bug#48307: Feature request: provide default keybindings to change the font size in all windows

[Eli Zaretskii]

> From: Clément Pit-Claudel <cpitclaudel@gmail.com>
> Date: Sun, 9 May 2021 03:09:45 -0400
> 
> Emacs has keybindings to change the font size in the current buffer (C-x C-=, 
> etc which use text-scale-adjust).  We don't have keybindings for commands to 
> change the font size globally, and in fact we don't have commands for that 
> purpose at all, AFAICT.
> 
> My students keep running into this issue, and it seems pretty common online, 
> too:

It is not clear what should the requested feature do, and the links
you provided each talk about different aspects of the problem without
actually completely defining the requested functionality.

So: what should be the effect of this "global" change of the "font
size"?  Some thought-provoking questions:

 . should this affect only the faces whose fonts don't define their
   own size, or should it affect _all_ fonts?
 . should this really affect _all_ the buffers? e.g., what about the
   minibuffer and the echo-area buffers?
 . should this affect all the frames or just the currently selected
   frame? what about future frames?
 . should this affect the mode line?
 . should this affect tooltips?
 . should this affect the fringes and their bitmaps?
 . should this affect the menu bar, the drop-down menus, and the GUI
   dialogs?

We need a clear understanding of the feature before we implement it,
IMO.

Thanks.