bug#63186: 30.0.50; Modeline is not fully repainted when being set to nil then back to having content

[Aaron Jensen]

On Sun, Apr 30, 2023 at 9:25 AM Eli Zaretskii <eliz@gnu.org> wrote:
>
> > From: Aaron Jensen <aaronjensen@gmail.com>
> > Date: Sun, 30 Apr 2023 05:54:50 -0400
> >
> > >From emacs -Q:
> >
> > In the scratch buffer, eval:
> >
> > (setq mode-line-format "foo")
> > (setq mode-line-format nil)
> > (setq mode-line-format "boo")
> >
> > After the last line, only the "b" of the mode line will be rendered.
> > Triggering a repaint with M-x or resizing the window causes the entire
> > mode line to repaint.
> >
> > If the buffer has enough content in it such that there is text where the
> > mode line is when it is set to `nil', most of that text will remain
> > painted in place when the mode line is set to "boo".
>
> Thanks, should be fixed now on the emacs-29 branch.
>
> (This is a regression from Emacs 28, but I have no idea which change
> caused it.)

Thanks, confirmed. Fixed when merged into Emacs 30 as well.

Aaron