[cairo] What's mean about CAIRO_OPERATOR_XXX?

[charles]

Hi, Carl Worth:

When I use cairo in my program, I have notice about the
cairo_set_operator and CAIRO_OPERATOR_XXX. But I can not find any
documentation about them. Abviously different CAIRO_OPERATOR_XXX will
lead to different effect, can you give me any ideas about the effects of
these values? And what is the default operator for a new created
cairo_t?

Another questions, is there any low cost way to clear the surface to all
transparent? CAIRO_OPERATOR_CLEAR can do it or not? If it can, how?

THANKS GREATLY. :)

Charles Wang  July 22, 2005