Enable using MenuBar as an alternative for ComboBox

Is your feature request related to a problem? Please describe.

I have been exploring using a MenuBar as a dropdown menu. It works like a dropdown style combo box and looks better and gives clearer indication of what the active/new selections will be.

But there is a problem in that the user cannot Tab to the view. I have tried setting the following but it does not work.

CanFocus = true,
TabStop = true

Describe the solution you’d like Tab to work for MenuBar when TabStop is set.

Describe alternatives you’ve considered I can probably still do a workaround by intercepting Tab on the View before it and adding a callback to manually popping the menu open.

I will probably have to do this anyway so that the user can Tab out of the menu and back to other views.

[tig]

Here’s a tweaked scenario. I realy love this!

		public override void Setup ()
		{
			var tf = new TextField () { Width = 10 };
			Application.Top.Add (tf);

			MenuBarItem menu = null;

			MenuItem CreateMenuItem (int i)
			{
				return new MenuItem ($"Item {i}", null, () => {
					tf.Text = menu.Children [i - 1].Title;
				});
			}

			menu = new MenuBarItem ($"{Application.Driver.DownArrow}",
				Enumerable.Range (1, 5).Select (
						(a) => CreateMenuItem (a))
					.ToArray ());

			var mb = new MenuBar (new [] { menu }) {
				CanFocus = true,
				Width = 1,
				Y = Pos.Top (tf),
				X = Pos.Right (tf)
			};

			// HACKS required to make this work:
			mb.Enter += (s, e) => {
				// BUG: This does not select menu item 0
				// Instead what happens is the first keystroke the user presses
				// gets swallowed and focus is moved to 0.  Result is that you have
				// to press down arrow twice to select first menu item and/or have to
				// press Tab twice to move focus back to TextField
				mb.OpenMenu ();
			};

			Application.Top.Add (mb);

This mostly works today as @tznind notes.

What needs to be fixed to make this really be done:

• The menu should pop down aligned to the left of the textField.
• MenuBorderStyle = LineStyle.None might look better

[tig]

Why isn’t Onfocus true by default?

Yesterday I was goofing with Focus stuff and realized it might make sense for Menubar to participate in tabstops along with the other subviews of a view.