Gestures: Add more details and introduce on_gesture_handled

Add information about whether a gesture will be handled. This might be used to
determine whether events are supposed to be consumed.
Add information about the origin of a gesture. This might be used to determine
whether a gesture should be handled (e.g. only allow swipe from screen edge).
Add common GestureBackend interface that all backends have to implement.
Add a on_gesture_handled signal to the GestureTracker which runs if and only if
true was returned in on_gesture_detected. Before it is emitted prepare_gesture_handling
will be called on the backend. This will be needed for the upcoming PanBackend to avoid
conflicts in event consuming.
Add a utility get_action to the GestureSettings that gets the corresponding action for a gesture.
This allows to remove some duplicated code.

src/Gestures/Gesture.vala

@@ -35,9 +35,25 @@ namespace Gala {
     }
 
     public class Gesture {
+        public const float INVALID_COORD = float.MAX;
+
         public Clutter.EventType type;
         public GestureDirection direction;
         public int fingers;
         public Clutter.InputDeviceType performed_on_device_type;
+
+        /**
+         * The x coordinate of the initial contact point for the gesture.
+         * Doesn't have to be set. In that case it is set to {@link INVALID_COORD}.
+         * Currently the only backend not setting this is {@link GestureTracker.enable_touchpad}.
+         */
+        public float origin_x = INVALID_COORD;
+
+        /**
+         * The y coordinate of the initial contact point for the gesture.
+         * Doesn't have to be set. In that case it is set to {@link INVALID_COORD}.
+         * Currently the only backend not setting this is {@link GestureTracker.enable_touchpad}.
+         */
+        public float origin_y = INVALID_COORD;
     }
 }

src/Gestures/GestureSettings.vala

@@ -20,6 +20,14 @@
  * Utility class to access the gesture settings. Easily accessible through GestureTracker.settings.
  */
 public class Gala.GestureSettings : Object {
+    public enum GestureAction {
+        NONE,
+        SWITCH_WORKSPACE,
+        MOVE_TO_WORKSPACE,
+        SWITCH_WINDOWS,
+        MULTITASKING_VIEW
+    }
+
     private static GLib.Settings gala_settings;
     private static GLib.Settings touchpad_settings;
 
@@ -69,4 +77,41 @@ public class Gala.GestureSettings : Object {
     public static string get_string (string setting_id) {
         return gala_settings.get_string (setting_id);
     }
+
+    public static GestureAction get_action (Gesture gesture) {
+        if (gesture.type == TOUCHPAD_SWIPE) {
+            var fingers = gesture.fingers;
+
+            if (gesture.direction == LEFT || gesture.direction == RIGHT) {
+                var three_finger_swipe_horizontal = get_string ("three-finger-swipe-horizontal");
+                var four_finger_swipe_horizontal = get_string ("four-finger-swipe-horizontal");
+
+                if (fingers == 3 && three_finger_swipe_horizontal == "switch-to-workspace" ||
+                    fingers == 4 && four_finger_swipe_horizontal == "switch-to-workspace") {
+                    return SWITCH_WORKSPACE;
+                }
+
+                if (fingers == 3 && three_finger_swipe_horizontal == "move-to-workspace" ||
+                    fingers == 4 && four_finger_swipe_horizontal == "move-to-workspace") {
+                    return MOVE_TO_WORKSPACE;
+                }
+
+
+                if (fingers == 3 && three_finger_swipe_horizontal == "switch-windows" ||
+                    fingers == 4 && four_finger_swipe_horizontal == "switch-windows") {
+                    return SWITCH_WINDOWS;
+                }
+            } else if (gesture.direction == UP || gesture.direction == DOWN) {
+                var three_finger_swipe_up = get_string ("three-finger-swipe-up");
+                var four_finger_swipe_up = get_string ("four-finger-swipe-up");
+
+                if (fingers == 3 && three_finger_swipe_up == "multitasking-view" ||
+                    fingers == 4 && four_finger_swipe_up == "multitasking-view") {
+                    return MULTITASKING_VIEW;
+                }
+            }
+        }
+
+        return NONE;
+    }
 }

src/Gestures/GestureTracker.vala

@@ -16,6 +16,15 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+public interface Gala.GestureBackend : Object {
+    public signal bool on_gesture_detected (Gesture gesture, uint32 timestamp);
+    public signal void on_begin (double delta, uint64 time);
+    public signal void on_update (double delta, uint64 time);
+    public signal void on_end (double delta, uint64 time);
+
+    public virtual void prepare_gesture_handling () { }
+}
+
 /**
  * Allow to use multi-touch gestures from different sources (backends).
  * Usage:
@@ -68,11 +77,24 @@ public class Gala.GestureTracker : Object {
 
     /**
      * Emitted when a new gesture is detected.
-     * If the receiving code needs to handle this gesture, it should call to connect_handlers to
-     * start receiving updates.
+     * This should only be used to determine whether the gesture should be handled. This shouldn't
+     * do any preparations instead those should be done in {@link on_gesture_handled}. This is because
+     * the backend might have to do some preparations itself before you are allowed to do some to avoid
+     * conflicts.
      * @param gesture Information about the gesture.
+     * @return true if the gesture will be handled false otherwise. If false is returned the other
+     * signals may still be emitted but aren't guaranteed to be.
      */
-    public signal void on_gesture_detected (Gesture gesture);
+    public signal bool on_gesture_detected (Gesture gesture);
+
+    /**
+     * Emitted if true was returned form {@link on_gesture_detected}. This should
+     * be used to do any preparations for gesture handling and to call {@link connect_handlers} to
+     * start receiving updates.
+     * @param gesture the same gesture as in {@link on_gesture_detected}
+     * @param timestamp the timestamp of the event that initiated the gesture or {@link Meta.CURRENT_TIME}.
+     */
+    public signal void on_gesture_handled (Gesture gesture, uint32 timestamp);
 
     /**
      * Emitted right after on_gesture_detected with the initial gesture information.
@@ -201,10 +223,14 @@ public class Gala.GestureTracker : Object {
         return value;
     }
 
-    private void gesture_detected (Gesture gesture) {
-        if (enabled) {
-            on_gesture_detected (gesture);
+    private bool gesture_detected (GestureBackend backend, Gesture gesture, uint32 timestamp) {
+        if (enabled && on_gesture_detected (gesture)) {
+            backend.prepare_gesture_handling ();
+            on_gesture_handled (gesture, timestamp);
+            return true;
         }
+
+        return false;
     }
 
     private void gesture_begin (double percentage, uint64 elapsed_time) {

src/Gestures/ScrollBackend.vala

@@ -19,18 +19,13 @@
 /**
  * This gesture backend transforms the touchpad scroll events received by an actor into gestures.
  */
-public class Gala.ScrollBackend : Object {
+public class Gala.ScrollBackend : Object, GestureBackend {
     // Mutter does not expose the size of the touchpad, so we use the same values as GTK apps.
     // From GNOME Shell, TOUCHPAD_BASE_[WIDTH|HEIGHT] / SCROLL_MULTIPLIER
     // https://gitlab.gnome.org/GNOME/gnome-shell/-/blob/master/js/ui/swipeTracker.js
     private const double FINISH_DELTA_HORIZONTAL = 40;
     private const double FINISH_DELTA_VERTICAL = 30;
 
-    public signal void on_gesture_detected (Gesture gesture);
-    public signal void on_begin (double delta, uint64 time);
-    public signal void on_update (double delta, uint64 time);
-    public signal void on_end (double delta, uint64 time);
-
     public Clutter.Actor actor { get; construct; }
     public Clutter.Orientation orientation { get; construct; }
     public GestureSettings settings { get; construct; }
@@ -62,7 +57,7 @@ public class Gala.ScrollBackend : Object {
             return false;
         }
 
-        uint64 time = event.get_time ();
+        var time = event.get_time ();
         double x, y;
         event.get_scroll_delta (out x, out y);
 
@@ -80,10 +75,12 @@ public class Gala.ScrollBackend : Object {
 
         if (!started) {
             if (delta_x != 0 || delta_y != 0) {
-                Gesture gesture = build_gesture (delta_x, delta_y, orientation);
+                float origin_x, origin_y;
+                event.get_coords (out origin_x, out origin_y);
+                Gesture gesture = build_gesture (origin_x, origin_y, delta_x, delta_y, orientation, time);
                 started = true;
                 direction = gesture.direction;
-                on_gesture_detected (gesture);
+                on_gesture_detected (gesture, time);
 
                 double delta = calculate_delta (delta_x, delta_y, direction);
                 on_begin (delta, time);
@@ -114,7 +111,7 @@ public class Gala.ScrollBackend : Object {
             && event.get_scroll_direction () == Clutter.ScrollDirection.SMOOTH;
     }
 
-    private static Gesture build_gesture (double delta_x, double delta_y, Clutter.Orientation orientation) {
+    private static Gesture build_gesture (float origin_x, float origin_y, double delta_x, double delta_y, Clutter.Orientation orientation, uint32 timestamp) {
         GestureDirection direction;
         if (orientation == Clutter.Orientation.HORIZONTAL) {
             direction = delta_x > 0 ? GestureDirection.RIGHT : GestureDirection.LEFT;
@@ -126,7 +123,9 @@ public class Gala.ScrollBackend : Object {
             type = Clutter.EventType.SCROLL,
             direction = direction,
             fingers = 2,
-            performed_on_device_type = Clutter.InputDeviceType.TOUCHPAD_DEVICE
+            performed_on_device_type = Clutter.InputDeviceType.TOUCHPAD_DEVICE,
+            origin_x = origin_x,
+            origin_y = origin_y
         };
     }
 

src/Gestures/ToucheggBackend.vala

@@ -20,12 +20,7 @@
  * Singleton class to manage the connection with Touchégg daemon and receive touch events.
  * See: [[https://github.com/JoseExposito/touchegg]]
  */
-public class Gala.ToucheggBackend : Object {
-    public signal void on_gesture_detected (Gesture gesture);
-    public signal void on_begin (double delta, uint64 time);
-    public signal void on_update (double delta, uint64 time);
-    public signal void on_end (double delta, uint64 time);
-
+public class Gala.ToucheggBackend : Object, GestureBackend {
     /**
      * Gesture type as returned by the daemon.
      */
@@ -202,7 +197,7 @@ public class Gala.ToucheggBackend : Object {
         switch (signal_name) {
             case DBUS_ON_GESTURE_BEGIN:
                 Idle.add (() => {
-                    on_gesture_detected (make_gesture (type, direction, fingers, performed_on_device_type));
+                    on_gesture_detected (make_gesture (type, direction, fingers, performed_on_device_type), Meta.CURRENT_TIME);
                     on_begin (delta, elapsed_time);
                     return false;
                 });

src/Widgets/MultitaskingView.vala

@@ -71,11 +71,16 @@ namespace Gala {
             multitasking_gesture_tracker = new GestureTracker (ANIMATION_DURATION, ANIMATION_DURATION);
             multitasking_gesture_tracker.enable_touchpad ();
             multitasking_gesture_tracker.on_gesture_detected.connect (on_multitasking_gesture_detected);
+            multitasking_gesture_tracker.on_gesture_handled.connect (() => toggle (true, false));
 
             workspace_gesture_tracker = new GestureTracker (AnimationDuration.WORKSPACE_SWITCH_MIN, AnimationDuration.WORKSPACE_SWITCH);
             workspace_gesture_tracker.enable_touchpad ();
             workspace_gesture_tracker.enable_scroll (this, Clutter.Orientation.HORIZONTAL);
             workspace_gesture_tracker.on_gesture_detected.connect (on_workspace_gesture_detected);
+            workspace_gesture_tracker.on_gesture_handled.connect ((gesture, timestamp) => {
+                var direction = workspace_gesture_tracker.settings.get_natural_scroll_direction (gesture);
+                switch_workspace_with_gesture (direction, timestamp);
+            });
 
             workspaces = new Clutter.Actor ();
 
@@ -290,39 +295,31 @@ namespace Gala {
             workspaces.add_transition ("nudge", nudge);
         }
 
-        private void on_multitasking_gesture_detected (Gesture gesture) {
-            if (gesture.type != Clutter.EventType.TOUCHPAD_SWIPE ||
-                (gesture.fingers == 3 && GestureSettings.get_string ("three-finger-swipe-up") != "multitasking-view") ||
-                (gesture.fingers == 4 && GestureSettings.get_string ("four-finger-swipe-up") != "multitasking-view")
-            ) {
-                return;
+        private bool on_multitasking_gesture_detected (Gesture gesture) {
+            if (GestureSettings.get_action (gesture) != MULTITASKING_VIEW) {
+                return false;
             }
 
-            if (gesture.direction == GestureDirection.UP && !opened) {
-                toggle (true, false);
-            } else if (gesture.direction == GestureDirection.DOWN && opened) {
-                toggle (true, false);
+            if (gesture.direction == UP && !opened || gesture.direction == DOWN && opened) {
+                return true;
             }
+
+            return false;
         }
 
-        private void on_workspace_gesture_detected (Gesture gesture) {
+        private bool on_workspace_gesture_detected (Gesture gesture) {
             if (!opened) {
-                return;
+                return false;
             }
 
-            var can_handle_swipe = gesture.type == Clutter.EventType.TOUCHPAD_SWIPE &&
-                (gesture.direction == GestureDirection.LEFT || gesture.direction == GestureDirection.RIGHT);
-
-            var fingers = (gesture.fingers == 3 && Gala.GestureSettings.get_string ("three-finger-swipe-horizontal") == "switch-to-workspace") ||
-                (gesture.fingers == 4 && Gala.GestureSettings.get_string ("four-finger-swipe-horizontal") == "switch-to-workspace");
-
-            if (gesture.type == Clutter.EventType.SCROLL || (can_handle_swipe && fingers)) {
-                var direction = workspace_gesture_tracker.settings.get_natural_scroll_direction (gesture);
-                switch_workspace_with_gesture (direction);
+            if (gesture.type == SCROLL || GestureSettings.get_action (gesture) == SWITCH_WORKSPACE) {
+                return true;
             }
+
+            return false;
         }
 
-        private void switch_workspace_with_gesture (Meta.MotionDirection direction) {
+        private void switch_workspace_with_gesture (Meta.MotionDirection direction, uint32 timestamp) {
             if (switching_workspace_in_progress) {
                 return;
             }
@@ -380,7 +377,7 @@ namespace Gala {
 
             switching_workspace_with_gesture = true;
             if (target_workspace != null) {
-                target_workspace.activate (display.get_current_time ());
+                target_workspace.activate (timestamp);
             }
 
             if (is_nudge_animation) {