[gnome-shell] windowManager: Update stacking during workspace switches

[Florian Müllner <fmuellner src gnome org>]

commit 0257a23c31244774a7dddec356cd98b85cb2a2a2
Author: Florian Müllner <fmuellner gnome org>
Date:   Wed Dec 17 22:57:44 2014 +0100

    windowManager: Update stacking during workspace switches
    
    When animating workspace switches, windows on the old and new workspaces
    are temporarily reparented. If windows are restacked, those windows will
    thus be ignored by mutter until meta_switch_workspace_completed() resyncs
    the stacking at the end of the animation.
    As a result, activating a window on another workspace that is not on top
    of the stack is very noticeably a two-step operation of switching workspace
    and raising the window. There is a technical reason for that order[0], but
    we can avoid the visible disruption by manually syncing the stack during
    the switch operation.
    
    [0] https://git.gnome.org/browse/mutter/tree/src/core/workspace.c#n590
    
    https://bugzilla.gnome.org/show_bug.cgi?id=741680

 js/ui/windowManager.js |   19 +++++++++++++++++++
 1 files changed, 19 insertions(+), 0 deletions(-)
---
diff --git a/js/ui/windowManager.js b/js/ui/windowManager.js
index d88c022..b8af0e0 100644
--- a/js/ui/windowManager.js
+++ b/js/ui/windowManager.js
@@ -618,6 +618,7 @@ const WindowManager = new Lang.Class({
         this._shellwm.connect('destroy', Lang.bind(this, this._destroyWindow));
         this._shellwm.connect('filter-keybinding', Lang.bind(this, this._filterKeybinding));
         this._shellwm.connect('confirm-display-change', Lang.bind(this, this._confirmDisplayChange));
+        global.screen.connect('restacked', Lang.bind(this, this._syncStacking));
 
         this._workspaceSwitcherPopup = null;
         this._tilePreview = null;
@@ -1248,6 +1249,24 @@ const WindowManager = new Lang.Class({
         return !(this._allowedKeybindings[binding.get_name()] & Main.actionMode);
     },
 
+    _syncStacking: function() {
+        if (this._switchData == null)
+            return;
+
+        // Update stacking of windows in inGroup (aka the workspace we are
+        // switching to). Windows in outGroup are about to be hidden anyway,
+        // so we just ignore them here.
+        let windows = global.get_window_actors();
+        let sibling = null;
+        for (let i = 0; i < windows.length; i++) {
+            if (windows[i].get_parent() != this._switchData.inGroup)
+                continue;
+
+            this._switchData.inGroup.set_child_above_sibling(windows[i], sibling);
+            sibling = windows[i];
+        }
+    },
+
     _switchWorkspace : function(shellwm, from, to, direction) {
         if (!Main.sessionMode.hasWorkspaces || !this._shouldAnimate()) {
             shellwm.completed_switch_workspace();