diff --git a/gtk/gtkgesture.c b/gtk/gtkgesture.c index fb913aa260..cfdd3d0699 100644 --- a/gtk/gtkgesture.c +++ b/gtk/gtkgesture.c @@ -904,6 +904,37 @@ gtk_gesture_get_sequence_state (GtkGesture *gesture, * * None → Claimed * * None → Claimed → Denied * + * Note: Due to event handling ordering, it may be unsafe to + * set the state on another gesture within a #GtkGesture::begin + * signal handler, as the callback might be executed before + * the other gesture knows about the sequence. A safe way to + * perform this could be: + * + * |[ + * static void + * first_gesture_begin_cb (GtkGesture *first_gesture, + * GdkEventSequence *sequence, + * gpointer user_data) + * { + * gtk_gesture_set_sequence_state (first_gesture, sequence, GTK_EVENT_SEQUENCE_ACCEPTED); + * gtk_gesture_set_sequence_state (second_gesture, sequence, GTK_EVENT_SEQUENCE_DENIED); + * } + * + * static void + * second_gesture_begin_cb (GtkGesture *second_gesture, + * GdkEventSequence *sequence, + * gpointer user_data) + * { + * if (gtk_gesture_get_sequence_state (first_gesture, sequence) == GTK_EVENT_SEQUENCE_ACCEPTED) + * gtk_gesture_set_sequence_state (second_gesture, sequence, GTK_EVENT_SEQUENCE_DENIED); + * } + * ]| + * + * If both gestures are in the same group, just set the state on + * the gesture emitting the event, the sequence will be already + * be initialized to the group's global state when the second + * gesture processes the event. + * * Returns: %TRUE if @sequence is handled by @gesture, * and the state is changed successfully *