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From: Jesper Harder <harder@myrealbox.com>
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Subject: Re: Unicode box-drawing chars
Date: Sat, 14 Sep 2002 22:49:11 +0200
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Oliver Scholz <alkibiades@gmx.de> writes:

> Yes. And even when there is a unicode font, it is quite possible that
> it does not contain the box-drawing glyphs.
>
> Is it possible to check from lisp if a font actually contains a glyph?

This isn't a very good solution (and it'll only work on X11):

You can determine which font Emacs will use with `internal-char-font'.
You could then call

    xlsfonts -lll -fn FONT

and parse the output to get the font metrics.  If the metrics for a
particular code point contains all zeros, say

           0x009f (159)	   0     0     0     0     0  0x0000  .

then the glyph doesn't exist in this font.