If we are dithering on the Xlib backend we can not simply repaint the
surface used for a solid pattern and must recreate it from scratch.
However, for ordinary XRender usage we do not want to have to pay that
price - so query the backend to see if we can reuse the surface.
A surface will have the chance to use span rendering at cairo_fill()
time by creating a renderer for a specific combination of
pattern/dst/op before the path is scan converted. The protocol is to
first call check_span_renderer() to see if the surface wants to render
with spans and then later call create_span_renderer() to create the
renderer for real once the extents of the path are known.
No backends have an implementation yet.
A new meta-surface backend for serialising drawing operations to a
CairoScript file. The principal use (as currently envisaged) is to provide
a round-trip testing mechanism for CairoScript - i.e. we can generate
script files for every test in the suite and check that we can replay them
with perfect fidelity. (Obviously this does not provide complete coverage
of CairoScript's syntax, but should give reasonable coverage over the
operators.)
