velocity_func receives nil for gravity

[erisdev]

Well, just what the title says. I tried implementing a custom velocity_func and discovered that chipmunk-ffi is passing me nil for the gravity parameter. Replacing Vect.by_value with CP_FLOAT, CP_FLOAT in the callback definition causes FFI to pass the vector as two float values and this works on OS X, but it's probably not portable.

[RavensKrag]

I am on Ubuntu linux, and I report a similar error. However, instead of getting nil, I receive a CP::Vect object. This does not have #struct defined, and thus generates an error.

/var/lib/gems/1.9.1/gems/chipmunk-ffi-1.1.0/lib/chipmunk-ffi/body.rb:193:in update_velocity': undefined methodstruct' for #CP::Vect:0x0000000334be00 (NoMethodError)
from /home/ravenskrag/Code/Source/eternity/Physics/Space.rb:10:in block in <class:Space>' from /var/lib/gems/1.9.1/gems/chipmunk-ffi-1.1.0/lib/chipmunk-ffi/body.rb:212:incall'
from /var/lib/gems/1.9.1/gems/chipmunk-ffi-1.1.0/lib/chipmunk-ffi/body.rb:212:in block in velocity_func=' from /var/lib/gems/1.9.1/gems/chipmunk-ffi-1.1.0/lib/chipmunk-ffi/space.rb:300:incall'
from /var/lib/gems/1.9.1/gems/chipmunk-ffi-1.1.0/lib/chipmunk-ffi/space.rb:300:in cpSpaceStep' from /var/lib/gems/1.9.1/gems/chipmunk-ffi-1.1.0/lib/chipmunk-ffi/space.rb:300:instep'
from /home/ravenskrag/Code/Source/eternity/Physics/Space.rb:118:in step' from ./init_game.rb:136:inupdate'
from ./init_game.rb:255:in show' from ./init_game.rb:255:in

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