[gnome-shell] DND: don't cancel a drag if the actor is destroyed inside acceptDrop

[Giovanni Campagna <gcampagna src gnome org>]

commit 57f27572ae147bba532b849ee0d56a5468b3c59f
Author: Giovanni Campagna <gcampagna src gnome org>
Date:   Sat Jan 19 02:25:14 2013 +0100

    DND: don't cancel a drag if the actor is destroyed inside acceptDrop
    
    This happens in the case of Workspace/WorkspaceThumbnail: they call
    meta_window_change_workspace_by_index(), which fires window-removed
    on the old workspace, thus destroying the window clone.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=685285

 js/ui/dnd.js |   12 +++++++++---
 1 files changed, 9 insertions(+), 3 deletions(-)
---
diff --git a/js/ui/dnd.js b/js/ui/dnd.js
index f8eecd3..4a61cd1 100644
--- a/js/ui/dnd.js
+++ b/js/ui/dnd.js
@@ -85,11 +85,13 @@ const _Draggable = new Lang.Class({
 
         this.actor.connect('destroy', Lang.bind(this, function() {
             this._actorDestroyed = true;
+
             // If the drag actor is destroyed and we were going to fix
             // up its hover state, fix up the parent hover state instead
             if (this.actor == this._firstLeaveActor)
                 this._firstLeaveActor = this._dragOrigParent;
-            if (this._dragInProgress)
+
+            if (this._dragInProgress && this._dragCancellable)
                 this._cancelDrag(global.get_current_time());
             this.disconnectAll();
         }));
@@ -102,6 +104,7 @@ const _Draggable = new Lang.Class({
         this._buttonDown = false; // The mouse button has been pressed and has not yet been released.
         this._dragInProgress = false; // The drag has been started, and has not been dropped or cancelled 
yet.
         this._animationInProgress = false; // The drag is over and the item is in the process of animating 
to its original position (snapping back or reverting).
+        this._dragCancellable = true;
 
         // During the drag, we eat enter/leave events so that actors don't prelight.
         // But we remember the actors that we first left/last entered so we can
@@ -439,6 +442,11 @@ const _Draggable = new Lang.Class({
                 }
         }
 
+        // At this point it is too late to cancel a drag by destroying
+        // the actor, the fate of which is decided by acceptDrop and its
+        // side-effects
+        this._dragCancellable = false;
+
         while (target) {
             if (target._delegate && target._delegate.acceptDrop) {
                 let [r, targX, targY] = target.transform_stage_point(dropX, dropY);
@@ -447,8 +455,6 @@ const _Draggable = new Lang.Class({
                                                 targX,
                                                 targY,
                                                 event.get_time())) {
-                    if (this._actorDestroyed)
-                        return true;
                     // If it accepted the drop without taking the actor,
                     // handle it ourselves.
                     if (this._dragActor.get_parent() == Main.uiGroup) {