Replace buggy circle seg intersection with a simpler test

src/Geometry/Intersect.hs

@@ -300,6 +300,7 @@ inSegArea a b c = param >= 0 && param <= dotV (b -.- a) (b -.- a)
   where
     param = dotV (b -.- a) (c -.- a)
 
+-- I suspect that this may not be correct...
 intersectCircSeg :: Point2 -> Float -> Point2 -> Point2 -> [Point2]
 intersectCircSeg c r a b
     | y < 0 = []
@@ -311,5 +312,12 @@ intersectCircSeg c r a b
     z = sqrt y
     v = z *.* normalizeV (b -.- a)
 
+intersectCircSegTest :: Point2 -> Float -> Point2 -> Point2 -> Bool
+intersectCircSegTest c r x y = intersectSegSegTest (c + z) (c - z) x y
+    || dist c x <= r
+    || dist c y <= r
+  where
+    z = r *.* vNormal (normalizeV x - y)
+
 intersectCircSegFirst :: Point2 -> Float -> Point2 -> Point2 -> Maybe Point2
 intersectCircSegFirst c r a = listToMaybe . intersectCircSeg c r a