If two marks want to ligate and they belong to different components of the
same ligature glyph, and said ligature glyph is to be ignored according to
mark-filtering rules, then allow.
Example Burmese senquence:
U+1004,U+103A,U+1039,U+101B,U+103D,U+102D
Test font provided by Norbert Lindenberg.
Fixes https://github.com/behdad/harfbuzz/issues/545
This test font had a upem of 769, which results in rounding-related errors with
the FreeType font funcs. Change the upem to 1024 to fix that.
Fixes https://github.com/behdad/harfbuzz/issues/201
We use three bits for lig_id these days, so we finally got a report of
two separate ligatures with the same lig_id happening adjacent to each
other, and then the component-handling code was breaking things.
Protect against that by ignoring same-lig-id but lig-comp=0 glyphs after
a new ligature.
Fixes https://github.com/behdad/harfbuzz/issues/198
Behdad Esfahbod