[cairo] Questions about operators, clipping and etc

Taekyun Kim podain77 at gmail.com
Sun Jun 19 05:30:23 PDT 2011

Hi all,

I have several questions about cairo internals.

1. Clipping and masking equation
According to http://cairographics.org/operators, there're three kinds of
clipping equations,
XRender, Bounded and Simple. However I couldn't find any case where XRender
Bounded equations produce different results. What's the difference between

2. Unbounded operation
Unbounded interpretation is introduced as follows:

  The area where the compositing operation is performed is not bounded by
  mask. Instead, any parts where the source layer is not transferred are
  to be fully transparent. We call this interpretation of the source *

So does this mean that following equations??
dst = (src IN mask) OP dst (mask is allowed)
dst = 0 (mask is not allowed)

3. Limit boxes
Boxes, traps, polygon can have there limit boxes. I thought the boxes should
be disjoint,
because I couldn't find any handling of overlapping boxes. Is this true?

4. cairo_composite_rectangle_t
In case of cairo_fill(), the member "bounded" is calculated by fill extents
So although a path is finally tessellated into a single box, it might not be
the same with
"bounded", right?

Thanks in advance

Best Regards,
Taekyun Kim
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