Improve subsetting of Context formats

When recursing for closure, just pass down glyphs that could have
actually matched the rule.

This can result in wrong results if the recursed lookup is NOT
one-to-one.  Fix coming.

In the mean time, test with NotoSansDevanagari-Bold.ttf and
chars uni91f,uni94d,uni930 to see the difference.
1 file changed
tree: 8b1753a71c820ba334ce6627b5013cfdc8b52786
  1. pyotlss.py