Fix lost mouse clicks on inactive window (#1021) (#1710)

* Fix lost mouse clicks on inactive window (#1021)

* Removed DialogHost.OnPreviewMouseDown (#1021)

* Restored DialogHost.OnPreviewMouseDown, removed logic to restore focus on activation (#1021)

Author: greuelpirat

MaterialDesignThemes.Wpf/DialogHost.cs

@@ -68,9 +68,7 @@ public class DialogHost : ContentControl
         private DialogOpenedEventHandler _attachedDialogOpenedEventHandler;
         private DialogClosingEventHandler _attachedDialogClosingEventHandler;
         private IInputElement _restoreFocusDialogClose;
-        private IInputElement _restoreFocusWindowReactivation;
         private Action _currentSnackbarMessageQueueUnPauseAction;
-        private Action _closeCleanUp = () => { };
 
         static DialogHost()
         {
@@ -241,7 +239,6 @@ private static void IsOpenPropertyChangedCallback(DependencyObject dependencyObj
 
             if (dialogHost.IsOpen)
             {
-                WatchWindowActivation(dialogHost);
                 dialogHost._currentSnackbarMessageQueueUnPauseAction = dialogHost.SnackbarMessageQueue?.Pause();
             }
             else
@@ -254,7 +251,6 @@ private static void IsOpenPropertyChangedCallback(DependencyObject dependencyObj
                 }
                 dialogHost.CurrentSession.IsEnded = true;
                 dialogHost.CurrentSession = null;
-                dialogHost._closeCleanUp();
                 //NB: _dialogTaskCompletionSource is only set in the case where the dialog is shown with Show
                 //To get into this case you need to display the dialog with Show and then hide it by setting IsOpen to false
                 //Setting this here ensures the other 
@@ -627,7 +623,7 @@ internal UIElement FocusPopup()
 
             return child;
         }
-
+        
         protected override void OnPreviewMouseDown(MouseButtonEventArgs e)
         {
             var window = Window.GetWindow(this);
@@ -712,39 +708,5 @@ private void OnLoaded(object sender, RoutedEventArgs routedEventArgs)
             LoadedInstances.Add(this);
         }
 
-        private static void WatchWindowActivation(DialogHost dialogHost)
-        {
-            var window = Window.GetWindow(dialogHost);
-            if (window != null)
-            {
-                window.Activated += dialogHost.WindowOnActivated;
-                window.Deactivated += dialogHost.WindowOnDeactivated;
-                dialogHost._closeCleanUp = () =>
-                {
-                    window.Activated -= dialogHost.WindowOnActivated;
-                    window.Deactivated -= dialogHost.WindowOnDeactivated;
-                };
-            }
-            else
-            {
-                dialogHost._closeCleanUp = () => { };
-            }
-        }
-
-        private void WindowOnDeactivated(object sender, EventArgs eventArgs)
-        {
-            _restoreFocusWindowReactivation = _popup != null ? FocusManager.GetFocusedElement((Window)sender) : null;
-        }
-
-        private void WindowOnActivated(object sender, EventArgs eventArgs)
-        {
-            if (_restoreFocusWindowReactivation != null)
-            {
-                Dispatcher.BeginInvoke(new Action(() =>
-                {
-                    Keyboard.Focus(_restoreFocusWindowReactivation);
-                }));
-            }
-        }
     }
 }