Only double switch if the dimension is the same. (#1977)

According to the protocol, a double respawn packet is only needed to be
sent if from the same dimension, so by storing the last known dimension,
we are able to compare and avoid the double packet.

This also maintains the same behaviour for Spigot
ad2f806097

proxy/src/main/java/net/md_5/bungee/ServerConnector.java

@@ -222,10 +222,15 @@ public class ServerConnector extends PacketHandler
             }
             user.getSentBossBars().clear();
 
-            user.sendDimensionSwitch();
+            user.setDimensionChange( true );
+            if ( login.getDimension() == user.getDimension() )
+            {
+                user.unsafe().sendPacket( new Respawn( ( login.getDimension() >= 0 ? -1 : 0 ), login.getDifficulty(), login.getGameMode(), login.getLevelType() ) );
+            }
 
             user.setServerEntityId( login.getEntityId() );
             user.unsafe().sendPacket( new Respawn( login.getDimension(), login.getDifficulty(), login.getGameMode(), login.getLevelType() ) );
+            user.setDimension( login.getDimension() );
 
             // Remove from old servers
             user.getServer().disconnect( "Quitting" );

proxy/src/main/java/net/md_5/bungee/UserConnection.java

@@ -55,6 +55,7 @@ import net.md_5.bungee.protocol.packet.ClientSettings;
 import net.md_5.bungee.protocol.packet.Kick;
 import net.md_5.bungee.protocol.packet.PlayerListHeaderFooter;
 import net.md_5.bungee.protocol.packet.PluginMessage;
+import net.md_5.bungee.protocol.packet.Respawn;
 import net.md_5.bungee.protocol.packet.SetCompression;
 import net.md_5.bungee.tab.ServerUnique;
 import net.md_5.bungee.tab.TabList;
@@ -80,6 +81,9 @@ public final class UserConnection implements ProxiedPlayer
     private ServerConnection server;
     @Getter
     @Setter
+    private int dimension;
+    @Getter
+    @Setter
     private boolean dimensionChange = true;
     @Getter
     private final Collection<ServerInfo> pendingConnects = new HashSet<>();
@@ -210,16 +214,9 @@ public final class UserConnection implements ProxiedPlayer
         connect( target, callback, false );
     }
 
-    void sendDimensionSwitch()
-    {
-        dimensionChange = true;
-        unsafe().sendPacket( PacketConstants.DIM1_SWITCH );
-        unsafe().sendPacket( PacketConstants.DIM2_SWITCH );
-    }
-
     public void connectNow(ServerInfo target)
     {
-        sendDimensionSwitch();
+        dimensionChange = true;
         connect(target);
     }
 

proxy/src/main/java/net/md_5/bungee/connection/DownstreamBridge.java

@@ -33,6 +33,7 @@ import net.md_5.bungee.protocol.PacketWrapper;
 import net.md_5.bungee.protocol.packet.BossBar;
 import net.md_5.bungee.protocol.packet.KeepAlive;
 import net.md_5.bungee.protocol.packet.PlayerListItem;
+import net.md_5.bungee.protocol.packet.Respawn;
 import net.md_5.bungee.protocol.packet.ScoreboardObjective;
 import net.md_5.bungee.protocol.packet.ScoreboardScore;
 import net.md_5.bungee.protocol.packet.ScoreboardDisplay;
@@ -504,6 +505,12 @@ public class DownstreamBridge extends PacketHandler
         }
     }
 
+    @Override
+    public void handle(Respawn respawn)
+    {
+        con.setDimension( respawn.getDimension() );
+    }
+
     @Override
     public String toString()
     {