Merge pull request #3360 from fonttools/fea-vars-multiple-tags

[featureVars] allow to assign same subst lookup to several feature tags

Doc/source/designspaceLib/xml.rst

@@ -438,8 +438,8 @@ glyphname pairs: the glyphs that need to be substituted. For a rule to be trigge
       See the following issues for more information:
       `fontTools#1371 <https://github.com/fonttools/fonttools/issues/1371#issuecomment-590214572>`__
       `fontTools#2050 <https://github.com/fonttools/fonttools/issues/2050#issuecomment-678691020>`__
-   -  If you want to use a different feature altogether, e.g. ``calt``,
+   -  If you want to use a different feature(s) altogether, e.g. ``calt``,
-      use the lib key ``com.github.fonttools.varLib.featureVarsFeatureTag``
+      use the lib key ``com.github.fonttools.varLib.featureVarsFeatureTag``.
 
       .. code:: xml
 
@@ -450,6 +450,9 @@ glyphname pairs: the glyphs that need to be substituted. For a rule to be trigge
                </dict>
            </lib>
 
+      This can also take a comma-separated list of feature tags, e.g. ``salt,ss01``,
+      if you wish the same rules to be applied with several features.
+
 
 
 ``<rule>`` element

Lib/fontTools/varLib/__init__.py

@@ -52,7 +52,8 @@ from .errors import VarLibError, VarLibValidationError
 log = logging.getLogger("fontTools.varLib")
 
 # This is a lib key for the designspace document. The value should be
-# an OpenType feature tag, to be used as the FeatureVariations feature.
+# a comma-separated list of OpenType feature tag(s), to be used as the
+# FeatureVariations feature.
 # If present, the DesignSpace <rules processing="..."> flag is ignored.
 FEAVAR_FEATURETAG_LIB_KEY = "com.github.fonttools.varLib.featureVarsFeatureTag"
 
@@ -781,7 +782,9 @@ def _merge_OTL(font, model, master_fonts, axisTags):
         font["GPOS"].table.remap_device_varidxes(varidx_map)
 
 
-def _add_GSUB_feature_variations(font, axes, internal_axis_supports, rules, featureTag):
+def _add_GSUB_feature_variations(
+    font, axes, internal_axis_supports, rules, featureTags
+):
     def normalize(name, value):
         return models.normalizeLocation({name: value}, internal_axis_supports)[name]
 
@@ -812,7 +815,7 @@ def _add_GSUB_feature_variations(font, axes, internal_axis_supports, rules, feat
 
         conditional_subs.append((region, subs))
 
-    addFeatureVariations(font, conditional_subs, featureTag)
+    addFeatureVariations(font, conditional_subs, featureTags)
 
 
 _DesignSpaceData = namedtuple(
@@ -1204,11 +1207,9 @@ def build(
     if "cvar" not in exclude and "glyf" in vf:
         _merge_TTHinting(vf, model, master_fonts)
     if "GSUB" not in exclude and ds.rules:
-        featureTag = ds.lib.get(
+        featureTags = _feature_variations_tags(ds)
-            FEAVAR_FEATURETAG_LIB_KEY, "rclt" if ds.rulesProcessingLast else "rvrn"
-        )
         _add_GSUB_feature_variations(
-            vf, ds.axes, ds.internal_axis_supports, ds.rules, featureTag
+            vf, ds.axes, ds.internal_axis_supports, ds.rules, featureTags
         )
     if "CFF2" not in exclude and ("CFF " in vf or "CFF2" in vf):
         _add_CFF2(vf, model, master_fonts)
@@ -1299,6 +1300,14 @@ class MasterFinder(object):
         return os.path.normpath(path)
 
 
+def _feature_variations_tags(ds):
+    raw_tags = ds.lib.get(
+        FEAVAR_FEATURETAG_LIB_KEY,
+        "rclt" if ds.rulesProcessingLast else "rvrn",
+    )
+    return sorted({t.strip() for t in raw_tags.split(",")})
+
+
 def main(args=None):
     """Build variable fonts from a designspace file and masters"""
     from argparse import ArgumentParser

Lib/fontTools/varLib/featureVars.py

@@ -43,9 +43,18 @@ def addFeatureVariations(font, conditionalSubstitutions, featureTag="rvrn"):
     # ... ]
     # >>> addFeatureVariations(f, condSubst)
     # >>> f.save(dstPath)
+
+    The `featureTag` parameter takes either a str or a iterable of str (the single str
+    is kept for backwards compatibility), and defines which feature(s) will be
+    associated with the feature variations.
+    Note, if this is "rvrn", then the substitution lookup will be inserted at the
+    beginning of the lookup list so that it is processed before others, otherwise
+    for any other feature tags it will be appended last.
     """
 
-    processLast = featureTag != "rvrn"
+    # process first when "rvrn" is the only listed tag
+    featureTags = [featureTag] if isinstance(featureTag, str) else sorted(featureTag)
+    processLast = "rvrn" not in featureTags or len(featureTags) > 1
 
     _checkSubstitutionGlyphsExist(
         glyphNames=set(font.getGlyphOrder()),
@@ -75,7 +84,7 @@ def addFeatureVariations(font, conditionalSubstitutions, featureTag="rvrn"):
             (conditionSet, [lookupMap[s] for s in substitutions])
         )
 
-    addFeatureVariationsRaw(font, font["GSUB"].table, conditionsAndLookups, featureTag)
+    addFeatureVariationsRaw(font, font["GSUB"].table, conditionsAndLookups, featureTags)
 
 
 def _checkSubstitutionGlyphsExist(glyphNames, substitutions):
@@ -324,13 +333,16 @@ def addFeatureVariationsRaw(font, table, conditionalSubstitutions, featureTag="r
     """Low level implementation of addFeatureVariations that directly
     models the possibilities of the FeatureVariations table."""
 
-    processLast = featureTag != "rvrn"
+    featureTags = [featureTag] if isinstance(featureTag, str) else sorted(featureTag)
+    processLast = "rvrn" not in featureTags or len(featureTags) > 1
 
     #
-    # if there is no <featureTag> feature:
+    # if a <featureTag> feature is not present:
     #     make empty <featureTag> feature
     #     sort features, get <featureTag> feature index
     #     add <featureTag> feature to all scripts
+    # if a <featureTag> feature is present:
+    #     reuse <featureTag> feature index
     # make lookups
     # add feature variations
     #
@@ -339,31 +351,48 @@ def addFeatureVariationsRaw(font, table, conditionalSubstitutions, featureTag="r
 
     table.FeatureVariations = None  # delete any existing FeatureVariations
 
-    varFeatureIndices = []
+    varFeatureIndices = set()
-    for index, feature in enumerate(table.FeatureList.FeatureRecord):
-        if feature.FeatureTag == featureTag:
-            varFeatureIndices.append(index)
 
-    if not varFeatureIndices:
+    existingTags = {
-        varFeature = buildFeatureRecord(featureTag, [])
+        feature.FeatureTag
-        table.FeatureList.FeatureRecord.append(varFeature)
+        for feature in table.FeatureList.FeatureRecord
+        if feature.FeatureTag in featureTags
+    }
+
+    newTags = set(featureTags) - existingTags
+    if newTags:
+        varFeatures = []
+        for featureTag in sorted(newTags):
+            varFeature = buildFeatureRecord(featureTag, [])
+            table.FeatureList.FeatureRecord.append(varFeature)
+            varFeatures.append(varFeature)
         table.FeatureList.FeatureCount = len(table.FeatureList.FeatureRecord)
 
         sortFeatureList(table)
-        varFeatureIndex = table.FeatureList.FeatureRecord.index(varFeature)
 
-        for scriptRecord in table.ScriptList.ScriptRecord:
+        for varFeature in varFeatures:
-            if scriptRecord.Script.DefaultLangSys is None:
+            varFeatureIndex = table.FeatureList.FeatureRecord.index(varFeature)
-                raise VarLibError(
-                    "Feature variations require that the script "
-                    f"'{scriptRecord.ScriptTag}' defines a default language system."
-                )
-            langSystems = [lsr.LangSys for lsr in scriptRecord.Script.LangSysRecord]
-            for langSys in [scriptRecord.Script.DefaultLangSys] + langSystems:
-                langSys.FeatureIndex.append(varFeatureIndex)
-                langSys.FeatureCount = len(langSys.FeatureIndex)
 
-        varFeatureIndices = [varFeatureIndex]
+            for scriptRecord in table.ScriptList.ScriptRecord:
+                if scriptRecord.Script.DefaultLangSys is None:
+                    raise VarLibError(
+                        "Feature variations require that the script "
+                        f"'{scriptRecord.ScriptTag}' defines a default language system."
+                    )
+                langSystems = [lsr.LangSys for lsr in scriptRecord.Script.LangSysRecord]
+                for langSys in [scriptRecord.Script.DefaultLangSys] + langSystems:
+                    langSys.FeatureIndex.append(varFeatureIndex)
+                    langSys.FeatureCount = len(langSys.FeatureIndex)
+            varFeatureIndices.add(varFeatureIndex)
+
+    if existingTags:
+        # indices may have changed if we inserted new features and sorted feature list
+        # so we must do this after the above
+        varFeatureIndices.update(
+            index
+            for index, feature in enumerate(table.FeatureList.FeatureRecord)
+            if feature.FeatureTag in existingTags
+        )
 
     axisIndices = {
         axis.axisTag: axisIndex for axisIndex, axis in enumerate(font["fvar"].axes)
@@ -380,7 +409,7 @@ def addFeatureVariationsRaw(font, table, conditionalSubstitutions, featureTag="r
             ct = buildConditionTable(axisIndices[axisTag], minValue, maxValue)
             conditionTable.append(ct)
         records = []
-        for varFeatureIndex in varFeatureIndices:
+        for varFeatureIndex in sorted(varFeatureIndices):
             existingLookupIndices = table.FeatureList.FeatureRecord[
                 varFeatureIndex
             ].Feature.LookupListIndex

Tests/varLib/data/FeatureVarsCustomTag.designspace

@@ -71,7 +71,7 @@
     <lib>
         <dict>
             <key>com.github.fonttools.varLib.featureVarsFeatureTag</key>
-            <string>calt</string>
+            <string>rclt,calt</string>
         </dict>
     </lib>
 </designspace>

Tests/varLib/data/test_results/FeatureVarsCustomTag.ttx

@@ -33,21 +33,28 @@
         <Script>
           <DefaultLangSys>
             <ReqFeatureIndex value="65535"/>
-            <!-- FeatureCount=1 -->
+            <!-- FeatureCount=2 -->
             <FeatureIndex index="0" value="0"/>
+            <FeatureIndex index="1" value="1"/>
           </DefaultLangSys>
           <!-- LangSysCount=0 -->
         </Script>
       </ScriptRecord>
     </ScriptList>
     <FeatureList>
-      <!-- FeatureCount=1 -->
+      <!-- FeatureCount=2 -->
       <FeatureRecord index="0">
         <FeatureTag value="calt"/>
         <Feature>
           <!-- LookupCount=0 -->
         </Feature>
       </FeatureRecord>
+      <FeatureRecord index="1">
+        <FeatureTag value="rclt"/>
+        <Feature>
+          <!-- LookupCount=0 -->
+        </Feature>
+      </FeatureRecord>
     </FeatureList>
     <LookupList>
       <!-- LookupCount=3 -->
@@ -95,7 +102,7 @@
         </ConditionSet>
         <FeatureTableSubstitution>
           <Version value="0x00010000"/>
-          <!-- SubstitutionCount=1 -->
+          <!-- SubstitutionCount=2 -->
           <SubstitutionRecord index="0">
             <FeatureIndex value="0"/>
             <Feature>
@@ -104,6 +111,14 @@
               <LookupListIndex index="1" value="1"/>
             </Feature>
           </SubstitutionRecord>
+          <SubstitutionRecord index="1">
+            <FeatureIndex value="1"/>
+            <Feature>
+              <!-- LookupCount=2 -->
+              <LookupListIndex index="0" value="0"/>
+              <LookupListIndex index="1" value="1"/>
+            </Feature>
+          </SubstitutionRecord>
         </FeatureTableSubstitution>
       </FeatureVariationRecord>
       <FeatureVariationRecord index="1">
@@ -122,7 +137,7 @@
         </ConditionSet>
         <FeatureTableSubstitution>
           <Version value="0x00010000"/>
-          <!-- SubstitutionCount=1 -->
+          <!-- SubstitutionCount=2 -->
           <SubstitutionRecord index="0">
             <FeatureIndex value="0"/>
             <Feature>
@@ -130,6 +145,13 @@
               <LookupListIndex index="0" value="2"/>
             </Feature>
           </SubstitutionRecord>
+          <SubstitutionRecord index="1">
+            <FeatureIndex value="1"/>
+            <Feature>
+              <!-- LookupCount=1 -->
+              <LookupListIndex index="0" value="2"/>
+            </Feature>
+          </SubstitutionRecord>
         </FeatureTableSubstitution>
       </FeatureVariationRecord>
       <FeatureVariationRecord index="2">
@@ -143,7 +165,7 @@
         </ConditionSet>
         <FeatureTableSubstitution>
           <Version value="0x00010000"/>
-          <!-- SubstitutionCount=1 -->
+          <!-- SubstitutionCount=2 -->
           <SubstitutionRecord index="0">
             <FeatureIndex value="0"/>
             <Feature>
@@ -151,6 +173,13 @@
               <LookupListIndex index="0" value="1"/>
             </Feature>
           </SubstitutionRecord>
+          <SubstitutionRecord index="1">
+            <FeatureIndex value="1"/>
+            <Feature>
+              <!-- LookupCount=1 -->
+              <LookupListIndex index="0" value="1"/>
+            </Feature>
+          </SubstitutionRecord>
         </FeatureTableSubstitution>
       </FeatureVariationRecord>
       <FeatureVariationRecord index="3">
@@ -164,7 +193,7 @@
         </ConditionSet>
         <FeatureTableSubstitution>
           <Version value="0x00010000"/>
-          <!-- SubstitutionCount=1 -->
+          <!-- SubstitutionCount=2 -->
           <SubstitutionRecord index="0">
             <FeatureIndex value="0"/>
             <Feature>
@@ -172,6 +201,13 @@
               <LookupListIndex index="0" value="0"/>
             </Feature>
           </SubstitutionRecord>
+          <SubstitutionRecord index="1">
+            <FeatureIndex value="1"/>
+            <Feature>
+              <!-- LookupCount=1 -->
+              <LookupListIndex index="0" value="0"/>
+            </Feature>
+          </SubstitutionRecord>
         </FeatureTableSubstitution>
       </FeatureVariationRecord>
     </FeatureVariations>