[cairo] Implementing PCL's display model using cairo.

[Carl Worth]

On Mon, 9 May 2005 09:45:01 +0200, Wolfgang Glas wrote:
> > >   Moreover, I played a bit with the PDF display model, which is claimed
> > > to be represented by cairo's display model. In PDF, I could map my 4
> > > operations in a suitable way by choosing the following mapping:
> > >
> > > 1) Lighten
> > > 2) Darken
> > > 3) Exclusion
> > > 4) Normal

Operators like these are fundamentally different from bitwise
operators such as AND, OR, and XOR. It's quite feasible that the PDF
operators could be added, (it just requires someone doing the
work). But I am quite certain that bitwise operators will never appear
in cairo[*].

> IMHO completing the set of perators should be an integral part of the API 
> shakeup process, which is currently in progress.

API-wise, new operators are very easy to add at any time. It's simply
a matter of extending an existing enum, so there's nothing
backwards-incompatible here.

-Carl

[*] Don't be confused by CAIRO_OPERATOR_XOR which provides the
Porter/Duff compositing operator named XOR, and not a bitwise XOR.
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