bug#20164: 25.0.50; Do not tell users that `x-show-tip' is internal

[Eli Zaretskii <eliz@gnu.org>]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Fri, 02 Aug 2019 14:28:45 +0200
> Cc: 20164@debbugs.gnu.org
> 
> Drew Adams <drew.adams@oracle.com> writes:
> 
> > The doc string says this:
> >
> >   This is an internal function; Lisp code should call `tooltip-show'.
> >
> > Why?  While it is true that you can get, using `tooltip-show', the
> > behavior of arg PARMS by binding `tooltip-frame-parameters', the behavior
> > of args DX and DY by binding `tooltip-x-offset' and `tooltip-y-offset',
> > and the behavior of arg TIMEOUT by binding `tooltip-hide-delay' (which is
> > not documented, BTW), you cannot the behavior of arg FRAME.  And binding
> > user options is not really a great way to control the function behavior,
> > in general.

I wonder when we will stop wasting time and energy on hair-splitting
reports such as this one.  Probably never.  Sigh.

> I agree that the calling conventions for `x-show-tip' seems to be much
> nicer than `tooltip-show'.  

If you do, please explain it to me, because the above arguments don't
convince me, certainly not that x-show-tip's API is "nicer".  Maybe
I'm missing something.

Tooltips are about showing short hints about various elements of the
UI, they are not general-purpose tools for showing arbitrary text in
arbitrary places.  And tooltip-show looks entirely reasonable and
adequate for the job as defined above.

It could be that someone tried to use tooltips as poor-man's child
frames, but we now have those as first-class objects, so any such
(ab)use would be unnecessary.

> > So `tooltip-show' is not really a user-level substitute for "internal"
> > `x-tooltip-show'.
> >
> > What's more, the doc of `tooltip-show' explicitly refers to how variable
> > `x-max-tooltip-size' affects the behavior.  Why refer to that "internal"
> > variable?  And if it is not "internal" then why does it have the prefix
> > `x-'?  Why isn't there a `tooltip-max-size' option, corresponding to the
> > other `tooltip-*' options?

I don't remember why I added a reference to that variable when I
extended the doc string of tooltip-show in 2001(!), but I hope no one
will argue that it's important to know the displayed text might be
truncated.

> The commit that added the line about it being internal just says "doc
> fix",

Guilty as charged ;-)

> so I can only guess what the reason behind it was

No need for guessing; see the short discussion starting at

  https://lists.gnu.org/archive/html/emacs-pretest-bug/2007-03/msg00261.html

The conclusion to take out of that discussion is that whoever uses
x-show-tip should know very well what they are doing, which is another
way of saying "kids, don't try that at home", a.k.a. "an internal
function".

> So perhaps the way forward here is to make `x-max-tooltip-size' an
> obsolete alias for a new variable `tooltip-max-size'?  And add a way to
> specify the FRAME parameter somehow...  but the calling convention for
> that function is kinda meh.

Before we do something like that, I'd like someone to explain why
would they need to call x-show-tip for showing a tooltip.