Pass voltage through to the trajectory python wrapper.

Add dependencies on python_init at suggestion of Brian.

Change-Id: I4fc7394bbe891115cf05f8604f2dde398f40e75f
diff --git a/frc971/control_loops/drivetrain/libspline.cc b/frc971/control_loops/drivetrain/libspline.cc
index 0d14f66..f931e59 100644
--- a/frc971/control_loops/drivetrain/libspline.cc
+++ b/frc971/control_loops/drivetrain/libspline.cc
@@ -149,6 +149,12 @@
 
   void TrajectoryPlan(Trajectory *t) { t->Plan(); }
 
+  void TrajectoryVoltage(Trajectory *t, double distance, double* res) {
+    double *val = t->FFVoltage(distance).data();
+    res[0] = val[0];
+    res[1] = val[1];
+  }
+
   double TrajectoryLength(Trajectory *t) { return t->length(); }
 
   int TrajectoryGetPathLength(Trajectory *t) { return t->plan().size(); }
diff --git a/frc971/control_loops/python/BUILD b/frc971/control_loops/python/BUILD
index 705aa38..9080e9a 100644
--- a/frc971/control_loops/python/BUILD
+++ b/frc971/control_loops/python/BUILD
@@ -84,6 +84,9 @@
     data = [
         "//frc971/control_loops/drivetrain:spline.so",
     ],
+    deps = [
+        ":python_init",
+    ],
 )
 
 py_test(
@@ -93,6 +96,7 @@
     ],
     deps = [
         ":libspline",
+        ":python_init",
     ]
 )
 
diff --git a/frc971/control_loops/python/libspline.py b/frc971/control_loops/python/libspline.py
index fd44cb4..7a77637 100644
--- a/frc971/control_loops/python/libspline.py
+++ b/frc971/control_loops/python/libspline.py
@@ -193,6 +193,16 @@
         """
         libSpline.TrajectoryPlan(self.__trajectory)
 
+    def Voltage(self, distance):
+        """
+        Returns a pair of voltages for a given distance.
+        Order is left-right.
+        """
+        result = np.zeros(2)
+        libSpline.TrajectoryVoltage(self.__trajectory, ct.c_double(distance),
+                                    np.ctypeslib.as_ctypes(result))
+        return result
+
     def Length(self):
         return libSpline.TrajectoryLength(self.__trajectory)