examples/touch: support touch cancel events

examples/touch.c

@@ -46,6 +46,7 @@ struct touch_state {
 	struct wl_listener down;
 	struct wl_listener up;
 	struct wl_listener motion;
+	struct wl_listener cancel;
 	struct wl_list link;
 	void *data;
 };
@@ -130,6 +131,19 @@ static void touch_motion_notify(struct wl_listener *listener, void *data) {
 	}
 }
 
+static void touch_cancel_notify(struct wl_listener *listener, void *data) {
+	struct wlr_touch_cancel_event *event = data;
+	struct touch_state *tstate = wl_container_of(listener, tstate, cancel);
+	struct sample_state *sample = tstate->sample;
+	struct touch_point *point, *tmp;
+	wl_list_for_each_safe(point, tmp, &sample->touch_points, link) {
+		if (point->touch_id == event->touch_id) {
+			wl_list_remove(&point->link);
+			break;
+		}
+	}
+}
+
 static void touch_destroy_notify(struct wl_listener *listener, void *data) {
 	struct touch_state *tstate = wl_container_of(listener, tstate, destroy);
 	wl_list_remove(&tstate->link);
@@ -137,6 +151,7 @@ static void touch_destroy_notify(struct wl_listener *listener, void *data) {
 	wl_list_remove(&tstate->down.link);
 	wl_list_remove(&tstate->up.link);
 	wl_list_remove(&tstate->motion.link);
+	wl_list_remove(&tstate->cancel.link);
 	free(tstate);
 }
 
@@ -231,6 +246,8 @@ static void new_input_notify(struct wl_listener *listener, void *data) {
 		wl_signal_add(&tstate->wlr_touch->events.motion, &tstate->motion);
 		tstate->up.notify = touch_up_notify;
 		wl_signal_add(&tstate->wlr_touch->events.up, &tstate->up);
+		tstate->cancel.notify = touch_cancel_notify;
+		wl_signal_add(&tstate->wlr_touch->events.cancel, &tstate->cancel);
 		wl_list_insert(&sample->touch, &tstate->link);
 		break;
 	default: