bug#28872: 26.0.90; non-native-fullscreen does not play well with ns-transparent-titlebar on macOS

[Alan Third]

On Mon, Oct 16, 2017 at 08:00:59PM -0700, Aaron Jensen wrote:
> 
> From emacs -Q:
> 
> (ns-toggle-toolbar)
> (set-frame-parameter nil 'ns-transparent-titlebar t)
> (setq ns-use-native-fullscreen nil)
> (toggle-frame-fullscreen)
> (toggle-frame-fullscreen)
> 
> This leaves you in a situation where the frame moves up into where the
> title bar should be. Resizing the frame manually fixes it.
> 
> Here's a screenshot: 
> https://screenshots-dx37.s3.amazonaws.com/20171016-195851-kfuhu.png

You don’t need to invoke transparent titlebars nor remove the toolbar
to see this problem.

The issue seems to be that when switching back to the non‐fullscreen
NSWindow the toolbar height calculation fails and produces a negative
value.

We used to use a hard‐coded value for this, but the calculation works
better in every circumstance except, apparently, this one.
-- 
Alan Third