http://www.adobe.com/devnet/opentype/afdko/topic_feature_file_syntax.html#10
For example, @mhosken is interested in experimenting with inlining
custom syntax (such as Python snippets) into feature files. After this
change, such experiments can be done on top of feaLib because the
Abstract Syntax Tree now contains the tag and content of `anonymous`
blocks.
* feaLib: limit language statements to 1 feature block
language exclude_dflt statements should only apply to lookups
defined in their feature block and not to lookups defined
in previous blocks sharing the same feature tag
* feaLib: add BuilderTest::test_FeatureFile_multiple_feature_blocks
Before, if someone tried to set the language before setting the script
a None/language language system would be created (with actual tag
"None" stored in the feature table). This defaults to tag DFLT and
fails when a non-dflt language is set for DFLT, since that's illegal.
This is to fix what I think was a misunderstanding of the exclude_dflt
keyword (and the implicit include_dflt option active by default).
Rather than including the following lookups in the default language
systems, I think it is used to include the lookups specific to default
language systems in the system defined by the current language
statement. Thus instead of registering a lookup in all default
systems when include_dflt is true, we should exclude the lookups
registered with default systems from the current system when
include_dflt is false.
Since py23 modifies some essential builtins, it's safe to import
everything all the time. At least, that's how it was designed.
It's a bug if importing * breaks some code.
Before this change, we had only emitted a SinglePos (GPOS type 1) lookup
for a statement like `pos A' B' 20`; after this change, we always emit a
chain rule even if there is no context. There is a semantic difference if
the rule is preceded by a `ignore pos` statement. Omitting context-free
contextual chains was actually not a (premature) optimization, but an
artifact that came from the representation of glyph patterns.
https://github.com/behdad/fonttools/issues/516
After this change, feaLib generates the exact same output as makeotf
for the test case in `bug453.fea`. Before this change, feaLib had
rejected the input as malformed.
Our new behavior is in blatant violation of the OpenType Feature File
Syntax specification, which writes: "NOTE! If a GDEF table is not
explicitly defined in the feature file, [...] all mark glyph classes
must be disjoint". However:
1. makeotf does not enforce this constraint;
2. existing feature files happily define non-disjoint markClasses;
3. existing tools such as the Glyphs font editor generate feature files
with non-disjoint markClasses;
4. it is not obvious what the intention of this constraint would be.
Therefore, fewLib now follows the makeotf implementation, intentionally
ignoring what is mandated by the specification. I've proposed a spec change
at https://github.com/adobe-type-tools/afdko/issues/106.
Resolves https://github.com/behdad/fonttools/issues/453.
There are no examples for `ignore pos` in the OpenType Feature File
Syntax specification, therefore using a made-up example for the test.
The output from feaLib is identical to what makeotf generates.
Resolves https://github.com/behdad/fonttools/issues/503.
This is another test case for the `ignore sub` statement.
After the recent changes to feaLib, the output is now identical
to the output generated by makeotf.
https://github.com/behdad/fonttools/issues/503
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
