Please note that because of a bug, all X11 fonts provide their metrics structures when loaded and queried. This allows the application to determine which glyphs actually exist. Thus, the code below is not being used any more.
In the work on Mozilla, it was found that knowing which glyphs are defined in a font is very useful. There is no simple way to do this for BDF fonts, so it was decided to add font properties that would provide a list of ranges of defined glyphs in the font using the _XFREE86_GLYPH_RANGES property.
The add_rngs.pl Perl script is used to add
the ranges of glyphs in the BDF font.
The get_rngs.c is a routine in C that will scan
the properties of an X font and build a bitmap of the defined glyphs.