Re: src/nsterm.m: fix window tabbing on macOS

["Paul W. Rankin" via "Emacs development discussions." <emacs-devel@gnu.org>]

On 2021-05-11 05:53, Alan Third wrote:
> On Sat, May 08, 2021 at 10:27:13PM +1000, Paul W. Rankin wrote:
> I reckon this is probably OK, but I'll leave it a bit longer to see if
> anyone else has an opinion.

If I'm not mistaken, it is the fourth commandment of emacs-devel that 
someone must raise an objection. Especially if the change does not 
affect them.

> IIRC, it would just crash pretty much at random, and without much
> prompting, so you'd likely know if it was still a problem.
> 
> Most likely the fullscreen crash fixes from a couple of years ago
> solved it.

I'm on macOS 10.13 Hi Sarah and previously was on 10.14 and 10.15, but 
if anyone is on macOS 11 Big Slurp it may be worth building/testing.

>> The user choice I refer to resides in the odd place of System 
>> Preferences >
>> Dock > Prefer tabs when opening documents: [Always | In Full Screen 
>> Only |
>> Manually]. The behaviour I've experienced with each of these is:
>> 
>> - Always: invoking `make-new-frame' will always create a frame in a 
>> new tab
>> - In Full Screen Only: invoking `make-new-frame' will create a frame 
>> in a
>> new tab only when `(frame-parameter nil 'fullscreen)' is non-nil
>> - Manually: `make-new-frame' will never create new tabs

I should clarify here that the macOS window manager is not querying 
Emacs frame parameters. Correlation not causation!

> That location really doesn't much sense! Certainly explains why I've
> never seen it before. :)
> 
> This is really my lastremaining concern, that it's such an obscure
> setting that we'll get a lot of bug reports about Emacs-doing-tabs
> when-I-don't-want-it-to. I'm not sure there's a good solution to that
> other than perhaps putting a note in the NS port documentation (which
> afaict nobody ever reads anyway).

You are correct. I only looked at the nextstep/README file today.

Given that tabs look much a part of the macOS window system I think/hope 
a person's first assumption would be that it's an Apple thing and 
hopefully first burn out their ire on Apple forums/reddits/etc. 
Nevertheless, we shouldn't inhibit all for the failings of a few.

The only thing that's a little weird is that this tab bar is not visible 
when in full screen, requiring moving the mouse up to reveal it. It 
would clearer what's happening if the tab bar behaved more like 
Terminal.app when in full screen: opening more than a single tab keeps 
the tab bar visible (in full screen or windowed).

Apple's documentation on this is very thin, so I doubt it's a simple 
boolean switch: 
https://developer.apple.com/documentation/appkit/nswindowtabgroup

> BTW, is there an advantage to explicitly enabling the default setting
> over just removing the code that disables it?

Sorry I am unqualified to offer an opinion here, other than if someone 
wants to change it the code is already there for them to easily make the 
change and rebuild Emacs.

Tangentially, this lead me to read a little about GNUstep. Does GNUstep 
provide the same kind of tabbing as macOS?