Re: [gtk-osx-users] crash on updateTrackingRect is BAAACK

[Allin Cottrell <cottrell wfu edu>]

On Thu, 19 Nov 2020, John Ralls wrote:

> > On Nov 19, 2020, at 1:41 PM, Allin Cottrell <cottrell wfu edu> wrote:
> >
> > On Tue, 17 Nov 2020, John Ralls wrote:
> >
> > > > On Nov 17, 2020, at 12:53 PM, Allin Cottrell <cottrell wfu edu> wrote:
> > > >
> > > > > I just tested full-screening and red button closing GnuCash built yesterday with Gtk+-3.24.23 on macOS 11 and 
> > > > > run with MallocScribble=1 to make sure that a use-after-free would crash. It closed cleanly, no crash. You 
> > > > > might diff GtkNSWindow.c between Gtk2 and Gtk3 to see if there's something helpful there.
> > > >
> > > > GtkNSWindow.c ? I'm not seeing a file of that name (or close) in the GTK 2 codebase.
> > >
> > > Sorry, gdk/quartz/GdkQuartzWindow.c.
> >
> > Thanks, I see now: it's GdkQuartzWindow.c in Gtk2 and GdkQuartzNSWindow.c in Gtk3. Looks like there are 
> > several updates for recent macOS in the latter, and backporting such changes to Gtk2 might be useful for 
> > retrogrades such as myself.
> >
> > One question. There's a trope that appears in several places in the Gtk2 version:
> >
> >  GdkWindow *window = [[self contentView] gdkWindow];
> >  GdkWindowObject *private = (GdkWindowObject *)window;
> >  GdkWindowImplQuartz *impl = GDK_WINDOW_IMPL_QUARTZ (private->impl);
> >
> > while in the Gtk3 version, in the corresponding places, we find:
> >
> >  GdkWindow *window = [[self contentView] gdkWindow];
> >  GdkWindowImplQuartz *impl = GDK_WINDOW_IMPL_QUARTZ (window->impl);
> >
> > Is this difference cosmetic, or is the intervening cast from *gdkWindow to *GdkWindowObject really required 
> > in the Gtk2 case?
>
> It's required in Gtk2 because there GdkWindow is a typedef of struct _GdkDrawable, which contains only an 
> instance of its parent class--in the case of GdkWindow that would be a GdkWindowObject. Without it the 
> compiler would look at struct _GdkDrawable for a member impl and fail to find it; with the cast it looks in 
> struct _GtkWindowObject instead where it does find it.
>
> That indirection was removed from Gtk3 so no more cast. There are lots of other changes in Gtk3, particularly 
> in the last couple of years as the architecture changed to ease migration to Gtk4. Quartz hasn't kept up with 
> all of it but you'll still need to spend significant time learning the internals and differences to 
> successfully backport.

Thanks for the clear explanation, John.

Allin Cottrell