Method fixDrawingSpace

src/main/java/fieldbox/boxes/Mouse.java:170–183

(Optional<Drawing> drawing, Window.MouseState after)

	}

	private void fixDrawingSpace(Optional<Drawing> drawing, Window.MouseState after) {
		Vec2 af = drawing.map(x -> x.windowSystemToDrawingSystem(new Vec2(after.x, after.y)))
				 .get();

		after.mx = af.x;
		after.my = af.y;

		Vec2 daf = drawing.map(x -> x.windowSystemToDrawingSystemDelta(new Vec2(after.dx, after.dy)))
				  .get();

		after.mdx = daf.x;
		after.mdy = daf.y;

	}

	public interface Dragger {
		boolean update(Window.Event<Window.MouseState> e, boolean termination);