[cairo] Alpha channel [pycairo]

Robert O'Callahan robert at ocallahan.org
Sun Mar 11 17:37:06 PDT 2007

On 3/12/07, Kalle Vahlman <kalle.vahlman at gmail.com> wrote:
> 2007/3/10, Manuel <origin.of at gmail.com>:
> > hi all, I've this "program" :
> [snip]
> > try execute it, the alpha channel doesn't work...
> > The windows isn't semi-transparent...
> > cr.set_source_rgba(0.0, 0.0, 0.0, 0.5) doesn't work ??
> That's because window transparency doesn't quite work that way.
> On X, windows traditionally are always fully opaque. One needs the
> help of the Composite extension to achieve transparency, which pretty
> much is out of scope for Cairo IMO.

Actually all the X *application* needs to do is to choose an RGBA visual for
its windows.

"Two men owed money to a certain moneylender. One owed him five hundred
denarii, and the other fifty. Neither of them had the money to pay him back,
so he canceled the debts of both. Now which of them will love him more?"
Simon replied, "I suppose the one who had the bigger debt canceled." "You
have judged correctly," Jesus said. [Luke 7:41-43]
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