Add cpSegmentShapeSetNeighbors() support

[ClockVapor]

It would be nice to have official support for this function in the Ruby gem. I keep having issues with "seams" when using adjacent, parallel segment shapes, resulting in objects getting stuck and hitting "bumps."

I forked and added the function myself, but I'm not sure if it's even working. I'm using it like this for line segments in a square shape:

# top of box, from left to right
segments[:top].set_neighbors!(
  segments[:top].a + CP::Vec2.new(-1, 0),
  segments[:top].b + CP::Vec2.new(1, 0)
)

# right side of box, from top to bottom
segments[:right].set_neighbors!(
  segments[:right].a + CP::Vec2.new(0, -1),
  segments[:right].b + CP::Vec2.new(0, 1)
)
# etc. etc.

I don't notice any effects after doing this. This and this are my only two modifications to add the cpSegmentShapeSetNeighbors function. Any ideas on this?

[shawn42]

@ClockVapor I added this to the latest build of chipmunk. Under the hood, it sets up some tangents for a and b on the segment shape. I did not add tests for this, but I'd like to know if you find it useful and if you find a good way to verify that it works. I found very little in the way of documentation on this function in Chipmunk.

[ClockVapor]

Thanks! Yeah, the documentation doesn't seem very transparent about this function. I haven't done any extensive testing yet, but I'll see if I can see a difference using it.