Subject: bug#63271: 29.0.90; broken mouse-face

From: Juri Linkov <[email-masked]>
Date: Sun, 07 May 2023 21:00:02 +0300

>> Very strange.  Are you sure the recipe above is all that is needed,
>> starting from "emacs -Q", to reproduce the problem?
>
> I don't see this on any X build.
> Would you please post details of the font that is displaying the tab
> line?

Here is the output of describe-char on the first char of the broken tab:

               position: 2 of 35 (3%), column: 1
              character: T (displayed as T) (codepoint 84, #o124, #x54)
                charset: ascii (ASCII (ISO646 IRV))
  code point in charset: 0x54
                 script: latin
                 syntax: w 	which means: word
               category: .:Base, L:Strong L2R, a:ASCII, l:Latin, r:Roman
               to input: type "C-x 8 RET 54" or "C-x 8 RET LATIN CAPITAL LETTER T"
            buffer code: #x54
              file code: #x54 (encoded by coding system utf-8-unix)
                display: by this font (glyph code):
      ftcrhb:-PfEd-DejaVu Sans-regular-normal-normal-*-10-*-*-*-*-0-iso10646-1 (#x37)

I think your guess about fonts involved is right
because the problem disappears when the tab-line face
doesn't inherit from the 'variable-pitch' face.