Fade out desktop icons when showing overview

As desktop icons don't have any purpose in the overview (except for
distracting the user), fade them out when entering the overview.

Unfortunately, the fading effect affects performance, therefore hide
icons directly when there are maximized windows on the desktop.

https://bugzilla.gnome.org/show_bug.cgi?id=600999

js/ui/main.js

@@ -47,8 +47,6 @@ let _errorLogStack = [];
 let _startDate;
 
 let background = null;
-let _windowAddedSignalId = null;
-let _windowRemovedSignalId = null;
 
 function start() {
     // Add a binding for "global" in the global JS namespace; (gjs
@@ -149,10 +147,8 @@ function start() {
     });
 
     background = global.create_root_pixmap_actor();
-    global.screen.connect('workspace-switched', _onWorkspaceSwitched);
     global.stage.add_actor(background);
     background.lower_bottom();
-    _onWorkspaceSwitched(global.screen, -1);
 
     global.connect('screen-size-changed', _relayout);
 
@@ -214,45 +210,6 @@ function _getAndClearErrorStack() {
     return errors;
 }
 
-function showBackground() {
-    background.show();
-}
-
-function hideBackground() {
-    background.hide();
-}
-
-function _onWorkspaceSwitched(screen, from) {
-    let workspace = screen.get_active_workspace();
-
-    if (from != -1) {
-        let old_workspace = screen.get_workspace_by_index(from);
-
-        if (_windowAddedSignalId !== null)
-            old_workspace.disconnect(_windowAddedSignalId);
-        if (background.windowRemovedSignalId !== null)
-            old_workspace.disconnect(_windowRemovedSignalId);
-    }
-
-    _windowAddedSignalId = workspace.connect('window-added', function(workspace, win) {
-        if (win.window_type == Meta.WindowType.DESKTOP)
-            hideBackground();
-    });
-    _windowRemovedSignalId = workspace.connect('window-removed', function(workspace, win) {
-        if (win.window_type == Meta.WindowType.DESKTOP)
-            showBackground();
-    });
-
-    function _isDesktop(win) {
-        return win.window_type == Meta.WindowType.DESKTOP;
-    }
-
-    if (workspace.list_windows().some(_isDesktop))
-        hideBackground();
-    else
-        showBackground();
-}
-
 function _relayout() {
     let primary = global.get_primary_monitor();
     panel.actor.set_position(primary.x, primary.y);

js/ui/workspace.js

@@ -283,20 +283,58 @@ function DesktopClone(window) {
 
 DesktopClone.prototype = {
     _init : function(window) {
+        this.actor = new Clutter.Group({ reactive: true });
+
+        let background = new Clutter.Clone({ source: Main.background.source });
+        this.actor.add_actor(background);
+
         if (window) {
-            this.actor = new Clutter.Clone({ source: window.get_texture(),
+            this._desktop = new Clutter.Clone({ source: window.get_texture() });
-                                             reactive: true });
+            this.actor.add_actor(this._desktop);
+            this._desktop.hide();
         } else {
-            this.actor = new Clutter.Clone({ source: Main.background.source,
+            this._desktop = null;
-                                             reactive: true,
-                                             width: global.screen_width,
-                                             height: global.screen_height });
         }
 
         this.actor.connect('button-release-event',
                            Lang.bind(this, this._onButtonRelease));
     },
 
+    zoomFromOverview: function(fadeInIcons) {
+        if (this._desktop == null)
+            return;
+
+        if (fadeInIcons) {
+            this._desktop.opacity = 0;
+            this._desktop.show();
+            Tweener.addTween(this._desktop,
+                             { opacity: 255,
+                               time: Overview.ANIMATION_TIME,
+                               transition: "easeOutQuad" });
+        }
+    },
+
+    zoomToOverview: function(fadeOutIcons) {
+        if (this._desktop == null)
+            return;
+
+        if (fadeOutIcons) {
+            this._desktop.opacity = 255;
+            this._desktop.show();
+            Tweener.addTween(this._desktop,
+                             { opacity: 0,
+                               time: Overview.ANIMATION_TIME,
+                               transition: "easeOutQuad",
+                               onComplete: Lang.bind(this,
+                                   function() {
+                                       this._desktop.hide();
+                                   })
+                             });
+        } else {
+            this._desktop.hide();
+        }
+    },
+
     _onButtonRelease : function (actor, event) {
         this.emit('selected', event.get_time());
     }
@@ -601,7 +639,6 @@ Workspace.prototype = {
     },
 
     _lookupIndex: function (metaWindow) {
-        let index, clone;
         for (let i = 0; i < this._windows.length; i++) {
             if (this._windows[i].metaWindow == metaWindow) {
                 return i;
@@ -1152,6 +1189,18 @@ Workspace.prototype = {
         this.positionWindows(WindowPositionFlags.ANIMATE);
     },
 
+    // check for maximized windows on the workspace
+    _haveMaximizedWindows: function() {
+        for (let i = 1; i < this._windows.length; i++) {
+            let metaWindow = this._windows[i].metaWindow;
+            if (metaWindow.showing_on_its_workspace() &&
+                metaWindow.maximized_horizontally &&
+                metaWindow.maximized_vertically)
+                return true;
+        }
+        return false;
+    },
+
     // Animate the full-screen to Overview transition.
     zoomToOverview : function(animate) {
         this.actor.set_position(this.gridX, this.gridY);
@@ -1163,6 +1212,12 @@ Workspace.prototype = {
         else
             this.positionWindows(WindowPositionFlags.ZOOM);
 
+        let active = global.screen.get_active_workspace_index();
+        let fadeInIcons = (animate &&
+                           active == this.workspaceNum &&
+                           !this._haveMaximizedWindows());
+        this._desktop.zoomToOverview(fadeInIcons);
+
         this._visible = true;
     },
 
@@ -1203,6 +1258,11 @@ Workspace.prototype = {
             }
         }
 
+        let active = global.screen.get_active_workspace_index();
+        let fadeOutIcons = (active == this.workspaceNum &&
+                            !this._haveMaximizedWindows());
+        this._desktop.zoomFromOverview(fadeOutIcons);
+
         this._visible = false;
     },