add check for arc step of 0

src/pixie/paths.nim

@@ -693,6 +693,8 @@ proc commandsToShapes(
         next = halfway
         halfway = compute(at, ctrl1, ctrl2, to, t + step / 4)
         step /= 2
+        if step == 0:
+          raise newException(PixieError, "Unable to discretize arc")
       else:
         shape.addSegment(prev, next)
         t += step
@@ -724,8 +726,10 @@ proc commandsToShapes(
       if error > errorMarginSq:
         next = halfway
         halfway = compute(at, ctrl, to, t + step / 4)
-        step /= 2
         halfStepping = true
+        step /= 2
+        if step == 0:
+          raise newException(PixieError, "Unable to discretize arc")
       else:
         shape.addSegment(prev, next)
         t += step
@@ -853,6 +857,8 @@ proc commandsToShapes(
           step = min(step / 2, 1 - t) # Assume next steps hould be the same size
         else:
           step = step / 4 # We know a half-step is too big
+        if step == 0:
+          raise newException(PixieError, "Unable to discretize arc")
       else:
         shape.addSegment(prev, next)
         prev = next

tests/test_paths.nim

@@ -699,3 +699,25 @@ block:
     let mask = newMask(100, 100)
     mask.fillPath(path)
     mask.writeFile(&"tests/paths/polygon{i}.png")
+
+block:
+  let image = newImage(200, 200)
+  image.fill(rgba(255, 255, 255, 255))
+
+  let
+    pathStr ="""
+  L -16370.0 -18156.0
+  A 4100 4100 0 1 0 -19670 -14134
+  Z
+  """
+
+  let path = parsePath(pathStr)
+
+  let paint = newPaint(SolidPaint)
+  paint.color = color(255, 255, 255, 255)
+
+  doAssertRaises PixieError:
+    image.strokePath(
+      path,
+      paint
+    )