Re: Fix some tooltip related problems

[martin rudalics]

> 1. Can users with a GTK build today use Lisp code that decides
> which to use in any given (Lisp) context?  How is that done
> in Lisp?

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.

> 2. What do you mean by "set up tooltip controls" on Windows?

Windows uses the term "tooltip controls" for its native tooltips.  In
order to use tooltip controls, an application programmer has to set
them up, that is, write the necessary API routines.

> Today, on Windows you can at least use faces in tooltips.
> (Dunno about using images, but I'm guessing that's OK too.)

A tooltip frame is a normal top-level frame that can be used like any
other frame.  It has some restrictions (no margins, fringes, scroll
bars) but a criminal mind might be able to relieve some of them.

> But perhaps you mean that on Windows there are _only_
> "Emacs" tooltips, not "system" tooltips?  From my point of
> view that's not a problem - flexible beats inflexible.  You
> say that tooltips on Windows are "heavyweight" and "incur
> an entire GC cycle", but I've never noticed any performance
> problem with them - on Emacs 20 through 26.

Probably because you don't use a battery or maybe you just don't care.

martin