Subject: bug#28496: 25.2; Crash when manipulating fullscreen frames on macOS

From: Duncan Harvey <[email-masked]>
Date: Tue, 19 Sep 2017 16:49:16 +0100

> On 18 Sep 2017, at 17:39, Alan Third <[email-masked]> wrote:
> 
> [...] the Emacs 26 branch does
> something quite strange. It doesn’t crash, it seems to leave the
> fullscreen window in the background with no contents.

I can replicate that strange behaviour with Emacs 25.2 on an older operating system (El Capitan, 10.11.6) running in a VM.

In GNU Emacs 25.2.1 (x86_64-apple-darwin13.4.0, NS appkit-1265.21 Version 10.9.5 (Build 13F1911))
 of 2017-04-21 built on builder10-9.porkrind.org
Windowing system distributor 'Apple', version 10.3.1404
Configured using:
 'configure --with-ns '--enable-locallisppath=/Library/Application
 Support/Emacs/${version}/site-lisp:/Library/Application
 Support/Emacs/site-lisp' --with-modules'

That suggests to me that it is not solely an Emacs 25 vs. 26 issue.

Other observations:

On macOS Sierra, creating the new frame appears to create a macOS-style tab in the same 'space'.
On El Capitan, creating the new frame creates a new Mac OS X 'space'.

Animating the creation of a new space certainly appears to be relatively slow (when running under a VM, at least), which lends weight to your suspicion that it's timing related.

-- Duncan