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

[Allin Cottrell <cottrell wfu edu>]

On Thu, 18 Feb 2016, John Ralls wrote:

> > 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.

Thanks, John, that's good to know.

> 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.

Oof, yes, you're right. In my messing around it seemed that the most 
reliable way to crash the application was to close a window when in 
fullscreen, but if just exiting fullscreen without closing can also 
result in a crash that won't be covered by the above.

Allin Cottrell