bug#53200: 29.0.50; C-S-u shortcut fails with 'PGTK' enable

[Po Lu via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Morgan Smith <morgan.j.smith@outlook.com> writes:

> Hello,
>
> daanturo <daanturo@gmail.com> writes:
>> Emacs is unable to recognize any Super-modified keys. 
>
> My bad, I gave the wrong git hash.  I meant this hash: 1c1ae6ba80. If
> you want to re-enable super modified keys you have to make the
> following change.  If I remember correctly Po Lu thinks this is a bug
> in some other software and that the GDK_SUPER_MASK bit should be set
> so they don't want to add the GDK_MOD4_MASK bit. Personally, I think
> GDK_MOD4_MASK should be added and we should just add a todo comment to
> look into it more later.
>
> I suppose the thought is that in theory someone could use MOD4 as a
> custom modifier instead of using it as super but realistically I think
> someone trying to do that would have lots of problems.  It would be
> cool if that was possible though so I do support trying to rid
> ourselves of odd grandfathered in quirks.

No.  It is safe to use Mod4 for something else than Super.  (On X
Windows it is often Hyper, or both at the same time, or else.)

The only modifier that is not safe to change is Mod1, which GTK always
assumes to be alt.

Please let the GTK developers know that the bug is important here:
https://gitlab.gnome.org/GNOME/gtk/-/issues/4913

Otherwise, they will keep ignoring it, as usual.