[cairo] Pixel consistency? (testing)

[Ian Britten]

Hi all,
I'm starting to write some unit tests for my Cairo-generated images,
and am wondering what expectations I should have for consistent
output from Cairo, regarding version upgrades, platforms, etc.
[ Esp. since I seem to be encountering some differences already :( ]

So:
- When producing images, is all the rendering controlled through
   cairo(mm) and pixman (And System calls)?  Are there any other
   factors that might alter the output (eg: Configuration options,
   64-bit, other dependencies, etc)?
   In other words, will the images generated by one platform/build
   be the same as those generated by a different build?

- For images generated through Cairo, are they currently
   consistent across different versions of Cairo?  If no, is it a
   goal of Cairo to eventually be consistent (Barring bug fixes, etc)?

- Can anyone offer any insight into how they approached their
   testing and these sorts of issues?  Currently, I'm just looking
   at doing a straight RGB(A) comparison of the pixels, so any
   difference will be reported as a failure.

Many thanks for any information!
Ian