bug#51550: 29.0.50; Customize Group INS buttons sometimes don't have a left box line

[Po Lu]

Eli Zaretskii <eliz@gnu.org> writes:

> So I guess someone will have to step through the relevant drawing code
> and see where do those two border lines come from.  I cannot do this
> because the problem doesn't exist on my system.

Thanks, I'll bisect when I get the time.  But you have got one minor
detail wrong: on 27.2, all buttons have a left box line, so the bug is
in the buttons that don't.