improved transition behavior

This is still not complete, but definitely should help a lot

app/widget/timelinewidget/tool/pointer.h

@@ -41,6 +41,8 @@ protected:
 
   virtual void InitiateDrag(Block* clicked_item, Timeline::MovementMode trim_mode, Qt::KeyboardModifiers modifiers);
 
+  TimelineViewGhostItem *GetExistingGhostFromBlock(Block *block);
+
   TimelineViewGhostItem* AddGhostFromBlock(Block *block, Timeline::MovementMode mode, bool check_if_exists = false);
 
   TimelineViewGhostItem* AddGhostFromNull(const rational& in, const rational& out, const Track::Reference& track, Timeline::MovementMode mode);
@@ -72,6 +74,8 @@ protected:
   const Timeline::MovementMode& drag_movement_mode() const { return drag_movement_mode_; }
   void set_drag_movement_mode(const Timeline::MovementMode &d) { drag_movement_mode_ = d; }
 
+  static bool CanTransitionMove(TransitionBlock *transit, const QVector<Block*> &clips);
+
   void SetMovementAllowed(bool e)
   {
     movement_allowed_ = e;