bug#66942: move-to-column behavior when newlines have a display property

[Eli Zaretskii]

unarchive 64988
forcemerge 66942 64988
thanks

> From: Sebastian Wålinder <s.walinder@gmail.com>
> Date: Sun, 05 Nov 2023 09:14:05 +1100
> 
> There was a bug that I encountered in a downstream Emacs package relating to 
> setting line-move-visual to nil and running line-move when the package has 
> created overlays on newlines.
> 
> The maintainer of the package has tracked down the bug to some incorrect 
> behavior in the function move-to-column when overlays are present on newlines.
> 
> Here's a link to the issue that describes the issue with move-to-column:
> https://github.com/jdtsmith/indent-bars/issues/22
> 
> Thoughts?

It's the intended behavior.  It is the best Emacs can do given the
limitations posed by such overlay strings, see the detailed
explanation in bug#64988.

My best recommendation is not to use overlay strings with embedded
newlines, if accurate movement by columns is important.