Discourage harvesters from wandering too far from the refinery.

OpenRA.Mods.Common/Activities/FindAndDeliverResources.cs

@@ -175,7 +175,8 @@ public override bool Tick(Actor self)
 			}
 
 			// Determine where to search from and how far to search:
-			var searchFromLoc = lastHarvestedCell ?? GetSearchFromProcLocation(self);
+			var procLoc = GetSearchFromProcLocation(self);
+			var searchFromLoc = lastHarvestedCell ?? procLoc;
 			var searchRadius = lastHarvestedCell.HasValue ? harvInfo.SearchFromHarvesterRadius : harvInfo.SearchFromProcRadius;
 			if (!searchFromLoc.HasValue)
 			{
@@ -184,6 +185,7 @@ public override bool Tick(Actor self)
 			}
 
 			var searchRadiusSquared = searchRadius * searchRadius;
+			var goalLoc = procLoc ?? lastHarvestedCell ?? self.Location;
 
 			// Find any harvestable resources:
 			List<CPos> path;
@@ -194,6 +196,10 @@ public override bool Tick(Actor self)
 					if ((loc - searchFromLoc.Value).LengthSquared > searchRadiusSquared)
 						return int.MaxValue;
 
+					// Prefer cells that are closer to the goal location (usually the refinery)
+					if (harv.CanHarvestCell(self, loc))
+						return (goalLoc - loc).Length;
+
 					return 0;
 				})
 				.FromPoint(searchFromLoc.Value)