What is CMAP table Unicode/Encoding ID=10?

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ClintGoss
ClintGoss Posts: 66
in Font Technology
Would anyone have a clue what Encoding ID 10 is for the Unicode platform (pid=0)?

I have 30 fonts out of a set of 1,894 Open Source fonts that have format 12 (Segmented Coverage) 'cmap' tables of with pid=0 and encoding ID=10. That combination is not in either the Microsoft or Apple version of the OT spec v1.8.3.

Some of the affected fonts are "fringe", but there are fonts such as DejaVu Sans Mono and some of the Linux Libertine fonts with these tables.

I'm thinking they are intended to have been Windows/Unicode Full tables (pid=3, eid=10) tables. This is supported by the fact that all of those fonts that have a Unicode/eid=10 'cmap' table also have a Windows/eid=10 table, and they typically have the same number of characters.

Maybe there's a secret OT spec somewhere that I'm missing?? 

Comments

  • Joshua Hadley
    Joshua Hadley Posts: 3
    edited April 2019
    Not a secret, but there is additional platform/encoding information under the 'name' table portion of the spec: https://docs.microsoft.com/en-us/typography/opentype/spec/name#enc0

    But nothing for EncodingID=10 under PlatformID=0 there, either. The correct EncodingID for "Unicode full repertoire" using cmap subtable format 12 would be 6.

    I agree with your thinking: this is very likely a mistake; the result of a copy/paste of subtables and someone forgot or didn't know that the EncodingID has different meaning under different PlatformIDs. To my mind, the duplication of subtables in this manner is itself a mistake, but probably fodder for a different discussion :smiley:
  • ClintGoss
    ClintGoss Posts: 66
    Thanks Joshua ...
    Joshua Hadley said:
    ... this is very likely a mistake; ...
    ... this is so helpful - just knowing I haven't taken some huge mis-step or missed something fundamental.

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