bug#36672: 27.0.50; NS build: Creating child frame leads to empty space

[Andrii Kolomoiets]

> On Jul 16, 2019, at 22:28, Alan Third <alan@idiocy.org> wrote:
> 
> The patch looks good to me, but lets see if we can find solutions to
> these other issues.

I made some progress on this issue.

The idea is to wait for fullscreen transition to complete:
- Set property isFullScreenTransition on windowWillEnterFullScreen and
  windowWillExitFullScreen events;
- Clear that property on windowDidEnterFullScreen and
  windowDidExitFullScreen events;
- Wait for property to be cleared when we need to.

Removing parent-frame property causes child frame to enter fullscreen
if some of parent frames is in fullscreen.

Setting parent-frame property to fullscreen window causes window to
leave fullscreen.

As a side effect (sleep-for 0.5) in toggle-frame-fullscreen is no
longer needed (bug#28496).

But I need help with some questions:

1. Is it the rigth way to wait for some NS event by calling
   wait_reading_process_output or is there a better way?

2. I commented some code in windowDidMove with FIXME comment.
   After windowDidMove event is triggered, windowDidExitFullScreen is
   not received and fullscreen transition is never "completed".
   With that code commented windowDidExitFullScreen is received.
   Is this code somehow breaks the events queue?

Actually it is the first time I'm working with the C side of Emacs.
And with AppKit. And with C :) Please let me know if my decisions
and conclusions are wrong.

Thanks!

ns-emacs-spaces.patch
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