+ float current_x_velocity = physic.get_velocity_x ();
+
+ if (frozen)
+ {
+ physic.set_velocity_x (0.0);
+ physic.set_acceleration_x (0.0);
+ }
+ /* We're very close to our target speed. Just set it to avoid oscillation */
+ else if ((current_x_velocity > (dest_x_velocity - 5.0))
+ && (current_x_velocity < (dest_x_velocity + 5.0)))
+ {
+ physic.set_velocity_x (dest_x_velocity);
+ physic.set_acceleration_x (0.0);
+ }
+ /* Check if we're going too slow or even in the wrong direction */
+ else if (((dest_x_velocity <= 0.0) && (current_x_velocity > dest_x_velocity))
+ || ((dest_x_velocity > 0.0) && (current_x_velocity < dest_x_velocity)))
+ {
+ /* acceleration == walk-speed => it will take one second to get from zero
+ * to full speed. */
+ physic.set_acceleration_x (dest_x_velocity);
+ }
+ /* Check if we're going too fast */
+ else if (((dest_x_velocity <= 0.0) && (current_x_velocity < dest_x_velocity))
+ || ((dest_x_velocity > 0.0) && (current_x_velocity > dest_x_velocity)))
+ {
+ /* acceleration == walk-speed => it will take one second to get twice the
+ * speed to normal speed. */
+ physic.set_acceleration_x ((-1.0) * dest_x_velocity);
+ }
+ else
+ {
+ /* The above should have covered all cases. */
+ assert (23 == 42);
+ }
+