callisto-debian/gtk3
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

gesture: Document pitfalls on foreign gesture state changes

Browse Source 
Add some docs/example about the possible event handling ordering issues
that may appear on GtkGesture::begin between multiple gesture groups.
Mostly relevant for state changes.
This commit is contained in:
Carlos Garnacho 2014-09-29 15:35:20 +02:00
parent 30149dabcf
commit 3985d69735
1 changed files with 31 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
gtk/gtkgesture.c
View File

@ -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
*