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googlefonts / fontmake

Compile fonts from sources (UFO, Glyphs) to binary (OpenType, TrueType).
Apache License 2.0
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Do we deal with overlapping rule ranges for the same glyph? #899

Open madig opened 2 years ago

madig commented 2 years ago

What does it mean when rule ranges overlap for the same glyph? How should it be handled? an internal bug report prompts me to think there is a behavioral difference between VFs and statics.

anthrotype commented 2 years ago

can you provide an example? How does fontTools.featureVars handle the situation? We should probably match that, provided is the right thing to do

anthrotype commented 2 years ago

How should it be handled?

did the font developer write those on purpose, if so what was the intended behavior?

madig commented 2 years ago

The example was (note the Hbar):

  <rules processing="last">
    <rule name="BRACKET.149.227">
      <conditionset>
        <condition name="Weight" minimum="149" maximum="227"/>
      </conditionset>
      <sub name="Hbar" with="Hbar.BRACKET.149"/>
      <sub name="cent" with="cent.BRACKET.149"/>
      <sub name="dollar" with="dollar.BRACKET.149"/>
    </rule>
    <rule name="BRACKET.186.227">
      <conditionset>
        <condition name="Weight" minimum="186" maximum="227"/>
      </conditionset>
      <sub name="Hbar" with="Hbar.BRACKET.186"/>
    </rule>
  </rules>

I didn't receive word yet whether this was intended, but probably not. In the VF, the last rule wins and in the statics, the first on does IIUC.