split various flying behaviors into own files

OpenRa.Game/Traits/Activities/FlyTimed.cs

@@ -0,0 +1,36 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace OpenRa.Game.Traits.Activities
+{
+	class FlyTimed : IActivity
+	{
+		public IActivity NextActivity { get; set; }
+		int remainingTicks;
+		int targetAltitude;
+
+		public FlyTimed(int ticks, int targetAltitude) { remainingTicks = ticks; this.targetAltitude = targetAltitude; }
+
+		public IActivity Tick(Actor self)
+		{
+			if (remainingTicks == 0)
+				return NextActivity;
+
+			--remainingTicks;
+
+			var unit = self.traits.Get<Unit>();
+			var speed = .2f * Util.GetEffectiveSpeed(self);
+			var angle = unit.Facing / 128f * Math.PI;
+
+			self.CenterLocation += speed * -float2.FromAngle((float)angle);
+			self.Location = ((1 / 24f) * self.CenterLocation).ToInt2();
+
+			unit.Altitude += Math.Sign(targetAltitude - unit.Altitude);
+			return this;
+		}
+
+		public void Cancel(Actor self) { remainingTicks = 0; NextActivity = null; }
+	}
+}