new heli movement

OpenRa.Game/Traits/Activities/HeliLand.cs

@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace OpenRa.Game.Traits.Activities
+{
+	class HeliLand : IActivity
+	{
+		public HeliLand(bool requireSpace) { this.requireSpace = requireSpace; }
+
+		bool requireSpace;
+		bool isCanceled;
+		public IActivity NextActivity { get; set; }
+
+		public IActivity Tick(Actor self)
+		{
+			if (isCanceled) return NextActivity;
+			var unit = self.traits.Get<Unit>();
+			if (unit.Altitude == 0)
+				return NextActivity;
+
+			if (requireSpace && !Game.IsCellBuildable(self.Location, UnitMovementType.Foot))
+				return this;	// fail to land if no space
+
+			--unit.Altitude;
+			return this;
+		}
+
+		public void Cancel(Actor self) { isCanceled = true; NextActivity = null; }
+	}
+}