Improve enter scene detection, fix backwards walking players

HKMP/Game/Client/ClientManager.cs

@@ -155,11 +155,6 @@ public string Username {
     /// </summary>
     private Vector3 _lastScale;
 
-    /// <summary>
-    /// Whether the scene has just changed and we are in a scene change.
-    /// </summary>
-    private bool _sceneChanged;
-
     /// <summary>
     /// Whether we have already determined whether we are scene host or not for the entity system.
     /// </summary>
@@ -193,6 +188,9 @@ ModSettings modSettings
         new GamePatcher(netClient).RegisterHooks();
         new FsmPatcher().RegisterHooks();
 
+        var customHooks = new CustomHooks();
+        customHooks.Initialize();
+
         _commandManager = new ClientCommandManager();
         var eventAggregator = new EventAggregator();
 
@@ -259,6 +257,8 @@ ModSettings modSettings
         On.HeroController.Start += OnHeroControllerStart;
         On.HeroController.Update += OnPlayerUpdate;
 
+        customHooks.AfterEnterSceneHeroTransformed += OnEnterScene;
+
         // Register client connect and timeout handler
         netClient.ConnectEvent += OnClientConnect;
         netClient.TimeoutEvent += OnTimeout;
@@ -871,8 +871,6 @@ private void OnSceneChange(Scene oldScene, Scene newScene) {
             return;
         }
 
-        _sceneChanged = true;
-
         // Reset the status of whether we determined the scene host or not
         _sceneHostDetermined = false;
 
@@ -910,38 +908,7 @@ private void OnPlayerUpdate(On.HeroController.orig_Update orig, HeroController s
             // Update the last position, since it changed
             _lastPosition = newPosition;
 
-            if (_sceneChanged) {
-                _sceneChanged = false;
-
-                // Set some default values for the packet variables in case we don't have a HeroController instance
-                // This might happen when we are in a non-gameplay scene without the knight
-                var position = Vector2.Zero;
-                var scale = Vector3.zero;
-                ushort animationClipId = 0;
-
-                // If we do have a HeroController instance, use its values
-                if (HeroController.instance != null) {
-                    var transform = HeroController.instance.transform;
-                    var transformPos = transform.position;
-
-                    position = new Vector2(transformPos.x, transformPos.y);
-                    scale = transform.localScale;
-                    animationClipId = (ushort) AnimationManager.GetCurrentAnimationClip();
-                }
-
-                Logger.Debug("Sending EnterScene packet");
-
-                _netClient.UpdateManager.SetEnterSceneData(
-                    SceneUtil.GetCurrentSceneName(),
-                    position,
-                    scale.x > 0,
-                    animationClipId
-                );
-            } else {
-                // If this was not the first position update after a scene change,
-                // we can simply send a position update packet
-                _netClient.UpdateManager.UpdatePlayerPosition(new Vector2(newPosition.x, newPosition.y));
-            }
+            _netClient.UpdateManager.UpdatePlayerPosition(new Vector2(newPosition.x, newPosition.y));
         }
 
         var newScale = heroTransform.localScale;
@@ -954,6 +921,36 @@ private void OnPlayerUpdate(On.HeroController.orig_Update orig, HeroController s
         }
     }
 
+    /// <summary>
+    /// Callback method for the local player enters a scene. Used to network to the server that a scene is entered.
+    /// </summary>
+    private void OnEnterScene() {
+        // Set some default values for the packet variables in case we don't have a HeroController instance
+        // This might happen when we are in a non-gameplay scene without the knight
+        var position = Vector2.Zero;
+        var scale = Vector3.zero;
+        ushort animationClipId = 0;
+
+        // If we do have a HeroController instance, use its values
+        if (HeroController.instance != null) {
+            var transform = HeroController.instance.transform;
+            var transformPos = transform.position;
+
+            position = new Vector2(transformPos.x, transformPos.y);
+            scale = transform.localScale;
+            animationClipId = (ushort) AnimationManager.GetCurrentAnimationClip();
+        }
+
+        Logger.Debug($"Sending EnterScene packet");
+
+        _netClient.UpdateManager.SetEnterSceneData(
+            SceneUtil.GetCurrentSceneName(),
+            position,
+            scale.x > 0,
+            animationClipId
+        );
+    }
+
     /// <summary>
     /// Callback method for when a chat message is received.
     /// </summary>

HKMP/Game/Client/CustomHooks.cs

@@ -0,0 +1,160 @@
+using System;
+using System.Reflection;
+using Hkmp.Logging;
+using Mono.Cecil.Cil;
+using MonoMod.Cil;
+using MonoMod.RuntimeDetour;
+
+namespace Hkmp.Game.Client;
+
+// TODO: create method for de-registering the hooks
+/// <summary>
+/// Class that manages and exposes custom hooks that are not possible with On hooks or ModHooks. Uses IL modification
+/// to embed event calls in certain methods.
+/// </summary>
+public class CustomHooks {
+    /// <summary>
+    /// The binding flags for obtaining certain types for hooking.
+    /// </summary>
+    private const BindingFlags BindingFlags = System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance;
+
+    /// <summary>
+    /// The instruction match set for matching the instructions below. This is the call to HeroInPosition.Invoke.
+    /// </summary>
+    // IL_01ae: ldloc.1      // V_1
+    // IL_01af: ldfld        class HeroController/HeroInPosition HeroController::heroInPosition
+    // IL_01b4: ldc.i4.0
+    // IL_01b5: callvirt     instance void HeroController/HeroInPosition::Invoke(bool)
+    private static readonly Func<Instruction, bool>[] HeroInPositionInstructions = [
+        i => i.MatchLdfld(typeof(HeroController), "heroInPosition"),
+        i => i.MatchLdcI4(out _),
+        i => i.MatchCallvirt(typeof(HeroController.HeroInPosition), "Invoke")
+    ];
+
+    /// <summary>
+    /// IL Hook instance for the HeroController EnterScene hook.
+    /// </summary>
+    private ILHook _heroControllerEnterSceneIlHook;
+    /// <summary>
+    /// IL Hook instance for the HeroController Respawn hook.
+    /// </summary>
+    private ILHook _heroControllerRespawnIlHook;
+
+    /// <summary>
+    /// Event for when the player object is done being transformed (changed position, scale) after entering a scene.
+    /// </summary>
+    public event Action AfterEnterSceneHeroTransformed;
+
+    /// <summary>
+    /// Initialize the class by registering the IL hooks.
+    /// </summary>
+    public void Initialize() {
+        IL.HeroController.Start += HeroControllerOnStart;
+        IL.HeroController.EnterSceneDreamGate += HeroControllerOnEnterSceneDreamGate;
+
+        var type = typeof(HeroController).GetNestedType("<EnterScene>d__469", BindingFlags);
+        _heroControllerEnterSceneIlHook = new ILHook(type.GetMethod("MoveNext", BindingFlags), HeroControllerOnEnterScene);
+
+        type = typeof(HeroController).GetNestedType("<Respawn>d__473", BindingFlags);
+        _heroControllerRespawnIlHook = new ILHook(type.GetMethod("MoveNext", BindingFlags), HeroControllerOnRespawn);
+    }
+
+    /// <summary>
+    /// IL Hook for the HeroController Start method. Calls an event within the method.
+    /// </summary>
+    private void HeroControllerOnStart(ILContext il) {
+        try {
+            // Create a cursor for this context
+            var c = new ILCursor(il);
+
+            EmitAfterEnterSceneEventHeroInPosition(c);
+        } catch (Exception e) {
+            Logger.Error($"Could not change HeroControllerOnStart IL: \n{e}");
+        }
+    }
+
+    /// <summary>
+    /// IL Hook for the HeroController EnterSceneDreamGate method. Calls an event within the method.
+    /// </summary>
+    private void HeroControllerOnEnterSceneDreamGate(ILContext il) {
+        try {
+            // Create a cursor for this context
+            var c = new ILCursor(il);
+
+            EmitAfterEnterSceneEventHeroInPosition(c);
+        } catch (Exception e) {
+            Logger.Error($"Could not change HeroControllerOnEnterSceneDreamGate IL: \n{e}");
+        }
+    }
+
+    /// <summary>
+    /// IL Hook for the HeroController EnterScene method. Calls an event multiple times within the method.
+    /// </summary>
+    private void HeroControllerOnEnterScene(ILContext il) {
+        try {
+            // Create a cursor for this context
+            var c = new ILCursor(il);
+
+            for (var i = 0; i < 2; i++) {
+                EmitAfterEnterSceneEventHeroInPosition(c);
+            }
+
+            // IL_0634: ldloc.1      // V_1
+            // IL_0635: callvirt     instance void HeroController::FaceRight()
+            Func<Instruction, bool>[] faceDirectionInstructions = [
+                i => i.MatchLdloc(1),
+                i => 
+                    i.MatchCallvirt(typeof(HeroController), "FaceRight") || 
+                    i.MatchCallvirt(typeof(HeroController), "FaceLeft")
+            ];
+
+            for (var i = 0; i < 2; i++) {
+                c.GotoNext(
+                    MoveType.After,
+                    HeroInPositionInstructions
+                );
+
+                c.GotoNext(
+                    MoveType.After,
+                    faceDirectionInstructions
+                );
+
+                c.EmitDelegate(() => { AfterEnterSceneHeroTransformed?.Invoke(); });
+            }
+
+            EmitAfterEnterSceneEventHeroInPosition(c);
+        } catch (Exception e) {
+            Logger.Error($"Could not change HeroController#EnterScene IL: \n{e}");
+        }
+    }
+
+    /// <summary>
+    /// IL Hook for the HeroController Respawn method. Calls an event multiple times within the method.
+    /// </summary>
+    private void HeroControllerOnRespawn(ILContext il) {
+        try {
+            // Create a cursor for this context
+            var c = new ILCursor(il);
+
+            for (var i = 0; i < 2; i++) {
+                EmitAfterEnterSceneEventHeroInPosition(c);
+            }
+        } catch (Exception e) {
+            Logger.Error($"Could not change HeroControllerOnRespawn IL: \n{e}");
+        }
+    }
+
+    /// <summary>
+    /// Emit the delegate for calling the <see cref="AfterEnterSceneHeroTransformed"/> event after the
+    /// 'HeroInPosition' instructions.
+    /// </summary>
+    /// <param name="c">The IL cursor on which to match the instructions and emit the delegate.</param>
+    private void EmitAfterEnterSceneEventHeroInPosition(ILCursor c) {
+        c.GotoNext(
+            MoveType.After,
+            HeroInPositionInstructions
+        );
+
+        c.EmitDelegate(() => { AfterEnterSceneHeroTransformed?.Invoke(); });
+    }
+}

HKMP/Game/Client/Save/SaveManager.cs

@@ -156,6 +156,10 @@ private void OnUpdatePlayerData() {
         }
 
         var gm = global::GameManager.instance;
+        if (gm == null) {
+            return;
+        }
+
         if (gm.gameState == GameState.MAIN_MENU) {
             return;
         }