Reproducable state & serialization of space

[viblo]

I just wanted to show & tell that Ive implemented reproducible state & serialization of the contact graph of the Space to Pymunk (Python library using Chipmunk) in case others are interested in adding this.

The changes (the c bits) are available here: https://github.com/viblo/pymunk/blob/master/pymunk/cffi/extensions.c

Pymunk has long had serialization of the public things (space, body, shapes etc) fully made from the Python side, but not of the contact graph which meant that loading a saved space meant that any collisions did not behave consistently. So, what I did was adding a couple of functions to get and set a couple of properties (shape.hashid space.shapeidcounter, space.stamp) and the cached arbiters form the space. Im not 100% sure I have all of it, but at least in my (tiny) test case it seemed to work. I you have any suggestions on my implementation please let me know, Im sure it can be made better!

ps. I wrote it here since the forums are quite unstable and dead.. hope its ok! Now, even if closed it will be easier to find I think.