bug#17588: 24.3.91; mouse-face glitchy

[Christopher Schmidt <ch@ristopher.com>]

Eli Zaretskii <eliz@gnu.org> writes:
>> From: Christopher Schmidt <ch@ristopher.com>
>> Date: Mon, 26 May 2014 16:17:11 -0400 (EDT)
>> Whenever the faulty behaviour is present, in clear_mouse_face
>> NILP (hlinfo->mouse_face_window) is always true and therefore the
>> highlighting is not cleared.
>
> Which faulty behavior: the one when there's no highlighting at all, or
> the one when it's present, but not cleared when the mouse pointer
> moves off the text?

The window, in which I moved my mouse pointer around, had working
highlighting that was not cleared.

Most of the time both issues are present.  That is, in one window
highlighting is present but not cleared whereas in another one there is
no highlighting at all.

>> clear_mouse_face w/o bug:
>
> "w/o bug" meaning what? a different Emacs version or the same version,
> but when it behaves correctly?

That is from the very same process that exposed the issue but then
recovered somehow.