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

[Eli Zaretskii]

> Cc: 63187@debbugs.gnu.org
> Date: Mon, 01 May 2023 07:58:26 +0800
> From:  Po Lu via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> Aaron Jensen <aaronjensen@gmail.com> writes:
> 
> > Is there anything specific to macOS that is involved in scrolling 
> > optimization?
> 
> Yes, Apple deleted the API used to perform bit blits, so Emacs uses a
> workaround that I don't really understand, and seems unreliable.

You mean, ns_scroll_run in nsterm.m?  Which parts of it do you not
understand?