Add Tab navigation for Editor UI

Source/Editor/Windows/EditorWindow.cs

@@ -24,6 +24,11 @@ namespace FlaxEditor.Windows
         /// </summary>
         protected virtual bool CanOpenContentFinder => true;
 
+        /// <summary>
+        /// Gets a value indicating whether this window can use UI navigation (tab/enter).
+        /// </summary>
+        protected virtual bool CanUseNavigation => true;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="EditorWindow"/> class.
         /// </summary>
@@ -184,6 +189,32 @@ namespace FlaxEditor.Windows
 
         #endregion
 
+        /// <inheritdoc />
+        public override bool OnKeyDown(KeyboardKeys key)
+        {
+            if (base.OnKeyDown(key))
+                return true;
+
+            switch (key)
+            {
+            case KeyboardKeys.Return:
+                if (CanUseNavigation && Root?.FocusedControl != null)
+                {
+                    Root.SubmitFocused();
+                    return true;
+                }
+                break;
+            case KeyboardKeys.Tab:
+                if (CanUseNavigation && Root != null)
+                {
+                    Root.Navigate(NavDirection.Next);
+                    return true;
+                }
+                break;
+            }
+            return false;
+        }
+
         /// <inheritdoc />
         public override void OnDestroy()
         {

Source/Editor/Windows/GameWindow.cs

@@ -323,12 +323,15 @@ namespace FlaxEditor.Windows
         /// <inheritdoc />
         protected override bool CanOpenContentFinder => false;
 
+        /// <inheritdoc />
+        protected override bool CanUseNavigation => false;
+
         /// <inheritdoc />
         public override void OnPlayBegin()
         {
             _gameStartTime = Time.UnscaledGameTime;
         }
-        
+
         /// <inheritdoc />
         public override void OnPlayEnd()
         {
@@ -533,6 +536,22 @@ namespace FlaxEditor.Windows
             Screen.CursorVisible = true;
         }
 
+        /// <inheritdoc />
+        public override Control OnNavigate(NavDirection direction, Vector2 location, Control caller, System.Collections.Generic.List<Control> visited)
+        {
+            // Block leaking UI navigation focus outside the game window
+            if (IsFocused && caller != this)
+            {
+                // Pick the first UI control if game UI is not focused yet
+                foreach (var child in _guiRoot.Children)
+                {
+                    if (child.Visible)
+                        return child.OnNavigate(direction, Vector2.Zero, this, visited);
+                }
+            }
+            return null;
+        }
+
         /// <inheritdoc />
         public override bool OnMouseDown(Vector2 location, MouseButton button)
         {