Support a maximum building range (Fixes #2156).

This also implements support for a per-provider
cooldown between placing structures, allowing mods
with multiple structure queues to rate-limit
placement around a single provider.

An initial delay parameter is included to
support units that deploy into a base provider and
require an initial setup time (e.g. the Surveyor
unit from C&C TW).

The range and time restrictions are not applied to
walls as a balance choice.

OpenRA.Mods.RA/Buildings/BaseProvider.cs

@@ -0,0 +1,88 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2011 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;
+using System.Drawing;
+using OpenRA.Graphics;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.RA.Buildings
+{
+	public class BaseProviderInfo : ITraitInfo
+	{
+		public readonly float Range = 10;
+		public readonly int Cooldown = 0;
+		public readonly int InitialDelay = 0;
+
+		public object Create(ActorInitializer init) { return new BaseProvider(init.self, this); }
+	}
+
+	public class BaseProvider : ITick, IPreRenderSelection, ISelectionBar
+	{
+		public readonly BaseProviderInfo Info;
+		DeveloperMode devMode;
+		Actor self;
+		int total;
+		int progress;
+
+		public BaseProvider(Actor self, BaseProviderInfo info)
+		{
+			Info = info;
+			this.self = self;
+			devMode = self.Owner.PlayerActor.Trait<DeveloperMode>();
+			progress = total = info.InitialDelay;
+		}
+
+		public void Tick(Actor self)
+		{
+			if (progress > 0)
+				progress--;
+		}
+
+		public void BeginCooldown()
+		{
+			progress = total = Info.Cooldown;
+		}
+
+		public bool Ready()
+		{
+			return devMode.FastBuild || progress == 0;
+		}
+
+		// Range circle
+		public void RenderBeforeWorld(WorldRenderer wr, Actor self)
+		{
+			// Visible to player and allies
+			if (self.World.RenderedPlayer != null && self.Owner.Stances[self.World.RenderedPlayer] != Stance.Ally)
+				return;
+
+			wr.DrawRangeCircleWithContrast(
+				Color.FromArgb(128, Ready() ? Color.White : Color.Red),
+				self.CenterLocation.ToFloat2(), Info.Range,
+				Color.FromArgb(96, Color.Black), 1);
+		}
+
+		// Selection bar
+		public float GetValue()
+		{
+			// Visible to player and allies
+			if (self.World.RenderedPlayer != null && self.Owner.Stances[self.World.RenderedPlayer] != Stance.Ally)
+				return 0f;
+
+			// Ready or delay disabled
+			if (progress == 0 || total == 0 || devMode.FastBuild)
+				return 0f;
+
+			return (float)progress / total;
+		}
+
+		public Color GetColor() { return Color.Purple; }
+	}
+}

OpenRA.Mods.RA/Buildings/Building.cs

@@ -31,17 +31,40 @@ namespace OpenRA.Mods.RA.Buildings
 		[Desc("x means space it blocks, _ is a part that is passable by actors.")]
 		public readonly string Footprint = "x";
 		public readonly int2 Dimensions = new int2(1, 1);
+		public readonly bool RequiresBaseProvider = false;
 
 		public readonly string[] BuildSounds = {"placbldg.aud", "build5.aud"};
 		public readonly string[] SellSounds = {"cashturn.aud"};
 
 		public object Create(ActorInitializer init) { return new Building(init, this); }
 
+		public PPos CenterLocation(CPos topLeft)
+		{
+			return (PPos)((2 * topLeft.ToInt2() + Dimensions) * Game.CellSize / 2);
+		}
+
+		bool HasBaseProvider(World world, Player p, CPos topLeft)
+		{
+			var center = CenterLocation(topLeft);
+			foreach (var bp in world.ActorsWithTrait<BaseProvider>())
+			{
+				if (bp.Actor.Owner.Stances[p] != Stance.Ally || !bp.Trait.Ready())
+					continue;
+
+				if (Combat.IsInRange(center, bp.Trait.Info.Range, bp.Actor.CenterLocation))
+					return true;
+			}
+			return false;
+		}
+
 		public bool IsCloseEnoughToBase(World world, Player p, string buildingName, CPos topLeft)
 		{
 			if (p.PlayerActor.Trait<DeveloperMode>().BuildAnywhere)
 				return true;
 
+			if (RequiresBaseProvider && !HasBaseProvider(world, p, topLeft))
+				return false;
+
 			var buildingMaxBounds = (CVec)Dimensions;
 			if (Rules.Info[buildingName].Traits.Contains<BibInfo>())
 				buildingMaxBounds += new CVec(0, 1);
@@ -103,7 +126,7 @@ namespace OpenRA.Mods.RA.Buildings
 
 			occupiedCells = FootprintUtils.UnpathableTiles( self.Info.Name, Info, TopLeft )
 				.Select(c => Pair.New(c, SubCell.FullCell)).ToArray();
-			pxPosition = (PPos) (( 2 * topLeft.ToInt2() + Info.Dimensions ) * Game.CellSize / 2);
+			pxPosition = Info.CenterLocation(topLeft);
 		}
 
 		public int GetPowerUsage()