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

From: Stephen Berman <[email-masked]>
Date: Tue, 09 May 2023 11:49:00 +0200

On Tue, 09 May 2023 11:36:01 +0300 Eli Zaretskii <[email-masked]> wrote:

>> From: Juri Linkov <[email-masked]>
>> Cc: [email-masked],  [email-masked]
>> Date: Tue, 09 May 2023 09:45:16 +0300
>>
>> > And what exactly is the manifestation of the problem in the image you
>> > posted? that wide black part that hides the letters "ODO"? or
>> > something else?
>>
>> The letters turn into black boxes while moving the cursor over them
>> when the mouse pointer is over the text.
>
> Could you or Stephen please perform the following experiment, using
> the latest emacs-29 branch, and report the results:
>
>   $ gdb ./emacs
>   ...
>   (gdb) break xdisp.c:33519
>   (gdb) run -Q
>
> The breakpoint is here:
>
> 	  if (end_hpos > start_hpos)
> 	    {
> 	      draw_row_with_mouse_face (w, start_x, row,
> 					start_hpos, end_hpos, draw);
>
> 	      row->mouse_face_p   <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
> 		= draw == DRAW_MOUSE_FACE || draw == DRAW_IMAGE_RAISED;
> 	    }
>
> Once inside Emacs after "run -Q", first turn off blink-cursor-mode and
> global-eldoc-mode, then evaluate the recipe:
>
>   M-: (insert " " (propertize "TODO" 'face '(:inherit variable-pitch) 'mouse-face 'highlight)) RET
>
> Then move the mouse pointer over the "TODO" text.  The breakpoint will
> break, and GDB will kick in.  Then type:
>
>   (gdb) pgrow
>   (gdb) continue
>
> The breakpoint will break again, and the display of Emacs you are
> debugging will show the mouse highlight.  Then type again:
>
>   (gdb) pgrow
>
> And show everything that GDB displays as result of the two "pgrow"
> commands.

Here's what I get:

Thread 1 "emacs" hit Breakpoint 3, show_mouse_face (
    hlinfo=hlinfo@entry=0x555556145870, draw=draw@entry=DRAW_MOUSE_FACE)
    at /home/steve/src/emacs/emacs-29/src/xdisp.c:33519
33519		      row->mouse_face_p
(gdb) pgrow
TEXT: 6 glyphs
  0    0: CHAR[ ] pos=146 blev=0,btyp=L w=8 a+d=13+4 MB
  1    8: CHAR[T] pos=147 blev=0,btyp=L w=8 a+d=13+4 MB
  2   16: CHAR[O] pos=148 blev=0,btyp=L w=8 a+d=13+4 MB
  3   24: CHAR[D] pos=149 blev=0,btyp=L w=8 a+d=13+4 MB
  4   32: CHAR[O] pos=150 blev=0,btyp=L w=8 a+d=13+4 MB
  5   40: CHAR[ ] pos=0 blev=0,btyp=B w=8 a+d=13+4 MB
(gdb) continue
Continuing.

Thread 1 "emacs" hit Breakpoint 3, show_mouse_face (hlinfo=0x555556145870,
    draw=draw@entry=DRAW_MOUSE_FACE)
    at /home/steve/src/emacs/emacs-29/src/xdisp.c:33519
33519		      row->mouse_face_p
(gdb) pgrow
TEXT: 6 glyphs
  0    0: CHAR[ ] pos=146 blev=0,btyp=L w=8 a+d=13+4 MB
  1    8: CHAR[T] pos=147 blev=0,btyp=L w=8 a+d=13+4 MB
  2   16: CHAR[O] pos=148 blev=0,btyp=L w=8 a+d=13+4 MB
  3   24: CHAR[D] pos=149 blev=0,btyp=L w=8 a+d=13+4 MB
  4   32: CHAR[O] pos=150 blev=0,btyp=L w=8 a+d=13+4 MB
  5   40: CHAR[ ] pos=0 blev=0,btyp=B w=8 a+d=13+4 MB

Steve Berman