Core/PacketIO: Documented possible values for SMSG_NEW_WORLD reason field

src/server/game/Entities/Player/Player.cpp

@@ -2162,7 +2162,7 @@ bool Player::TeleportTo(uint32 mapid, float x, float y, float z, float orientati
                 WorldPackets::Movement::NewWorld packet;
                 packet.MapID = mapid;
                 packet.Pos = m_teleport_dest;
-                packet.Reason = 16;
+                packet.Reason = NEW_WORLD_NORMAL;
 
                 SendDirectMessage(packet.Write());
                 SendSavedInstances();

src/server/game/Entities/Player/Player.h

@@ -822,6 +822,12 @@ enum TransferAbortReason
     */
 };
 
+enum NewWorldReason
+{
+    NEW_WORLD_NORMAL    = 16,   // Normal map change
+    NEW_WORLD_SEAMLESS  = 21,   // Teleport to another map without a loading screen, used for outdoor scenarios
+};
+
 enum InstanceResetWarningType
 {
     RAID_INSTANCE_WARNING_HOURS     = 1,                    // WARNING! %s is scheduled to reset in %d hour(s).