wlr_drag: Destroy drag after releasing grabs

wlr_drag sets up keyboard, pointer and touch grabs, which block 'enter'
events (and thus focus changes). For the compositor to be able to update
focus (e.g. to focus the drop target) from the destroy handler, the
grabs must be released before the destroy event is signalled.

types/data_device/wlr_drag.c

@@ -124,8 +124,6 @@ static void drag_destroy(struct wlr_drag *drag) {
 	}
 	drag->cancelling = true;
 
-	wlr_signal_emit_safe(&drag->events.destroy, drag);
-
 	if (drag->started) {
 		wlr_seat_keyboard_end_grab(drag->seat);
 		switch (drag->grab_type) {
@@ -138,7 +136,12 @@ static void drag_destroy(struct wlr_drag *drag) {
 			wlr_seat_touch_end_grab(drag->seat);
 			break;
 		}
+	}
 
+	// We issue destroy after ending the grab to allow focus changes.
+	wlr_signal_emit_safe(&drag->events.destroy, drag);
+
+	if (drag->started) {
 		drag_set_focus(drag, NULL, 0, 0);
 
 		assert(drag->seat->drag == drag);