[Overview] Delay repositioning after closing windows

When closing windows in the window picker, the remaining windows
move to their new positions, which prevents the user from performing
additional actions in the picker until the animation stops and the
user adjusts to the new layout.

Instead we try to be smart and delay the repositioning, either until
the pointer stops moving or until it leaves the workspace.

https://bugzilla.gnome.org/show_bug.cgi?id=611167

js/ui/workspace.js

@@ -662,6 +662,7 @@ Workspace.prototype = {
                                                           Lang.bind(this, this._windowAdded));
         this._windowRemovedId = this._metaWorkspace.connect('window-removed',
                                                             Lang.bind(this, this._windowRemoved));
+        this._repositionWindowsId = 0;
 
         this._visible = false;
 
@@ -1017,6 +1018,11 @@ Workspace.prototype = {
      *  ANIMATE - Indicates that we need animate changing position.
      */
     positionWindows : function(flags) {
+        if (this._repositionWindowsId > 0) {
+            Mainloop.source_remove(this._repositionWindowsId);
+            this._repositionWindowsId = 0;
+        }
+
         let totalVisible = 0;
 
         let visibleClones = this._getVisibleClones();
@@ -1132,6 +1138,27 @@ Workspace.prototype = {
         }
     },
 
+    _delayedWindowRepositioning: function() {
+        let [child, x, y, mask] =
+            Gdk.Screen.get_default().get_root_window().get_pointer();
+        let wsWidth = this.actor.width * this.scale;
+        let wsHeight = this.actor.height * this.scale;
+
+        let pointerHasMoved = (this._cursorX != x && this._cursorY != y);
+        let inWorkspace = (this.gridX < x && x < this.gridX + wsWidth &&
+                           this.gridY < y && y < this.gridY + wsHeight);
+
+        if (pointerHasMoved && inWorkspace) {
+            // store current cursor position
+            this._cursorX = x;
+            this._cursorY = y;
+            return true;
+        }
+
+        this.positionWindows(WindowPositionFlags.ANIMATE);
+        return false;
+    },
+
     _windowRemoved : function(metaWorkspace, metaWin) {
         let win = metaWin.get_compositor_private();
 
@@ -1163,7 +1190,26 @@ Workspace.prototype = {
         }
         clone.destroy();
 
-        this.positionWindows(WindowPositionFlags.ANIMATE);
+
+        // We need to reposition the windows; to avoid shuffling windows
+        // around while the user is interacting with the workspace, we delay
+        // the positioning until the pointer remains still for at least 750 ms
+        // or is moved outside the workspace
+
+        // remove old handler
+        if (this._repositionWindowsId > 0) {
+            Mainloop.source_remove(this._repositionWindowsId);
+            this._repositionWindowsId = 0;
+        }
+
+        // setup new handler
+        let [child, x, y, mask] =
+            Gdk.Screen.get_default().get_root_window().get_pointer();
+        this._cursorX = x;
+        this._cursorY = y;
+
+        this._repositionWindowsId = Mainloop.timeout_add(750,
+            Lang.bind(this, this._delayedWindowRepositioning));
     },
 
     _windowAdded : function(metaWorkspace, metaWin) {
@@ -1354,6 +1400,9 @@ Workspace.prototype = {
         this._metaWorkspace.disconnect(this._windowAddedId);
         this._metaWorkspace.disconnect(this._windowRemovedId);
 
+        if (this._repositionWindowsId > 0)
+            Mainloop.source_remove(this._repositionWindowsId);
+
         // Usually, the windows will be destroyed automatically with
         // their parent (this.actor), but we might have a zoomed window
         // which has been reparented to the stage - _windows[0] holds