TrueType maxp.maxZones does not agree with OpenType spec

Originator:sascha.brawer
Number:rdar://31606020 Date Originated:2017-04-13
Status:Open Resolved:
Product:Documentation Product Version:
Classification: Reproducible:
 
Summary:
Apple’s ftxvalidator rejects OpenType fonts with maxp.maxZones set to 1, although this is valid according to the OpenType spec. Currently, Apple’s TrueType spec disagrees with OpenType on the valid range for maxp.maxZones, but perhaps Apple could follow OpenType on this? See also https://github.com/googlei18n/fontmake/issues/286.

Steps to Reproduce:
1. Run an OpenType font with maxp.maxZones==1 to ftxvalidator.

Expected Results:
ftxvalidator should get accept the font because the font complies with OpenType. (So, the propsal would be to change the TrueType spec to follow OpenType, and to change ftxvalidator to enforce OpenType compliance in this regard).

Actual Results:
maxp: The maxZones field is equal to 1; it should be equal to 2



Version:
https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6maxp.html

Notes:
Change description for maxZones to: “1 if instructions do not use the twilight zone (Z0), or 2 if instructions do use Z0; should be set to 2 in most cases.”

Comments


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