[docs] Document feaLib
* Rearrange docs by user intention, highlighting the things you can do with each component.
* Remove reference to lexer and error modules from documentation tree, since they’re not user-facing.
* I’ve added docstrings to the parser even though we only provide access to the user-facing part of the API in the main documentation, just to clarify what some of the more obscure methods do and provide links to the spec.
* AST *is* user-facing if you’re building your own feature files in code, so all classes are documented with the user in mind.
Note UI change : `fonttools varLib.models` now takes prefixed options `-d` or `-l` instead of guessing the intended feature from the number of arguments.
We have a number of command line tools which are somewhat opaque. (varLib.models in particular was very confusing.) This ensures that they all use argparse to have a consistent interface, and all have --help documentation which at least details their parameters, and hopefully therefore gives more of a clue about what they do. Those which use logging have had a command-line logging parameter added.
Does not add any new documentation (there is already some documentation for user-facing functions). It just makes colorLib.builder the top-level documentation entry, because that’s the part the user needs to care about.
This adds a `help` verb (and `--help` option) to the `fonttools` command line tool. Submodules will be listed in the help text if they have an importable `main` function with a docstring, and `main`'s docstring will be used as the one-line description for the help text.
This allows for more than one "lookup ..." chaining statements at each glyph position in a chaining contextual substitution or positioning rule: e.g.
sub a b c' lookup lookup1 lookup lookup2 d;
The corresponding change in the Adobe OpenType Feature File Specification (and implementation in makeotf) happened in adobe-type-tools/afdko#1132.
Fixes https://github.com/fonttools/fonttools/issues/1879
In ChainContext{Subst,Pos}Format3, the array of input coverages is called
InputCoverage, whereas in non-Chain Context{Subst,Pos}Format3 subtables it
is called simply Coverage.
* add nameTable.findMultilingualName(), to find an existing multilingual name
* Make addMultilingualName() reuse nameIDs if possible when asking for a new nameID, by calling findMultilingualName()
This removes some boilerplate code, and also helps when using static type checkers like mypy.
The typing.NamedTuple class was added with python 3.6 which is our min required python, so we are good.
Support was added in db49f20d6b2629e1ba25c4afd3fb60817387f3d6, but there
was only a parser test and no builder test, fix the build and add a
builder test based on the existing parser one.
Fixes https://github.com/fonttools/fonttools/issues/1901
Raise if lookup_index is None, which would happen only of the lookup
referenced belongs to the wrong table. The error message needs to be less
cryptic, though.
Fixes https://github.com/fonttools/fonttools/issues/1896
