bug#30399: 27.0.50; tooltips are broken

[martin rudalics <rudalics@gmx.at>]

 > Can you clarify the warning, please?

That when the behavior of 'x-show-tip' changes, applications will
have to adapt.

 > If there is a reason to replace `x-show-tip', can you not
 > replace it with something that is just as general?  Why
 > would we take away something that lets you specify the
 > appearance and behavior, replacing it by something that
 > just hard-codes properties etc.?

Currently there are no plans to replace 'x-show-tip' AFAICT.

 >> Make sure to use (selected-frame) as second argument for
 >> Emacs < 27.  nil is broken but you might not notice it.
 >
 > Thank you.  I didn't know that.  And you're right that
 > I haven't noticed it, so far.
 >
 > Can you please say what the brokenness is?  Is there
 > a bug # for that, so we can learn about the brokenness
 > that we might not notice?  Thx.

Internally, Emacs tries to not delete/recreate a tooltip frame when
the text of the tooltip remains the same and only its position
changes.  This optimization may get broken when using nil as the
second argument.  As mentioned, you probably won't notice it.

martin