Core/Movement: Added new immediate movement generator that handles movement without delaying anything to next update tick (for use with instant "movement" like facing changes)

Author: Shauren

src/server/game/Entities/Unit/Unit.h

@@ -1918,7 +1918,7 @@ class TC_GAME_API Unit : public WorldObject
         virtual void AtDisengage() {}
 
     private:
-
+        friend class ImmediateMovementGenerator; // for UpdateSplineMovement
         void UpdateSplineMovement(uint32 t_diff);
         void UpdateSplinePosition();
         void InterruptMovementBasedAuras();

src/server/game/Movement/MotionMaster.cpp

@@ -344,6 +344,15 @@ void MotionMaster::Add(MovementGenerator* movement, MovementSlot slot/* = MOTION
         return;
     }
 
+    if (movement->HasFlag(MOVEMENTGENERATOR_FLAG_IMMEDIATE) && movement->HasFlag(MOVEMENTGENERATOR_FLAG_INITIALIZATION_PENDING))
+    {
+        if (!movement->Initialize(_owner))
+        {
+            delete movement;
+            return;
+        }
+    }
+
     if (HasFlag(MOTIONMASTER_FLAG_DELAYED))
     {
         DelayedActionDefine action = [this, movement, slot]()
@@ -1189,7 +1198,7 @@ void MotionMaster::DirectAdd(MovementGenerator* movement, MovementSlot slot/* =
                 }
                 else
                 {
-                    auto itr = std::find_if(_generators.begin(), _generators.end(), [movement](MovementGenerator const* a) -> bool
+                    auto itr = std::ranges::find_if(_generators, [movement](MovementGenerator const* a) -> bool
                     {
                         return a->Priority == movement->Priority && a->Mode == movement->Mode;
                     });
@@ -1201,8 +1210,16 @@ void MotionMaster::DirectAdd(MovementGenerator* movement, MovementSlot slot/* =
             else
                 _defaultGenerator->Deactivate(_owner);
 
-            _generators.emplace(movement);
-            AddBaseUnitState(movement);
+            if (!movement->HasFlag(MOVEMENTGENERATOR_FLAG_IMMEDIATE))
+            {
+                _generators.emplace(movement);
+                AddBaseUnitState(movement);
+            }
+            else
+            {
+                movement->Finalize(_owner, true, true);
+                delete movement;
+            }
             break;
         default:
             break;

src/server/game/Movement/MovementGenerator.h

@@ -40,6 +40,7 @@ enum MovementGeneratorFlags : uint16
     MOVEMENTGENERATOR_FLAG_INFORM_ENABLED         = 0x080,
     MOVEMENTGENERATOR_FLAG_FINALIZED              = 0x100,
     MOVEMENTGENERATOR_FLAG_PERSIST_ON_DEATH       = 0x200,
+    MOVEMENTGENERATOR_FLAG_IMMEDIATE              = 0x400,
 
     MOVEMENTGENERATOR_FLAG_TRANSITORY = MOVEMENTGENERATOR_FLAG_SPEED_UPDATE_PENDING | MOVEMENTGENERATOR_FLAG_INTERRUPTED
 };

src/server/game/Movement/MovementGenerators/GenericMovementGenerator.cpp

@@ -91,3 +91,34 @@ void GenericMovementGenerator::MovementInform(Unit* owner)
             creature->AI()->MovementInform(_type, _pointId);
     }
 }
+
+ImmediateMovementGenerator::ImmediateMovementGenerator(std::function<void(Movement::MoveSplineInit& init)>&& initializer, MovementGeneratorType type, uint32 id)
+    : _splineInit(std::move(initializer)), _type(type), _pointId(id)
+{
+    Mode = MOTION_MODE_DEFAULT;
+    Priority = MOTION_PRIORITY_NORMAL;
+    Flags = MOVEMENTGENERATOR_FLAG_INITIALIZATION_PENDING | MOVEMENTGENERATOR_FLAG_IMMEDIATE;
+    BaseUnitState = 0;
+}
+
+bool ImmediateMovementGenerator::Initialize(Unit* owner)
+{
+    RemoveFlag(MOVEMENTGENERATOR_FLAG_INITIALIZATION_PENDING);
+    AddFlag(MOVEMENTGENERATOR_FLAG_INITIALIZED);
+
+    Movement::MoveSplineInit init(owner);
+    _splineInit(init);
+    int32 duration = init.Launch();
+    if (duration <= 0)
+        return false;
+
+    owner->UpdateSplineMovement(duration); // immediately consume the entire spline
+    return true;
+}
+
+void ImmediateMovementGenerator::Finalize(Unit* owner, bool /*active*/, bool /*movementInform*/)
+{
+    if (Creature* creature = owner->ToCreature())
+        if (creature->AI())
+            creature->AI()->MovementInform(_type, _pointId);
+}

src/server/game/Movement/MovementGenerators/GenericMovementGenerator.h

@@ -48,4 +48,23 @@ class GenericMovementGenerator : public MovementGenerator
         TimeTracker _duration;
 };
 
+class ImmediateMovementGenerator : public MovementGenerator
+{
+public:
+    explicit ImmediateMovementGenerator(std::function<void(Movement::MoveSplineInit& init)>&& initializer, MovementGeneratorType type, uint32 id);
+
+    bool Initialize(Unit* owner) override;
+
+    bool Reset(Unit* /*owner*/) override { return true; }
+    bool Update(Unit* /*owner*/, uint32 /*diff*/) override { return true; }
+    void Deactivate(Unit* /*owner*/) override { }
+    void Finalize(Unit* owner, bool active, bool movementInform) override;
+    MovementGeneratorType GetMovementGeneratorType() const override { return _type; }
+
+private:
+    std::function<void(Movement::MoveSplineInit& init)> _splineInit;
+    MovementGeneratorType _type;
+    uint32 _pointId;
+};
+
 #endif