Fix OpenPerpetuum/PerpetuumServer#342

src/Perpetuum/Zones/Movements/WaypointMovement.cs

@@ -24,9 +24,22 @@ public override void Start(Unit unit)
             unit.Direction = unit.CurrentPosition.DirectionTo(_target);
             unit.CurrentSpeed = 1.0;
 
-            _velocity = Vector2.Subtract(_target,unit.CurrentPosition.ToVector2());
-            _distance = Vector2.Abs(_velocity);
-            _velocity = Vector2.Normalize(_velocity);
+            // Vector to destination
+            var path = Vector2.Subtract(_target, unit.CurrentPosition.ToVector2());
+            // The absolute path along each coordinate
+            _distance = Vector2.Abs(path);
+            if (path.Length().IsApproximatelyEqual(0.0f))
+            {
+                // If the path is zero, then is already at the destination
+                Arrived = true;
+                // Velocity vector in the direction of the unit.
+                _velocity = MathHelper.DirectionToVector(unit.Direction);
+            }
+            else
+            {
+                // Velocity vector in the direction of the path.
+                _velocity = Vector2.Normalize(path);
+            }
 
             base.Start(unit);
         }

src/Perpetuum/Zones/NpcSystem/AI/CombatAI.cs

@@ -24,6 +24,8 @@ public class CombatAI : BaseAI
         private const int UpdateFrequency = 1650;
         private const int Sqrt2 = 141;
         private const int Weight = 1000;
+        // Timer for periodically checking the main hostile target.
+        private readonly IntervalTimer updateHostileTimer = new IntervalTimer(UpdateFrequency, true);
         private readonly IntervalTimer processHostilesTimer = new IntervalTimer(UpdateFrequency);
         private readonly IntervalTimer primarySelectTimer = new IntervalTimer(UpdateFrequency);
         private List<ModuleActivator> moduleActivators;
@@ -261,7 +263,17 @@ protected void UpdateHostile(TimeSpan time, bool moveThreatToPseudoThreat = true
                 return;
             }
 
-            if (!mostHated.Unit.CurrentPosition.IsEqual2D(this.lastTargetPosition))
+            var forceCheckPrimary = false;
+            updateHostileTimer.Update(time);
+            if (updateHostileTimer.Passed)
+            {
+                updateHostileTimer.Reset();
+
+                // Forced check of the main hostile target.
+                forceCheckPrimary = movement?.Arrived ?? true;
+            }
+
+            if (!mostHated.Unit.CurrentPosition.IsEqual2D(this.lastTargetPosition) || forceCheckPrimary)
             {
                 this.lastTargetPosition = mostHated.Unit.CurrentPosition;
 
@@ -393,6 +405,8 @@ private List<Point> FindNewAttackPosition(Unit hostile, CancellationToken cancel
             var end = hostile.CurrentPosition.GetRandomPositionInRange2D(0, smartCreature.BestActionRange - 1).ToPoint();
 
             smartCreature.StopMoving();
+            // Nulling movement so that the unit does not resume it at zero speed if the path is not found.
+            movement = null;
 
             var maxNode = Math.Pow(smartCreature.HomeRange, 2) * Math.PI;
             var priorityQueue = new PriorityQueue<Node>((int)maxNode);