Add Tick scale plumbing

OpenRA.Game/Network/Connection.cs

@@ -299,17 +299,23 @@ namespace OpenRA.Network
 			// Orders from other players
 			while (receivedPackets.TryDequeue(out var p))
 			{
-				var record = true;
 				if (OrderIO.TryParseDisconnect(p, out var disconnect))
+				{
 					orderManager.ReceiveDisconnect(disconnect.ClientId, disconnect.Frame);
+					Recorder?.Receive(p.FromClient, p.Data);
+				}
 				else if (OrderIO.TryParseSync(p.Data, out var sync))
+				{
 					orderManager.ReceiveSync(sync);
+					Recorder?.Receive(p.FromClient, p.Data);
+				}
+				else if (OrderIO.TryParseTickScale(p, out var scale))
+					orderManager.ReceiveTickScale(scale);
 				else if (OrderIO.TryParsePingRequest(p, out var timestamp))
 				{
 					// Note that processing this here, rather than in NetworkConnectionReceive,
 					// so that poor world tick performance can be reflected in the latency measurement
 					Send(OrderIO.SerializePingResponse(timestamp, (byte)orderManager.OrderQueueLength));
-					record = false;
 				}
 				else if (OrderIO.TryParseAck(p, out var ackFrame, out var ackCount))
 				{
@@ -331,7 +337,6 @@ namespace OpenRA.Network
 
 					orderManager.ReceiveOrders(clientId, (ackFrame, packet));
 					Recorder?.Receive(clientId, packet.Serialize(ackFrame));
-					record = false;
 				}
 				else if (OrderIO.TryParseOrderPacket(p.Data, out var orders))
 				{
@@ -339,13 +344,12 @@ namespace OpenRA.Network
 						orderManager.ReceiveImmediateOrders(p.FromClient, orders.Orders);
 					else
 						orderManager.ReceiveOrders(p.FromClient, orders);
+
+					Recorder?.Receive(p.FromClient, p.Data);
 				}
 				else
 					throw new InvalidDataException($"Received unknown packet from client {p.FromClient} with length {p.Data.Length}");
 
-				if (record)
-					Recorder?.Receive(p.FromClient, p.Data);
-
 				// An immediate order may trigger a chain of actions that disposes the OrderManager and connection.
 				// Bail out to avoid potential problems from acting on disposed objects.
 				if (disposed)

OpenRA.Game/Network/Order.cs

@@ -20,6 +20,7 @@ namespace OpenRA
 		Ack = 0x10,
 		Ping = 0x20,
 		SyncHash = 0x65,
+		TickScale = 0x76,
 		Disconnect = 0xBF,
 		Handshake = 0xFE,
 		Fields = 0xFF

OpenRA.Game/Network/OrderIO.cs

@@ -133,6 +133,27 @@ namespace OpenRA.Network
 			return true;
 		}
 
+		public static bool TryParseTickScale((int FromClient, byte[] Data) packet, out float scale)
+		{
+			// Valid tick scale commands are only ever generated by the server
+			if (packet.FromClient != 0 || packet.Data.Length != 9 || packet.Data[4] != (byte)OrderType.TickScale)
+			{
+				scale = 1;
+				return false;
+			}
+
+			// Valid tick scale packets always have frame 0
+			var frame = BitConverter.ToInt32(packet.Data, 0);
+			if (frame != 0)
+			{
+				scale = 1;
+				return false;
+			}
+
+			scale = BitConverter.ToSingle(packet.Data, 5);
+			return true;
+		}
+
 		public static bool TryParsePingRequest((int FromClient, byte[] Data) packet, out long timestamp)
 		{
 			// Valid Ping requests are only ever generated by the server

OpenRA.Game/Network/OrderManager.cs

@@ -58,6 +58,7 @@ namespace OpenRA.Network
 		bool disposed;
 		bool generateSyncReport = false;
 		int sentOrdersFrame = 0;
+		float tickScale = 1f;
 
 		public struct ClientOrder
 		{
@@ -157,6 +158,11 @@ namespace OpenRA.Network
 				syncForFrame.Add(sync.Frame, (sync.SyncHash, sync.DefeatState));
 		}
 
+		public void ReceiveTickScale(float scale)
+		{
+			tickScale = scale;
+		}
+
 		public void ReceiveImmediateOrders(int clientId, OrderPacket orders)
 		{
 			foreach (var o in orders.GetOrders(World))
@@ -184,7 +190,7 @@ namespace OpenRA.Network
 
 		bool IsReadyForNextFrame => GameStarted && pendingOrders.All(p => p.Value.Count > 0);
 
-		int SuggestedTimestep
+		public int SuggestedTimestep
 		{
 			get
 			{
@@ -197,6 +203,9 @@ namespace OpenRA.Network
 				if (World.IsReplay)
 					return World.ReplayTimestep;
 
+				if (tickScale != 1f)
+					return Math.Max((int)(tickScale * World.Timestep), 1);
+
 				return World.Timestep;
 			}
 		}