Re: Submenu breakage

[Owen Taylor <otaylor redhat com>]

Tim Janik <timj gtk org> writes:

> On 7 Feb 2001, Owen Taylor wrote:
> 
> > 
> > Alexander Larsson <alla lysator liu se> writes:
> > 
> > > Has anyone actually looked deeper in the submenu horkage? Is it 100% sure
> > > that it is the boxed type changes that causes it. 
> > 
> > Well, the boxed typed stuff BREAKS a lot of stuff BADLY, so it's probably 
> > not worth debugging until we get the boxed type fixed.
> 
> that's exagerating, boxed copying breaks signals that pass boxed
> arguments in to signal handlers and rely on them to make modifications
> which have to be available to the caller after emission.

Which of course, is only rare, unusual signals like ::size_request...

> that in itself should not break menus as menus don't have strange
> text iterators or non-NULL terminated strings.

Or GtkRequisition, or GtkSelectionData, or...

> however the boxed type copying uses gdk_event_copy() upon GtkWidget::event
> now, and that relies on the event structures properly setup.
> now gtk_menu_motion_notify() creates a syntesized event that's
> only half setup:
> 
>           GdkEvent send_event;
> 
>           send_event.crossing.type = GDK_ENTER_NOTIFY;
>           send_event.crossing.window = event->window;
>           send_event.crossing.time = event->time;
>           send_event.crossing.send_event = TRUE;
>           send_event.crossing.x_root = event->x_root;
>           send_event.crossing.y_root = event->y_root;
>           send_event.crossing.x = event->x;
>           send_event.crossing.y = event->y;
> 
> specifically send_event.crossing.subwindow can contain garbage this way,
> which will obviously break gdk_window_ref (event->crossing.subwindow) in 
> gdk_event_copy().
> 
> i just had to figure that plain:
> 
>           GdkEvent send_event = { 0, };
> 
> won't fix this because default-zero-initialization of unions only
> applies to the first member, so that code actually needs to read:
> 
>           GdkEvent send_event;
>           memset (&send_event, 0, sizeof (send_event));

How about 

 GdkEventCrossing send_event = { 0 };

 [...]

 gtk_widget_event (widget, (GdkEvent *)send_event);

Seems just a bit cleaner to me. (Or, simply filling in the
missing subwindow field explicitely....)

                                        Owen