private static Rect CreateEmptyRect()
{
Rect rect = new Rect();
// TODO: for consistency with width/height we should change these
// to assign directly to the backing fields.
rect.X = EmptyX;
rect.Y = EmptyY;
// the width and height properties prevent assignment of
// negative numbers so assign directly to the backing fields.
rect._width = (float)EmptyWidth;
rect._height = (float)EmptyHeight;
return rect;
}