Fixes #3691. Adds Popover

[tig]

Fixes

• Fixes Popover - A consistent way of enabling a Subview to popup outside of a View #3691

• Fixes ShadowView throws System.IndexOutOfRangeException if left is less than zero. #3757

Proposed Changes/Todos

• Prototype in View Experiments the concept described in Popover - A consistent way of enabling a Subview to popup outside of a View #3691 to prove concept.
• Prototype in Bars to show how ContextMenu and MenuBar could utilize
• Re-implement ContextMenu using MenuV2 - Initially no cascading menus for simplicity
• Re-implement AutocompletePopup
• Re-implement Combobox
• Add more ShadowView unit tests (see ShadowView throws System.IndexOutOfRangeException if left is less than zero. #3757)

Future PRs

• Replace Menu and MenuBar using Bar (aka finish Menuv2

Pull Request checklist:

• I've named my PR in the form of "Fixes #issue. Terse description."
• My code follows the style guidelines of Terminal.Gui - if you use Visual Studio, hit CTRL-K-D to automatically reformat your files before committing.
• My code follows the Terminal.Gui library design guidelines
• I ran dotnet test before commit
• I have made corresponding changes to the API documentation (using /// style comments)
• My changes generate no new warnings
• I have checked my code and corrected any poor grammar or misspellings
• I conducted basic QA to assure all features are working

[tig]

FWIW, here's the API in action (the prototype for the File menubar item in Bars):

var fileMenuBarItem = new Shortcut
{
    Title = "_File",
    HelpText = "File Menu",
    Key = Key.D0.WithAlt,
};

fileMenuBarItem.Accept += (sender, args) =>
                          {
                              var fileMenu = new Menuv2
                              {
                                  Id = "fileMenu",
                              };
                              ConfigureMenu (fileMenu);
                              fileMenu.VisibleChanged += (sender, args) =>
                                                         {
                                                             if (Application.Popover == _popoverMenu && Application.Popover is { Visible: false })
                                                             {
                                                                 Application.Popover?.Dispose ();
                                                                 Application.Popover = null;
                                                             }
                                                         };
                              Application.Popover = fileMenu;
                              Rectangle screen = fileMenuBarItem.FrameToScreen ();
                              fileMenu.X = screen.X;
                              fileMenu.Y = screen.Y + screen.Height;
                              fileMenu.Visible = true;

                          };

Here's the entirety of the new API (on Application):

    /// <summary>Gets or sets the Application Popover View.</summary>
    /// <remarks>
    ///     <para>
    ///         To show or hide the Popover, set it's <see cref="View.Visible"/> property.
    ///     </para>
    /// </remarks>
    public static View? Popover

[tig]

[tig]

Kinda cool. Mouse wheel will now be able to nav within a Bar (or Menu).

[tig]

A new ContextMenuv2 implementation.

TextField now uses it instead of the old one.

[tig]

The TextField has no sense to start his position at cursor position, TextView has. TextField must start his position at (0,1), but never over it unless it doesn't fit.

I don't understand.

TextView does know the cursor pos. I've used it to position the CM in this PR. I'm travelling today so can't send a video. Try it and let me know what you think.

[BDisp]

Nothing of this is working in your PR. You put a zig zag menus for what? To show that this will stopping working? UseSubMenusSingleFrame will also not working in the new Popover? To me a ContextMenu must work like a Menu but without a visible MenuBar. Popover should be used for floated view that will show content on front of others views. But that only my opinion.

[BDisp]

In this PR:

In v2_develop the MenuBar is not showing.

[tig]

Nothing of this is working in your PR. You put a zig zag menus for what? To show that this will stopping working? UseSubMenusSingleFrame will also not working in the new Popover? To me a ContextMenu must work like a Menu but without a visible MenuBar. Popover should be used for floated view that will show content on front of others views. But that only my opinion.

This is a WIP. I will add the more advanced features as I progress.

[tig]

In this PR:

In v2_develop the MenuBar is not showing.

This is because Window is set for Overlapped/Movable/Sizable.

Please file a bug for me to make it so arrange mode is disabled if Top.