[cairo] Hit detect surface?

[Christof Petig]

David Trallero Mena wrote:
> I also have needed to do that. In fact I think complicating cairo is
> unnecessary. I just create another surface of 32 bits-per-color and
> render everything again there. This new surface I use I refer to as
> select surface (hit-surface for you). The color used when re-rendering
> is indeed and ID (I have to talk with cairo guys about this) of the
> figure (rectangle, ellipse, circle...) that was rendered on the
> "original-surface".

IIRC the cairo developers still look for a sane reason to provide a
surface which does not antialias. If indead this is the best way to
implement hit detection, we have a case where antialiasing is a really
bad idea (also interpreting one part of the color as the opacity is a
bad idea).

   Christof

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