[cairo] operator CAIRO_OPERATOR_XOR

[Roman Bednarek]

Hi.
  Is there any example with CAIRO_OPERATOR_XOR? I cannot make it work:-(
When I add
cairo_set_operator (ct, CAIRO_OPERATOR_XOR);
to draw_shapes() in cairo demo the window is black(with only text), the
same happens in my program.
  Do I have to set another setting to make XOR operator work?

  Thanks for any help.

   Roman Bednarek