Ensure frozen actors are rendered on the first tick they become visible.

The previous lazy rendering means the snapshot of the render state might be more up to date then when the frozen actor actually did become visible. Now, we take this snapshot as soon as needed. We still retain the performance of only doing this rendering when needed by avoiding extra rendering until the visibility cycles again.

OpenRA.Mods.Common/Traits/Modifiers/FrozenUnderFog.cs

@@ -27,7 +27,7 @@ namespace OpenRA.Mods.Common.Traits
 		public object Create(ActorInitializer init) { return new FrozenUnderFog(init, this); }
 	}
 
-	public class FrozenUnderFog : IRenderModifier, IDefaultVisibility, ITick, ISync
+	public class FrozenUnderFog : IRenderModifier, IDefaultVisibility, ITick, ITickRender, ISync
 	{
 		[Sync] public int VisibilityHash;
 
@@ -41,6 +41,7 @@ namespace OpenRA.Mods.Common.Traits
 		ITooltip tooltip;
 		Health health;
 		bool initialized;
+		bool isRendering;
 
 		class FrozenState
 		{
@@ -143,11 +144,35 @@ namespace OpenRA.Mods.Common.Traits
 			initialized = true;
 		}
 
+		public void TickRender(WorldRenderer wr, Actor self)
+		{
+			if (!initialized)
+				return;
+
+			IRenderable[] renderables = null;
+			foreach (var player in self.World.Players)
+			{
+				var frozen = stateByPlayer[player].FrozenActor;
+				if (!frozen.NeedRenderables)
+					continue;
+
+				if (renderables == null)
+				{
+					isRendering = true;
+					renderables = self.Render(wr).ToArray();
+					isRendering = false;
+				}
+
+				frozen.NeedRenderables = false;
+				frozen.Renderables = renderables;
+			}
+		}
+
 		public IEnumerable<IRenderable> ModifyRender(Actor self, WorldRenderer wr, IEnumerable<IRenderable> r)
 		{
 			return
 				IsVisible(self, self.World.RenderPlayer) ||
-				(initialized && stateByPlayer[self.World.RenderPlayer].FrozenActor.IsRendering) ?
+				(initialized && isRendering) ?
 				r : SpriteRenderable.None;
 		}
 	}