Java2d rendering waits for the window to exit

This prevents the window being closed as soon as rendering has
completed. I'm not sure of the impact on animations.

java2d/src/main/scala/doodle/java2d/effect/Java2dRenderer.scala

@@ -26,6 +26,8 @@ object Java2dRenderer extends Renderer[Algebra, Frame, Canvas] {
   def canvas(description: Frame): Resource[IO, Canvas] =
     Canvas(description)
 
-  def render[A](canvas: Canvas)(picture: Picture[A]): IO[A] =
-    canvas.render(picture)
+  def render[A](canvas: Canvas)(picture: Picture[A]): IO[A] = {
+    val result = canvas.render(picture)
+    canvas.closed >> result
+  }
 }