Comments on ISO/IEC 14496-22 "Open Font Format"

[Levantovsky, Vladimir]

Dear AHG members,

I received an annotated copy of the 3rd edition OFF text with user comments. While few of those comments are irrelevant, and many comments have already been addressed in the 4th edition text, some of them do need to be considered for further discussion. Upon reviewing the comments and the text I also came up with few additional questions; among them:

-          Question about clarifying version numbers encoded in Fixed format, in particular about providing an example of how e.g. version 1.11 should be encoded;

-          Question about the normative scope of uint16 version numbers, and whether the requirement to treat it as a minor version number (and consider all format changes as compatible extensions) should be considered as a mandate or as a recommendation (as it is now defined as "should");

-          In "Calculating checksums" section - [editorial] suggestion to replace "the hex value B1B0AFBA" with 0XB1B0AFBA;

-          Definition of lineGap in 'hhea' table - question on whether historical references to Win 3.1 and MacOS 6 and 7 still need to be preserved;

-          Definition of maxStackElements in 'maxp' table - question about using a footnote instead of simply including it as part of the description;

-          'kern' table, Format 0 - the description states that it is the only format (!) that will be properly interpreted by Windows and OS/2 - do we still need to state this?

-          LookupFlag Bit enumeration table - the first table column should probably have title "Value" instead of "Type"

-          GPOS table description - many table headers have "Value / Type / Description" columns, which is incorrect and should be revised to match other table definitions using "Type / Name / Description" format.

-          GPOS Example 5 - needs review as I suspect Class2Count field has redundant comments.

-          General comment: there are quite a few figures used in the OT/OFF text that show text rendered in low quality, low resolution bitmaps (e.g., see first three sections of https://www.microsoft.com/typography/otspec/base.htm and many other figures including illustrations for GSUB/GPOS/JSTF tables). Maybe it is the time to redo them - will need a lot of work but it's a bit awkward when a document describing font format for high-quality text rendering uses low-res, low quality images as illustrations.

-          Recommendations: It may be a good time reconsider parts of the "Recommendation" section as some of them seem to be requirements (e.g. Big Endian byte ordering, table alignment, etc.) and some of them (e.g. device resolutions) may be outdated and no longer relevant.

Thank you,
Vladimir


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