windowManager: Add TouchpadWorkspaceSwitchAction

This object (not really a Clutter.GestureAction) sets up a captured-event
handler, which exclusively looks for 4 finger touchpad swipes, emitting
an ::activated signal under the same terms than WorkspaceSwitchAction.

js/ui/windowManager.js

@@ -477,6 +477,64 @@ const TilePreview = new Lang.Class({
     }
 });
 
+const TouchpadWorkspaceSwitchAction = new Lang.Class({
+    Name: 'TouchpadWorkspaceSwitchAction',
+
+    _checkActivated: function() {
+        const MOTION_THRESHOLD = 50;
+        let allowedModes = Shell.ActionMode.NORMAL | Shell.ActionMode.OVERVIEW;
+        let dir;
+
+        if ((allowedModes & Main.actionMode) == 0)
+            return;
+
+        if (this._dy < MOTION_THRESHOLD)
+            dir = Meta.MotionDirection.DOWN;
+        else if (this._dy > MOTION_THRESHOLD)
+            dir = Meta.MotionDirection.UP;
+        else if (this._dx < MOTION_THRESHOLD)
+            dir = Meta.MotionDirection.RIGHT;
+        else if (this._dx > MOTION_THRESHOLD)
+            dir = Meta.MotionDirection.LEFT;
+        else
+            return;
+
+        this.emit('activated', dir);
+    },
+
+    _handleEvent: function(actor, event) {
+        if (event.type() != Clutter.EventType.TOUCHPAD_SWIPE_BEGIN &&
+            event.type() != Clutter.EventType.TOUCHPAD_SWIPE_UPDATE &&
+            event.type() != Clutter.EventType.TOUCHPAD_SWIPE_END)
+            return Clutter.EVENT_PROPAGATE;
+
+        if (event.get_gesture_swipe_finger_count() != 4)
+            return Clutter.EVENT_PROPAGATE;
+
+        if (event.type() == Clutter.EventType.TOUCHPAD_SWIPE_UPDATE) {
+            let [dx, dy] = event.get_gesture_motion_delta(event);
+
+            this._dx += dx;
+            this._dy += dy;
+        } else {
+            if (event.type() == Clutter.EventType.TOUCHPAD_SWIPE_END)
+                this._checkActivated();
+
+            this._dx = 0;
+            this._dy = 0;
+        }
+
+        return Clutter.EVENT_STOP;
+    },
+
+    _init: function(actor) {
+        this._dx = 0;
+        this._dy = 0;
+        actor.connect('captured-event', Lang.bind(this, this._handleEvent));
+    },
+});
+Signals.addSignalMethods(TouchpadWorkspaceSwitchAction.prototype);
+
 const WorkspaceSwitchAction = new Lang.Class({
     Name: 'WorkspaceSwitchAction',
     Extends: Clutter.SwipeAction,
@@ -866,15 +924,22 @@ const WindowManager = new Lang.Class({
                                                 false, -1, 1);
 
         let gesture = new WorkspaceSwitchAction();
-        gesture.connect('activated', Lang.bind(this, function(action, direction) {
+        gesture.connect('activated', Lang.bind(this, this._actionSwitchWorkspace));
-            let newWs = global.screen.get_active_workspace().get_neighbor(direction);
-            this.actionMoveWorkspace(newWs);
-        }));
         global.stage.add_action(gesture);
 
+        // This is not a normal Clutter.GestureAction, doesn't need add_action()
+        gesture = new TouchpadWorkspaceSwitchAction(global.stage);
+        gesture.connect('activated', Lang.bind(this, this._actionSwitchWorkspace));
+
         gesture = new AppSwitchAction();
         gesture.connect('activated', Lang.bind(this, this._switchApp));
         global.stage.add_action(gesture);
+
+    },
+
+    _actionSwitchWorkspace: function(action, direction) {
+            let newWs = global.screen.get_active_workspace().get_neighbor(direction);
+            this.actionMoveWorkspace(newWs);
     },
 
     _lookupIndex: function (windows, metaWindow) {