[gnome-shell] ScreenShield: fix positioning of background with multimonitor

[Giovanni Campagna <gcampagna src gnome org>]

commit d5e647a191b23c8a153223976e720b64c336d638
Author: Giovanni Campagna <gcampagna src gnome org>
Date:   Thu Feb 21 23:32:25 2013 +0100

    ScreenShield: fix positioning of background with multimonitor
    
    Previously, we would create one StBin per monitor, but each was positioned
    at 0,0 and sized as the screen, so they would overlap and draw the box shadows
    on top of the other backgrounds.
    Instead, we need to size appropriately the bin, and then we need to position
    the actual MetaBacgroundActor at 0,0, so add a flag to BackgroundManager
    for this.
    Also, get rid of MetaBackgroundGroup, they do nothing because the screenshield
    is not a descendant of the MetaWindowGroup and because the widget in between
    blocks the propagation of the visible region. At the same time, use a
    widget, not a bin, because StBin requires you to set .child, not call add_child().
    
    https://bugzilla.gnome.org/show_bug.cgi?id=694394

 js/ui/background.js   |   11 ++++++++---
 js/ui/screenShield.js |   23 ++++++++++++-----------
 2 files changed, 20 insertions(+), 14 deletions(-)
---
diff --git a/js/ui/background.js b/js/ui/background.js
index ef4dad3..3268059 100644
--- a/js/ui/background.js
+++ b/js/ui/background.js
@@ -635,12 +635,14 @@ const BackgroundManager = new Lang.Class({
         params = Params.parse(params, { container: null,
                                         layoutManager: Main.layoutManager,
                                         monitorIndex: null,
-                                        effects: Meta.BackgroundEffects.NONE });
+                                        effects: Meta.BackgroundEffects.NONE,
+                                        controlPosition: true });
 
         this._container = params.container;
         this._layoutManager = params.layoutManager;
         this._effects = params.effects;
         this._monitorIndex = params.monitorIndex;
+        this._controlPosition = params.controlPosition;
 
         this.background = this._createBackground();
         this._newBackground = null;
@@ -700,9 +702,12 @@ const BackgroundManager = new Lang.Class({
         this._container.add_child(background.actor);
 
         let monitor = this._layoutManager.monitors[this._monitorIndex];
-        background.actor.set_position(monitor.x, monitor.y);
+
         background.actor.set_size(monitor.width, monitor.height);
-        background.actor.lower_bottom();
+        if (this._controlPosition) {
+            background.actor.set_position(monitor.x, monitor.y);
+            background.actor.lower_bottom();
+        }
 
         let signalId = background.connect('changed', Lang.bind(this, function() {
             background.disconnect(signalId);
diff --git a/js/ui/screenShield.js b/js/ui/screenShield.js
index 5ab593f..7b3953b 100644
--- a/js/ui/screenShield.js
+++ b/js/ui/screenShield.js
@@ -447,7 +447,7 @@ const ScreenShield = new Lang.Class({
 
         this._lockScreenGroup.add_actor(this._lockScreenContents);
 
-        this._backgroundGroup = new Meta.BackgroundGroup();
+        this._backgroundGroup = new Clutter.Actor();
 
         this._lockScreenGroup.add_actor(this._backgroundGroup);
         this._backgroundGroup.lower_bottom();
@@ -538,21 +538,22 @@ const ScreenShield = new Lang.Class({
     },
 
     _createBackground: function(monitorIndex) {
-        let bin = new St.Bin({ style_class: 'screen-shield-background' });
-
-        let group = new Meta.BackgroundGroup();
-        bin.child = group;
-
-        let bgManager = new Background.BackgroundManager({ container: group,
+        let monitor = Main.layoutManager.monitors[monitorIndex];
+        let widget = new St.Widget({ style_class: 'screen-shield-background',
+                                     x: monitor.x,
+                                     y: monitor.y,
+                                     width: monitor.width,
+                                     height: monitor.height });
+
+        let bgManager = new Background.BackgroundManager({ container: widget,
                                                            monitorIndex: monitorIndex,
-                                                           effects: Meta.BackgroundEffects.BLUR | 
Meta.BackgroundEffects.DESATURATE });
-
+                                                           effects: Meta.BackgroundEffects.BLUR | 
Meta.BackgroundEffects.DESATURATE,
+                                                           controlPosition: false });
         bgManager.background.saturation = 0.6;
 
         this._bgManagers.push(bgManager);
 
-        this._backgroundGroup.add_child(bin);
-        bin.lower_bottom();
+        this._backgroundGroup.add_child(widget);
     },
 
     _updateBackgrounds: function() {