Added WithMoveAnimation trait

RenderUnitFlying -> WithUnitBody + WithMoveAnimation upgrade rule

Make TD Orca use WithMoveAnimation
Remove RenderUnitFlying

OpenRA.Mods.Common/Traits/Render/WithMoveAnimation.cs

@@ -0,0 +1,54 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2015 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation. For more information,
+ * see COPYING.
+ */
+#endregion
+
+using System.Linq;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.Common.Traits
+{
+	public class WithMoveAnimationInfo : ITraitInfo, Requires<WithFacingSpriteBodyInfo>, Requires<IMoveInfo>
+	{
+		[Desc("Displayed while moving.")]
+		public readonly string MoveSequence = "move";
+
+		public object Create(ActorInitializer init) { return new WithMoveAnimation(init, this); }
+	}
+
+	public class WithMoveAnimation : ITick
+	{
+		readonly WithMoveAnimationInfo info;
+		readonly IMove movement;
+		readonly WithFacingSpriteBody wfsb;
+
+		WPos cachedPosition;
+
+		public WithMoveAnimation(ActorInitializer init, WithMoveAnimationInfo info)
+		{
+			this.info = info;
+			movement = init.Self.Trait<IMove>();
+			wfsb = init.Self.Trait<WithFacingSpriteBody>();
+
+			cachedPosition = init.Self.CenterPosition;
+		}
+
+		public void Tick(Actor self)
+		{
+			var oldCachedPosition = cachedPosition;
+			cachedPosition = self.CenterPosition;
+
+			// Flying units set IsMoving whenever they are airborne, which isn't enough for our purposes
+			var isMoving = movement.IsMoving && !self.IsDead && (oldCachedPosition - cachedPosition).HorizontalLengthSquared != 0;
+			if (isMoving ^ (wfsb.DefaultAnimation.CurrentSequence.Name != info.MoveSequence))
+				return;
+
+			wfsb.DefaultAnimation.ReplaceAnim(isMoving ? info.MoveSequence : wfsb.Info.Sequence);
+		}
+	}
+}