Re: [gtk-osx-users] crash on maximize/unmaximize

[John Ralls <jralls ceridwen us>]

> On Feb 18, 2016, at 8:24 AM, Allin Cottrell <cottrell wfu edu> wrote:
>
> On Fri, 12 Feb 2016, Miroslav Rajcic wrote:
>
> > This [see report below] sounds similar to the crashes reported to me by users of my app (I reported this 
> > case on this list in January) where crashes happen only on El Capitan and are related to using app in full 
> > screen or new split view.
> >
> > It seems that El Capitan version changed something internally, because searching on the net finds many 
> > similar issues.
>
> > For example Atom editor crashes:
> > https://github.com/atom/atom/issues/9692
> > https://github.com/atom/atom/issues/9584
> >
> > I know Atom is not a GTK+ app, but I believe that the crashes are related.
> > The fix for these particular crashes in Atom are explained here:
> > https://github.com/atom/electron/pull/3588
> >
> > Quote: "Since EL Capitan it is possible that the methods of delegate would get called after the window has 
> > been closed."
> >
> > Could something like this be a case for GTK+ code too?
>
> Thanks, this sounds very plausible; it fits the facts that I have observed. My first resort here will be to 
> try to implement in GdkQuartzWindow.c the fix that the Atom guys came up with. That is, add a callback for 
> the windowWillClose signal that detaches the delegate.
>
> I'm totally unfamiliar with Objective C and Apple APIs, but from looking at the Atom and GdkQuartz code it 
> seems that the callback should look like this:
>
> - (void)windowWillClose:(NSNotification*)notification
> {
>  NSWindow *nsw = get_the_window();
>
>  [nsw setDelegate:nil];
> }
>
> So my question is, what should the notional call "get_the_window()" actually look like? I see in 
> GdkQuartzWindow.c code to get the relevant GdkWindow in this sort of notification context, namely
>
> GdkWindow *window = [[self contentView] gdkWindow];
>
> and I also see in gdkwindow-quartz.c a function
>
> gdk_quartz_window_get_nswindow(GdkWindow *window);
>
> I guess one could chain these, but I suspect this would be more roundabout than need be. Is "self" already 
> the relevant NSWindow, by any chance, or is there a more direct way of getting it?

The GtkQuartzNSWindow is its own delegate, so [self setDelegate:nil] will do the job. It's probably the right 
thing to do, too: If NSWindow's destructor releases the delegate and then whatever's calling it releases the 
NSWindow that would be a double-free.

That's not going to do anything for exiting fullscreen, though. The problem shown by your crash report seems 
to be that the GdkQuartzView's GdkWindow* member has gotten a bogus value and the crash is from trying to 
dereference it.

Regards,
John Ralls