Minimize fullscreen windows when they end up in the background

Alt-Tab away from a monitor sized on the primary monitor results into the top
panel being displayed on top of the window which looks very bad.

So just hide those windows by minimizing them.

The icon geometry animation does not really make sense for fullscreen windows
so just fade them out.

https://bugzilla.gnome.org/show_bug.cgi?id=693991

js/ui/layout.js

@@ -816,6 +816,23 @@ const LayoutManager = new Lang.Class({
         }
 
         if (primaryWasInFullscreen != this.primaryMonitor.inFullscreen) {
+            let windows = this._getWindowActorsForWorkspace(global.screen.get_active_workspace());
+            for (let i = 0; i < windows.length - 1; i++) {
+                let window = windows[i];
+                let metaWindow = window.meta_window;
+
+                // Skip minimized windows
+                if (!metaWindow.showing_on_its_workspace())
+                    continue;
+
+                // Skip windows that aren't on the primary monitor
+                if (!metaWindow.is_on_primary_monitor())
+                    continue;
+
+                // Minimize monitor sized windows
+                if (metaWindow.is_monitor_sized())
+                    metaWindow.minimize();
+            }
             this.emit('primary-fullscreen-changed', this.primaryMonitor.inFullscreen);
         }
     },

js/ui/windowManager.js

@@ -245,6 +245,19 @@ const WindowManager = new Lang.Class({
 
         this._minimizing.push(actor);
 
+        if (actor.meta_window.is_monitor_sized()) {
+            Tweener.addTween(actor,
+                         { opacity: 0,
+                           time: WINDOW_ANIMATION_TIME,
+                           transition: 'easeOutQuad',
+                           onComplete: this._minimizeWindowDone,
+                           onCompleteScope: this,
+                           onCompleteParams: [shellwm, actor],
+                           onOverwrite: this._minimizeWindowOverwritten,
+                           onOverwriteScope: this,
+                           onOverwriteParams: [shellwm, actor]
+                         });
+        } else {
             let xDest, yDest, xScale, yScale;
             let [success, geom] = actor.meta_window.get_icon_geometry();
             if (success) {
@@ -276,12 +289,14 @@ const WindowManager = new Lang.Class({
                                onOverwriteScope: this,
                                onOverwriteParams: [shellwm, actor]
                              });
+        }
     },
 
     _minimizeWindowDone : function(shellwm, actor) {
         if (this._removeEffect(this._minimizing, actor)) {
             Tweener.removeTweens(actor);
             actor.set_scale(1.0, 1.0);
+            actor.set_opacity(255);
             actor.move_anchor_point_from_gravity(Clutter.Gravity.NORTH_WEST);
 
             shellwm.completed_minimize(actor);