Re: Sticky tooltips

[Eli Zaretskii]

> From: Arthur Miller <arthur.miller@live.com>
> Cc: emacs-devel@gnu.org
> Date: Tue, 29 Sep 2020 23:30:14 +0200
> 
> Yeah, you are correct, what tooltip already does, as you say is
> logically what I described, but the implementation is different:
> tooltip.el seems to outsource all it's work to xfns.c, and the code for
> tooltip frame creation; I used just "a naked frame" and some Lisp to
> create an effect of a tooltip.

The C-level implementation notwithstanding, we still insert the
tooltip text into a buffer, so we could snatch it from there, right?
We could have a command that took that text and displayed it in *Help*
buffer, for example.

> By the way; "tooltip-show" (in tooltip.el) seems to take a string
> argument; rather than a buffer, and that widget library "widget.el",
> needs a buffer (for the minor mode, etc).

See above.

> Just as a side curious question: did tooltips really needed own c
> implementation? Isn't code in x-create-tip-frame and x-show-tip seems
> redundant to other frame creation routines/display? Couldn't tooltips be
> implemented using normal frames, with "tooltip-special" code written in
> lisp? 

If you compare x-create-frame and x-create-tip-frame, you will see
that the tip frame is special, and some of the differences are in
fields of the frame object that are not exposed to Lisp.  To move this
to Lisp would mean we'd have to expose them to Lisp first, and I'm not
sure we want to do that.

> I dont' mean to ditch it away, just a reflection on complexity. Maybe I
> don't see all the complexity with tooltips; but it is still ~900+ lines
> of c code that need to be maintained for X11, and there are well w32 and
> ns implementations, so around 3k locs? 

The code replication is a separate issue: we did make an effort lately
to extract some common code and have it only once.  Patches are
welcome to do that in x-create-frame and x-create-tip-frame as well.
It isn't entirely trivial, because the common code is interspersed
with window-system specific API calls.