This makes the output of feaLib more compact, using a similar technique
as seems to be used by makeotf.
After this change, feaLib generates output that more similar to makeotf:
* For the test cases in `bug512.fea` and `bug463.fea`, feaLib now
generates the exact same output as makeotf v2.0.90.
* For the test cases in `GSUB_6.fea`, it is hard to say because makeotf
crashes on the test file; our test contains language constructs that
are valid according to the spec, but didn't yet get implemented by makeotf.
When commenting out those constructs, feaLib generates the exact same
output as makeotf v2.0.90.
* For the test cases in `feature_aalt.fea`, the output of feaLib is now
structually the same as the output of makeotf v2.0.90. However, two
lookups are in different order. feaLib's ordering reflects the order
of statements in the compiled input source; no idea why makeotf would
want to reverse the ordering. Since this ordering difference only
affects the _targets_ of chain substitutions, there is no semantic
difference.
Resolves https://github.com/behdad/fonttools/issues/512.
Although this construct is in violation of the `ignore sub` grammar
given by the current OpenType Feature File syntax specification,
the very same specification document illustrates (in example 3
of section 5.f.ii) the `ignore sub` statement with a comma-separated
list of backgrack/input/lookahead triples.
See https://github.com/adobe-type-tools/afdko/issues/105 for a request
to amend the OpenType Feature File syntax specification.
After this code change, feaLib can now parse testdata/spec5f_ii_3.fea;
the output is identical to what is generated by Adobe's makeotf tool.
https://github.com/behdad/fonttools/issues/503
Before this change, the `script` statement had inherited global
defaults. After this change, it overrides them. The new behavior
matches the behavior of makeotf v2.0.90.
Resolves https://github.com/behdad/fonttools/issues/505.
For the test case of https://github.com/behdad/fonttools/issues/501,
which was about an unrelated problem, feaLib now produces the exact
same output as makeotf v2.0.90.
Although the specification writes the exact opposite, makeotf does
accept script and language statements inside named lookup blocks.
Since Glyphs.app (and possibly other tools, too) produce feature files
that make use of this syntax, enforcing the spec would break existing
files.
Resolves https://github.com/behdad/fonttools/issues/501.
In f0eb7e98ca0642f17ac82433db8c957fffd6a9d3, the various subclasses
of otTables.ClassDef were merged into one single class. Therefore,
we can now always instantiate otTables.ClassDef() which is simpler.
Make the output of otlLib.buildLigatureSubst() deterministic.
Before this change, otlLib ligatures were emitted in a non-deterministic
sorting order (depending on what hash value Python would give
to a string tuple).
After b4919b6c0a5ea0ca6747fe7699554e8a14d1f77f, the tests were
named correctly but they always used the exact same feature file,
irrespective of what file they were supposed to test.
Resolves https://github.com/behdad/fonttools/issues/465
Before this change, feaLib did not handle feature files that specified
`feature aalt` whose block just was referring to other features without
defining any lookups on its own. After this change, we can handle it.
Resolves https://github.com/behdad/fonttools/issues/441
Resolves https://github.com/behdad/fonttools/issues/445 for single
substitutions. The compact forms for chaining to other GSUB types
are not yet supported; these will get fixed in follow-up changes.
Before this change, we silently generated bad fonts. After this
change, we emit the exact same output like `makeotf` for specific
kerning pairs, and reject the input file for the not yet implemented
class-based kerning. (The implementation of class-based kerning
is coming soon).
Before this change, the compiler would enumerate only the first
glyph class of a kerning pair. However, that behavior did not match
the behavior of the `makeotf` tool.
