3.10 is out next week, while 3.6 reaches end of life by the end of this year.
It's time to require 3.7 or greater, so we can finally use built-in dataclasses and more.
Fixes https://github.com/fonttools/fonttools/issues/2350
relying on ClipList.compile to drop unused clips based on updated glyphOrder won't work when font is loaded lazily (default for subsetter), because ClipList gets decompiled too late (after glyphOrder has already been modified) and this produces warnings about missing glyphIDs.
Better to make the subsetter explicilty prune unused clips.
4294967295 (0xFFFFFFFF in decimal form) is not very memorable.
Still, using hex notation for all VarIndexBases would make the non-default values less readable (when interpreted as an index into the DeltaSetIndexMap array, decimal makes more sense).
Since 0xFFFFFFFF means 'no variation data', it makes sense to omit it from the ttx dump and write an empty <VarIndexBase/> element with no value.
We also allow to build Var tables without needing to pass "VarIndexBase": 0xFFFFFFFF in the source dict.
See pull request: https://github.com/fonttools/fonttools/pull/2326
The new module `otlLib.optimize.gpos` provides `compact` functions that
can reduce the file size of GPOS PairPos lookups by splitting subtables
in a smart way to avoid storing zero-valued pairs.
The compaction methods are called from `otlLib.builder` and
`varLib.merger` so that static and variable fonts can benefit from the
optimization at compile time.
The new module `otlLib.optimize` is also executable, to allow running
the optimization on existing fonts.
The optimization is a trade-off because on the one hand it can reduce
significantly the byte size of the GPOS table (up to 50% in random
Google Fonts) but on the other hand it adds to the compilation time and
may make fonts very slightly bigger once compressed to WOFF2 (because
WOFF2 doesn't mind about zero values and compresses them very well).
As such, the optimization is off by default, and you can activate it by
providing the environment variable `FONTTOOLS_GPOS_COMPACT_MODE=5` for
example (values from 0 = off to 9 = max file size savings, but many more
subtables).
