RE: Fix some tooltip related problems

[Drew Adams <drew.adams@oracle.com>]

>  >> The option `x-gtk-use-system-tooltips' decides whether to use system
>  >> or Emacs tooltips.  This is a user option and should never be set by
>  >> Lisp code.
>  >
>  > Then that doesn't satisfy what I requested:
>  >    "being able to choose for any given context which to use"
>  >                          ---------------------
>  >    "Can we let Lisp code (and so users too) decide, here or
>  >     there, which kind of tooltip to use (heavyweight "Emacs"
>  >     or lightweight "system")?"
> 
> Right.  Such decisions must be left to the user.

Users have the right to use Lisp.  Users have the right
to choose whether to define or use this or that command
or this or that Lisp code.

There's no contradiction between allowing Lisp code to
choose whether to use faces etc. in a given tooltip and
allowing users to choose whether to allow that and choose
whether all or none or some tooltips should allow it.

Users choose.  The existence of that user option does
not and should not preclude more choice.

The fact that we have a user option for the global choice
of all or none is a red herring in a discussion of whether
and how to let Lisp code (not just C code) take part here.

Of course it is the user who gets to decide whether any
given Lisp code does its thing, whatever that might be.

>  > And users on gtk-build systems can choose.  Choice should
>  > also be available to Lisp functions, as use cases differ.
>  > It's of course possible to let a user option allow for
>  > Lisp control or override/prevent it, au choix.
>  >
>  > Today, does changing the value of that user option change
>  > the behavior dynamically?  E.g., if you did change the
>  > value using a given Lisp function would the behavior change?
>  >
>  > If so then some specific contexts could, by default, use
>  > "Emacs" tooltips, while other contexts did not.
> 
> I'd rather advise to set `x-gtk-use-system-tooltips' once in the init
> file and never change it during the session.

You are free to give anyone any such advice, of course.
It's the individual user who should be able to choose
what she wants.

A tooltip that shows each key as you type it, in, e.g.,
a large, red face (user-configurable) can be helpful
when doing a demo or recording a demo video, to show
which keys you are pressing, at relevant places on the
screen.

There are a zillion uses for tooltips that can take
advantage of using faces (and other Emacs artifacts).

Letting a user decide when, whether, and where to take
advantage of that is normal for Emacs.  Saying that you
shouldn't be able to do that is not normal for Emacs.