[bezierTools] make curveCurveIntersections more precise, improve de-d…

…uplication

#3354 (comment)

Lib/fontTools/misc/bezierTools.py

@@ -1323,7 +1323,8 @@ def midpoint(r):
         return 0.5 * (r[0] + r[1])
 
     # If they do overlap but they're tiny, approximate
-    if rectArea(bounds1) < precision and rectArea(bounds2) < precision:
+    precision2 = precision * precision
+    if rectArea(bounds1) < precision2 and rectArea(bounds2) < precision2:
         return [(midpoint(range1), midpoint(range2))]
 
     c11, c12 = _split_segment_at_t(curve1, 0.5)
@@ -1356,7 +1357,7 @@ def midpoint(r):
         )
     )
 
-    unique_key = lambda ts: (int(ts[0] / precision), int(ts[1] / precision))
+    unique_key = lambda ts: (round(ts[0] / precision), round(ts[1] / precision))
     seen = set()
     unique_values = []
 

Tests/misc/bezierTools_test.py

@@ -202,5 +202,7 @@ def test_intersections_linelike():
 def test_curve_curve_touching_each_other():
     seg1 = [(0, 0), (0, 100), (100, 100), (100, 0)]
     seg2 = [(0, 150), (0, 50), (100, 50), (100, 150)]
-    pt = curveCurveIntersections(seg1, seg2)[0][0]
-    assert pt == pytest.approx((50.0, 75.0), rel=1e-2)
+    intersections = curveCurveIntersections(seg1, seg2)
+    assert len(intersections) == 1
+    pt = intersections[0][0]
+    assert pt == pytest.approx((50.0, 75.0), rel=1e-3)