bug#37829: 27.0.50; Overlay behaviour changed without documentation.

[Zhu Zihao]

On Sun, 20 Oct 2019 19:05:26 +0800,
Eli Zaretskii wrote:
> 
> > Date: Sun, 20 Oct 2019 16:49:10 +0800
> > From: Zhu Zihao <all_but_last@163.com>
> > 
> > 1. open a empty buffer, type "Lorem ipsum" in it, then goto point-min
> > 2. Eval this code
> > 
> > (let ((ov (make-overlay (point-min) (1+ (point-at-eol)))))
> >   (overlay-put ov 'face 'mode-line))
> > 
> > In current version of Emacs, the mode line overlay will only cover the 
> > string
> > "Lorem ipsum", but in 26.2, the overlay will cover the hole line(every 
> > pixel in
> > line).
> > 
> > It may be a bug because no documentation or NEWS mentioned this change.
> 
> Crystal ball says it's because the mode-line face doesn't have the
> :extend attribute by default.  If so, this change _is_ in NEWS and in
> the ELisp manual.
> 
> Thanks.

Thanks, I just search "overlay" in NEWS so I didn't notice it's the issue of
face, not the overlay.