drop kern pairs with mixed bidi type #361
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khaledhosny
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Feb 6, 2020
khaledhosny
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Feb 6, 2020
anthrotype
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… numbers as per Khaled's comment googlefonts#361 (comment)
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@anthrotype Thank you very much for the help debugging this and the quick solution ❤️ |
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... as kerning across direction runs doesn't work in current implementations.
Also, we can't guess the designer's intention as to the "true" direction of these kern pairs with mixed bidi. So for now we warn and prune them. Maybe revise once we'll have defined that new "visual" hkerning.plist.
PTAL @khaledhosny
Incidentally also this fixes #341 because it removes the chance that feaLib will produce two PairPos2 subtables with overlapping coverages.
The split occurs when, within the same FEA lookup block definition, there are mutliple pos rules with different value record format (format A is used for LTR kern pairs [modifying only XAdvance of first glyph], format B for RTL kern pairs[modifying both XAdvance and XPlacement]).
Instead of splitting, feaLib should fill with 0 the missing values then figure out a heuristic to store the matrix optimally (see fonttools/fonttools#1731).