Added capability to handle setting the maximum speed first to 0, and then

later to a higher value (which happens in overworld, which sets max speed
to 0, but the value got later overwritten with the normal supertuxkart max_speed
handling.

lib/bullet/src/BulletDynamics/Dynamics/btActionInterface.h

@@ -39,7 +39,7 @@ public:
 	virtual void updateAction( btCollisionWorld* collisionWorld, btScalar deltaTimeStep)=0;
 
 	virtual void debugDraw(btIDebugDraw* debugDrawer) = 0;
-
+    virtual void resetMaxSpeed() = 0;
 };
 
 #endif //_BT_ACTION_INTERFACE_H

lib/bullet/src/BulletDynamics/Dynamics/btDiscreteDynamicsWorld.cpp

@@ -297,6 +297,12 @@ int	btDiscreteDynamicsWorld::stepSimulation( btScalar timeStep,int maxSubSteps,
 	}
 
 	clearForces();
+    // Reset the max speeds of all karts, so that supertuxkart can
+    // set any new max_speed.
+    for (int i = 0; i<m_actions.size(); i++)
+    {
+        m_actions[i]->resetMaxSpeed();
+    }
 
 #ifndef BT_NO_PROFILE
 	CProfileManager::Increment_Frame_Counter();

src/physics/btKart.cpp

@@ -128,7 +128,7 @@ void btKart::reset()
     m_additional_rotation        = btVector3(0,0,0);
     m_time_additional_rotation   = 0;
     m_visual_rotation            = 0;
-    m_max_speed                  = 9999.9f;
+    m_max_speed                  = -1.0f;
     m_min_speed                  = 0.0f;
 
     // Set the brakes so that karts don't slide downhill
@@ -1056,7 +1056,7 @@ void btKart::adjustSpeed(btScalar min_speed, btScalar max_speed)
             m_chassisBody->setLinearVelocity(velocity * velocity_ratio);
         }
     }
-    else if (speed >0 && speed>max_speed)
+    else if (speed >0 && max_speed >= 0 && speed > max_speed)
     {
         const float velocity_ratio = max_speed / speed;
         m_chassisBody->setLinearVelocity(velocity * velocity_ratio);

src/physics/btKart.hpp

@@ -129,7 +129,8 @@ private:
      *  speed requested (in the next physics step). */
     btScalar m_min_speed;
 
-    /** Maximum speed for the kart. */
+    /** Maximum speed for the kart. It is reset to -1 at the end of each
+     *  physics steps, so need to be set again by the application. */
     btScalar m_max_speed;
 
     /** True if the visual wheels touch the ground. */
@@ -285,7 +286,20 @@ public:
     float getInstantSpeedIncrease() const { return m_zipper_speed; }
     // ------------------------------------------------------------------------
     /** Sets the maximum speed for this kart. */
-    void setMaxSpeed(float s) { m_max_speed = s;  }
+    void setMaxSpeed(float new_max_speed) 
+    {
+        // Only change m_max_speed if it has not been set (<0), or
+        // the new value is smaller than the current maximum. For example,
+        // overworld will set the max_speed to 0 in case of teleporting to
+        // a bubble, but set it again later (based on zipper etc activated).
+        // We need to make sure that the 0 is maintained.
+        if(m_max_speed <0 || m_max_speed > new_max_speed)
+            m_max_speed = new_max_speed;
+    }   // setMaxSpeed
+    // ------------------------------------------------------------------------
+    /** Resets the maximum so any new maximum value from the application will
+     *  be accepted. */
+    virtual void resetMaxSpeed() { m_max_speed = -1.0f; }
     // ------------------------------------------------------------------------
     /** Sets the minimum speed for this kart. */
     void setMinSpeed(float s) { m_min_speed = s; }