On 2021-05-14 07:05, Alan Third wrote:
> On Thu, May 13, 2021 at 03:46:54PM +1000, Paul W. Rankin via Emacs
> development discussions. wrote:
>> On 2021-05-13 07:23, Alan Third wrote:
>> You're right and I can't find another macOS app with a tab bar that 
>> behaves
>> the way Emacs.app does, so I gotta assume there is something somewhere
>> overriding the Cocoa window manager behaviour. But I'm really only 
>> qualified
>> to guess; I looked through nsterm.m and changed a few suspected BOOL 
>> values
>> and recompiled a few times but nothing had an effect on the hidden tab 
>> bar.
>> 
>> Relatedly, tool-bar-mode is in the same boat; hidden in full screen, 
>> but
>> probably shouldn't be.
> 
> Search in nsterm.m for "autohide", there are a couple of places where
> hiding various bits and bobs is done, all related to fullscreen
> afaict.
> 
> I'm not on a Mac just now or I'd try removing them all to see what it
> does.

Looks like you're on the money!

I've attached two patches: 0001 is to remove the explicit setting of 
NSWindowTabbingModeDisallowed; 0002 allows visibility of the toolbar and 
tab bar in fullscreen (screenshot attached), but reliably causes a 
segmentation fault with the following steps:

1. System Preferences > Dock > Prefer tabs... [Always]
2. $ emacs -Q
3. M-x toggle-frame-full
4. M-x make-frame
5. M-x delete-frame

Attached crash.log.

Interestingly, calling delete-other-frames does not trigger a crash and 
when in windowed (non-fullscreen) a crash is only triggered with the 
following:

1. System Preferences > Dock > Prefer tabs... [Always]
2. $ emacs -Q
3. M-x make-frame
4. M-x make-frame
5. click close background tab
6. wait for animation to finish
7. click close foreground tab

> As I said, I suspect this change could be contentious, so we may want
> to provide a variable to enable or disable it.
> 
>> > If you just remove it completely does it do anything different from
>> > your patch?
>> 
>> It appears that removing the code has the same effect as
>> NSWindowTabbingModeAutomatic. I like minimalism so happy to just 
>> remove it.
> 
> 👍

Let's view these as two separate but related changes, one to remove the 
explicit setting of NSWindowTabbingModeDisallowed (patch 0001), the 
other to fix the code that's preventing toolbar visibility when in 
fullscreen (WIP patch 0002). I think the former is easy and not 
contentious, whereas the latter -- obviously once it's not crashing -- 
may be another story.

There are three positions someone could take:

1. wants tabs in all macOS apps including Emacs.app
2. does not want tabs in any macOS apps including Emacs.app
3. wants tabs in all other macOS except for Emacs.app

Anyone in categories 1 and 2 will be covered by the option in System 
Preferences. Given that all I think we're doing here is removing old 
barrier code to have Emacs function with an OS's native window manager, 
anyone in the third category would be putting the onus on themselves to 
write code for additional functionality.