Add internal physics tick callback methods in EventListener class

src/engine/DynamicsWorld.cpp

@@ -107,6 +107,9 @@ void DynamicsWorld::update() {
     // While the time accumulator is not empty
     while(mTimer.isPossibleToTakeStep()) {
 
+        // Notify the event listener about the beginning of an internal tick
+        if (mEventListener != NULL) mEventListener->beginInternalTick();
+
         // Reset all the contact manifolds lists of each body
         resetContactManifoldListsOfBodies();
 		
@@ -135,6 +138,9 @@ void DynamicsWorld::update() {
         updateBodiesState();
 
         if (mIsSleepingEnabled) updateSleepingBodies();
+
+        // Notify the event listener about the end of an internal tick
+        if (mEventListener != NULL) mEventListener->endInternalTick();
     }
 
     // Reset the external force and torque applied to the bodies

src/engine/EventListener.h

@@ -55,6 +55,17 @@ class EventListener {
         /// Called when a new contact point is found between two bodies
         virtual void newContact(const ContactPointInfo& contact) {}
 
+        /// Called at the beginning of an internal tick of the simulation step.
+        /// Each time the DynamicsWorld::update() method is called, the physics
+        /// engine will do several internal simulation steps. This method is
+        /// called at the beginning of each internal simulation step.
+        virtual void beginInternalTick() {}
+
+        /// Called at the end of an internal tick of the simulation step.
+        /// Each time the DynamicsWorld::update() metho is called, the physics
+        /// engine will do several internal simulation steps. This method is
+        /// called at the end of each internal simulation step.
+        virtual void endInternalTick() {}
 };
 
 }