[otlLib] Move building of LigGlyphs from feaLib to otlLib

Lib/fontTools/feaLib/builder.py

@@ -216,16 +216,11 @@ class Builder(object):
         result.LigGlyphCount = len(glyphs)
         result.LigGlyph = []
         for glyph in glyphs:
-            ligGlyph = otTables.LigGlyph()
-            result.LigGlyph.append(ligGlyph)
-            ligGlyph.CaretValue = []
-            for caretPos in sorted(self.ligatureCaretByPos_.get(glyph, [])):
-                ligGlyph.CaretValue.append(
-                    otl.buildCaretValueForCoord(caretPos))
-            for point in sorted(self.ligatureCaretByIndex_.get(glyph, [])):
-                ligGlyph.CaretValue.append(
-                    otl.buildCaretValueForPoint(point))
-            ligGlyph.CaretCount = len(ligGlyph.CaretValue)
+            coords = self.ligatureCaretByPos_.get(glyph)
+            points = self.ligatureCaretByIndex_.get(glyph)
+            ligGlyph = otl.buildLigGlyph(coords, points)
+            if ligGlyph:
+                result.LigGlyph.append(ligGlyph)
         return result
 
     def buildGDEFMarkAttachClassDef_(self):

Lib/fontTools/otlLib/builder.py

@@ -258,3 +258,18 @@ def buildCaretValueForPoint(point):
     self.Format = 2
     self.CaretValuePoint = point
     return self
+
+
+def buildLigGlyph(coords, points):
+    """([500], [4]) --> otTables.LigGlyph; None for empty coords/points"""
+    carets = []
+    if coords:
+        carets.extend([buildCaretValueForCoord(c) for c in sorted(coords)])
+    if points:
+        carets.extend([buildCaretValueForPoint(p) for p in sorted(points)])
+    if not carets:
+        return None
+    self = ot.LigGlyph()
+    self.CaretCount = len(carets)
+    self.CaretValue = carets
+    return self

Lib/fontTools/otlLib/builder_test.py

@@ -173,6 +173,35 @@ class BuilderTest(unittest.TestCase):
                          '  <DeltaValue value="[77, 0, 0, 0, 3]"/>'
                          '</Device>')
 
+    def test_buildLigGlyph_coords(self):
+        lig = builder.buildLigGlyph([500, 800], None)
+        self.assertEqual(getXML(lig.toXML),
+                         '<LigGlyph>'
+                         '  <!-- CaretCount=2 -->'
+                         '  <CaretValue index="0" Format="1">'
+                         '    <Coordinate value="500"/>'
+                         '  </CaretValue>'
+                         '  <CaretValue index="1" Format="1">'
+                         '    <Coordinate value="800"/>'
+                         '  </CaretValue>'
+                         '</LigGlyph>')
+
+    def test_buildLigGlyph_empty(self):
+        self.assertIsNone(builder.buildLigGlyph([], []))
+
+    def test_buildLigGlyph_None(self):
+        self.assertIsNone(builder.buildLigGlyph(None, None))
+
+    def test_buildLigGlyph_points(self):
+        lig = builder.buildLigGlyph(None, [2])
+        self.assertEqual(getXML(lig.toXML),
+                         '<LigGlyph>'
+                         '  <!-- CaretCount=1 -->'
+                         '  <CaretValue index="0" Format="2">'
+                         '    <CaretValuePoint value="2"/>'
+                         '  </CaretValue>'
+                         '</LigGlyph>')
+
     def test_buildSinglePos(self):
         subtables = builder.buildSinglePos({
             "one": builder.buildValue({"XPlacement": 500}),