This is a more useful definition that is able to individually track the
rectangles that compose the composite operation. This will be used by
the specialist compositors as a means to perform the common extents
determination for an operation.
For the simple cases where the clip is an unaligned box (or boxes), apply
the clip directly to the geometry and avoid having to use an intermediate
clip-mask.
Based on feedback from Jeff Muizelaar, there is a case for a very quick
and dirty extents approximation based solely on the curve control points
(for example when computing the clip intersect rectangle of a path) and
by moving the stroke extension into a core function we can clean up the
interface for all users, and centralise the logic of approximating the
stroke extents.
When analysing the stroke extents, we need the original fixed-point
extents so that we do not incur an OBO when we round-to-integer a second
time. We also need a more accurate estimate than simply using the control
points of the curve, so pass in tolerance and decompose until someone
discovers a cheaper algorithm to determine the precise aligned bounding
box of a bezier curve.
A cairo_composite_rectangles_t contains the coordinates of rectangular
windows into each of the source pattern, mask, clip and destination
surface containing the pixels that will combine in a compositing
operation. The idea is to have a uniform way to represent all the
translations involved rather than overloading parameters like src_x/y,
dst_x/y, etc., sometimes with different incompatible meanings across
functions.
Adrian Johnson discovered cases where we mistakenly compared the result
of unsigned arithmetic where we need signed quantities. Look for similar
cases in the users of cairo_rectangle_int_t.
Make sure that we don't test lines that start or end inside the box,
since our algorithm will find intersections on the wrong ends on the
line, and not count them.
This rectangle has regular integer values, not fixed-point values.
So the old name was horribly wrong and misleading, (and yes I think
it was even I that had suggested it).
