#124 Clean up

Author: sshukurov

Source/ExcelDna.IntelliSense/UIMonitor/WindowWatcher.cs

@@ -117,11 +117,11 @@ internal WindowChangedEventArgs(IntPtr windowHandle, WinEventHook.WinEvent winEv
         const string _nuiDialogClass = "NUIDialog";
         const string _selectDataSourceTitle = "Select Data Source";     // TODO: How does localization work?
 
-        private readonly SynchronizationContext _syncContextAuto;
-        private readonly SynchronizationContext _syncContextMain;
+        readonly SynchronizationContext _syncContextAuto;
+        readonly SynchronizationContext _syncContextMain;
 
         List<WinEventHook> _windowStateChangeHooks = new List<WinEventHook>();
-        private WinEventHook _locationChangeEventHook;
+        WinEventHook _locationChangeEventHook;
 
         // These track keyboard focus for Windows in the Excel process
         // Used to synthesize the 'Unfocus' change events
@@ -162,8 +162,6 @@ public WindowWatcher(SynchronizationContext syncContextAuto, SynchronizationCont
             //  EVENT_OBJECT_SELECTIONREMOVE
             //  EVENT_OBJECT_SELECTIONWITHIN
             //  EVENT_OBJECT_STATECHANGE (0x800A = 32778)
-            // NB: Including the next event 'EVENT_OBJECT_LOCATIONCHANGE (0x800B = 32779)' will cause the Excel main window to lag when dragging.
-            // This drag issue seems to have been introduced with an Office update around November 2022.
             _windowStateChangeHooks.Add(new WinEventHook(WinEventHook.WinEvent.EVENT_OBJECT_CREATE, WinEventHook.WinEvent.EVENT_OBJECT_STATECHANGE, syncContextAuto, syncContextMain, IntPtr.Zero));
             _windowStateChangeHooks.Add(new WinEventHook(WinEventHook.WinEvent.EVENT_SYSTEM_CAPTURESTART, WinEventHook.WinEvent.EVENT_SYSTEM_CAPTURESTART, syncContextAuto, syncContextMain, IntPtr.Zero));
 
@@ -175,8 +173,12 @@ public WindowWatcher(SynchronizationContext syncContextAuto, SynchronizationCont
             SetUpLocationChangeEventListener();
         }
 
-        private void SetUpLocationChangeEventListener()
+        void SetUpLocationChangeEventListener()
         {
+            // NB: Including the next event 'EVENT_OBJECT_LOCATIONCHANGE (0x800B = 32779)' will cause the Excel main window to lag when dragging.
+            // This drag issue seems to have been introduced with an Office update around November 2022.
+            // To workaround this, we unhook from this event upon encountering EVENT_SYSTEM_MOVESIZESTART and then hook again upon encountering
+            // EVENT_SYSTEM_MOVESIZEEND (see UnhookFromLocationChangeUponDraggingExcelMainWindow).
             _locationChangeEventHook = new WinEventHook(WinEventHook.WinEvent.EVENT_OBJECT_LOCATIONCHANGE, WinEventHook.WinEvent.EVENT_OBJECT_LOCATIONCHANGE, _syncContextAuto, _syncContextMain, IntPtr.Zero);
             _locationChangeEventHook.WinEventReceived += _windowStateChangeHook_WinEventReceived;
         }
@@ -228,6 +230,22 @@ bool UpdateFocus(IntPtr windowHandle, string windowClassName)
             return true;
         }
 
+        // 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);
+            }
+
+            if (e.EventType == WinEventHook.WinEvent.EVENT_SYSTEM_MOVESIZEEND)
+            {
+                _syncContextMain.Post(_ => SetUpLocationChangeEventListener(), null);
+            }
+        }
+
         // This runs on the Automation thread, via SyncContextAuto passed in to WinEventHook when we created this WindowWatcher
         // CONSIDER: We would be able to run all the watcher updates from WinEvents, including Location and Selection changes,
         //           but since WinEvents have no hwnd filter, UIAutomation events might be more efficient.
@@ -240,15 +258,7 @@ void _windowStateChangeHook_WinEventReceived(object sender, WinEventHook.WinEven
                 Debug.Fail("WinEvent with window 0!?");
             }
 
-            if (e.EventType == WinEventHook.WinEvent.EVENT_SYSTEM_MOVESIZESTART)
-            {
-                _syncContextMain.Post(_ => _locationChangeEventHook.Dispose(), null);
-            }
-
-            if (e.EventType == WinEventHook.WinEvent.EVENT_SYSTEM_MOVESIZEEND)
-            {
-                _syncContextMain.Post(_ => SetUpLocationChangeEventListener(), null);
-            }
+            UnhookFromLocationChangeUponDraggingExcelMainWindow(e);
 
             if (e.EventType == WinEventHook.WinEvent.EVENT_OBJECT_FOCUS)
             {