bug#41454: 28.0.50; [".+" 0 font-shape-gstring] composition rule breaks paren highlighting

[Pip Cet]

On Fri, May 22, 2020 at 1:01 PM Eli Zaretskii <eliz@gnu.org> wrote:
> > From: Pip Cet <pipcet@gmail.com>
> > Date: Fri, 22 May 2020 12:50:13 +0000
> >
> > There seems to be a general problem using such regexps in the
> > composition-function-table.
>
> Could be, because it's a very unusual thing to do.

I also see the problem when I change the pattern to "(a)" and enter
"(a)", so it's not a problem with variable-length regexps.

> I think this is expected, since you told Emacs all those characters
> are a single grapheme cluster.

I don't think it's expected for characters to stay highlighted after
the blink delay is over.

> The regexps in composition-function-table should match only characters
> that are supposed to be composed.

So it's invalid to have a regexp for a composition not supported by
the current font?