bug#56561: 29.0.50; Infloop in try_window

[Po Lu via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

> What I had in mind is an assertion in x-show-tip that the glyph matrix
> produced by try_window includes all of the tooltip text, i.e. that
> there's a glyph row there whose ends_at_zv_p flag is set.  This is an
> indication that all of the text was processed and will appear in the
> tooltip.
>
> Note that in the case in point this is precisely what's happened: the
> entire text of the tip was processed and produced its glyphs, and the
> problem happened while try_window was producing empty glyph rows
> beyond ZV.

Thanks, but we can't guarantee that the tooltip frame's window is large
enough to hold the entire contents of the tooltip buffer.  The size can
be changed (on various different platforms) by the window manager or the
toolkit.

> No, because as I explained in my message, I don't think this should
> be needed.  If the above assertion ever triggers, we will see what
> kind of situation causes it, and can then discuss solutions.

How about simply asserting that try_window never returns 0?