[cairo] How to draw a inverted area?

[Carlos Garcia Campos]

Excerpts from Magicloud Magiclouds's message of lun jun 07 09:44:10 +0200 2010:
> Hi, sorry the subject is not clear.
> I mean that, first I draw something in the cairo context, then I draw
> a circle in it, which acts like a invert mask. All colors in its area
> are inverted.

I think filling with white with the difference operator is what you
want

cairo_set_source_rgb (cr, 1., 1., 1.);
cairo_set_operator (cr, CAIRO_OPERATOR_DIFFERENCE);
cairo_fill(cr);

> I thought xor operator helped, but it did not....
> Thanks.

Regards, 
-- 
Carlos Garcia Campos
PGP key: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x523E6462
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