His Deeds Are Dust

I’ve just been looking at packaging a font for Fedora, and have found that there is no separate licence file, though the font metadata contains the full licence text. I should ask upstream to put a copy of the licence in their archive, the next time they do a release, but what if they aren’t interested? How would I extract the licence text?

The simplest starting point seems to be TTX, which can take a TrueType font and convert some or all of it to an XML document. From then, anything that can parse XML or plain text should help. I’ll just extract the TrueType “name” table:

$ ttx -t name font.ttf

This creates a file called font.ttx. Annoying, I can’t send the output to stdout, and I can’t ask that it overwrites any old file of the same name; it’ll just insist on creating font.ttx, font#1.ttx, font#2.ttx and so on.

If we take a look at font.ttx, we can see the field I’m interested in, in a namerecord element with attribute nameID of 13:

<namerecord nameID="13" platformID="1" platEncID="0" langID="0x0">
       This font software is copyright (c) 2007, Frixxon Wanglewurx. All rights reserved.&#13;&#10;"Frixxon Muck" is a Reserved ...
</namerecord>

The entire licence is extracted as one line in the XML output, with carriage returns and line feeds encoded as 
 and 
, respectively. There may be more than one copy of this licence, with different platformID values.

To go from here to a text file with no more than 80 characters per line and LF endings, I could either use sed or xsltproc. Let’s take a look at how both would work. Here’s getlicence.sed:

/<namerecord nameID="13"/ {
  n
  s/^ \+//
  s/&#13;//g
  s/&#9;/\t/g
  s/&#10;/\n/g
  s/&amp;/\&/g
  p
  q
}

Which reads as: find the namerecord, skip to the next line, strip leading spaces, convert some XML entities to text, print it and quit.

I’d invoke this with:

$ sed -nf getlicence.sed font.ttx | fold -s > LICENSE.txt

Yes, despite using the British spelling of licence normally, I’ll use license for packaging.

The XML entity conversion is a bit of a faff which a proper XML tool could take care of for me. Here’s getlicence.xsl:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text"/>
<xsl:template match='/'>
  <xsl:value-of select="//namerecord[@nameID='13'][position()=1]"/>
</xsl:template>
</xsl:stylesheet>

I’d use this with:

$ xsltproc getlicence.xsl font.ttx | dos2unix | fold -s > LICENSE.txt

There are plenty more tiny hacks that TTX and XSLT can help with. I haven’t yet tried many round trip conversions with TTX, but if I lose my way in FontForge’s Font Information menus and dialogs, I could be tempted.