[cairo] operator CAIRO_OPERATOR_XOR

Roman Bednarek roman at mikronika.com.pl
Wed Jul 7 01:03:52 PDT 2004

On Mon, 5 Jul 2004, Carl Worth wrote:

> On Wed, 19 May 2004 14:34:58 +0200 (CEST), Roman Bednarek wrote:
> >   Is there any example with CAIRO_OPERATOR_XOR? I cannot make it work:-(
> Here's an example:
> 	http://cairographics.org/samples/operator_xor.html
> > 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.
> An important point here is that CAIRO_OPERATOR_XOR is the Porter/Duff
> XOR compositing operator [1]. It is not a bitwise XOR operator.
> -Carl

   Thanks for explanation. The bitwise xor operator was used mainly for
achiving "rubber-band" effect, when you draw something twice it
disappears. Is it possible to achive the same effect with cairo API? I
hope yes, so is there an example of this?

  Roman Bednarek

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