Merge pull request #765 from VitalElement/fixes/allow-alt-modifier-for-text-input

Fixes/allow alt modifier for text input

src/Avalonia.Input/AccessKeyHandler.cs

@@ -43,6 +43,16 @@ namespace Avalonia.Input
         /// </summary>
         private bool _ignoreAltUp;
 
+        /// <summary>
+        /// Whether the AltKey is down.
+        /// </summary>
+        private bool _altIsDown;
+
+        /// <summary>
+        /// Element to restore folowing AltKey taking focus.
+        /// </summary>
+        private IInputElement _restoreFocusElement;
+
         /// <summary>
         /// Gets or sets the window's main menu.
         /// </summary>
@@ -110,8 +120,14 @@ namespace Avalonia.Input
         {
             if (e.Key == Key.LeftAlt)
             {
+                _altIsDown = true;
+
                 if (MainMenu == null || !MainMenu.IsOpen)
                 {
+                    // TODO: Use FocusScopes to store the current element and restore it when context menu is closed.
+                    // Save currently focused input element.
+                    _restoreFocusElement = FocusManager.Instance.Current;                    
+
                     // When Alt is pressed without a main menu, or with a closed main menu, show
                     // access key markers in the window (i.e. "_File").
                     _owner.ShowAccessKeys = _showingAccessKeys = true;
@@ -121,11 +137,18 @@ namespace Avalonia.Input
                     // If the Alt key is pressed and the main menu is open, close the main menu.
                     CloseMenu();
                     _ignoreAltUp = true;
+
+                    _restoreFocusElement?.Focus();
+                    _restoreFocusElement = null;
                 }
 
                 // We always handle the Alt key.
                 e.Handled = true;
             }
+            else if (_altIsDown)
+            {
+                _ignoreAltUp = true;
+            }
         }
 
         /// <summary>
@@ -179,6 +202,8 @@ namespace Avalonia.Input
             switch (e.Key)
             {
                 case Key.LeftAlt:
+                    _altIsDown = false;
+
                     if (_ignoreAltUp)
                     {
                         _ignoreAltUp = false;