[CREATE] Font Validator 2.1 release note/status, and libre font test results a year on after FontVal 2.0.

[Hin-Tak Leung]

A year after Font Validator 2.0, I have finished testing what is to be 2.1 on all the 3283
libre fonts shipped with Fedora 26. However, my main dev computer went out of action
soon after, before I can upload the test results somewhere or tag the release; so people
who want it ( googlefonts certainly does, see https://github.com/googlefonts/fontbakery/issues/1335 ),
please just build from my git master.

The widest functionality is offered by running it under wine, actually(on Linux or Mac OS X).

Below is the release notes. As I don't have the test results with me, I can only write from
memory: out of the 3283 fonts shipped by fedora 26 ( a slightly larger number than fedora 24
for which FontVal 2.0 was tested against), about 139x + 149x are uninteresting CFF fonts
- which the hinting test skips, and those that passes - I can't remember which is which, but
that adds up to 288x fonts.

394 have some degree of problems with their hinting instructions;
this is about the same as last year, so obviously this needs to be better publicised.
One was a bad packaging of an zero-length file ( filed as https://bugzilla.redhat.com/show_bug.cgi?id=1473437 ).

-------

Font Validator is a tool for testing fonts prior to release.
It was initially developed by Microsoft, to ensure that fonts meet Microsoft's
high quality standards and perform exceptionally well on Microsoft's
platform.

In 2015 the source code was published under the MIT license ([see release
discussion](http://typedrawers.com/discussion/1222/microsoft-font-validato
r-lives))

Most (only?) active development happens at
http://github.com/HinTak/Font-Validator .

FontVal 2.1
===========

- Backend b70+10.5, based on FreeType 2.8+ (VER-2-8-73-g38bdf22bf)

  - 16 Errors/Warnings in 1.0 which has no FreeType equivalent
    are implemented. This includes incomplete conditionals (e.g.
    IF without THEN) and maths overflows, etc.

  - 15 FreeType-specific additions are added. This includes endless loops
    and backward jumps, etc.

  - C Python wrapper available ( https://github.com/HinTak/freetype-py
    fontval-diag branch ). Perl wrapper in dev.

- Robustness: still produce a report for some seriously buggy fonts

- Speed/Resources improvements:

  - avoid unnecessary repeated processing of identical EBDT/glyf tables
    and rasterization for TTCs
    (down from half-days to an hour or two in some cases)

  - much smaller memory foot-prints for EBDT check
    (down from 15 to 20+ GB RAM to 1 or 2 GB in some extreme cases)

- Windows-only problem fixed: can now accept non-ascii font names
  (2.0 did not, 1.0 did).

- New opentype tables supported: meta (partial)

- glyf table: cope with broken contours with hair pins, and extremely
  tight loops etc and correctly warn those.

- DSIG table: supports stronger cryptographic digest algorithms (Apparently
  Adobe started signing with those). correct previous mis-diagnosis of very
  old TTCs' signature.

- A lot of misc documentation updates.

- Known Caveats:
  - E6053 (Value exceeds capacity of 2 byte number) also warns on
    values exceeding Fixed 2.14 (FontVal 1.0 did not).
  - W6028 (number of twilight points unreasonably large) too frequent/noisy.
  - W6029 (Setting the loop variable to zero is an error) may be withdrawn
          later as ttfauthint does it and there is no known problem, despite
          some apple and macrosoft docs saying so.
  - The check for maths overflows in hinting instructions requires gcc 5+ to
    build, so it is not offered on the Mac OS X backend for the time being.

FontVal 2.0 , Jul 17 2016
===========

- backend b54, based on FreeType 2.6.4

FontVal 1.1, Apr 07 2009
===========
- Microsoft released to Github on Nov 11 2015; incomplete

FontVal 1.0 , Jul 10 2003
===========
- last known Microsoft's proprietary binary