered_map<ObjectId, Object*> objects;
+// TODO Profile this and see if an unordered_map works best.
+static std::map<ObjectId, Object*> objects;
 
 Object::Object(ObjectType type)
   : m_type(type)
diff --git a/src/render/render.cpp b/src/render/render.cpp
index 60cf23f7e..511b6b0cb 100644
--- a/src/render/render.cpp
+++ b/src/render/render.cpp
@@ -415,10 +415,6 @@ void Render::renderLayer(
   if (!scaled_func)
     return;
 
-  const LayerImage* background = m_sprite->backgroundLayer();
-  bool need_checked_bg = (background != NULL ? !background->isVisible(): true);
-  color_t bg_color = 0;
-
   m_globalOpacity = 255;
   renderLayer(layer, dstImage, area,
     frame, Zoom(1, 1), scaled_func,
diff --git a/src/ui/popup_window.cpp b/src/ui/popup_window.cpp
index 949f21308..8c6c7fed3 100644
--- a/src/ui/popup_window.cpp
+++ b/src/ui/popup_window.cpp
@@ -187,6 +187,23 @@ void PopupWindow::onInitTheme(InitThemeEvent& ev)
   this->border_width.b = 3 * guiscale();
 }
 
+void PopupWindow::onHitTest(HitTestEvent& ev)
+{
+  Widget* picked = getManager()->pick(ev.getPoint());
+  if (picked) {
+    WidgetType type = picked->getType();
+    if ((type == kWindowWidget && picked == this) ||
+        type == kBoxWidget ||
+        type == kLabelWidget ||
+        type == kGridWidget ||
+        type == kSeparatorWidget) {
+      ev.setHit(HitTestCaption);
+      return;
+    }
+  }
+  Window::onHitTest(ev);
+}
+
 void PopupWindow::startFilteringMessages()
 {
   if (!m_filtering) {
diff --git a/src/ui/popup_window.h b/src/ui/popup_window.h
index 4bf139416..ee0a5d256 100644
--- a/src/ui/popup_window.h
+++ b/src/ui/popup_window.h
@@ -34,6 +34,7 @@ namespace ui {
     void onPreferredSize(PreferredSizeEvent& ev) override;
     void onPaint(PaintEvent& ev) override;
     void onInitTheme(InitThemeEvent& ev) override;
+    void onHitTest(HitTestEvent& ev) override;
 
   private:
     void startFilteringMessages();