Added DampedRotarySpring

lib/chipmunk-ffi/constraint.rb

@@ -44,4 +44,5 @@ def self.included(other)
   require 'chipmunk-ffi/constraints/ratchet_joint'
   require 'chipmunk-ffi/constraints/gear_joint'
   require 'chipmunk-ffi/constraints/simple_motor'
+  require 'chipmunk-ffi/constraints/damped_rotary_spring'
 end

lib/chipmunk-ffi/constraints/damped_rotary_spring.rb

@@ -0,0 +1,43 @@
+module CP
+
+  callback :cpDampedRotarySpringTorqueFunc, [:pointer, CP_FLOAT], CP_FLOAT
+
+  class DampedRotarySpringStruct < NiceFFI::Struct
+    layout(:constraint, ConstraintStruct,
+             :rest_angle, CP_FLOAT,
+             :stiffness, CP_FLOAT,
+             :damping, CP_FLOAT,
+             :spring_torque_func, :cpDampedRotarySpringTorqueFunc,
+             :dt, CP_FLOAT,
+             :target_wrn, CP_FLOAT,
+             :i_sum, CP_FLOAT)
+  end
+
+  func :cpDampedRotarySpringNew, [:pointer, :pointer, CP_FLOAT, CP_FLOAT, CP_FLOAT], :pointer
+
+  class DampedRotarySpring
+    include Constraint
+    struct_accessor DampedRotarySpringStruct, :rest_angle, :damping, :stiffness
+    def initialize(a_body, b_body,rest_angle, stiffness, damping)
+      @body_a, @body_b = a_body, b_body
+      @struct = DampedRotarySpringStruct.new(CP.cpDampedRotarySpringNew(
+        a_body.struct.pointer,b_body.struct.pointer, rest_angle, stiffness, damping))
+    end
+
+
+    # FIXME: Ideally, we'd prefer to pass DampedSprings, rather than DampedSpringStructs,
+    # to the user's lambda; or, better still, pass no spring at all, and allow them to refer
+    # to self. However, this means using wrapper procs in both the getter and the setter; in
+    # the case where the user takes a lambda recieved from a reader and supplies it to a writer;
+    # Each time this happens, we get a more deeply nested chain of lambdas.
+    def spring_torque_func
+      @struct.spring_torque_func
+    end
+
+    def spring_torque_func=(l)
+      @spring_torque_lambda = l # Keep the lambda from being GCed
+      @struct.spring_torque_func = @spring_torque_lambda
+    end
+  end
+end
+

spec/constraint_spec.rb

@@ -312,4 +312,50 @@
       joint.rate.should == -2.0
     end
   end
+
+  describe 'DampedRotarySpring class' do
+    it 'can be created' do
+      boda = Body.new 90, 46
+      bodb = Body.new 9, 6
+      CP::DampedRotarySpring.new(boda,bodb,3,4,5)
+    end
+
+    it 'can get and set its rest angle' do
+      boda = CP::Body.new 90, 46
+      bodb = CP::Body.new 9, 6
+      joint = CP::DampedRotarySpring.new(boda,bodb,3,4,5)
+      joint.rest_angle.should == 3.0
+      joint.rest_angle = 1
+      joint.rest_angle.should == 1.0
+    end
+
+    it 'can get and set its stiffness' do
+      boda = CP::Body.new 90, 46
+      bodb = CP::Body.new 9, 6
+      joint = CP::DampedRotarySpring.new(boda,bodb,3,4,5)
+      joint.stiffness.should == 4.0
+      joint.stiffness = 1
+      joint.stiffness.should == 1.0
+    end
+
+    it 'can get and set its damping' do
+      boda = CP::Body.new 90, 46
+      bodb = CP::Body.new 9, 6
+      joint = CP::DampedRotarySpring.new(boda,bodb,3,4,5)
+      joint.damping.should == 5.0
+      joint.damping = 1
+      joint.damping.should == 1.0
+    end
+
+    it 'can get and set its spring torque function' do
+      boda = CP::Body.new 90, 46
+      bodb = CP::Body.new 9, 6
+      joint = CP::DampedRotarySpring.new(boda,bodb,3,4,5)
+      joint.spring_torque_func.call(joint.struct,1.0).should == -8.0
+      joint.spring_torque_func = lambda {|spring,float| float + 1.0 }
+      joint.spring_torque_func.call(joint.struct,1.0).should == 2.0
+    end
+  end
+
+
 end