seat: Allow to cancel touches

After cancelation we destroy the touch points associated with this
surface as the Wayland spec says:

No further events are sent to the clients from that particular gesture.
Touch cancellation applies to all touch points currently active on this
client's surface. The client is responsible for finalizing the touch
points, future touch points on this surface may re-use the touch point
ID.

Closes: https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/2999

include/wlr/types/wlr_seat.h

@@ -119,9 +119,11 @@ struct wlr_touch_grab_interface {
 	void (*enter)(struct wlr_seat_touch_grab *grab, uint32_t time_msec,
 			struct wlr_touch_point *point);
 	void (*frame)(struct wlr_seat_touch_grab *grab);
-	// XXX this will conflict with the actual touch cancel which is different so
-	// we need to rename this
+	// Cancel grab
 	void (*cancel)(struct wlr_seat_touch_grab *grab);
+	// Send wl_touch::cancel
+	void (*wl_cancel)(struct wlr_seat_touch_grab *grab,
+			struct wlr_surface *surface);
 };
 
 /**
@@ -613,6 +615,14 @@ void wlr_seat_touch_send_up(struct wlr_seat *seat, uint32_t time_msec,
 void wlr_seat_touch_send_motion(struct wlr_seat *seat, uint32_t time_msec,
 		int32_t touch_id, double sx, double sy);
 
+/**
+ * Notify the seat that this is a global gesture and the client should cancel
+ * processing it. The event will go to the client for the surface given.
+ * This function does not respect touch grabs: you probably want
+ * `wlr_seat_touch_notify_cancel()` instead.
+ */
+void wlr_seat_touch_send_cancel(struct wlr_seat *seat, struct wlr_surface *surface);
+
 void wlr_seat_touch_send_frame(struct wlr_seat *seat);
 
 /**
@@ -639,6 +649,13 @@ void wlr_seat_touch_notify_up(struct wlr_seat *seat, uint32_t time_msec,
 void wlr_seat_touch_notify_motion(struct wlr_seat *seat, uint32_t time_msec,
 		int32_t touch_id, double sx, double sy);
 
+/**
+ * Notify the seat that this is a global gesture and the client should
+ * cancel processing it. Defers to any grab of the touch device.
+ */
+void wlr_seat_touch_notify_cancel(struct wlr_seat *seat,
+		struct wlr_surface *surface);
+
 void wlr_seat_touch_notify_frame(struct wlr_seat *seat);
 
 /**

types/seat/wlr_seat_touch.c

@@ -41,6 +41,11 @@ static void default_touch_cancel(struct wlr_seat_touch_grab *grab) {
 	// cannot be cancelled
 }
 
+static void default_touch_wl_cancel(struct wlr_seat_touch_grab *grab,
+		struct wlr_surface *surface) {
+	wlr_seat_touch_send_cancel(grab->seat, surface);
+}
+
 const struct wlr_touch_grab_interface default_touch_grab_impl = {
 	.down = default_touch_down,
 	.up = default_touch_up,
@@ -48,6 +53,7 @@ const struct wlr_touch_grab_interface default_touch_grab_impl = {
 	.enter = default_touch_enter,
 	.frame = default_touch_frame,
 	.cancel = default_touch_cancel,
+	.wl_cancel = default_touch_wl_cancel,
 };
 
 
@@ -238,6 +244,26 @@ void wlr_seat_touch_notify_frame(struct wlr_seat *seat) {
 	}
 }
 
+void wlr_seat_touch_notify_cancel(struct wlr_seat *seat,
+		struct wlr_surface *surface) {
+	struct wlr_seat_touch_grab *grab = seat->touch_state.grab;
+	if (grab->interface->wl_cancel) {
+		grab->interface->wl_cancel(grab, surface);
+	}
+
+	struct wl_client *client = wl_resource_get_client(surface->resource);
+	struct wlr_seat_client *seat_client = wlr_seat_client_for_wl_client(seat, client);
+	if (seat_client == NULL) {
+		return;
+	}
+	struct wlr_touch_point *point, *tmp;
+	wl_list_for_each_safe(point, tmp, &seat->touch_state.touch_points, link) {
+		if (point->client == seat_client) {
+			touch_point_destroy(point);
+		}
+	}
+}
+
 static void handle_point_focus_destroy(struct wl_listener *listener,
 		void *data) {
 	struct wlr_touch_point *point =
@@ -376,6 +402,22 @@ void wlr_seat_touch_send_frame(struct wlr_seat *seat) {
 	}
 }
 
+void wlr_seat_touch_send_cancel(struct wlr_seat *seat, struct wlr_surface *surface) {
+	struct wl_client *client = wl_resource_get_client(surface->resource);
+	struct wlr_seat_client *seat_client = wlr_seat_client_for_wl_client(seat, client);
+	if (seat_client == NULL) {
+		return;
+	}
+
+	struct wl_resource *resource;
+	wl_resource_for_each(resource, &seat_client->touches) {
+		if (seat_client_from_touch_resource(resource) == NULL) {
+			continue;
+		}
+		wl_touch_send_cancel(resource);
+	}
+}
+
 int wlr_seat_touch_num_points(struct wlr_seat *seat) {
 	return wl_list_length(&seat->touch_state.touch_points);
 }