bug#66190: 30.0.50; ns-use-proxy-icon has no effect on macOS 12.6.9

[Alan Third <alan@idiocy.org>]

On Mon, Sep 25, 2023 at 02:20:51AM -0700, Stefan Kangas wrote:
> In emacs -Q, the `ns-use-proxy-icon' option (introduced in Emacs 27)
> doesn't appear to have any effect on macOS 12.6.9.  See the attached
> screenshot, and compare it to the one here:
> 
> https://emacs.stackexchange.com/questions/33680/how-to-remove-the-icon-in-the-titlebar
> 
> Changing the value to nil also seems to have no effect.

A quick search indicates that you may need to enable it in the system
Accessibility settings. Or possibly just mouse-over the space next to
the title.

I've never even seen a real machine running macOS > 10, so I've no
idea what Apple have done to the title bar.

> While we're at it, the documentation of this could be clearer; neither
> the manual nor the docstring explain what a "proxy icon" even is.  I had
> to search online, and find the above link, to understand what it is
> supposed to do.

I honestly don't know what it's for. I think you can maybe drag it to
other applications like you can drag icons from Finder?

IIRC the main driver for implementing that option was that we used to
have one single variable that controlled the text in the titlebar and
the proxy icon, and it was inflexible and behaved very differently
from other terms. So I separated it out and made it compatible.

> In addition, can this variable be set in a running Emacs?  The above
> Stackoverflow link suggests that you might need to restart Emacs, but
> AFAICT there is nothing about that in our documentation.

I'm pretty sure he only suggests restarting because he's setting it in
his .emacs file and doesn't realise he can run it right there.

-- 
Alan Third