Add EditorDecorator::getInvalidDecoratoredRegion() needed in #873

src/app/ui/editor/editor.cpp

@@ -362,10 +362,20 @@ void Editor::setEditorScroll(const gfx::Point& scroll, bool blitValidRegion)
   View* view = View::getView(this);
   Point oldScroll;
   Region region;
+  Region invalidRegion;
 
   if (blitValidRegion) {
     getDrawableRegion(region, kCutTopWindows);
     oldScroll = view->viewScroll();
+
+    // Remove decorated region that cannot be just moved because it
+    // must be redrawn in another position when the Editor's scroll
+    // changes (e.g. symmetry handles).
+    if ((m_flags & kShowDecorators) && m_decorator) {
+      m_decorator->getInvalidDecoratoredRegion(this, invalidRegion);
+      if (!invalidRegion.isEmpty())
+        region.createSubtraction(region, invalidRegion);
+    }
   }
 
   view->setViewScroll(scroll);

src/app/ui/editor/editor_decorator.h

@@ -12,6 +12,10 @@
 #include "gfx/color.h"
 #include "gfx/rect.h"
 
+namespace gfx {
+  class Region;
+}
+
 namespace doc {
   class Image;
 }
@@ -49,6 +53,7 @@ namespace app {
     virtual ~EditorDecorator() { }
     virtual void preRenderDecorator(EditorPreRender* render) = 0;
     virtual void postRenderDecorator(EditorPostRender* render) = 0;
+    virtual void getInvalidDecoratoredRegion(Editor* editor, gfx::Region& region) = 0;
   };
 
 } // namespace app

src/app/ui/editor/select_box_state.cpp

@@ -321,6 +321,11 @@ void SelectBoxState::postRenderDecorator(EditorPostRender* render)
   }
 }
 
+void SelectBoxState::getInvalidDecoratoredRegion(Editor* editor, gfx::Region& region)
+{
+  // Do nothing
+}
+
 void SelectBoxState::updateContextBar()
 {
   ContextBar* contextBar = App::instance()->getMainWindow()->getContextBar();

src/app/ui/editor/select_box_state.h

@@ -86,6 +86,7 @@ namespace app {
     // EditorDecorator overrides
     virtual void preRenderDecorator(EditorPreRender* render) override;
     virtual void postRenderDecorator(EditorPostRender* render) override;
+    virtual void getInvalidDecoratoredRegion(Editor* editor, gfx::Region& region) override;
 
   private:
     typedef std::vector<Ruler> Rulers;

src/app/ui/editor/standby_state.cpp

@@ -671,6 +671,15 @@ void StandbyState::Decorator::postRenderDecorator(EditorPostRender* render)
   }
 }
 
+void StandbyState::Decorator::getInvalidDecoratoredRegion(Editor* editor, gfx::Region& region)
+{
+  gfx::Rect box1, box2;
+  if (getSymmetryHandles(editor, box1, box2)) {
+    region.createUnion(region, gfx::Region(box1));
+    region.createUnion(region, gfx::Region(box2));
+  }
+}
+
 bool StandbyState::Decorator::getSymmetryHandles(Editor* editor, gfx::Rect& box1, gfx::Rect& box2)
 {
   // Draw transformation handles (if the mask is visible and isn't frozen).

src/app/ui/editor/standby_state.h

@@ -65,6 +65,7 @@ namespace app {
       // EditorDecorator overrides
       void preRenderDecorator(EditorPreRender* render) override;
       void postRenderDecorator(EditorPostRender* render) override;
+      void getInvalidDecoratoredRegion(Editor* editor, gfx::Region& region) override;
 
     private:
       TransformHandles* m_transfHandles;