bug#61361: cursor cannot be at the start of overlay that starts with a newline

[Dmitry Gutov]

Hi Eli,

On 08/02/2023 15:08, Eli Zaretskii wrote:
> tags 61361 wontfix
> thanks
>
> > From: Xinyang Chen<chenxy@mit.edu>
> > Date: Tue, 7 Feb 2023 23:29:31 -0500
> >
> > steps to reproduce:
> > ;; test line
> > (if (and (boundp 'overlay) (overlayp overlay)) (delete-overlay overlay))
> > (setq overlay (make-overlay 1 2))
> > (overlay-put overlay 'display "\nhello")
> > ;; same result if you do this intead
> > ;; (overlay-put overlay 'display (propertize "\nhello" 'cursor 0))
> >
> > cursor does not display in the first line.
> Emacs cannot do what you are asking because the newline leaves no
> glyph on display.  So the display engine cannot place the cursor on
> the newline as it does on other characters, which do have glyphs.
>
> This is a limitation of the 'cursor' property feature.  Sorry.

Could you explain that a little further?

When I have a line with text and move point to the end of it, the cursor 
is rendered, right? Does that use some other method than "glyphs", 
making it unavailable to the handling of 'cursor' in a display spec?