add filter pen that explicitly emits closing line when lastPt != movePt

it can be useful when comparing two paths and testing whether then contain the same number/types of segments

Lib/fontTools/pens/explicitClosingLinePen.py

@@ -0,0 +1,101 @@
+from fontTools.pens.filterPen import ContourFilterPen
+
+
+class ExplicitClosingLinePen(ContourFilterPen):
+    """A filter pen that adds an explicit lineTo to the first point of each closed
+    contour if the end point of the last segment is not already the same as the first point.
+    Otherwise, it passes the contour through unchanged.
+
+    >>> from pprint import pprint
+    >>> from fontTools.pens.recordingPen import RecordingPen
+    >>> rec = RecordingPen()
+    >>> pen = ExplicitClosingLinePen(rec)
+    >>> pen.moveTo((0, 0))
+    >>> pen.lineTo((100, 0))
+    >>> pen.lineTo((100, 100))
+    >>> pen.closePath()
+    >>> pprint(rec.value)
+    [('moveTo', ((0, 0),)),
+     ('lineTo', ((100, 0),)),
+     ('lineTo', ((100, 100),)),
+     ('lineTo', ((0, 0),)),
+     ('closePath', ())]
+    >>> rec = RecordingPen()
+    >>> pen = ExplicitClosingLinePen(rec)
+    >>> pen.moveTo((0, 0))
+    >>> pen.lineTo((100, 0))
+    >>> pen.lineTo((100, 100))
+    >>> pen.lineTo((0, 0))
+    >>> pen.closePath()
+    >>> pprint(rec.value)
+    [('moveTo', ((0, 0),)),
+     ('lineTo', ((100, 0),)),
+     ('lineTo', ((100, 100),)),
+     ('lineTo', ((0, 0),)),
+     ('closePath', ())]
+    >>> rec = RecordingPen()
+    >>> pen = ExplicitClosingLinePen(rec)
+    >>> pen.moveTo((0, 0))
+    >>> pen.curveTo((100, 0), (0, 100), (100, 100))
+    >>> pen.closePath()
+    >>> pprint(rec.value)
+    [('moveTo', ((0, 0),)),
+     ('curveTo', ((100, 0), (0, 100), (100, 100))),
+     ('lineTo', ((0, 0),)),
+     ('closePath', ())]
+    >>> rec = RecordingPen()
+    >>> pen = ExplicitClosingLinePen(rec)
+    >>> pen.moveTo((0, 0))
+    >>> pen.curveTo((100, 0), (0, 100), (100, 100))
+    >>> pen.lineTo((0, 0))
+    >>> pen.closePath()
+    >>> pprint(rec.value)
+    [('moveTo', ((0, 0),)),
+     ('curveTo', ((100, 0), (0, 100), (100, 100))),
+     ('lineTo', ((0, 0),)),
+     ('closePath', ())]
+    >>> rec = RecordingPen()
+    >>> pen = ExplicitClosingLinePen(rec)
+    >>> pen.moveTo((0, 0))
+    >>> pen.curveTo((100, 0), (0, 100), (0, 0))
+    >>> pen.closePath()
+    >>> pprint(rec.value)
+    [('moveTo', ((0, 0),)),
+     ('curveTo', ((100, 0), (0, 100), (0, 0))),
+     ('closePath', ())]
+    >>> rec = RecordingPen()
+    >>> pen = ExplicitClosingLinePen(rec)
+    >>> pen.moveTo((0, 0))
+    >>> pen.closePath()
+    >>> pprint(rec.value)
+    [('moveTo', ((0, 0),)), ('closePath', ())]
+    >>> rec = RecordingPen()
+    >>> pen = ExplicitClosingLinePen(rec)
+    >>> pen.closePath()
+    >>> pprint(rec.value)
+    [('closePath', ())]
+    >>> rec = RecordingPen()
+    >>> pen = ExplicitClosingLinePen(rec)
+    >>> pen.moveTo((0, 0))
+    >>> pen.lineTo((100, 0))
+    >>> pen.lineTo((100, 100))
+    >>> pen.endPath()
+    >>> pprint(rec.value)
+    [('moveTo', ((0, 0),)),
+     ('lineTo', ((100, 0),)),
+     ('lineTo', ((100, 100),)),
+     ('endPath', ())]
+    """
+
+    def filterContour(self, contour):
+        if (
+            not contour
+            or contour[0][0] != "moveTo"
+            or contour[-1][0] != "closePath"
+            or len(contour) < 3
+        ):
+            return
+        movePt = contour[0][1][0]
+        lastSeg = contour[-2][1]
+        if lastSeg and movePt != lastSeg[-1]:
+            contour[-1:] = [("lineTo", (movePt,)), ("closePath", ())]