bug#50177: Support U+20DD COMBINING ENCLOSING CIRCLE

[Eli Zaretskii]

> From: 積丹尼 Dan Jacobson
>  <jidanni@jidanni.org>
> Date: Tue, 24 Aug 2021 07:14:17 +0800
> 
> How do
> 檢⃝  x⃝
> look to you?

Look correctly: as a single grapheme cluster.

> In https://bugs.chromium.org/p/chromium/issues/detail?id=1242732#c2
> only Firefox puts them in the circles.
> 
> Emacs is at least a little better than chrome, but still puts the circle
> at back, instead of around.

You need a font that has glyphs for both the character and the circle.
Emacs can only compose character glyphs from the same font.

I see no bug here.