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

[John Ralls <jralls ceridwen us>]

> On Feb 20, 2016, at 10:58 AM, Allin Cottrell <cottrell wfu edu> wrote:
>
> On Thu, 18 Feb 2016, John Ralls wrote:
>
> > On Feb 18, 2016, at 8:24 AM, Allin Cottrell <cottrell wfu edu> wrote:
> > > 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? [...]
> >
> > 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.
>
> Some progress to report. Based on John's information I added this function to GdkQuartzWindow.c:
>
> - (void)windowWillClose:(NSNotification*)notification
> {
>  // Clears the delegate when window is going to be closed; since EL
>  // Capitan it is possible that the methods of delegate would get
>  // called after the window has been closed.
>  [self setDelegate:nil];
> }
>
> This was not itself sufficient to avert a crash when closing a maximized GTK window on El Capitan, but it 
> turned out it was necessary. The other component became apparent when I stuck some NSLog statements into 
> GdkQuartzView.c. After a window close from fullscreen, the function updateTrackingRect was proceeding with
> a NULL value of "impl", as in
>
>  GdkWindowImplQuartz *impl =
>    GDK_WINDOW_IMPL_QUARTZ (private->impl);
>
> The fix was then to replace the "don't-go-ahead" check
>
>  if (!impl->toplevel)
>
> (which provoked the crash) with
>
>  if (!impl || !impl->toplevel)
>
> With these two changes I'm not seeing any problems. I'm attaching a patch against GTK 2.24.29.
>
> BTW, I think I mistitled this thread: it seems that it was close on maximized that was the real problem 
> rather than maximize/unmaximize. The confusing thing is that on El Capitan, maximize produces a truly 
> "fullscreen" view, with no window controls shown, and to close the window you have to mouse up to the top 
> of screen to reveal the window controls (and menu bar), hence generating a resize signal.
>
> For refence, here's the relevant portion of my debugging output,
> following a click on close:
>
> gretl[40729] calling: -[GdkQuartzWindow windowShouldClose:]
> gretl[40729]  created event
> gretl[40729]  returning
> gretl[40729] calling: -[GdkQuartzWindow windowWillClose:]
> gretl[40729]  self: <GdkQuartzWindow: 0x109f15870>
> gretl[40729] calling: -[GdkQuartzView setFrame:]
> gretl[40729]  self: <GdkQuartzView: 0x109f180c0>
> gretl[40729] calling: -[GdkQuartzView updateTrackingRect]
> gretl[40729]  private = 0x10286bd80
> gretl[40729]  impl = 0x0
>
> Allin Cottrell<el_capitan.diff>

Thanks, I've pushed your patch to gtk-2-24, gtk-3-18, and master.

Regards,
John Ralls