cairo/canvas.go
func (v *Context) SetOperator(op Operator) {
	C.cairo_set_operator(v.native(), C.cairo_operator_t(op))
}
func (v *Context) SetOperator(op Operator) {
	C.cairo_set_operator(v.native(), C.cairo_operator_t(op))
}
// SetOperator is a wrapper around cairo_set_operator().