Fixes the race condition when one thread uses cairo_mask_compositor_t
pointer returned by _cairo_image_mask_compositor_get, while another one
started but has not finished it's initialisation yet
Usage:
static cairo_atomic_once_t once = CAIRO_ATOMIC_ONCE_INIT;
if (_cairo_atomic_init_once_enter(&once)) {
/* Initialization code */
_cairo_atomic_init_once_leave(&once);
}
https://bugs.freedesktop.org/show_bug.cgi?id=103037
The actual span rasterisers may be able to specialise if they know that
the spans will be pixel aligned.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Having spent the last dev cycle looking at how we could specialize the
compositors for various backends, we once again look for the
commonalities in order to reduce the duplication. In part this is
motivated by the idea that spans is a good interface for both the
existent GL backend and pixman, and so they deserve a dedicated
compositor. xcb/xlib target an identical rendering system and so they
should be using the same compositor, and it should be possible to run
that same compositor locally against pixman to generate reference tests.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
P.S. This brings massive upheaval (read breakage) I've tried delaying in
order to fix as many things as possible but now this one patch does far,
far, far too much. Apologies in advance for breaking your favourite
backend, but trust me in that the end result will be much better. :)
