Update LocationWatcher to try to address GC-collected delegate crash

Author: govert

Source/ExcelDna.IntelliSense/IntelliSenseServer.cs

@@ -30,7 +30,7 @@ namespace ExcelDna.IntelliSense
     // REMEMBER: COM events are not necessarily safe macro contexts.
     public static class IntelliSenseServer
     {
-        const string ServerVersion = "1.7.2";  // TODO: Define and manage this somewhere else
+        const string ServerVersion = "1.7.3";  // TODO: Define and manage this somewhere else
 
         // NOTE: Do not change these constants in custom versions. 
         //       They are part of the co-operative safety mechanism allowing different add-ins providing IntelliSense to work together safely.

Source/ExcelDna.IntelliSense/UIMonitor/WinEvents.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.ComponentModel;
 using System.Diagnostics;
 using System.Runtime.InteropServices;
@@ -63,7 +64,7 @@ public enum WinEvent : uint
             EVENT_OBJECT_DESTROY = 0x8001, // hwnd ID idChild is destroyed item
             EVENT_OBJECT_SHOW = 0x8002, // hwnd ID idChild is shown item
             EVENT_OBJECT_HIDE = 0x8003, // hwnd ID idChild is hidden item
-            EVENT_OBJECT_REORDER = 0x8004, // hwnd ID idChild is parent of zordering children
+            EVENT_OBJECT_REORDER = 0x8004, // hwnd ID idChild is parent of zordering children // NOTE: Gets fired constantly when an Excel function is selected in the function list
             EVENT_OBJECT_FOCUS = 0x8005, // hwnd ID idChild is focused item
             EVENT_OBJECT_SELECTION = 0x8006, // hwnd ID idChild is selected item (if only one), or idChild is OBJID_WINDOW if complex
             EVENT_OBJECT_SELECTIONADD = 0x8007, // hwnd ID idChild is item added
@@ -121,6 +122,8 @@ public enum WinEventObjectId : int
         readonly WinEvent _eventMin;
         readonly WinEvent _eventMax;
 
+        public Dictionary<WinEvent, Action<WinEvent>> DirectCallEvents = new Dictionary<WinEvent, Action<WinEvent>>();
+
         // Can be called on any thread, but installed by calling into the main thread, and will only start receiving events then
         public WinEventHook(WinEvent eventMin, WinEvent eventMax, SynchronizationContext syncContextAuto, SynchronizationContext syncContextMain, IntPtr hWndFilterOrZero)
         {
@@ -184,9 +187,16 @@ void UninstallWinEventHook(object _)
         void HandleWinEvent(IntPtr hWinEventHook, WinEvent eventType, IntPtr hWnd,
                             WinEventObjectId idObject, int idChild, uint dwEventThread, uint dwmsEventTime)
         {
-            // Debug.Print($"++++++++++++++ WinEvent Received: {eventType} on thread {Thread.CurrentThread.ManagedThreadId} from thread {dwEventThread} +++++++++++++++++++++++++++");
+            Debug.Print($"++++++++++++++ WinEvent Received: {eventType} on thread {Thread.CurrentThread.ManagedThreadId} from thread {dwEventThread} +++++++++++++++++++++++++++");
             try
             {
+                // Some events we want to handle immediately on the main thread, particularly for the move strat / end that we use for the on-demand hook
+                if (DirectCallEvents.TryGetValue(eventType, out var action))
+                {
+                    action(eventType);
+                    return;
+                }
+
                 if (_hWndFilterOrZero != IntPtr.Zero && hWnd != _hWndFilterOrZero)
                     return;
 

Source/ExcelDna.IntelliSense/UIMonitor/WindowLocationWatcher.cs

@@ -27,38 +27,71 @@ public class WindowLocationWatcher : IDisposable
         //       and then hook again upon encountering EVENT_SYSTEM_MOVESIZEEND (see UnhookFromLocationChangeUponDraggingExcelMainWindow).
         public WindowLocationWatcher(IntPtr hWnd, SynchronizationContext syncContextAuto, SynchronizationContext syncContextMain)
         {
+            Debug.Print("===========>>>>>>>>  WindowsLocationWatcher      <<<<<<<<<<<<===========");
+
             _hWnd = hWnd;
             _syncContextAuto = syncContextAuto;
             _syncContextMain = syncContextMain;
-            _windowMoveSizeHook = new WinEventHook(WinEventHook.WinEvent.EVENT_SYSTEM_MOVESIZESTART, WinEventHook.WinEvent.EVENT_SYSTEM_MOVESIZEEND, _syncContextAuto, syncContextMain, _hWnd);
-            _windowMoveSizeHook.WinEventReceived += _windowMoveSizeHook_WinEventReceived;
+
+            _syncContextMain.Post(_ => SetUpHooks(), null);
+        }
+
+        void SetUpHooks()
+        {
+            _windowMoveSizeHook = new WinEventHook(WinEventHook.WinEvent.EVENT_SYSTEM_MOVESIZESTART, WinEventHook.WinEvent.EVENT_SYSTEM_MOVESIZEEND, _syncContextAuto, _syncContextMain, _hWnd);
+            // _windowMoveSizeHook.WinEventReceived += _windowMoveSizeHook_WinEventReceived;
+            _windowMoveSizeHook.DirectCallEvents[WinEventHook.WinEvent.EVENT_SYSTEM_MOVESIZESTART] = _ => 
+            {
+                // Runs on the main thread
+                ClearLocationChangeEventListener();
+            };
+            _windowMoveSizeHook.DirectCallEvents[WinEventHook.WinEvent.EVENT_SYSTEM_MOVESIZEEND] = _ =>
+            {
+                // Runs on the main thread
+                SetUpLocationChangeEventListener();
+                _syncContextAuto.Post(__ => NotifyLocationChanged(), null);
+            };
 
             SetUpLocationChangeEventListener();
         }
 
         void SetUpLocationChangeEventListener()
         {
-            
+            Debug.Assert(Thread.CurrentThread.ManagedThreadId == 1);
+            Debug.Assert(_locationChangeEventHook == null);
             _locationChangeEventHook = new WinEventHook(WinEventHook.WinEvent.EVENT_OBJECT_LOCATIONCHANGE, WinEventHook.WinEvent.EVENT_OBJECT_LOCATIONCHANGE, _syncContextAuto, _syncContextMain, IntPtr.Zero);
             _locationChangeEventHook.WinEventReceived += _windowMoveSizeHook_WinEventReceived;
         }
 
+        void ClearLocationChangeEventListener()
+        {
+            Debug.Assert(Thread.CurrentThread.ManagedThreadId == 1);
+            if (_locationChangeEventHook != null)
+            {
+                _locationChangeEventHook.Dispose();
+                _locationChangeEventHook = null;
+            }
+        }
+
         // This allows us to temporarily stop listening to EVENT_OBJECT_LOCATIONCHANGE events when the user is dragging the Excel main window.
         // Otherwise we are going to bump into https://github.com/Excel-DNA/IntelliSense/issues/123. The rest of the time we need to stay
         // hooked to EVENT_OBJECT_LOCATIONCHANGE for IntelliSense to work correctly (see https://github.com/Excel-DNA/IntelliSense/issues/124).
         void UnhookFromLocationChangeUponDraggingExcelMainWindow(WinEventHook.WinEventArgs e)
         {
             if (e.EventType == WinEventHook.WinEvent.EVENT_SYSTEM_MOVESIZESTART)
             {
-                _syncContextMain.Post(_ => _locationChangeEventHook?.Dispose(), null);
+                Debug.WriteLine("===========>>>>>>>>  EVENT_SYSTEM_MOVESIZESTART   <<<<<<<<<<<<===========");
+                _syncContextMain.Post(_ => ClearLocationChangeEventListener(), null);
             }
 
             if (e.EventType == WinEventHook.WinEvent.EVENT_SYSTEM_MOVESIZEEND)
             {
+                Debug.WriteLine("===========>>>>>>>>  EVENT_SYSTEM_MOVESIZEEND   <<<<<<<<<<<<===========");
                 _syncContextMain.Post(_ => SetUpLocationChangeEventListener(), null);
             }
         }
 
+        // Runs on the automation thread
         void _windowMoveSizeHook_WinEventReceived(object sender, WinEventHook.WinEventArgs winEventArgs)
         {
 #if DEBUG
@@ -67,6 +100,11 @@ void _windowMoveSizeHook_WinEventReceived(object sender, WinEventHook.WinEventAr
 
             UnhookFromLocationChangeUponDraggingExcelMainWindow(winEventArgs);
 
+            NotifyLocationChanged();
+        }
+
+        void NotifyLocationChanged()
+        {
             LocationChanged?.Invoke(this, EventArgs.Empty);
         }
 
@@ -85,6 +123,7 @@ public void Dispose()
                 _locationChangeEventHook.Dispose();
                 _locationChangeEventHook = null;
             }
+            Debug.Print("===========>>>>>>>>  WindowsLocationWatcher  Disposed    <<<<<<<<<<<<===========");
         }
     }
 }

Source/ExcelDna.IntelliSense/UIMonitor/WindowWatcher.cs

@@ -154,14 +154,15 @@ public WindowWatcher(SynchronizationContext syncContextAuto, SynchronizationCont
             //  EVENT_OBJECT_DESTROY
             //  EVENT_OBJECT_SHOW
             //  EVENT_OBJECT_HIDE
-            //  EVENT_OBJECT_REORDER
+            //  >>>>>>>>>>>>>>>>>>>>>>>  EVENT_OBJECT_REORDER  <<<<<<<<<<<<<<<<< NOT THIS ONE
             //  EVENT_OBJECT_FOCUS
             //  EVENT_OBJECT_SELECTION
-            //  EVENT_OBJECT_SELECTIONADD
-            //  EVENT_OBJECT_SELECTIONREMOVE
-            //  EVENT_OBJECT_SELECTIONWITHIN
-            //  EVENT_OBJECT_STATECHANGE (0x800A = 32778)
-            _windowStateChangeHooks.Add(new WinEventHook(WinEventHook.WinEvent.EVENT_OBJECT_CREATE, WinEventHook.WinEvent.EVENT_OBJECT_STATECHANGE, syncContextAuto, syncContextMain, IntPtr.Zero));
+            //  >>>>>>>>>>>>>>>>>>>>>>>  EVENT_OBJECT_SELECTIONADD       <<<<<<<<<<<<<<<<< NOT THIS ONE
+            //  >>>>>>>>>>>>>>>>>>>>>>>  EVENT_OBJECT_SELECTIONREMOVE    <<<<<<<<<<<<<<<<< NOT THIS ONE
+            //  >>>>>>>>>>>>>>>>>>>>>>>  EVENT_OBJECT_SELECTIONWITHIN    <<<<<<<<<<<<<<<<< NOT THIS ONE
+            //  >>>>>>>>>>>>>>>>>>>>>>>  EVENT_OBJECT_STATECHANGE (0x800A = 32778)    <<<<<<<<<<<<<<<<< NOT THIS ONE
+            _windowStateChangeHooks.Add(new WinEventHook(WinEventHook.WinEvent.EVENT_OBJECT_CREATE, WinEventHook.WinEvent.EVENT_OBJECT_HIDE, syncContextAuto, syncContextMain, IntPtr.Zero));
+            _windowStateChangeHooks.Add(new WinEventHook(WinEventHook.WinEvent.EVENT_OBJECT_FOCUS, WinEventHook.WinEvent.EVENT_OBJECT_SELECTION, syncContextAuto, syncContextMain, IntPtr.Zero));
             _windowStateChangeHooks.Add(new WinEventHook(WinEventHook.WinEvent.EVENT_SYSTEM_CAPTURESTART, WinEventHook.WinEvent.EVENT_SYSTEM_CAPTURESTART, syncContextAuto, syncContextMain, IntPtr.Zero));
 
             foreach (var windowStateChangeHook in _windowStateChangeHooks)