Keep selection after clear moving pixels (fix #1334)

If Aseprite is configured to keep the selection actived after clearing
the selection, we must keep the selection active anyway if we've moved
it.

src/app/ui/editor/moving_pixels_state.cpp

@@ -525,8 +525,15 @@ void MovingPixelsState::onBeforeCommandExecution(CommandExecutionEvent& ev)
     if (command->id() != CommandId::Copy) {
       m_pixelsMovement->trim();
 
+      // Should we keep the mask after an Edit > Clear command?
+      auto keepMask = PixelsMovement::DontKeepMask;
+      if (command->id() == CommandId::Clear &&
+          Preferences::instance().selection.keepSelectionAfterClear()) {
+        keepMask = PixelsMovement::KeepMask;
+      }
+
       // Discard the dragged image.
-      m_pixelsMovement->discardImage();
+      m_pixelsMovement->discardImage(PixelsMovement::CommitChanges, keepMask);
       m_discarded = true;
 
       // Quit from MovingPixelsState, back to standby.
@@ -610,7 +617,7 @@ void MovingPixelsState::onDropPixels(ContextBarObserver::DropAction action)
       break;
 
     case ContextBarObserver::CancelDrag:
-      m_pixelsMovement->discardImage(false);
+      m_pixelsMovement->discardImage(PixelsMovement::DontCommitChanges);
       m_discarded = true;
 
       // Quit from MovingPixelsState, back to standby.

src/app/ui/editor/pixels_movement.cpp

@@ -581,14 +581,16 @@ void PixelsMovement::dropImage()
   m_document->setExtraCel(ExtraCelRef(nullptr));
 }
 
-void PixelsMovement::discardImage(bool commit)
+void PixelsMovement::discardImage(const CommitChangesOption commit,
+                                  const KeepMaskOption keepMask)
 {
   m_isDragging = false;
 
   // Deselect the mask (here we don't stamp the image)
-  m_transaction.execute(new cmd::DeselectMask(m_document));
+  if (keepMask == DontKeepMask)
+    m_transaction.execute(new cmd::DeselectMask(m_document));
 
-  if (commit)
+  if (commit == CommitChanges)
     m_transaction.commit();
 
   // Destroy the extra cel and regenerate the mask boundaries (we've

src/app/ui/editor/pixels_movement.h

@@ -47,6 +47,16 @@ namespace app {
       ScaleFromPivot = 32,
     };
 
+    enum CommitChangesOption {
+      DontCommitChanges,
+      CommitChanges,
+    };
+
+    enum KeepMaskOption {
+      DontKeepMask,
+      KeepMask,
+    };
+
     PixelsMovement(Context* context,
                    Site site,
                    const Image* moveThis,
@@ -76,7 +86,8 @@ namespace app {
 
     void dropImageTemporarily();
     void dropImage();
-    void discardImage(bool commit = true);
+    void discardImage(const CommitChangesOption commit = CommitChanges,
+                      const KeepMaskOption keepMask = DontKeepMask);
     bool isDragging() const;
 
     gfx::Rect getImageBounds();