GNU bug report logs - #75931
31.0.50; mouse-face and pointer properties make pointer change back and forth

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Message #26 received at 75931 <at> debbugs.gnu.org (full text, mbox):

From: Mauro Aranda <maurooaranda <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 75931 <at> debbugs.gnu.org
Subject: Re: bug#75931: 31.0.50; mouse-face and pointer properties make
 pointer change back and forth
Date: Thu, 30 Jan 2025 06:57:32 -0300

Eli Zaretskii <eliz <at> gnu.org> writes:

>> Date: Wed, 29 Jan 2025 20:30:05 -0300
>> Cc: 75931 <at> debbugs.gnu.org
>> From: Mauro Aranda <maurooaranda <at> gmail.com>
>>
>> On 29/1/25 16:11, Eli Zaretskii wrote:
>>  >> Date: Wed, 29 Jan 2025 15:27:24 -0300
>>  >> From: Mauro Aranda <maurooaranda <at> gmail.com>
>>  >> Cc: Eli Zaretskii <eliz <at> gnu.org>
>>  >>
>>  >> I bisected it down to this commit:
>>  >>
>>  >> commit 64f9fdc812bb2e1f533ae294355d33396985e469
>>  >> Author: Eli Zaretskii <eliz <at> gnu.org>
>>  >> Date:   Thu Oct 14 11:57:07 2021 +0300
>>  >>
>>  >>      Fix display of cursor in mouse-highlighted face with ':box'
>>  >>
>>  >>      * src/xdisp.c (erase_phys_cursor, show_mouse_face): Adjust
>>  >>      phys_cursor.x as needed if the cursor is inside 
mouse-highlight.
>>  >>      (get_cursor_offset_for_mouse_face): New function.
>>  >>      * src/dispnew.c (gui_update_window_end): Set
>>  >>      'mouse_face_overwritten_p' if the cursor is in mouse-face, to
>>  >>      trigger more thorough redisplay of the cursor.
>>  >>      (Bug#50660)
>>  >
>>  > Thanks, but it would still be good to know which code changes the
>>  > mouse pointer to hand.  In the above patch, the only part that could
>>  > perhaps cause that is the first hunk, in dispnew.c, but I don't 
see an
>>  > immediate connection, especially since the answer is probably
>>  > somewhere in X-specific code (xterm.c etc.).
>>
>> I'll keep digging.
>
> Thanks.  Can you verify that reverting the first hunk of that
> changeset (2 added lines in dispnew.c:gui_update_window_end) solves
> the problem?  If not, then I'm afraid I'm on the wrong track and don't
> understand how the rest of that changeset could cause this regression.

Reverting that hunk on master doesn't solve it, but has a minor effect:
Previously, the back and forth change between hand and arrow happens
when showing the cursor and when hidding it.  If I revert the hunk, it
only happens when hidding it, so it solves half the problem.

Now, if I go back to your commit, then commenting out that change in
dispnew.c does indeed solve the problem.  But the next commit to xdisp.c
is this:
commit 2028df7826bb2c2909b2aaeba47282ca70c514e3
Author: Po Lu <luangruo <at> yahoo.com>
Date:   Thu Oct 14 18:38:26 2021 +0800

    Fix minor issues with text display when cursor is in mouse face

     * src/xdisp.c (get_cursor_offset_for_mouse_face): Don't calculate
    offsets for the glyph the cursor is on, and move some logic to
    get_glyph_pixel_width_delta_for_mouse_face.
    (fill_composite_glyph_string)
    (fill_gstring_glyph_string)
    (fill_glyphless_glyph_string)
    (fill_glyph_string)
    (fill_image_glyph_string)
    (fill_xwidget_glyph_string)
    (fill_stretch_glyph_string): Set s->face to mouse face whenever
    appropriate.
    (get_glyph_pixel_width_delta_for_mouse_face): New function.
    (set_glyph_string_background_width): Update background width and
    s->width to take into account differing :box properties of the mouse
    face, when producing strings for the cursor.
    (erase_phys_cursor): Redraw mouse face when erasing a cursor on top of
    the mouse face.
     * src/xterm.c (x_set_mouse_face_gc): Stop setting s->face when under
    mouse face because redisplay now does that for us.
     * src/w32term.c (w32_set_mouse_face_gc): Likewise.

And that commit makes the issue reappear.  And as I said, now reverting
the change in dispnew.c only solves half the problem.

Perhaps it is the call to show_mouse_face that was added to
erase_phys_cursor.

> (I wouldn't be asking these questions if I could reproduce the problem
> on my machine, but I cannot, unfortunately.)

That's OK.  I just hope I can help you figure it out, I doubt I could do
it on my own.

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