Handle more degenerate cases

fonttools · Dec 15, 2023 · 42d8e2f · 42d8e2f
1 parent 8695d19
commit 42d8e2f
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Showing 2 changed files with 13 additions and 4 deletions.
diff --git a/Lib/fontTools/misc/bezierTools.py b/Lib/fontTools/misc/bezierTools.py
@@ -1184,8 +1184,11 @@ def lineLineIntersections(s1, e1, s2, e2):
     if math.isclose(s1x, e1x) and math.isclose(s1y, e1y):  # Line segment is tiny
         return []
     if math.isclose(e1x, s1x):
-        if math.isclose(e2x, s2x) and math.isclose(s1y, s2y):
-            return [Intersection(pt=(s1x, s1y), t1=0, t2=0)]
+        if math.isclose(e2x, s2x):  # Same start
+            if math.isclose(s1y, s2y):
+                return [Intersection(pt=(s1x, s1y), t1=0, t2=0)]
+            # Degenerate coincident case
+            return []
         x = s1x
         slope34 = (e2y - s2y) / (e2x - s2x)
         y = slope34 * (x - s2x) + s2y
@@ -1196,8 +1199,11 @@ def lineLineIntersections(s1, e1, s2, e2):
             )
         ]
     if math.isclose(s2x, e2x):
-        if math.isclose(s1x, e1x) and math.isclose(e1y, e2y):
-            return [Intersection(pt=(e1x, e1y), t1=1, t2=1)]
+        if math.isclose(s1x, e1x):
+            if math.isclose(e1y, e2y):  # Same end
+                return [Intersection(pt=(e1x, e1y), t1=1, t2=1)]
+            # Degenerate coincident case
+            return []
         x = s2x
         slope12 = (e1y - s1y) / (e1x - s1x)
         y = slope12 * (x - s1x) + s1y

diff --git a/Tests/misc/bezierTools_test.py b/Tests/misc/bezierTools_test.py
@@ -205,3 +205,6 @@ def test_intersections_samestart():
     seg2 = [(250, 1000), (250, 400)]
     pt = lineLineIntersections(*seg1, *seg2)[0][0]
     assert pt == (250.0, 1000.0)
+    seg3 = [(250, 810), (250, 500)]
+    assert lineLineIntersections(*seg1, *seg3) == []
+