Phinney on Fonts

Tag: AFDKO

  • Greek Support in Fonts: Truth & Lies

    A recent thread over on Typophile prompts me to explain why one sometimes sees OpenType CFF fonts that don’t actually support Greek, claiming that they do (by means of the Unicode Range and Codepage bit settings).

    Originally, when Adobe converted the Adobe Type Library to OpenType, in the early stages we were thinking we wanted to be as compatible as possible with the Type 1 versions of the fonts.

    In the absence of codepage bits and the like in Type 1 fonts, Windows GDI used to do a test for specific codepoints in the font to determine whether given codepages were supported, I believe one codepoint per codepage. I believe the codepoint to determine Greek support was the one for the “mu”… but it was definitely a test for a character that was present in the basic ISO-​Adobe character set (now Adobe Latin 1). This even though the character set didn’t really support Greek, it just had a few Greek characters because of their use as math symbols.

    So, the Type 1 fonts were (arguably erroneously) detected as supporting Greek by GDI. The idea at the time was that the OpenType fonts with the equivalent character set should behave the exact same way, and therefore the determination of whether to give them the flag saying they support the Greek codepage should be based on the same test… so basically all the fonts would claim to support Greek, even though they really didn’t.

    Somehow, even though the idea of near-​perfect compatibility between the OpenType fonts and their Type 1 predecessors was abandoned, this principle stuck during the initial conversion of the Adobe Type Library (“Alchemy”). Unicode ranges were set more-​or-​less in compatibility. Additionally, the AFDKO “makeOTF” tool used to build fonts would automatically do this, unless specifically over-​ridden. So you could see third-​party fonts doing this as well if they were made with older versions of Adobe tools.

    I thought this was a mistake, and eventually convinced other folks of my opinion, so this decision was changed in the revision of the Adobe Type Library (“Facelift”) a couple of years ago, released about October 2007. The AFDKO was changes as well, to match this new preferred behavior.

    So, you’ll find that the 1.x version of Adobe Caslon Pro built in 2001 has bits set to claim it supports the Windows Greek codepage and the Greek Unicode range, but this claim was dropped in the 2.0 version of 2007.

  • AFDKO 2.5 released

    Adobe has just released a new version of the Font Development Kit for OpenType (AFDKO). This is an important milestone for font developers.

    Why care?

    Even if you don’t use it yourself, the AFDKO code is licensed at no cost to developers of other font tools such as FontLab and DTL FontMaster. It forms the basis of the OpenType generation and OpenType features support in those tools. So very often new functionality in the AFDKO is a preview of new functionality in these other tools, and hence indirectly of capabilities of both Adobe and other vendors’ fonts. It’s reasonable to suspect that features in the AFDKO will preview new features in future versions of FontLab Studio (maybe 6.0?) and DTL FontMaster (look at the DataMaster tool in particular).

    So, with the new FDK, and one hopes in future versions of FontLab Studio and DTL FontMaster, users are able to build fonts which support complex scripts (Arabic, Indic, etc.), without using Microsoft’s VOLT as a separate process. All (yes all) OpenType GSUB and GPOS lookup types are supported. There’s support for Unicode Variation Sequences, especially useful for Japanese and ideographic languages. Plus one can give “friendly” names to stylistic sets, although this last will also need to be supported by applications, and I wouldn’t hold my breath waiting for that. Plus there are various bug fixes and lesser features.

    What is the AFDKO, exactly?

    The AFDKO is a set of command-​line (yes, really) font development tools available for Mac, Windows and Unix. They cover compiling, proofing, testing and some editing of OpenType fonts. Compiling a font requires a basic TrueType, Type 1 or OpenType font as input; what the AFDKO does is add OpenType layout features to an existing font (as in, you still need a font editor).

    I’m particularly fond of the “CompareFamily” tool, which is unusual in that it not only does tests on individual fonts, but looks at how information and key values are coodinated across a family. This is very useful for checking things such as style linking, or making sure your trademark statement is identical in all members of the family.

    Because this stuff is command-​line driven, it may not be for the average user. Besides which, many folks may prefer to use functionality which is integrated with their font editing environment. But for those who need reliability and a controlled, repeatable build process, the FDK is a nice option to have.


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