Use client prediction for item collection.

src/items/network_item_manager.cpp

@@ -99,7 +99,7 @@ void NetworkItemManager::collectedItem(Item *item, AbstractKart *kart,
         m_item_events.unlock();
         ItemManager::collectedItem(item, kart, add_info);
     }
-    else if (!RewindManager::get()->isRewinding())
+    else
     {
         // If we are predicting (i.e. not rewinding), the client
         // predicts item collection:
@@ -269,7 +269,6 @@ void NetworkItemManager::restoreState(BareNetworkString *buffer, int count)
     {
         Item *item = m_all_items[i];
         const ItemState *is = m_confirmed_state[i];
-        item->setTicksTillReturn(is->getTicksTillReturn());
         *(ItemState*)item = *is;
     }
 

src/items/powerup.cpp

@@ -480,16 +480,25 @@ void Powerup::hitBonusBox(const Item &item, int add_info)
     if(m_type == PowerupManager::POWERUP_RUBBERBALL)
         powerup_manager->setBallCollectTicks(0);
 
+    World *world = World::getWorld();
     // Check if two bouncing balls are collected less than getRubberBallTimer()
     //seconds apart. If yes, then call getRandomPowerup again. If no, then break.
     if (add_info<0)
     {
         for(int i=0; i<20; i++)
         {
-            new_powerup = powerup_manager->getRandomPowerup(position, &n);
+            // Determine the item based on index and time - random enough for
+            // the player, and reduces network synchronisation overhead.
+            // Dividing the time by 10 does not really allow exploiting the
+            // non-random selection (e.g. by displaying which item is collecte
+            // where), since it's only around 83 ms - but it is bit more
+            // relaxed when client prediction should be a frame or so earlier.
+            int random_number = item.getItemId() + world->getTimeTicks()/10;
+            new_powerup = 
+                powerup_manager->getRandomPowerup(position, &n, random_number);
             if(new_powerup != PowerupManager::POWERUP_RUBBERBALL ||
-                ( World::getWorld()->getTicksSinceStart() - powerup_manager->getBallCollectTicks()) >
-                  RubberBall::getTicksBetweenRubberBalls() )
+                ( world->getTicksSinceStart() - powerup_manager->getBallCollectTicks()) 
+                    > RubberBall::getTicksBetweenRubberBalls()                         )
                 break;
         }
     }
@@ -500,7 +509,7 @@ void Powerup::hitBonusBox(const Item &item, int add_info)
     }
 
     if(new_powerup == PowerupManager::POWERUP_RUBBERBALL)
-        powerup_manager->setBallCollectTicks(World::getWorld()->getTimeTicks());
+        powerup_manager->setBallCollectTicks(world->getTimeTicks());
 
     // Always add a new powerup in ITEM_MODE_NEW (or if the kart
     // doesn't have a powerup atm).

src/items/powerup_manager.cpp

@@ -354,10 +354,13 @@ PowerupManager::PositionClass
  *  items depending on the weights defined. See updateWeightsForRace()
  *  \param pos Position of the kart (1<=pos<=number of karts) - ignored in
  *         case of a battle mode.
- *  \param n Number of times this item is given to the kart
+ *  \param n Number of times this item is given to the kart.
+ *  \param random_number A random number used to select the item. Important
+ *         for networking to be able to reproduce item selection.
  */
 PowerupManager::PowerupType PowerupManager::getRandomPowerup(unsigned int pos,
-                                                             unsigned int *n)
+                                                             unsigned int *n,
+                                                             int random_number)
 {
     // Positions start with 1, while the index starts with 0 - so subtract 1
     PositionClass pos_class =
@@ -366,7 +369,7 @@ PowerupManager::PowerupType PowerupManager::getRandomPowerup(unsigned int pos,
          (race_manager->isTutorialMode() ? POSITION_TUTORIAL_MODE :
                                      m_position_to_class[pos-1]));
 
-    int random = rand()%m_powerups_for_position[pos_class].size();
+    int random = random_number%m_powerups_for_position[pos_class].size();
     int i=m_powerups_for_position[pos_class][random];
     if(i>=POWERUP_MAX)
     {

src/items/powerup_manager.hpp

@@ -139,7 +139,7 @@ public:
     void          LoadPowerup     (PowerupType type, const XMLNode &node);
     void          updateWeightsForRace(unsigned int num_karts);
     PowerupManager::PowerupType
-        getRandomPowerup(unsigned int pos, unsigned int *n);
+        getRandomPowerup(unsigned int pos, unsigned int *n, int random_number);
     // ------------------------------------------------------------------------
     /** Returns the icon(material) for a powerup. */
     Material* getIcon(int type) const {return m_all_icons [type];}