[ttGlyphPen] Add outputImpliedClosingLine argument

Fixes https://github.com/fonttools/fonttools/issues/2913

Lib/fontTools/pens/ttGlyphPen.py

@@ -164,6 +164,15 @@ class TTGlyphPen(_TTGlyphBasePen, LoggingPen):
     drawMethod = "draw"
     transformPen = TransformPen
 
+    def __init__(
+        self,
+        glyphSet: Optional[Dict[str, Any]] = None,
+        handleOverflowingTransforms: bool = True,
+        outputImpliedClosingLine: bool = False,
+    ) -> None:
+        super().__init__(glyphSet, handleOverflowingTransforms)
+        self.outputImpliedClosingLine = outputImpliedClosingLine
+
     def _addPoint(self, pt: Tuple[float, float], onCurve: int) -> None:
         self.points.append(pt)
         self.types.append(onCurve)
@@ -205,13 +214,14 @@ class TTGlyphPen(_TTGlyphBasePen, LoggingPen):
             self._popPoint()
             return
 
-        # if first and last point on this path are the same, remove last
-        startPt = 0
-        if self.endPts:
-            startPt = self.endPts[-1] + 1
-        if self.points[startPt] == self.points[endPt]:
-            self._popPoint()
-            endPt -= 1
+        if not self.outputImpliedClosingLine:
+            # if first and last point on this path are the same, remove last
+            startPt = 0
+            if self.endPts:
+                startPt = self.endPts[-1] + 1
+            if self.points[startPt] == self.points[endPt]:
+                self._popPoint()
+                endPt -= 1
 
         self.endPts.append(endPt)
 

Tests/pens/ttGlyphPen_test.py

@@ -294,6 +294,27 @@ class TTGlyphPenTest(TTGlyphPenTestBase):
         uni0302_uni0300.recalcBounds(glyphSet)
         self.assertGlyphBoundsEqual(uni0302_uni0300, (-278, 745, 148, 1025))
 
+    def test_outputImpliedClosingLine(self):
+        glyphSet = {}
+
+        pen = TTGlyphPen(glyphSet)
+        pen.moveTo((0, 0))
+        pen.lineTo((10, 0))
+        pen.lineTo((0, 10))
+        pen.lineTo((0, 0))
+        pen.closePath()
+        glyph = pen.glyph()
+        assert len(glyph.coordinates) == 3
+
+        pen = TTGlyphPen(glyphSet, outputImpliedClosingLine=True)
+        pen.moveTo((0, 0))
+        pen.lineTo((10, 0))
+        pen.lineTo((0, 10))
+        pen.lineTo((0, 0))
+        pen.closePath()
+        glyph = pen.glyph()
+        assert len(glyph.coordinates) == 4
+
 
 class TTGlyphPointPenTest(TTGlyphPenTestBase):
     penClass = TTGlyphPointPen
@@ -574,7 +595,6 @@ class TTGlyphPointPenTest(TTGlyphPenTestBase):
         assert pen1.types == pen2.types == [1, 1, 0, 1]
 
 
-
 class _TestGlyph(object):
     def __init__(self, glyph):
         self.coordinates = glyph.coordinates