bug#31968: 26.1.50; Allow to hide title bar on maximize (gtk/gnome/csd)

[Carlos Pita]

In gnome decorations are considered part of the client (even classic
titlebars) in the sense that it's the client who decides to show them or
not (see [1] and [2]). In waylan there is no other way around, but they
also decided to pretend X apps behave like that. This is very frustrating
since the reality is that many clients don't work in that way yet.

So this is a request to add a gtk-hide-titlebar-if-maximized or similar
variable since I assume emacs won't be using proper CSDs for a long
time, maybe for good. Without that variable it's not possible to achieve
the same humble goal in the strange new world of gnome, at least not without
lots of xprop, xwinifo, xdotool, wmctrl, etc. horrible hacks. As I said,
it's supposed to be the client who knows what to show and when to show
it.

---

[1] https://blogs.gnome.org/tbernard/2018/01/26/csd-initiative/
[2] https://bugzilla.gnome.org/show_bug.cgi?id=775061

In GNU Emacs 26.1.50 (build 3, x86_64-pc-linux-gnu, GTK+ Version 3.22.30)
 of 2018-06-18 built on carlos
Repository revision: 0a8b7f365cbc8de02ddb4e806dd76b1bf6302565
Windowing system distributor 'The X.Org Foundation', version 11.0.11906000
System Description:     Manjaro Linux

Recent messages:
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Loading a theme can run Lisp code.  Really load? (y or n) y
Treat this theme as safe in future sessions? (y or n) y
[yas] Prepared just-in-time loading of snippets successfully.
Saving file /home/carlos/.emacs.d/init.el...
Wrote /home/carlos/.emacs.d/init.el [2 times]
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
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Major mode: Lisp Interaction

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