RE: Fix some tooltip related problems

[Drew Adams]

> >    Given that limitation, I repeat the question: Can't we
> >    use a ("normal") Emacs frame, where things such as faces
> >    do work, to implement tooltips?
> 
> I believe it should be possible now we have undecorated frames
> available. I’ve made a (really bad) attempt at proving we can do it.
> Patch attached.
>
> My emacs lisp skills are rather bad, so I couldn’t work out how to get
> tooltip-hide to work, or how exactly I should set the size of the
> tooltip, or how to not display the modeline, but it kind of works...
> Someone who knows what they’re doing should be able to make a better
> fist of it than me.

Thanks for working on this.

I would hope that whatever implementation is ultimately used
is used for the existing functions (e.g. `x-tooltip-show'),
so that nothing changes for users/Lisp.

> One possible issue is that it might be difficult to stop frame‐based
> tooltips from crossing screens on multi‐monitor setups. I know we fix
> that in Objective‐C code in NS, I don’t know if lisp knows enough
> about screen geometry to get round it.

I don't think we should _necessarily_ force all of a tooltip's
text to be on a single monitor.  Though that might make sense
in some cases in others it might not.  At most, the ability to
do that would be a nice-to-have and not something needed or to
be imposed (IMO).

Put differently, it can be useful to _be able_ to position
_any_ frame so that it does not extend across monitors, when
possible.  But that shouldn't necessarily be imposed on any
frame, including, I think a tooltip.

> >    Did someone have to explain to you what a dimmed menu item
> >    is all about?  Is that inherently confusing the first time
> >    someone sees it?  I think not.  A tooltip with dimmed text
> >    is no more confusing.
> 
> I disagree, a menu item is interactive, or not if it’s dimmed, so it
> becomes clear quite quickly what dimming means. A dimmed tooltip is
> still a tooltip, just a bit harder to read. It takes further action to
> discover that the information its giving you isn’t currently usable.

That's reasonable.  Not a big deal/difference though (IMO).

The ability to get the general info is more important than
any possible confusion (which I expect to be none) someone
might have from not immediately understanding that dim means
that trying the indicated action produces no effect.