Allow variable scaler in ligature caret position and build
CaretValueFormat3 with DeviceTable. Does not support non-variable device
table, but can be added if someone really really wants it.
This is a GlyphsApp extension, (partially) documented [here][1], but it is a
useful one as it allows concise glyph insertion using decomposition
without having to maintain the list of glyphs in two places. E.g.
```fea
@upper = [A-Z];
lookup insert {
sub @upper by @upper connector;
} insert;
feature ccmp {
sub @upper' lookup insert x;
} ccmp;
```
As apposed to:
```fea
@upper = [A-Z];
lookup insert {
sub A by A connector;
sub B by B connector;
sub C by C connector;
sub D by D connector;
sub E by E connector;
sub F by F connector;
sub G by G connector;
sub H by H connector;
sub I by I connector;
sub J by J connector;
sub K by K connector;
sub L by L connector;
sub M by M connector;
sub N by N connector;
sub O by O connector;
sub P by P connector;
sub R by R connector;
sub S by S connector;
sub T by T connector;
sub U by U connector;
sub V by V connector;
sub W by W connector;
sub X by X connector;
sub Y by Y connector;
sub Z by Z connector;
} insert;
feature ccmp {
sub @upper' lookup insert x;
} ccmp;
```
1. http://handbook.glyphsapp.com/en/layout/multiple-substitution-with-classes/
Fixes https://github.com/fonttools/fonttools/issues/2949
- If there are no marked glyphs in an "ignore" statement, issue a
warning. The spec disallows this but makeotf allows it. It is most
likely a typo, so a warning is warranted.
- Mark the first glyph not all the glyphs, this matches makeotf.
- In asFea() always mark the input glyph.
- Udpate the tests.
* add test that fails for #2293
* fixing #2293: rewrite of contextual positioning logic, ensure len(suffix) > 1 yields the correct result; checking more edge cases and raising errors inspired by makeotf
* test error cases
* only check when we actually have a value
* catch one more case that makeotf errors on and we didn't
* Replaced all from ...py23 import * with explicit name imports, or removed completely when possible.
* Replaced tounicode() with tostr()
* Changed all BytesIO ans StringIO imports to from io import ..., replaced all UnicodeIO with StringIO.
* Replaced all unichr() with chr()
* Misc minor tweaks and fixes
This makes the directory to search for included files explicit.
Also use Python 3's FileNotFoundError to catch non-existant files instead of a workaround for Python 2.
[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.
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.
This checks that glyph names that appear in a feature file are actually
in the glyph set provided in glyphNames. If the set is empty, no check
is done. This preempts a KeyError later during saving of a TTFont object
and makes this case much more easily catchable.
Closes#1723.
If the single substitution involved a glyph class, we were incorrectly
using only the first glyph in the class.
Broken since ec6ff821f0e72022d7aec8794b6bb589d8f81808, apparently no one
else uses this feature!
