font/sfnt: support fonts with "true" apple version tag

OpenType specification mentions that fonts might contain Apple
version tag that is equal to "true" (see note in [1]). Currently,
the library returns a parsing error for those fonts.

CL adds Apple this version tag to the validation code and allows
fonts to omit OS/2 table, as mentioned in the TrueType spec [2].

[1] https://docs.microsoft.com/en-us/typography/opentype/spec/otff#organization-of-an-opentype-font

[2] https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6OS2.html

Change-Id: I13406fe97b091f24aaabf9b477df9c8fc8df883c
Reviewed-on: https://go-review.googlesource.com/c/146078
Reviewed-by: Nigel Tao <nigeltao@golang.org>
1 file changed
tree: bc4f96703836efb4d962ebac83e6e770fd19ca1c
  1. .gitattributes
  2. .gitignore
  3. AUTHORS
  4. CONTRIBUTING.md
  5. CONTRIBUTORS
  6. LICENSE
  7. PATENTS
  8. README.md
  9. bmp/
  10. cmd/
  11. codereview.cfg
  12. colornames/
  13. draw/
  14. example/
  15. font/
  16. math/
  17. riff/
  18. testdata/
  19. tiff/
  20. vector/
  21. vp8/
  22. vp8l/
  23. webp/
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