RE: Fix some tooltip related problems

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

> System tooltips are lightweight objects with restricted abilities.
> They have uniform appearance and the single tooltip window is usually
> shared among all running programs and the operating system.
> 
> Emacs tooltips are merely an emulation of system tooltips.  Most
> restrictions of system tooltips have been retrofit artificially, like
> uniform faces which are built into `tooltip-show' (but can be avoided
> by using `x-show-tip' as you mention above) or the fact that only one
> tooltip can be present at any time.
> 
> The great disadvantage of Emacs tooltips is that they are heavyweight
> precisely due to their versatility.  Showing an Emacs tooltip here on
> Windows with -Q incurs an entire GC cycle.  Also, there are some minor
> annoyances like the one that showing Emacs tooltips for menu items
> depends on the presence of a blinking cursor.

Thanks for this clear background description.

If none of the limitations of system tooltips can be
eliminated easily, and none of the limitations of
non-system (i.e., "Emacs") tooltips can be eliminated
easily, can we perhaps have both, being able to choose
for any given context which to use?

Being able to use different, and multiple faces, or
images, or whatever, in a tooltip can be great for
some contexts/applications, even if it is not needed
for others.  Can we let Lisp code (and so users too)
decide, here or there, which kind of tooltip to use
(heavyweight "Emacs" or lightweight "system")?

 "The great disadvantage of Emacs tooltips is that
  they are heavyweight precisely due to their
  versatility."

Good summary.  And their great advantage is their
versatility.  Let's please offer both, if that's
not too difficult.