basic Sync checking. No protocol stuff yet; just checks that input events are well-behaved.

OpenRa.DataStructures/TypeDictionary.cs

@@ -46,5 +46,10 @@ namespace OpenRa
 				if( i.Value is T )
 					yield return (T)i.Value;
 		}
+
+		public IEnumerator<object> GetEnumerator()
+		{
+			return WithInterface<object>().GetEnumerator();
+		}
 	}
 }

OpenRa.Game/Actor.cs

@@ -10,12 +10,16 @@ namespace OpenRa.Game
 {
 	class Actor
 	{
+		[Sync]
 		public readonly TypeDictionary traits = new TypeDictionary();
 		public readonly UnitInfo Info;
 
 		public readonly uint ActorID;
+		[Sync]
 		public int2 Location;
+		[Sync]
 		public Player Owner;
+		[Sync]
 		public int Health;
 		IActivity currentActivity;
 

OpenRa.Game/Controller.cs

@@ -146,15 +146,25 @@ namespace OpenRa.Game
 		public float2 MousePosition { get { return dragEnd; } }
 
 		public Cursor ChooseCursor()
+		{
+			int sync = Game.world.SyncHash();
+
+			try
 			{
 				var mi = new MouseInput
 				{
-				Location = (Game.CellSize * MousePosition - Game.viewport.Location).ToInt2(),
+					Location = ( Game.CellSize * MousePosition - Game.viewport.Location ).ToInt2(),
 					Button = MouseButton.Right,
 					Modifiers = GetModifierKeys(),
 				};
 
-			return orderGenerator.GetCursor(MousePosition.ToInt2(), mi);
+				return orderGenerator.GetCursor( MousePosition.ToInt2(), mi );
+			}
+			finally
+			{
+				if( sync != Game.world.SyncHash() )
+					throw new InvalidOperationException( "Desync in Controller.ChooseCursor" );
+			}
 		}
 
 		Cache<int, List<Actor>> controlGroups = new Cache<int, List<Actor>>(_ => new List<Actor>());

OpenRa.Game/MainWindow.cs

@@ -95,6 +95,8 @@ namespace OpenRa.Game
 
 		void DispatchMouseInput(MouseInputEvent ev, MouseEventArgs e)
 		{
+			int sync = Game.world.SyncHash();
+
 			Game.viewport.DispatchMouseInput(
 				new MouseInput
 				{
@@ -103,6 +105,9 @@ namespace OpenRa.Game
 					Location = new int2(e.Location),
 					Modifiers = (Modifiers)(int)ModifierKeys,
 				});
+
+			if( sync != Game.world.SyncHash() )
+				throw new InvalidOperationException( "Desync in DispatchMouseInput" );
 		}
 
 		protected override void OnMouseDown(MouseEventArgs e)
@@ -136,6 +141,8 @@ namespace OpenRa.Game
 		{
 			base.OnKeyDown(e);
 
+			int sync = Game.world.SyncHash();
+
 			/* hack hack hack */
 			if (e.KeyCode == Keys.F8 && !Game.orderManager.GameStarted)
 			{
@@ -156,16 +163,24 @@ namespace OpenRa.Game
 			if (!Game.chat.isChatting)
 				if (e.KeyCode >= Keys.D0 && e.KeyCode <= Keys.D9)
 					Game.controller.DoControlGroup( (int)e.KeyCode - (int)Keys.D0, (Modifiers)(int)e.Modifiers );
+
+			if( sync != Game.world.SyncHash() )
+				throw new InvalidOperationException( "Desync in OnKeyDown" );
 		}
 
 		protected override void OnKeyPress(KeyPressEventArgs e)
 		{
 			base.OnKeyPress(e);
 
+			int sync = Game.world.SyncHash();
+
 			if (e.KeyChar == '\r')
 				Game.chat.Toggle();
 			else if (Game.chat.isChatting)
 				Game.chat.TypeChar(e.KeyChar);
+
+			if( sync != Game.world.SyncHash() )
+				throw new InvalidOperationException( "Desync in OnKeyPress" );
 		}
 	}
 

OpenRa.Game/OpenRa.Game.csproj

@@ -129,6 +129,7 @@
     <Compile Include="SupportPowers\NullPower.cs" />
     <Compile Include="Support\Stopwatch.cs" />
     <Compile Include="Support\PerfHistory.cs" />
+    <Compile Include="Sync.cs" />
     <Compile Include="Traits\AcceptsOre.cs" />
     <Compile Include="Traits\Activities\Attack.cs" />
     <Compile Include="Traits\Activities\CaptureBuilding.cs" />

OpenRa.Game/Sync.cs

@@ -0,0 +1,57 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Reflection;
+
+namespace OpenRa.Game
+{
+	class SyncAttribute : Attribute { }
+
+	static class Sync
+	{
+		public static int CalculateSyncHash( object obj )
+		{
+			int hash = 0; // TODO: start with a more interesting initial value.
+
+			// TODO: cache the Syncable fields; maybe use DynamicMethod to make this fast?
+			// FIXME: does GetFields even give fields in a well-defined order?
+			const BindingFlags bf = BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance;
+			foreach( var field in obj.GetType().GetFields( bf ).Where( x => x.GetCustomAttributes( typeof( SyncAttribute ), true ).Length != 0 ) )
+			{
+				if( field.FieldType == typeof( int ) )
+					hash ^= (int)field.GetValue( obj );
+
+				else if( field.FieldType == typeof( Actor ) )
+				{
+					var a = (Actor)field.GetValue( obj );
+					if( a != null )
+						hash ^= (int)( a.ActorID << 16 );
+				}
+				else if( field.FieldType == typeof( TypeDictionary ) )
+				{
+					foreach( var o in (TypeDictionary)field.GetValue( obj ) )
+						hash += CalculateSyncHash( o );
+				}
+				else if( field.FieldType == typeof( bool ) )
+					hash ^= (bool)field.GetValue( obj ) ? 0xaaa : 0x555;
+
+				else if( field.FieldType == typeof( int2 ) )
+				{
+					var i2 = (int2)field.GetValue( obj );
+					hash ^= ( ( i2.X * 5 ) ^ ( i2.Y * 3 ) ) / 4;
+				}
+				else if( field.FieldType == typeof( Player ) )
+				{
+					var p = (Player)field.GetValue( obj );
+					if( p != null )
+					hash ^= p.Index * 0x567;
+				}
+				else
+					throw new NotImplementedException( "SyncAttribute on unhashable field" );
+			}
+
+			return hash;
+		}
+	}
+}

OpenRa.Game/Traits/AttackBase.cs

@@ -8,10 +8,12 @@ namespace OpenRa.Game.Traits
 {
 	class AttackBase : IIssueOrder, IResolveOrder, ITick
 	{
-		public Actor target;
+		[Sync] public Actor target;
 
 		// time (in frames) until each weapon can fire again.
+		[Sync]
 		protected int primaryFireDelay = 0;
+		[Sync]
 		protected int secondaryFireDelay = 0;
 
 		int primaryBurst;

OpenRa.Game/Traits/AttackFrontal.cs

@@ -7,7 +7,7 @@ namespace OpenRa.Game.Traits
 		public AttackFrontal(Actor self, int facingTolerance)
 			: base(self) { FacingTolerance = facingTolerance; }
 
-		int FacingTolerance;
+		readonly int FacingTolerance;
 
 		public override void Tick(Actor self)
 		{

OpenRa.Game/Traits/Building.cs

@@ -13,7 +13,9 @@ namespace OpenRa.Game.Traits
 	{
 		readonly Actor self;
 		public readonly BuildingInfo unitInfo;
+		[Sync]
 		bool isRepairing = false;
+		[Sync]
 		bool manuallyDisabled = false;
 		public bool ManuallyDisabled { get { return manuallyDisabled; } }
 		public bool Disabled { get { return (manuallyDisabled || (unitInfo.Powered && self.Owner.GetPowerState() != PowerState.Normal)); } }

OpenRa.Game/Traits/ChronoshiftDeploy.cs

@@ -7,8 +7,9 @@ namespace OpenRa.Game.Traits
 	class ChronoshiftDeploy : IIssueOrder, IResolveOrder, ISpeedModifier, ITick, IPips
 	{
 		// Recharge logic
+		[Sync]
 		int chargeTick = 0; // How long until we can chronoshift again?
-		int chargeLength = (int)(Rules.Aftermath.ChronoTankDuration * 60 * 25); // How long between shifts?
+		readonly int chargeLength = (int)(Rules.Aftermath.ChronoTankDuration * 60 * 25); // How long between shifts?
 
 		public ChronoshiftDeploy(Actor self) { }
 		

OpenRa.Game/Traits/Chronoshiftable.cs

@@ -8,7 +8,9 @@ namespace OpenRa.Game.Traits
 	class Chronoshiftable : IResolveOrder, ISpeedModifier, ITick
 	{
 		// Return-to-sender logic
+		[Sync]
 		int2 chronoshiftOrigin;
+		[Sync]
 		int chronoshiftReturnTicks = 0;
 
 		public Chronoshiftable(Actor self) { }

OpenRa.Game/Traits/Cloak.cs

@@ -6,6 +6,7 @@ namespace OpenRa.Game.Traits
 {
 	class Cloak : IRenderModifier, INotifyAttack, ITick
 	{
+		[Sync]
 		int remainingUncloakTime = 2;		/* setup for initial cloak */
 
 		public Cloak(Actor self) {}

OpenRa.Game/Traits/Harvester.cs

@@ -5,7 +5,9 @@ namespace OpenRa.Game.Traits
 {
 	class Harvester : IIssueOrder, IResolveOrder, IPips
 	{
+		[Sync]
 		public int oreCarried = 0;					/* sum of these must not exceed capacity */
+		[Sync]
 		public int gemsCarried = 0;
 
 		public bool IsFull { get { return oreCarried + gemsCarried == Rules.General.BailCount; } }

OpenRa.Game/Traits/IronCurtainable.cs

@@ -5,6 +5,7 @@ namespace OpenRa.Game.Traits
 {
 	class IronCurtainable : IResolveOrder, IDamageModifier, ITick
 	{
+		[Sync]
 		int RemainingTicks = 0;
 
 		public IronCurtainable(Actor self) { }

OpenRa.Game/Traits/LimitedAmmo.cs

@@ -4,6 +4,7 @@ namespace OpenRa.Game.Traits
 {
 	class LimitedAmmo : INotifyAttack, IPips
 	{
+		[Sync]
 		int ammo;
 		Actor self;
 

OpenRa.Game/Traits/Mobile.cs

@@ -9,6 +9,7 @@ namespace OpenRa.Game.Traits
 	{
 		readonly Actor self;
 
+		[Sync]
 		int2 __fromCell;
 		public int2 fromCell
 		{

OpenRa.Game/Traits/ProductionQueue.cs

@@ -74,6 +74,7 @@ namespace OpenRa.Game.Traits
 		}
 
 		// Key: Production category.
+		// TODO: sync this
 		readonly Cache<string, List<ProductionItem>> production 
 			= new Cache<string, List<ProductionItem>>( _ => new List<ProductionItem>() );
 

OpenRa.Game/Traits/RallyPoint.cs

@@ -6,6 +6,7 @@ namespace OpenRa.Game.Traits
 {
 	class RallyPoint : IRender, IIssueOrder, IResolveOrder, ITick
 	{
+		[Sync]
 		public int2 rallyPoint;
 		public Animation anim;
 

OpenRa.Game/Traits/RenderBuildingWarFactory.cs

@@ -7,7 +7,9 @@ namespace OpenRa.Game.Traits
 	class RenderWarFactory : IRender, INotifyBuildComplete, INotifyDamage, ITick, INotifyProduction
 	{
 		public Animation roof;
+		[Sync]
 		bool doneBuilding;
+		[Sync]
 		bool isOpen;
 		public readonly Actor self;
 

OpenRa.Game/Traits/Submarine.cs

@@ -6,6 +6,7 @@ namespace OpenRa.Game.Traits
 {
 	class Submarine : IRenderModifier, INotifyAttack, ITick, INotifyDamage
 	{
+		[Sync]
 		int remainingSurfaceTime = 2;		/* setup for initial dive */
 
 		public Submarine(Actor self) { }

OpenRa.Game/Traits/TakeCover.cs

@@ -8,6 +8,7 @@ namespace OpenRa.Game.Traits
 		const float proneDamage = .5f;
 		const float proneSpeed = .5f;
 
+		[Sync]
 		int remainingProneTime = 0;
 
 		public bool IsProne { get { return remainingProneTime > 0; } }

OpenRa.Game/Traits/TraitsInterfaces.cs

@@ -13,15 +13,15 @@ namespace OpenRa.Game.Traits
 
 	interface ITick { void Tick(Actor self); }
 	interface IRender { IEnumerable<Renderable> Render(Actor self); }
+	interface IIssueOrder { Order IssueOrder( Actor self, int2 xy, MouseInput mi, Actor underCursor ); }
+	interface IResolveOrder { void ResolveOrder( Actor self, Order order ); }
+
 	interface INotifySold { void Sold(Actor self); }
 	interface INotifyDamage { void Damaged(Actor self, AttackInfo e); }
 	interface INotifyBuildComplete { void BuildingComplete (Actor self); }
 	interface INotifyProduction { void UnitProduced(Actor self, Actor other); }
 	interface IAcceptThief { void OnSteal(Actor self, Actor thief); }
 
-	interface IIssueOrder { Order IssueOrder(Actor self, int2 xy, MouseInput mi, Actor underCursor); }
-	interface IResolveOrder { void ResolveOrder(Actor self, Order order); }
-	
 	interface IProducer
 	{
 		bool Produce( Actor self, UnitInfo producee );

OpenRa.Game/Traits/Turreted.cs

@@ -3,6 +3,7 @@ namespace OpenRa.Game.Traits
 {
 	class Turreted : ITick
 	{
+		[Sync]
 		public int turretFacing = 0;
 		public int? desiredFacing;
 

OpenRa.Game/Traits/Unit.cs

@@ -3,7 +3,9 @@ namespace OpenRa.Game.Traits
 {
 	class Unit : INotifyDamage
 	{
+		[Sync]
 		public int Facing;
+		[Sync]
 		public int Altitude;
 
 		public Unit( Actor self ) { }

OpenRa.Game/World.cs

@@ -52,5 +52,14 @@ namespace OpenRa.Game
 		{
 			return nextAID++;
 		}
+
+		public int SyncHash()
+		{
+			int ret = 0;
+			foreach( var a in Actors )
+				ret += (int)a.ActorID * Sync.CalculateSyncHash( a );
+
+			return ret;
+		}
 	}
 }