bug#63271: 29.0.90; broken mouse-face

[Stephen Berman <stephen.berman@gmx.net>]

On Wed, 10 May 2023 08:34:56 +0800 Po Lu <luangruo@yahoo.com> wrote:

> Stephen Berman <stephen.berman@gmx.net> writes:
>
>> On Tue, 09 May 2023 16:35:50 +0300 Eli Zaretskii <eliz@gnu.org> wrote:
>>
>>>> From: Stephen Berman <stephen.berman@gmx.net>
>>>> Cc: Eli Zaretskii <eliz@gnu.org>,  juri@linkov.net,  63271@debbugs.gnu.org
>>>> Date: Tue, 09 May 2023 15:12:06 +0200
>>>>
>>>> On Tue, 09 May 2023 20:52:24 +0800 Po Lu <luangruo@yahoo.com> wrote:
>>>>
>>>> > What if you change the font driver in use to something else, like X?
>>>> > i.e.
>>>> >
>>>> >   (set-frame-parameter (selected-frame) 'font-backend "x")
>>>>
>>>> With that the highlighting problem in fundamental-mode vanishes: all
>>>> problematic strings show mouse-highlighting. (FTR, with the "x"
>>>> font-backend, the default face here is displayed with adobe-courier and
>>>> variable-pitch face is displayed with adobe-helvetica.)
>>>
>>> Does changing the font backend also changes the font used for the
>>> variable-pitch face?  If it does, then perhaps you could force Emacs
>>> to use the same font by customizing the variable-pitch face?  Since we
>>> already know that the font somehow affects this issue, we need to try
>>> to use the same font with different backends, to be sure it's the
>>> backend that counts, not the font.
>>
>> As I noted previously, here with ftcrhb variable-pitch face is displayed
>> with DejaVu Sans.  When I change the font-backend to "x", variable-pitch
>> face is displayed with adobe-helvetica, as noted, but when I change its
>> Font Family attribute to DejaVu Sans, the "TODO" string in
>> fundamental-mode, propertized to inherit variable-pitch, is displayed
>> with adobe-times.  So it seems that DejaVu Sans cannot be used by the x
>> font-backend.
>>
>> Steve Berman
>
> X doesn't support the same fonts that Cairo does.  But does the same
> thing happen if you use a build with Xft (i.e. --without-cairo), with
> the same font?

After rebuilding --without-cairo (and retaining the change in
a1aa9cbf57, which Gregory Heytings found to be the cause of the problem,
at least in builds with Cairo), the problem no longer occurs,
i.e. mouse-highlighting works with "TODO" and the other test cases, with
DejaVu Sans as the font displaying variable-pitch face.

Steve Berman