From: Jonas Ådahl <jadahl@gmail.com>
Date: Thu, 3 Jan 2019 10:53:13 +0000 (+0100)
Subject: dnd: Repick target actor if destroyed mid iteration
X-Git-Tag: archive/raspbian/50.5-1+rpi1~1^2~897^2~1^2~6
X-Git-Url: https://dgit.raspbian.org/%22http://www.example.com/cgi/%22/%22http:/www.example.com/cgi/%22?a=commitdiff_plain;h=4259676f6e09de275d29dcae5b00026f26faa9ab;p=gnome-shell.git

dnd: Repick target actor if destroyed mid iteration

The picked target actor may be destroyed (e.g. hover style change
resulting in the ClutterTexture to be destroyed). If we don't handle
this, GJS will abort when it sees the exception caused by Javascript
code trying to access the destroyed target actor.

To handle it, listen on the 'destroy' signal on the target actor, and
repick, so a valid actor is passed to the next motion callback.

Fixes: https://gitlab.gnome.org/GNOME/gnome-shell/issues/632
---

diff --git a/js/ui/dnd.js b/js/ui/dnd.js
index 8483e89fc..665881363 100644
--- a/js/ui/dnd.js
+++ b/js/ui/dnd.js
@@ -411,10 +411,15 @@ var _Draggable = new Lang.Class({
         return true;
     },
 
+    _pickTargetActor() {
+        return this._dragActor.get_stage().get_actor_at_pos(Clutter.PickMode.ALL,
+                                                            this._dragX, this._dragY);
+    },
+
     _updateDragHover() {
         this._updateHoverId = 0;
-        let target = this._dragActor.get_stage().get_actor_at_pos(Clutter.PickMode.ALL,
-                                                                  this._dragX, this._dragY);
+        let target = this._pickTargetActor();
+
         let dragEvent = {
             x: this._dragX,
             y: this._dragY,
@@ -422,6 +427,18 @@ var _Draggable = new Lang.Class({
             source: this.actor._delegate,
             targetActor: target
         };
+
+        let targetActorDestroyHandlerId;
+        let handleTargetActorDestroyClosure;
+        handleTargetActorDestroyClosure = () => {
+            target = this._pickTargetActor();
+            dragEvent.targetActor = target;
+            targetActorDestroyHandlerId =
+                target.connect('destroy', handleTargetActorDestroyClosure);
+        };
+        targetActorDestroyHandlerId =
+            target.connect('destroy', handleTargetActorDestroyClosure);
+
         for (let i = 0; i < dragMonitors.length; i++) {
             let motionFunc = dragMonitors[i].dragMotion;
             if (motionFunc) {
@@ -432,6 +449,7 @@ var _Draggable = new Lang.Class({
                 }
             }
         }
+        dragEvent.targetActor.disconnect(targetActorDestroyHandlerId);
 
         while (target) {
             if (target._delegate && target._delegate.handleDragOver) {