[flatten] if > 1 starting points, use closest to origin

When merging two or more contours, there could be more than one possible original starting points to be restored. Here we choose the one that is closest to the origin.

Author: Cosimo Lupo

Lib/booleanOperations/flatten.py

@@ -973,15 +973,17 @@ def drawPoints(self, pointPen):
             points.extend(segment.points)
 
         hasOnCurve = False
-        foundOriginalStartingPoint = False
+        originalStartingPoints = []
         for index, point in enumerate(points):
             if point.segmentType is not None:
                 hasOnCurve = True
                 if point.kwargs is not None and point.kwargs.get("startingPoint"):
-                    foundOriginalStartingPoint = True
-                    break
-        if foundOriginalStartingPoint:
-            points = points[index:] + points[:index]
+                    distanceFromOrigin = math.hypot(*point)
+                    originalStartingPoints.append((distanceFromOrigin, index))
+        if originalStartingPoints:
+            # use the original starting point that is closest to the origin
+            startingPointIndex = sorted(originalStartingPoints)[0][1]
+            points = points[startingPointIndex:] + points[:startingPointIndex]
         elif hasOnCurve:
             while points[0].segmentType is None:
                 p = points.pop(0)