[mpeg-OTspec] ISO/IEC 14496-22 Amendment for Font Collections [1 Attachment]

John H. Jenkins jenkins at apple.com
Fri Apr 3 19:45:34 CEST 2015

I don't know that we've ever thought of this is really being for a file, because for a long time the primary delivery mechanism for TrueType fonts at Apple was the 'sfnt' resource. At the moment, when we calculate the checksum adjustment, we treat the font as if it were a file (that is, as a contiguous block of data). The folding of the fonts into a collection happens later.

> On 3 Apr 2015, at 10:18, Ken Lunde lunde at adobe.com [mpeg-OTspec] <mpeg-OTspec-noreply at yahoogroups.com> wrote:
> With regard to the "checkSumAdjustment" field of the 'head' table, long-time implementers of TrueType Collections, meaning Apple and Microsoft, are the ones who should weigh in on this particular issue. Given that the definition of this field is for a file, and because a Font Collection is merely a bucket of multiple 'sfnt' tables, and contains two or more "virtual" font files, my guess is that this field is ignored in the context of Font Collections. But again, Apple and Microsoft should weigh in for clarity and guidance.

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