Merge pull request #3103 from fonttools/multiple-subst-classes

feaLib: support multiple substitution with classes

Lib/fontTools/feaLib/ast.py

@@ -1256,23 +1256,29 @@ class MultipleSubstStatement(Statement):
         """Calls the builder object's ``add_multiple_subst`` callback."""
         prefix = [p.glyphSet() for p in self.prefix]
         suffix = [s.glyphSet() for s in self.suffix]
-        if not self.replacement and hasattr(self.glyph, "glyphSet"):
-            for glyph in self.glyph.glyphSet():
-                builder.add_multiple_subst(
-                    self.location,
-                    prefix,
-                    glyph,
-                    suffix,
-                    self.replacement,
-                    self.forceChain,
-                )
+        if hasattr(self.glyph, "glyphSet"):
+            originals = self.glyph.glyphSet()
         else:
+            originals = [self.glyph]
+        count = len(originals)
+        replaces = []
+        for r in self.replacement:
+            if hasattr(r, "glyphSet"):
+                replace = r.glyphSet()
+            else:
+                replace = [r]
+            if len(replace) == 1 and len(replace) != count:
+                replace = replace * count
+            replaces.append(replace)
+        replaces = list(zip(*replaces))
+
+        for i, original in enumerate(originals):
             builder.add_multiple_subst(
                 self.location,
                 prefix,
-                self.glyph,
+                original,
                 suffix,
-                self.replacement,
+                replaces and replaces[i] or (),
                 self.forceChain,
             )
 

Lib/fontTools/feaLib/parser.py

@@ -925,22 +925,27 @@ class Parser(object):
 
         # GSUB lookup type 2: Multiple substitution.
         # Format: "substitute f_f_i by f f i;"
-        if (
-            not reverse
-            and len(old) == 1
-            and len(old[0].glyphSet()) == 1
-            and len(new) > 1
-            and max([len(n.glyphSet()) for n in new]) == 1
-            and num_lookups == 0
-        ):
+        #
+        # GlyphsApp introduces two additional formats:
+        # Format 1: "substitute [f_i f_l] by [f f] [i l];"
+        # Format 2: "substitute [f_i f_l] by f [i l];"
+        # http://handbook.glyphsapp.com/en/layout/multiple-substitution-with-classes/
+        if not reverse and len(old) == 1 and len(new) > 1 and num_lookups == 0:
+            count = len(old[0].glyphSet())
             for n in new:
                 if not list(n.glyphSet()):
                     raise FeatureLibError("Empty class in replacement", location)
+                if not isinstance(n, self.ast.GlyphName) and len(n.glyphSet()) != count:
+                    raise FeatureLibError(
+                        f'Expected a glyph class with {count} elements after "by", '
+                        f"but found a glyph class with {len(n.glyphSet())} elements",
+                        location,
+                    )
             return self.ast.MultipleSubstStatement(
                 old_prefix,
-                tuple(old[0].glyphSet())[0],
+                old[0],
                 old_suffix,
-                tuple([list(n.glyphSet())[0] for n in new]),
+                new,
                 forceChain=hasMarks,
                 location=location,
             )

Tests/feaLib/data/GSUB_2.fea

@@ -12,3 +12,20 @@ feature f2 {
     sub f_i by f i;
     sub f_f_i by f f i;
 } f2;
+
+feature f3 {
+    sub [f_i f_l f_f_i f_f_l] by f [i l f_i f_l];
+} f3;
+
+feature f4 {
+    sub [f_i f_l f_f_i f_f_l] by [f f f_f f_f] [i l i l];
+} f4;
+
+@class = [f_i f_l];
+lookup l1 {
+   sub @class by f [i l];
+} l1;
+
+feature f5 {
+   sub @class' lookup l1 [i l];
+} f5;

Tests/feaLib/data/GSUB_2.ttx

@@ -10,16 +10,19 @@
         <Script>
           <DefaultLangSys>
             <ReqFeatureIndex value="65535"/>
-            <!-- FeatureCount=2 -->
+            <!-- FeatureCount=5 -->
             <FeatureIndex index="0" value="0"/>
             <FeatureIndex index="1" value="1"/>
+            <FeatureIndex index="2" value="2"/>
+            <FeatureIndex index="3" value="3"/>
+            <FeatureIndex index="4" value="4"/>
           </DefaultLangSys>
           <!-- LangSysCount=0 -->
         </Script>
       </ScriptRecord>
     </ScriptList>
     <FeatureList>
-      <!-- FeatureCount=2 -->
+      <!-- FeatureCount=5 -->
       <FeatureRecord index="0">
         <FeatureTag value="f1  "/>
         <Feature>
@@ -34,9 +37,30 @@
           <LookupListIndex index="0" value="1"/>
         </Feature>
       </FeatureRecord>
+      <FeatureRecord index="2">
+        <FeatureTag value="f3  "/>
+        <Feature>
+          <!-- LookupCount=1 -->
+          <LookupListIndex index="0" value="2"/>
+        </Feature>
+      </FeatureRecord>
+      <FeatureRecord index="3">
+        <FeatureTag value="f4  "/>
+        <Feature>
+          <!-- LookupCount=1 -->
+          <LookupListIndex index="0" value="3"/>
+        </Feature>
+      </FeatureRecord>
+      <FeatureRecord index="4">
+        <FeatureTag value="f5  "/>
+        <Feature>
+          <!-- LookupCount=1 -->
+          <LookupListIndex index="0" value="5"/>
+        </Feature>
+      </FeatureRecord>
     </FeatureList>
     <LookupList>
-      <!-- LookupCount=2 -->
+      <!-- LookupCount=6 -->
       <Lookup index="0">
         <LookupType value="2"/>
         <LookupFlag value="0"/>
@@ -57,6 +81,60 @@
           <Substitution in="f_i" out="f,i"/>
         </MultipleSubst>
       </Lookup>
+      <Lookup index="2">
+        <LookupType value="2"/>
+        <LookupFlag value="0"/>
+        <!-- SubTableCount=1 -->
+        <MultipleSubst index="0">
+          <Substitution in="f_f_i" out="f,f_i"/>
+          <Substitution in="f_f_l" out="f,f_l"/>
+          <Substitution in="f_i" out="f,i"/>
+          <Substitution in="f_l" out="f,l"/>
+        </MultipleSubst>
+      </Lookup>
+      <Lookup index="3">
+        <LookupType value="2"/>
+        <LookupFlag value="0"/>
+        <!-- SubTableCount=1 -->
+        <MultipleSubst index="0">
+          <Substitution in="f_f_i" out="f_f,i"/>
+          <Substitution in="f_f_l" out="f_f,l"/>
+          <Substitution in="f_i" out="f,i"/>
+          <Substitution in="f_l" out="f,l"/>
+        </MultipleSubst>
+      </Lookup>
+      <Lookup index="4">
+        <LookupType value="2"/>
+        <LookupFlag value="0"/>
+        <!-- SubTableCount=1 -->
+        <MultipleSubst index="0">
+          <Substitution in="f_i" out="f,i"/>
+          <Substitution in="f_l" out="f,l"/>
+        </MultipleSubst>
+      </Lookup>
+      <Lookup index="5">
+        <LookupType value="6"/>
+        <LookupFlag value="0"/>
+        <!-- SubTableCount=1 -->
+        <ChainContextSubst index="0" Format="3">
+          <!-- BacktrackGlyphCount=0 -->
+          <!-- InputGlyphCount=1 -->
+          <InputCoverage index="0">
+            <Glyph value="f_l"/>
+            <Glyph value="f_i"/>
+          </InputCoverage>
+          <!-- LookAheadGlyphCount=1 -->
+          <LookAheadCoverage index="0">
+            <Glyph value="i"/>
+            <Glyph value="l"/>
+          </LookAheadCoverage>
+          <!-- SubstCount=1 -->
+          <SubstLookupRecord index="0">
+            <SequenceIndex value="0"/>
+            <LookupListIndex value="4"/>
+          </SubstLookupRecord>
+        </ChainContextSubst>
+      </Lookup>
     </LookupList>
   </GSUB>
 

Tests/feaLib/parser_test.py

@@ -44,7 +44,7 @@ GLYPHNAMES = (
     a.swash b.swash x.swash y.swash z.swash
     foobar foo.09 foo.1234 foo.9876
     one two five six acute grave dieresis umlaut cedilla ogonek macron
-    a_f_f_i o_f_f_i f_i f_f_i one.fitted one.oldstyle a.1 a.2 a.3 c_t
+    a_f_f_i o_f_f_i f_i f_l f_f_i one.fitted one.oldstyle a.1 a.2 a.3 c_t
     PRE SUF FIX BACK TRACK LOOK AHEAD ampersand ampersand.1 ampersand.2
     cid00001 cid00002 cid00003 cid00004 cid00005 cid00006 cid00007
     cid12345 cid78987 cid00999 cid01000 cid01001 cid00998 cid00995
@@ -1610,24 +1610,47 @@ class ParserTest(unittest.TestCase):
         doc = self.parse("lookup Look {substitute f_f_i by f f i;} Look;")
         sub = doc.statements[0].statements[0]
         self.assertIsInstance(sub, ast.MultipleSubstStatement)
-        self.assertEqual(sub.glyph, "f_f_i")
-        self.assertEqual(sub.replacement, ("f", "f", "i"))
+        self.assertEqual(glyphstr([sub.glyph]), "f_f_i")
+        self.assertEqual(glyphstr(sub.replacement), "f f i")
 
     def test_substitute_multiple_chained(self):  # chain to GSUB LookupType 2
         doc = self.parse("lookup L {sub [A-C] f_f_i' [X-Z] by f f i;} L;")
         sub = doc.statements[0].statements[0]
         self.assertIsInstance(sub, ast.MultipleSubstStatement)
-        self.assertEqual(sub.glyph, "f_f_i")
-        self.assertEqual(sub.replacement, ("f", "f", "i"))
+        self.assertEqual(glyphstr([sub.glyph]), "f_f_i")
+        self.assertEqual(glyphstr(sub.replacement), "f f i")
 
     def test_substitute_multiple_force_chained(self):
         doc = self.parse("lookup L {sub f_f_i' by f f i;} L;")
         sub = doc.statements[0].statements[0]
         self.assertIsInstance(sub, ast.MultipleSubstStatement)
-        self.assertEqual(sub.glyph, "f_f_i")
-        self.assertEqual(sub.replacement, ("f", "f", "i"))
+        self.assertEqual(glyphstr([sub.glyph]), "f_f_i")
+        self.assertEqual(glyphstr(sub.replacement), "f f i")
         self.assertEqual(sub.asFea(), "sub f_f_i' by f f i;")
 
+    def test_substitute_multiple_classes(self):
+        doc = self.parse("lookup Look {substitute [f_i f_l] by [f f] [i l];} Look;")
+        sub = doc.statements[0].statements[0]
+        self.assertIsInstance(sub, ast.MultipleSubstStatement)
+        self.assertEqual(glyphstr([sub.glyph]), "[f_i f_l]")
+        self.assertEqual(glyphstr(sub.replacement), "[f f] [i l]")
+
+    def test_substitute_multiple_classes_mixed(self):
+        doc = self.parse("lookup Look {substitute [f_i f_l] by f [i l];} Look;")
+        sub = doc.statements[0].statements[0]
+        self.assertIsInstance(sub, ast.MultipleSubstStatement)
+        self.assertEqual(glyphstr([sub.glyph]), "[f_i f_l]")
+        self.assertEqual(glyphstr(sub.replacement), "f [i l]")
+
+    def test_substitute_multiple_classes_mismatch(self):
+        self.assertRaisesRegex(
+            FeatureLibError,
+            'Expected a glyph class with 2 elements after "by", '
+            "but found a glyph class with 1 elements",
+            self.parse,
+            "lookup Look {substitute [f_i f_l] by [f] [i l];} Look;",
+        )
+
     def test_substitute_multiple_by_mutliple(self):
         self.assertRaisesRegex(
             FeatureLibError,