func (gc *GraphicContext) ClearRect(x1, y1, x2, y2 int) {
	clearRect(gc, float64(x1), float64(y1), float64(x2), float64(y2))
}
func (gc *GraphicContext) ClearRect(x1, y1, x2, y2 int) {
	clearRect(gc, float64(x1), float64(y1), float64(x2), float64(y2))
}
// ClearRect draws a white rectangle over the specified area.
// Samples: line.