Re: Support fullscreen values fullheight and fullwidth on pgtk

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: Eli Zaretskii <eliz@gnu.org>,  emacs-devel@gnu.org
> Date: Fri, 08 Jul 2022 10:30:16 +0800
> 
> Actually, I think we need a more general mechanism to report which
> `fullscreen' states can be set, and then to use that in
> `toggle-frame-fullscreen' (and other places that set the
> `fullscreen-restore' frame parameter.)
> 
> So this:
> 
>   (if (memq fullscreen-restore '(maximized fullheight fullwidth))
> 
> would probably become
> 
>   (if (display-supports-fullscreen-p fullscreen-restore)
> 
> WDYT?

If this is useful and makes the code clearer and easier to maintain,
sure.  But the display-*-p predicates need to be implemented for all
the supported frame types, not just for PGTK and X.