Improved mergeFirstSegments handling

Author: skef

Lib/booleanOperations/flatten.py

@@ -692,23 +692,50 @@ def reCurveSubSegments(self, inputContours):
                     fp = segmentedFlatPoints[0][0]
                     lp = segmentedFlatPoints[-1][-1]
                     mergeFirstSegments = False
+                    duplicatePoint = 0
                     if fp in flatInputPoints and lp in flatInputPoints:
+                        # fp and lp are "known" points with associated input
+                        # segments. If they're on the same segment, merge
+                        # them.
+                        # Otherwise, if the opposite segment is curved we
+                        # need to duplicate the point so that we have
+                        # the full curve when processing that segment.
+                        # However, there is an exception case: If the
+                        # inputSegment type is "curved" but it was encoded
+                        # for pyClipper as a line anyway, do nothing.
                         firstInputSegment = flatInputPointsSegmentDict[fp]
                         lastInputSegment = flatInputPointsSegmentDict[lp]
                         reversedFirstInputSegment = reversedFlatInputPointsSegmentDict[fp]
                         reversedLastInputSegment = reversedFlatInputPointsSegmentDict[lp]
-                        if (firstInputSegment.segmentType == reversedFirstInputSegment.segmentType == "curve") or (lastInputSegment.segmentType == reversedLastInputSegment.segmentType == "curve"):
+                        # Note: len(segmentedFlatPoints[0]) == 0 in this code,
+                        # so firstCurved is at least very unlikely. I don't
+                        # think I've hit the firstCurved conditions below in
+                        # my generated test data.
+                        firstCurved = firstInputSegment.segmentType == reversedFirstInputSegment.segmentType == "curve"
+                        lastCurved = lastInputSegment.segmentType == reversedLastInputSegment.segmentType == "curve"
+                        if firstCurved or lastCurved:
                             if firstInputSegment == lastInputSegment or reversedFirstInputSegment == reversedLastInputSegment:
                                 mergeFirstSegments = True
-                            # elif len(firstInputSegment.points) > 1 and len(lastInputSegment.points) > 1:
-                            elif fp == lastInputSegment.scaledPreviousOnCurve:
-                                mergeFirstSegments = True
-                            elif lp == firstInputSegment.scaledPreviousOnCurve:
-                                mergeFirstSegments = True
-                            elif fp == reversedLastInputSegment.scaledPreviousOnCurve:
-                                mergeFirstSegments = True
-                            elif lp == reversedFirstInputSegment.scaledPreviousOnCurve:
-                                mergeFirstSegments = True
+                            elif fp == lastInputSegment.scaledPreviousOnCurve and lastCurved:
+                                if lp == lastInputSegment.flat[-1]:
+                                    pass
+                                else:
+                                    duplicatePoint = 1
+                            elif lp == firstInputSegment.scaledPreviousOnCurve and firstCurved:
+                                if fp == firstInputSegment.flat[-1]:
+                                    pass
+                                else:
+                                    duplicatePoint = -1
+                            elif fp == reversedLastInputSegment.scaledPreviousOnCurve and lastCurved:
+                                if lp == reversedLastInputSegment.flat[-1]:
+                                    pass
+                                else:
+                                    duplicatePoint = 1
+                            elif lp == reversedFirstInputSegment.scaledPreviousOnCurve and firstCurved:
+                                if fp == reversedFirstInputSegment.flat[-1]:
+                                    pass
+                                else:
+                                    duplicatePoint = -1
                     elif not hasOncurvePoints and _distance(fp, lp):
                         # Merge last segment with first segment if the distance between the last point and the first
                         # point is less than the step distance between the last two points. _approximateSegmentLength
@@ -726,6 +753,10 @@ def reCurveSubSegments(self, inputContours):
                         segmentedFlatPoints[0] = segmentedFlatPoints[-1] + segmentedFlatPoints[0]
                         segmentedFlatPoints.pop(-1)
                         mergeFirstSegments = False
+                    elif duplicatePoint == 1:
+                        segmentedFlatPoints[-1].append(segmentedFlatPoints[0][0])
+                    elif duplicatePoint == -1:
+                        segmentedFlatPoints[0].insert(0, segmentedFlatPoints[-1][-1])
                 convertedSegments = []
                 previousIntersectionPoint = None
                 if segmentedFlatPoints[-1][-1] in intersectionPoints: