Initial commit: OpenRA game engine

Fork from OpenRA/OpenRA with one-click launch script (start-ra.cmd)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

OpenRA.Mods.Common/Activities/Air/FlyFollow.cs

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+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * 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, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.Collections.Generic;
+using OpenRA.Activities;
+using OpenRA.Mods.Common.Traits;
+using OpenRA.Primitives;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.Common.Activities
+{
+	public class FlyFollow : Activity
+	{
+		readonly Aircraft aircraft;
+		readonly WDist minRange;
+		readonly WDist maxRange;
+		readonly Color? targetLineColor;
+		Target target;
+		Target lastVisibleTarget;
+		bool useLastVisibleTarget;
+		bool wasMovingWithinRange;
+
+		public FlyFollow(Actor self, in Target target, WDist minRange, WDist maxRange,
+			WPos? initialTargetPosition, Color? targetLineColor = null)
+		{
+			this.target = target;
+			aircraft = self.Trait<Aircraft>();
+			this.minRange = minRange;
+			this.maxRange = maxRange;
+			this.targetLineColor = targetLineColor;
+
+			// The target may become hidden between the initial order request and the first tick (e.g. if queued)
+			// Moving to any position (even if quite stale) is still better than immediately giving up
+			if ((target.Type == TargetType.Actor && target.Actor.CanBeViewedByPlayer(self.Owner))
+				|| target.Type == TargetType.FrozenActor || target.Type == TargetType.Terrain)
+				lastVisibleTarget = Target.FromPos(target.CenterPosition);
+			else if (initialTargetPosition.HasValue)
+				lastVisibleTarget = Target.FromPos(initialTargetPosition.Value);
+		}
+
+		public override bool Tick(Actor self)
+		{
+			// Refuse to take off if it would land immediately again.
+			if (aircraft.ForceLanding)
+				Cancel(self);
+
+			if (IsCanceling)
+				return true;
+
+			target = target.Recalculate(self.Owner, out var targetIsHiddenActor);
+			if (!targetIsHiddenActor && target.Type == TargetType.Actor)
+				lastVisibleTarget = Target.FromTargetPositions(target);
+
+			useLastVisibleTarget = targetIsHiddenActor || !target.IsValidFor(self);
+
+			// If we are ticking again after previously sequencing a MoveWithRange then that move must have completed
+			// Either we are in range and can see the target, or we've lost track of it and should give up
+			if (wasMovingWithinRange && targetIsHiddenActor)
+				return true;
+
+			wasMovingWithinRange = false;
+
+			// Target is hidden or dead, and we don't have a fallback position to move towards
+			if (useLastVisibleTarget && !lastVisibleTarget.IsValidFor(self))
+				return true;
+
+			var pos = self.CenterPosition;
+			var checkTarget = useLastVisibleTarget ? lastVisibleTarget : target;
+
+			// We've reached the required range - if the target is visible and valid then we wait
+			// otherwise if it is hidden or dead we give up
+			if (checkTarget.IsInRange(pos, maxRange) && !checkTarget.IsInRange(pos, minRange))
+			{
+				if (!aircraft.Info.CanHover)
+					Fly.FlyTick(self, aircraft, aircraft.Facing, aircraft.Info.CruiseAltitude);
+
+				return useLastVisibleTarget;
+			}
+
+			wasMovingWithinRange = true;
+			QueueChild(aircraft.MoveWithinRange(target, minRange, maxRange, checkTarget.CenterPosition, targetLineColor));
+			return false;
+		}
+
+		public override IEnumerable<TargetLineNode> TargetLineNodes(Actor self)
+		{
+			if (targetLineColor != null)
+				yield return new TargetLineNode(useLastVisibleTarget ? lastVisibleTarget : target, targetLineColor.Value);
+		}
+	}
+}