Hook up the pixman renderer into the headless backend, enabled by command line or weston.ini option renderer=pixman.
The headless backend should create a buffer acting as a fake screen, and render with Pixman to it. The intention is, that when the test extension is extended to do screenshots, there is something to actually capture.
Add a test, that excercises the Pixman renderer; just start Weston on headless with Pixman, map a window, wait for a frame callback, and exit.
Also display timings need to be faked, see e.g. the fbdev backend.
It looks that this feature got implemented http://cgit.freedesktop.org/wayland/weston/commit/?id=a04e9133047e389f060835278de082491f224a4d Or is there still something missing?
Hmm, yeah, and looks like the fake timings are there, too.