[gnome-shell] boxpointer: Unset the sourceActor on destruction

[Florian Müllner <fmuellner src gnome org>]

commit 2fd120162fe49bc85d7773435ac1412c512c5af4
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Thu Jun 13 18:57:38 2019 +0200

    boxpointer: Unset the sourceActor on destruction
    
    A boxpointer sourceActor could be destroyed before the boxpointer itself.
    In such case, unset the sourceActor reference, connecting to 'destroy' signal.
    
    Fixes: https://gitlab.gnome.org/GNOME/gnome-shell/issues/1295
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/576

 js/ui/boxpointer.js | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)
---
diff --git a/js/ui/boxpointer.js b/js/ui/boxpointer.js
index 188e8386f..5615614e1 100644
--- a/js/ui/boxpointer.js
+++ b/js/ui/boxpointer.js
@@ -48,6 +48,15 @@ var BoxPointer = GObject.registerClass({
         this._sourceAlignment = 0.5;
         this._capturedEventId = 0;
         this._muteInput();
+
+        this.connect('destroy', this._onDestroy.bind(this));
+    }
+
+    _onDestroy() {
+        if (this._sourceActorDestroyId) {
+            this._sourceActor.disconnect(this._sourceActorDestroyId);
+            delete this._sourceActorDestroyId;
+        }
     }
 
     get arrowSide() {
@@ -452,9 +461,26 @@ var BoxPointer = GObject.registerClass({
         // so that we can query the correct size.
         this.show();
 
-        this._sourceActor = sourceActor;
+        if (!this._sourceActor || sourceActor != this._sourceActor) {
+            if (this._sourceActorDestroyId) {
+                this._sourceActor.disconnect(this._sourceActorDestroyId);
+                delete this._sourceActorDestroyId;
+            }
+
+            this._sourceActor = sourceActor;
+
+            if (this._sourceActor) {
+                this._sourceActorDestroyId = this._sourceActor.connect('destroy', () => {
+                    this._sourceActor = null;
+                    delete this._sourceActorDestroyId;
+                })
+            }
+        }
         this._arrowAlignment = alignment;
 
+        if (!this._sourceActor)
+            return;
+
         this._reposition();
         this._updateFlip();
     }