Pathfind cancellation support.

vnavmesh/Debug/DebugNavmeshManager.cs

@@ -56,6 +56,7 @@ public void Draw()
         }
         ImGui.SameLine();
         ImGui.TextUnformatted(_manager.CurrentKey);
+        ImGui.TextUnformatted($"Num pathfinding tasks: {(_manager.PathfindInProgress ? 1 : 0)} in progress, {_manager.NumQueuedPathfindRequests} queued");
 
         if (_manager.Navmesh == null || _manager.Query == null)
             return;

vnavmesh/IPCProvider.cs

@@ -2,6 +2,7 @@
 using System;
 using System.Collections.Generic;
 using System.Numerics;
+using System.Threading;
 
 namespace Navmesh
 {
@@ -16,6 +17,9 @@ public IPCProvider(NavmeshManager navmeshManager, FollowPath followPath, AsyncMo
             RegisterFunc("Nav.Reload", () => navmeshManager.Reload(true));
             RegisterFunc("Nav.Rebuild", () => navmeshManager.Reload(false));
             RegisterFunc("Nav.Pathfind", (Vector3 from, Vector3 to, bool fly) => navmeshManager.QueryPath(from, to, fly));
+            RegisterFunc("Nav.PathfindCancelable", (Vector3 from, Vector3 to, bool fly, CancellationToken cancel) => navmeshManager.QueryPath(from, to, fly, cancel));
+            RegisterFunc("Nav.PathfindInProgress", () => navmeshManager.PathfindInProgress);
+            RegisterFunc("Nav.PathfindNumQueued", () => navmeshManager.NumQueuedPathfindRequests);
             RegisterFunc("Nav.IsAutoLoad", () => navmeshManager.AutoLoad);
             RegisterAction("Nav.SetAutoLoad", (bool v) => navmeshManager.AutoLoad = v);
 
@@ -77,6 +81,13 @@ private void RegisterFunc<TRet, T1, T2, T3>(string name, Func<T1, T2, T3, TRet>
             _disposeActions.Add(p.UnregisterFunc);
         }
 
+        private void RegisterFunc<TRet, T1, T2, T3, T4>(string name, Func<T1, T2, T3, T4, TRet> func)
+        {
+            var p = Service.PluginInterface.GetIpcProvider<T1, T2, T3, T4, TRet>("vnavmesh." + name);
+            p.RegisterFunc(func);
+            _disposeActions.Add(p.UnregisterFunc);
+        }
+
         private void RegisterAction(string name, Action func)
         {
             var p = Service.PluginInterface.GetIpcProvider<object>("vnavmesh." + name);

vnavmesh/NavmeshManager.cs

@@ -20,6 +20,8 @@ public class NavmeshManager : IDisposable
     public NavmeshQuery? Query => _query;
     public float LoadTaskProgress => _loadTask != null ? _loadTaskProgress : -1; // returns negative value if task is not running
     public string CurrentKey => _lastKey;
+    public bool PathfindInProgress => _currentPathfindTask != null;
+    public int NumQueuedPathfindRequests => _queuedPathfindTasks.Count;
 
     private DirectoryInfo _cacheDir;
     private NavmeshSettings _settings = new();
@@ -29,6 +31,8 @@ public class NavmeshManager : IDisposable
     private Navmesh? _navmesh;
     private NavmeshQuery? _query;
     private CancellationTokenSource? _queryCancelSource;
+    private List<Task<List<Vector3>>> _queuedPathfindTasks = new(); // will be executed one by one in order after current task completes
+    private Task<List<Vector3>>? _currentPathfindTask;
 
     public NavmeshManager(DirectoryInfo cacheDir)
     {
@@ -53,7 +57,7 @@ public void Update()
         if (_loadTask != null)
         {
             if (!_loadTask.IsCompleted)
-                return; // async task is still in progress, do nothing; note that we don't want to start multiple concurrent tasks on rapid transitions
+                return; // async mesh load task is still in progress, do nothing; note that we don't want to start multiple concurrent tasks on rapid transitions
 
             Service.Log.Information($"Finishing transition to '{_lastKey}'");
             try
@@ -72,19 +76,38 @@ public void Update()
         }
 
         var curKey = GetCurrentKey();
-        if (curKey == _lastKey)
-            return; // everything up-to-date
-
-        if (!AutoLoad)
+        if (curKey != _lastKey)
         {
-            if (_lastKey.Length == 0)
-                return; // nothing is loaded, and auto-load is forbidden
-            curKey = ""; // just unload existing mesh
+            // navmesh needs to be reloaded
+            if (!AutoLoad)
+            {
+                if (_lastKey.Length == 0)
+                    return; // nothing is loaded, and auto-load is forbidden
+                curKey = ""; // just unload existing mesh
+            }
+
+            Service.Log.Info($"Starting transition from '{_lastKey}' to '{curKey}'");
+            _lastKey = curKey;
+            Reload(true);
+            return; // mesh load is now in progress
         }
 
-        Service.Log.Info($"Starting transition from '{_lastKey}' to '{curKey}'");
-        _lastKey = curKey;
-        Reload(true);
+        // at this point, we're not loading a mesh
+        if (_query != null)
+        {
+            if (_currentPathfindTask != null && _currentPathfindTask.IsCompleted)
+            {
+                _currentPathfindTask = null;
+            }
+
+            if (_currentPathfindTask == null && _queuedPathfindTasks.Count > 0)
+            {
+                // kick off new pathfind task
+                _currentPathfindTask = _queuedPathfindTasks[0];
+                _queuedPathfindTasks.RemoveAt(0);
+                _currentPathfindTask.Start();
+            }
+        }
     }
 
     public bool Reload(bool allowLoadFromCache)
@@ -107,7 +130,7 @@ public bool Reload(bool allowLoadFromCache)
         return true;
     }
 
-    public Task<List<Vector3>>? QueryPath(Vector3 from, Vector3 to, bool flying)
+    public Task<List<Vector3>>? QueryPath(Vector3 from, Vector3 to, bool flying, CancellationToken externalCancel = default)
     {
         var query = _query;
         if (_queryCancelSource == null || query == null)
@@ -116,12 +139,15 @@ public bool Reload(bool allowLoadFromCache)
             return null;
         }
 
-        var token = _queryCancelSource.Token;
-        var task = Task.Run(() =>
+        // task can be cancelled either by internal request (i.e. when navmesh is reloaded) or external
+        var combined = CancellationTokenSource.CreateLinkedTokenSource(_queryCancelSource.Token, externalCancel);
+        var task = new Task<List<Vector3>>(() =>
         {
-            token.ThrowIfCancellationRequested();
-            return flying ? query.PathfindVolume(from, to, UseRaycasts, UseStringPulling, token) : query.PathfindMesh(from, to, UseRaycasts, UseStringPulling, token);
+            using var autoDisposeCombined = combined;
+            combined.Token.ThrowIfCancellationRequested();
+            return flying ? query.PathfindVolume(from, to, UseRaycasts, UseStringPulling, combined.Token) : query.PathfindMesh(from, to, UseRaycasts, UseStringPulling, combined.Token);
         });
+        _queuedPathfindTasks.Add(task);
         return task;
     }
 
@@ -154,8 +180,10 @@ private unsafe string GetCacheKey(SceneDefinition scene)
     private void ClearState()
     {
         _queryCancelSource?.Cancel();
-        //_queryCancelSource?.Dispose(); - i don't think it's safe to call dispose at this point...
+        _queryCancelSource?.Dispose();
         _queryCancelSource = null;
+        _queuedPathfindTasks.Clear();
+        _currentPathfindTask = null;
 
         OnNavmeshChanged?.Invoke(null, null);
         _query = null;