bug#41645: 27.0.91; Combining Grapheme Joiner (#x34f) gui artifacts

[David Fussner]

Thank you. I shall build the updated master and report back.

On Tue, 2 Jun 2020 at 16:51, Eli Zaretskii <eliz@gnu.org> wrote:
>
> > From: David Fussner <dfussner@googlemail.com>
> > Date: Tue, 2 Jun 2020 14:45:50 +0100
> > Cc: Eli Zaretskii <eliz@gnu.org>, 41645@debbugs.gnu.org
> >
> > A couple of data points, in case they're helpful:
> >
> > On 27.0.91 _unpatched_, I see the artifact whenever the font of the
> > CGJ is different from that of the glyph before it, no matter which
> > script I'm using. When the font of the CGJ and the previous glyph are
> > the same, I don't see the artifact, except in Hebrew, where it's still
> > present. C-u C-x = displays the CGJ on its own, as a separate glyph,
> > whenever it's used in Hebrew and also whenever its font doesn't match
> > that of the glyph before it. When the font does match, in Latin or
> > Greek script, the cursor doesn't stop on the CGJ, and C-u C-x = shows
> > it as composed with the previous character.
>
> The visual artifact is due to the font you have that is used to
> display CGJ, a font that is different from the one used for displaying
> the surrounding text.  More about this in a separate message.
>
> Regardless, the effect of CGJ on Hebrew points that you wanted to
> have---the details can be seen in this URL:
>
>   https://en.wikipedia.org/wiki/Combining_Grapheme_Joiner
>
> did not work in Emacs, because Hebrew has its own composition rules,
> and those rules didn't allow for the CGJ among the points.  I've now
> added that, so if you rebuild the master branch, and use a font that
> can support both Hebrew characters and CGJ, you should see the effect
> of that on reordering the Hebrew points.