[cairo] bounded operators

[Andrea Canciani]

On Tue, Nov 9, 2010 at 10:53 AM, L A <l.thee.a at gmail.com> wrote:
> + cairo list  ,sorry about the repost..
>
> On Sat, Nov 6, 2010 at 3:11 AM, Andrea Canciani <ranma42 at gmail.com> wrote:
>> On Sat, Nov 6, 2010 at 11:03 AM, L A <l.thee.a at gmail.com> wrote:
>>> Probably a stupid question: why are CAIRO_OPERATOR_SOURCE and
>>> CAIRO_OPERATOR_CLEAR not bounded? _cairo_operator_bounded_by_source
>>> call seems to be returning false for these two.
>>
>> They are bounded by the mask, not by the souce (see
>> _cairo_operator_bounded_by_mask).
>> You might also want a high level overview of the operators:
>> http://cairographics.org/operators/
>> Notice that throughout the whole document "bounded" means "bounded by mask" (as
>> explained in the section "The Source").
>>
>> Andrea
>>
>
> Thanks, that makes sense. Another question: if the mask is empty (ie:
> NULL), can we assume that op is source bounded?
>

The shape of the mask does not affect the definition of op.

If by "empty mask" you mean the one that you would get for a
paint operation (opposed to the one that would be used for
fill/stroke/mask), then...
Example:
If you paint with op==CLEAR, you will make the whole clipping region
clear (no matter what your source is).

Andrea