Add arrivals (#14755)

* Arrivals

* More arrivals and shitty uhh preload

* cvar

* a

* clockin + maps

* shitter prevention

* Placement

* a

* cvar for tests and dev

* weh

Content.Server/GameTicking/GameTicker.RoundFlow.cs

@@ -69,6 +69,16 @@ namespace Content.Server.GameTicking
         [ViewVariables]
         public int RoundId { get; private set; }
 
+        /// <summary>
+        /// Returns true if the round's map is eligible to be updated.
+        /// </summary>
+        /// <returns></returns>
+        public bool CanUpdateMap()
+        {
+            return RunLevel == GameRunLevel.PreRoundLobby &&
+                   _roundStartTime - RoundPreloadTime > _gameTiming.CurTime;
+        }
+
         /// <summary>
         ///     Loads all the maps for the given round.
         /// </summary>
@@ -77,11 +87,13 @@ namespace Content.Server.GameTicking
         /// </remarks>
         private void LoadMaps()
         {
+            if (_mapManager.MapExists(DefaultMap))
+                return;
+
             AddGamePresetRules();
 
             DefaultMap = _mapManager.CreateMap();
             _mapManager.AddUninitializedMap(DefaultMap);
-            var startTime = _gameTiming.RealTime;
 
             var maps = new List<GameMapPrototype>();
 
@@ -121,9 +133,6 @@ namespace Content.Server.GameTicking
 
                 LoadGameMap(map, toLoad, null);
             }
-
-            var timeSpan = _gameTiming.RealTime - startTime;
-            _sawmill.Info($"Loaded maps in {timeSpan.TotalMilliseconds:N2}ms.");
         }
 
 
@@ -170,6 +179,7 @@ namespace Content.Server.GameTicking
 
             SendServerMessage(Loc.GetString("game-ticker-start-round"));
 
+            // Just in case it hasn't been loaded previously we'll try loading it.
             LoadMaps();
 
             // map has been selected so update the lobby info text
@@ -487,14 +497,23 @@ namespace Content.Server.GameTicking
                 RoundLengthMetric.Inc(frameTime);
             }
 
-            if (RunLevel != GameRunLevel.PreRoundLobby || Paused ||
-                _roundStartTime > _gameTiming.CurTime ||
+            if (RunLevel != GameRunLevel.PreRoundLobby ||
+                Paused ||
+                _roundStartTime - RoundPreloadTime > _gameTiming.CurTime ||
                 _roundStartCountdownHasNotStartedYetDueToNoPlayers)
             {
                 return;
             }
 
-            StartRound();
+            if (_roundStartTime < _gameTiming.CurTime)
+            {
+                StartRound();
+            }
+            // Preload maps so we can start faster
+            else if (_roundStartTime - RoundPreloadTime < _gameTiming.CurTime)
+            {
+                LoadMaps();
+            }
         }
 
         public TimeSpan RoundDuration()