bug#63187: 30.0.50; Tail of longer lines painted after end of nearby lines on macOS

[Eli Zaretskii]

> Date: Tue, 2 May 2023 11:14:56 +0100
> From: Alan Third <alan@idiocy.org>
> Cc: Eli Zaretskii <eliz@gnu.org>, Po Lu <luangruo@yahoo.com>,
>       63187@debbugs.gnu.org
> 
> Although, on reflection, your description sounds more like it's just
> not clearing the end of lines correctly, which wouldn't necessarily
> have anything to do with scrolling as such...

Can that happen in this case?  You will see in the code that (AFAIU)
it copies a rectangle whose width is the total width of the window, so
why would (not) clearing ends of lines be an issue?