Merge pull request #398 from treeform/dev

Fix for #393 and other polygon improvements.

src/pixie/paths.nim

@@ -632,13 +632,14 @@ proc polygon*(
   path: Path, x, y, size: float32, sides: int
 ) {.raises: [PixieError].} =
   ## Adds an n-sided regular polygon at (x, y) with the parameter size.
-  if sides <= 0:
+  ## Polygons "face" north.
+  if sides <= 2:
     raise newException(PixieError, "Invalid polygon sides value")
-  path.moveTo(x + size * cos(0.0), y + size * sin(0.0))
-  for side in 0 .. sides:
+  path.moveTo(x + size * sin(0.0), y - size * cos(0.0))
+  for side in 1 .. sides:
     path.lineTo(
-      x + size * cos(side.float32 * 2.0 * PI / sides.float32),
-      y + size * sin(side.float32 * 2.0 * PI / sides.float32)
+      x + size * sin(side.float32 * 2.0 * PI / sides.float32),
+      y - size * cos(side.float32 * 2.0 * PI / sides.float32)
     )
 
 proc polygon*(

tests/test_paths.nim

@@ -690,3 +690,12 @@ block:
     mask = newMask(100, 100)
     pathStr = "M0 0 L0 1 L0 0 Z"
   mask.fillPath(pathStr)
+
+block:
+  # Test different polygons.
+  for i in 3 .. 8:
+    let path = newPath()
+    path.polygon(vec2(50, 50), 30, i)
+    let mask = newMask(100, 100)
+    mask.fillPath(path)
+    mask.writeFile(&"tests/paths/polygon{i}.png")