Add "ui::dirty_display_flag" flag to avoid flipping to the screen continuously.

This is a temporal fix to save more CPU. It will be refactored for next
versions.

src/commands/cmd_play_animation.cpp

@@ -115,6 +115,8 @@ void PlayAnimationCommand::onExecute(Context* context)
 
     current_editor->drawSpriteSafe(0, 0, sprite->getWidth(), sprite->getHeight());
 
+    ui::dirty_display_flag = true;
+
     do {
       poll_mouse();
       poll_keyboard();

src/commands/cmd_preview.cpp

@@ -143,6 +143,7 @@ void PreviewCommand::onExecute(Context* context)
     // Redraw the screen
     if (redraw) {
       redraw = false;
+      dirty_display_flag = true;
 
       x = pos_x + ((delta_x >> zoom) << zoom);
       y = pos_y + ((delta_y >> zoom) << zoom);

src/commands/cmd_undo.cpp

@@ -27,6 +27,7 @@
 #include "modules/editors.h"
 #include "modules/gui.h"
 #include "raster/sprite.h"
+#include "ui/system.h"
 #include "widgets/editor/editor.h"
 #include "widgets/status_bar.h"
 
@@ -82,6 +83,8 @@ void UndoCommand::onExecute(Context* context)
 
       current_editor->drawSpriteSafe(0, 0, sprite->getWidth(), sprite->getHeight());
       update_screen_for_document(document);
+
+      ui::dirty_display_flag = true;
       gui_feedback();
 
       base::this_thread::sleep_for(0.01);

src/modules/gui.cpp

@@ -310,6 +310,10 @@ void gui_feedback()
 
   ui::UpdateCursorOverlay();
 
+  // Avoid updating a non-dirty screen over and over again.
+  if (!dirty_display_flag)
+    return;
+
   // Draw overlays.
   overlays->captureOverlappedAreas();
   overlays->drawOverlays();
@@ -322,6 +326,8 @@ void gui_feedback()
   }
   else
     overlays->restoreOverlappedAreas();
+
+  dirty_display_flag = false;
 }
 
 // Sets the ji_screen variable. This routine should be called

src/ui/manager.cpp

@@ -1090,6 +1090,8 @@ void Manager::pumpQueue()
 #endif
         /* rectfill(ji_screen, 0, 0, JI_SCREEN_W-1, JI_SCREEN_H-1, makecol(255, 0, 0)); */
         /* vsync(); vsync(); vsync(); vsync(); */
+
+        dirty_display_flag = true;
       }
 
       /* call message handler */

src/ui/overlay.h

@@ -30,6 +30,7 @@ namespace ui {
 
     she::Surface* setSurface(she::Surface* newSurface);
 
+    const gfx::Point& getPosition() const { return m_pos; }
     gfx::Rect getBounds() const;
 
     void captureOverlappedArea(she::LockedSurface* screen);

src/ui/system.cpp

@@ -37,6 +37,8 @@ JRegion ji_dirty_region = NULL;
 int ji_screen_w = 0;
 int ji_screen_h = 0;
 
+bool dirty_display_flag = true;
+
 /* Global timer.  */
 
 volatile int ji_clock = 0;
@@ -148,9 +150,15 @@ void SetDisplay(she::Display* display)
 
 void UpdateCursorOverlay()
 {
-  if (mouse_cursor_overlay != NULL && mouse_scares == 0)
-    mouse_cursor_overlay->moveOverlay(gfx::Point(m_x[0]-mouse_cursor->getFocus().x,
-                                                 m_y[0]-mouse_cursor->getFocus().y));
+  if (mouse_cursor_overlay != NULL && mouse_scares == 0) {
+    gfx::Point newPos(m_x[0]-mouse_cursor->getFocus().x,
+                      m_y[0]-mouse_cursor->getFocus().y);
+
+    if (newPos != mouse_cursor_overlay->getPosition()) {
+      mouse_cursor_overlay->moveOverlay(newPos);
+      dirty_display_flag = true;
+    }
+  }
 }
 
 CursorType jmouse_get_cursor()
@@ -174,6 +182,8 @@ void jmouse_set_cursor(CursorType type)
     show_mouse(NULL);
     set_mouse_cursor(theme->getCursor(type));
   }
+
+  dirty_display_flag = true;
 }
 
 void jmouse_hide()

src/ui/system.h

@@ -27,6 +27,10 @@ namespace ui {
   extern int ji_screen_w;
   extern int ji_screen_h;
 
+  // Simple flag to indicate that something in the screen was modified
+  // so a flip to the real screen is needed.
+  extern bool dirty_display_flag;
+
   void SetDisplay(she::Display* display);
 
   /***********************************************************************/
@@ -37,6 +41,8 @@ namespace ui {
   /***********************************************************************/
   /* mouse related */
 
+  // Updates the position of the mouse cursor overlay depending on the
+  // current mouse position.
   void UpdateCursorOverlay();
 
   CursorType jmouse_get_cursor();