How can one find the Unicode codepoints that a font has glyphs for, on a Debian-based system?

Question

From a scripting language (Python or Ruby, say) on a Debian-based system, I would like to find either one of:

1. All the Unicode codepoints that a particular font

Answer 1

I would try any of the FreeType 2 language bindings. Here's a Perl solution to list the Unicode code points of a font using Font::FreeType:

use Font::FreeType;
Font::FreeType->new->face('DejaVuSans.ttf')->foreach_char(sub {
    printf("%04X\n", $_->char_code);
});

Answer 2

I've recently listed the mapping from unicode codepoints to glypths in a TTF using TTX/FontTools. That tool is written in Python, so it matches the Python tag in your post. The command

ttx -t cmap foo.ttf

will generate an XML file foo.ttx which describes that mapping, for various environments and encodings. See e.g. this reference for a description of what the platform and encoding identifiers actually mean. I assume that the package can be used as a library as well as a command line tool, but I have no experience there.