[gnome-shell] background.js: fix updating a BackgroundSource on monitor changes

[Owen Taylor <otaylor src gnome org>]

commit 0992bd41ed27d5f1243e9111a10e48d4631b5751
Author: Owen W. Taylor <otaylor fishsoup net>
Date:   Fri Sep 12 17:07:31 2014 -0400

    background.js: fix updating a BackgroundSource on monitor changes
    
    It was assumed that BackgroundSource objects were always destroyed
    on monitor changes because the BackgroundManager objects that hold
    references were destroyed, but sequencing of updating of different
    BackgroundManager objects meant that was not the case.
    
    Properly update any cached Background objects held by the
    BackgroundSource on a change to the monitor layout; in particular this
    means updating animations in case they are multi-resolution.

 js/ui/background.js |   50 +++++++++++++++++++++++++++++++++++++++++---------
 1 files changed, 41 insertions(+), 9 deletions(-)
---
diff --git a/js/ui/background.js b/js/ui/background.js
index 00b9d63..9ca9312 100644
--- a/js/ui/background.js
+++ b/js/ui/background.js
@@ -242,11 +242,7 @@ const Background = new Lang.Class({
 
     destroy: function() {
         this._cancellable.cancel();
-
-        if (this._updateAnimationTimeoutId) {
-            GLib.source_remove (this._updateAnimationTimeoutId);
-            this._updateAnimationTimeoutId = 0;
-        }
+        this._removeAnimationTimeout();
 
         let i;
         let keys = Object.keys(this._fileWatches);
@@ -260,6 +256,13 @@ const Background = new Lang.Class({
         this._settingsChangedSignalId = 0;
     },
 
+    updateResolution: function() {
+        if (this._animation) {
+            this._removeAnimationTimeout();
+            this._updateAnimation();
+        }
+    },
+
     _setLoaded: function() {
         if (this.isLoaded)
             return;
@@ -303,6 +306,13 @@ const Background = new Lang.Class({
         this._fileWatches[filename] = signalId;
     },
 
+    _removeAnimationTimeout: function() {
+        if (this._updateAnimationTimeoutId) {
+            GLib.source_remove(this._updateAnimationTimeoutId);
+            this._updateAnimationTimeoutId = 0;
+        }
+    },
+
     _updateAnimation: function() {
         this._updateAnimationTimeoutId = 0;
 
@@ -477,6 +487,23 @@ const BackgroundSource = new Lang.Class({
         this._overrideImage = GLib.getenv('SHELL_BACKGROUND_IMAGE');
         this._settings = new Gio.Settings({ schema_id: settingsSchema });
         this._backgrounds = [];
+
+        this._monitorsChangedId = global.screen.connect('monitors-changed',
+                                                        Lang.bind(this, this._onMonitorsChanged));
+    },
+
+    _onMonitorsChanged: function() {
+        for (let monitorIndex in this._backgrounds) {
+            let background = this._backgrounds[monitorIndex];
+
+            if (monitorIndex < this._layoutManager.monitors.length) {
+                background.updateResolution();
+            } else {
+                background.disconnect(background._changedId);
+                background.destroy();
+                delete this._backgrounds[monitorIndex];
+            }
+        }
     },
 
     getBackground: function(monitorIndex) {
@@ -513,8 +540,8 @@ const BackgroundSource = new Lang.Class({
                 style: style
             });
 
-            let changedId = background.connect('changed', Lang.bind(this, function() {
-                background.disconnect(changedId);
+            background._changedId = background.connect('changed', Lang.bind(this, function() {
+                background.disconnect(background._changedId);
                 background.destroy();
                 delete this._backgrounds[monitorIndex];
             }));
@@ -526,8 +553,13 @@ const BackgroundSource = new Lang.Class({
     },
 
     destroy: function() {
-        for (let monitorIndex in this._backgrounds)
-            this._backgrounds[monitorIndex].destroy();
+        global.screen.disconnect(this._monitorsChangedId);
+
+        for (let monitorIndex in this._backgrounds) {
+            let background = this._backgrounds[monitorIndex];
+            background.disconnect(background._changedId);
+            background.destroy();
+        }
 
         this._backgrounds = null;
     }