bug#63271: 29.0.90; broken mouse-face

[Stephen Berman]

On Tue, 09 May 2023 14:50:30 +0300 Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Stephen Berman <stephen.berman@gmx.net>
>> Cc: juri@linkov.net,  luangruo@yahoo.com,  63271@debbugs.gnu.org
>> Date: Tue, 09 May 2023 12:35:35 +0200
>>
>> > OK, thanks.  This is still OK, so please do this with the new
>> > breakpoint as described in my other email.  It would be interesting to
>> > see the difference between fundamental-mode and lisp-interaction-mode
>> > with that second breakpoint.
[...]
> This looks OK to me: it says we display 4 characters in one face and 1
> more in another.  Which agrees with pgrow and with what I understand
> should happen here: the 4 characters T O D O are displayed using the
> font of the variable-pitch face, and the blank space after it is
> displayed using the default face.
>
> What do you see on the screen in this case?  Please describe the
> visual appearance of each character in the case of fundamental-mode,
> and perhaps also show a screenshot of the window as it is displayed
> when the mouse-highlight becomes visible during this scenario.

Here's a screenshot of lisp-interaction-mode when the mouse-highlight
appears:

Screenshot_2023-05-09_14-10-03.png
Description: PNG image

And here's one of fundamental-mode:

Screenshot_2023-05-09_14-20-12.png
Description: PNG image

Aside from the difference in highlighting, another difference I failed
to notice before is that in fundamental-mode the string "TODO" is
displayed with DejaVu Sans but in lisp-interaction-mode with DejaVu Sans
Mono, although I used the same Lisp code with the face property
(:inherit variable-pitch) to enter the string in both buffers.  I guess
lisp-interaction-mode inhibits variable-pitch face and that's the reason
the mouse-highlighting appears on the problematic characters in that
mode, in contrast to fundamental-mode.

Steve Berman