When one is not using the msys2 python, the header files that are passed in as environment
variable cannot be found.
https://ci.appveyor.com/project/fonttools/ttfautohint-py/build/1.0.65/job/rkremny4jjid9nl2#L803
This is because msys2 shell and make use POSIX paths (e.g. /c/Users/clupo/...)
whereas non-msys2 python.exe uses native Windows paths (e.g. C:\Users\clupo\...).
Msys2 will automatically convert command line arguments (but not environment variables) from
POSIX to Windows paths when calling a native win32 executable, so we pass the header paths
as arguments instead of environment variables.
This way the gen-def.py script can support both mingw python running in an MSYS2 shell, and
native win32 python.
From the new code (first paragraph is from the OT Devanagari spec.):
/* o Reorder matras:
*
* If a pre-base matra character had been reordered before applying basic
* features, the glyph can be moved closer to the main consonant based on
* whether half-forms had been formed. Actual position for the matra is
* defined as “after last standalone halant glyph, after initial matra
* position and before the main consonant”. If ZWJ or ZWNJ follow this
* halant, position is moved after it.
*
* IMPLEMENTATION NOTES:
*
* It looks like the last sentence is wrong. Testing, with Windows 7 Uniscribe
* and Devanagari shows that the behavior is best described as:
*
* "If ZWJ follows this halant, matra is NOT repositioned after this halant.
* If ZWNJ follows this halant, position is moved after it."
*
* Test case, with Adobe Devanagari or Nirmala UI:
*
* U+091F,U+094D,U+200C,U+092F,U+093F
* (Matra moves to the middle, after ZWNJ.)
*
* U+091F,U+094D,U+200D,U+092F,U+093F
* (Matra does NOT move, stays to the left.)
Fixes https://github.com/harfbuzz/harfbuzz/issues/1070
Test case added with Adobe Devanagari.
The get_table imple was wrong, as table offsets in a dfont are
relative to the resource. We were treating them as relative to
the big blob itself. To be fixed.
Part of https://github.com/harfbuzz/harfbuzz/pull/1085
