`IPopover` is not sufficiently documented and needs more runtime checks

[ChristopheI]

Describe the bug
Since I'm suing last version of v2_develop (commit: 7490ac9), my revisited version of combobox are no more working on my project ... I'm stuck :(

To Reproduce
Using the example provide below:

1. Click on "Forwarding Immediate" menu
2. Select any option using mouse => event SelectedItemChanged of ListView is NOT triggered 😑
   to be more precise OnMouseEvent() method of ListView is not called
3. Use Mouse Up / or Mouse Down => event SelectedItemChanged of ListView is triggered 👍

Expected behavior
Event SelectedItemChanged of ListView must be triggered

Screenshots

Desktop (please complete the following information):

• OS: [Windows 11]

Code to reproduce:

using System.Collections.ObjectModel;
using System.Drawing;
using Terminal.Gui.Drawing;
using Terminal.Gui.Input;
using Terminal.Gui.ViewBase;
using Terminal.Gui.Views;
using RuntimeEnvironment = Microsoft.DotNet.PlatformAbstractions.RuntimeEnvironment;

public class Item
{
    public String Id { get; set; }
    
    public string Text { get; set; }

    public Item()
    {
        Id = Text = "";
    }

    public Item(String id, String text)
    {
        Id = id;
        Text = text;
    }

    public override string ToString()
    {
        if (String.IsNullOrEmpty(Text))
            return Id;
        return Text;
    }
}

public class ContextMenuSelector : PopoverMenu
{
    protected override void OnAccepted(CommandEventArgs args)
    {
        args.Handled = true;
    }
}

public class ItemSelector : View
{
    private Label lbl;
    private Label lblSelector;
    private Label lblArrow;
    private ContextMenuSelector contextMenu;

    private ListViewSelector categoryList;
    private int maxItemLength = 0;

    List<Item>? items;
    Item? itemSelected;


    public event EventHandler<Item>? SelectedItemUpdated;

    public Item? ItemSelected
    {
        get => itemSelected;
    }

    public ItemSelector(String? label = null, List<Item>? items = null, Item? itemSelected = null)
    {
        lbl = new()
        {
            X = 0,
            Y = 0,
            Height = 1,
            Width = (label is null) ? 0 : label.Length + 1,
            Text = $"{label}:",
            CanFocus = true,
            //SchemeName = "BlackOnGray"
        };

        lblSelector = new()
        {
            X = Pos.Right(lbl) + 1,
            Y = 0,
            Height = 1,
            Width = Dim.Func(() =>
            {
                var textLength = (lblSelector is null) ? 0 : lblSelector.Text.Length;
                var spaceAvailable = Frame.Width - lbl.Frame.Width - ((lblArrow is null) ? 0 : lblArrow.Frame.Width) - 2;
                if (spaceAvailable < 0) spaceAvailable = 0;
                return Math.Min(textLength, spaceAvailable);
            }),
            CanFocus = true
            //SchemeName = "BlueOnGray"
        };
        lblSelector.MouseClick += View_MouseClick;

        lblArrow = new()
        {
            X = Pos.Right(lblSelector) + 1,
            Y = 0,
            Height = 1,
            Width = 2,
            Text = Emojis.TRIANGLE_DOWN,
            //SchemeName = "BlueOnGray"
        };
        lblArrow.MouseClick += View_MouseClick;

        Add(lbl, lblSelector, lblArrow);

        Height = 1;
        Width = Dim.Fill();

        // Create categoryList
        categoryList = new()
        {
            X = Pos.Func(() => lblSelector.FrameToScreen().X),
            Y = Pos.Func(() => lblSelector.FrameToScreen().Y + 1),
            Width = Dim.Fill(
                        Dim.Func(() =>
                        {
                            var delta = (categoryList?.VerticalScrollBar.Visible == true) ? 4 : 3;
                            var nbElements = maxItemLength + delta;
                            var spaceAvailable = Terminal.Gui.App.Application.Screen.Width - lblSelector.FrameToScreen().X;
                            return spaceAvailable - Math.Min(nbElements, spaceAvailable);
                        })),
            Height = Dim.Fill(
                         Dim.Func(() =>
                         {
                             var delta = (categoryList?.HorizontalScrollBar.Visible == true) ? 4 : 3;
                             var nbElements = ((this.items is null) ? 0 : this.items.Count) + delta;
                             var spaceAvailable = Terminal.Gui.App.Application.Screen.Height - lblSelector.FrameToScreen().Y;
                             return spaceAvailable - Math.Min(nbElements, spaceAvailable);
                         })),
            AllowsMarking = false,
            CanFocus = true,
            BorderStyle = LineStyle.Rounded,
            SuperViewRendersLineCanvas = false,
            //Source = new ListWrapper<Item>(null),
            //SchemeName = "BlueOnGray" // /!\ Need to be set !!!
        };
        categoryList.VerticalScrollBar.AutoShow = true;
        categoryList.HorizontalScrollBar.AutoShow = true;

        categoryList.SelectedItemChanged += CategoryList_SelectedItemChanged;
        categoryList.SameItemSelected += CategoryList_SameItemSelected;

        // Create contextMenu
        contextMenu = new()
        {
            CanFocus = true,
            //SchemeName = "BlueOnGray"
        };
        contextMenu.Add(categoryList);

        this.itemSelected = itemSelected;
        SetItems(items);
        CanFocus = true;
        //SchemeName = "BlueOnGray";
    }

    protected override void OnViewportChanged(DrawEventArgs e)
    {
        HideViewSelection();
    }

    public void HideViewSelection()
    {
        Terminal.Gui.App.Application.Popover?.Hide(contextMenu);
    }

    public void ShowViewSelection()
    {
        if (items?.Count > 0)
        {
            Point position = new Point(lblSelector.FrameToScreen().X, lblSelector.FrameToScreen().Y + 1);
            contextMenu.MakeVisible(position);
            contextMenu.MouseClick += ContextMenu_MouseClick;
        }
    }

    private void ContextMenu_MouseClick(object? sender, MouseEventArgs e)
    {
        e.Handled = false;
    }

    private void View_MouseClick(object? sender, MouseEventArgs e)
    {
        e.Handled = true;
        ShowViewSelection();
    }

    private void CategoryList_SelectedItemChanged(object? sender, ListViewItemEventArgs e)
    {
        HideViewSelection();

        itemSelected = (Item)e.Value;

        Terminal.Gui.App.Application.Invoke(() =>
        {
            UpdateDisplay();
        });

        SelectedItemUpdated?.Invoke(this, (Item)e.Value);
    }

    private void CategoryList_SameItemSelected(object? sender, EventArgs e)
    {
        HideViewSelection();
    }

    private void UpdateDisplay()
    {
        if (itemSelected is null)
        {
            lblSelector.Text = "NONE";
            lblSelector.Enabled = false;
            lblArrow.Width = 0;
        }
        else
        {
            lblSelector.Text = itemSelected.Text;
            lblSelector.Enabled = true;
            lblArrow.Width = 2;
        }
        HideViewSelection();
    }

    public void SetItems(List<Item>? items)
    {
        this.items = items;

        var previousItemSelected = itemSelected;

        // Check itemSelected value
        if (items?.Count > 0)
        {
            if ((itemSelected is null)
                || (items.FirstOrDefault(i => i.Id == itemSelected.Id) is null))
                itemSelected = items[0];
        }
        else
        {
            itemSelected = null;
        }

        if (items?.Count > 0)
        {
            var strings = items.Select(i => i.ToString());
            maxItemLength = strings.Aggregate("", (max, cur) => max.Length > cur.Length ? max : cur).Length;

            categoryList.SetSource(new ObservableCollection<Item>(items));
            categoryList.SelectedItem = 0;
        }
        else
        {
            maxItemLength = 0;
            categoryList.SetSource(new ObservableCollection<Item>());
        }

        // Do we need to update the display ?
        if (previousItemSelected?.Id == itemSelected?.Id)
            return;

        Terminal.Gui.App.Application.Invoke(() =>
        {
            UpdateDisplay();
        });

    }

    public void SetItems(List<String>? elements)
    {
        List<Item>? items = null;
        if (elements?.Count > 0)
        {
            items = [];
            int count = 0;
            foreach (var elm in elements)
            {
                var item = new Item()
                {
                    Id = $"{count++}",
                    Text = elm,
                };
                items.Add(item);
            }
        }
        SetItems(items);
    }

    public Boolean SetItemSelected(Item? item)
    {
        if ((item is not null) && (items is not null))
        {
            var index = items.FindIndex(x => x.Id == item.Id);
            if (index > 0)
                return SetItemSelected(index);
        }
        return false;
    }

    public Boolean SetItemSelected(int index)
    {
        if ((index >= 0) && (items?.Count > index))
        {
            var item = items[index];
            if (item.Id != itemSelected?.Id)
            {
                itemSelected = items[index];
                Terminal.Gui.App.Application.Invoke(() =>
                {
                    categoryList.SelectedItem = index;
                    UpdateDisplay();
                });
                return true;
            }
        }
        return false;
    }
}


public class ListViewSelector : ListView
{
    public event EventHandler<EventArgs> SameItemSelected;

    public override bool OnSelectedChanged()
    {
        var result = base.OnSelectedChanged();
        if (!result)
            SameItemSelected?.Invoke(this, EventArgs.Empty);
        return result;
    }
}

public class TestWindow: Window
{
    readonly List<string> listFwdType = ["Forwarding Immediate", "Forward on busy", "Forward on no reply", "Forward on busy/no reply"];
    private Shortcut ShVersion;

    public TestWindow()
    {
        BorderStyle = LineStyle.None;

        

        var callForwardSelector = new ItemSelector("Call forward")
        {
            X = 0,
            Y = 0,
            Width = 80,
            CanFocus = true
        };
        callForwardSelector.SetItems(listFwdType);
        callForwardSelector.SelectedItemUpdated += CallForwardSelector_SelectedItemUpdated; ;

        Add(callForwardSelector);

        // Create StatusBar
        StatusBar statusBar = new()
        {
            Visible = true,
            AlignmentModes = AlignmentModes.IgnoreFirstOrLast,
            CanFocus = false
        };

        ShVersion = new()
        {
            Title = "Version Info",
            CanFocus = false
        };
        statusBar.Add(ShVersion); // always add it as the last one
        Add(statusBar);

        Height = Dim.Fill();
        Width = Dim.Fill();

        // Need to manage Loaded event
        Loaded += LoadedHandler;
    }

    private void CallForwardSelector_SelectedItemUpdated(object? sender, Item e)
    {
        var id = (int.Parse(e.Id));
    }

    private void LoadedHandler(object? sender, EventArgs? args)
    {
        if (ShVersion is { })
        {
            ShVersion.Title = $"{RuntimeEnvironment.OperatingSystem} {RuntimeEnvironment.OperatingSystemVersion}, {Terminal.Gui.App.Application.Driver.GetVersionInfo()}";
        }
    }
}

[ChristopheI]

I suppose that the MouseEvent is intercepted and cancelled by PopoverMenu. It why I tried to override PopoverMenu.OnAccepted but without success

[tig]

First, see this : #4050

(IOW, this stuff isn't fully baked).
Second, I just tweaked the ContextMenu Scenario like this:

private void CreateWinContextMenu ()
{
    if (_winContextMenu is { })
    {
        _winContextMenu.Dispose ();
        _winContextMenu = null;
    }

    ListView? listView = new ListView (){
        Width = Dim.Auto (),
        Height = Dim.Fill (),
        CanFocus = true,
        Source = new ListWrapper<string> (
                                          ["item #1", "item 2", "Со_хранить", "Quattro"]
                                         )
    };

    _winContextMenu = new (
                           [
                               new MenuItemv2
                               {
                                   Title = "C_ultures",
                                   SubMenu = GetSupportedCultureMenu (),
                               },
                               new Line (),
                               new MenuItemv2
                               {
                                   Title = "_Configuration...",
                                   HelpText = "Show configuration",
                                   Action = () => MessageBox.Query (
                                                                    50,
                                                                    10,
                                                                    "Configuration",
                                                                    "This would be a configuration dialog",
                                                                    "Ok"
                                                                   )
                               },
                               new MenuItemv2
                               {
                                   Title = "M_ore options",
                                   SubMenu = new (
                                                  [
                                                      new MenuItemv2
                                                      {
                                                          Title = "_Setup...",
                                                          HelpText = "Perform setup",
                                                          Action = () => MessageBox
                                                                       .Query (
                                                                               50,
                                                                               10,
                                                                               "Setup",
                                                                               "This would be a setup dialog",
                                                                               "Ok"
                                                                              ),
                                                          Key = Key.T.WithCtrl
                                                      },
                                                      new MenuItemv2
                                                      {
                                                          Title = "_Maintenance...",
                                                          HelpText = "Maintenance mode",
                                                          Action = () => MessageBox
                                                                       .Query (
                                                                               50,
                                                                               10,
                                                                               "Maintenance",
                                                                               "This would be a maintenance dialog",
                                                                               "Ok"
                                                                              )
                                                      }
                                                  ])
                               },
                               new Line (),
                               new MenuItemv2
                               {
                                   Title = "_Quit",
                                   Action = () => Application.RequestStop ()
                               },
                               listView
                           ])
    {
        Key = _winContextMenuKey
    };
}

Lets' use this to explore further...

ListView has bugs relative to Select/Activate and Accepting -

• It should be calling RaiseSelecting here:

        AddCommand (Command.Select, (ctx) =>
                                    {
                                        if (_allowsMarking)
                                        {
                                            if (RaiseSelecting (ctx) == true)
                                            {
                                                return true;
                                            }

                                            if (MarkUnmarkSelectedItem ())
                                            {
                                                return true;
                                            }
                                        }

                                        if (RaiseSelecting (ctx) == true)
                                        {
                                            return true;
                                        }
                                        return false;
                                    });

This doesn't really help you. I'll file an issue on it.

I found with the above ContextMenu scenario, OnSelectedChanged does get fired when it should:

So, there's something else going on in your code.

[tig]

FWIW, given:

• Rename/Refactor Command.Select and Selecting Event to Activate #4050

If I were you I wouldn't try to put a ListView in a PopoverMenu right now.

Instead, I'd just make what you're doing a Menuv2 and each of your items at MenuItemv2.

[ChristopheI]

Ok . So I tried to create my own context menu using IPopover.
If I click outside of my IPopover the app crash.

Here is the small full example:

using System.Drawing;
using Terminal.Gui.App;
using Terminal.Gui.Drawing;
using Terminal.Gui.Input;
using Terminal.Gui.ViewBase;
using Terminal.Gui.Views;
using RuntimeEnvironment = Microsoft.DotNet.PlatformAbstractions.RuntimeEnvironment;

public class MyPopover : View, IPopover
{
    public Toplevel? Toplevel { get; set; }

    public MyPopover()
    {
        Label lbl = new()
        {
            Width = Dim.Fill(),
            Height = 1,
            Text = "Just a label in MyPopover - A click outside this label will crash the app ...",
            SchemeName = "Error"
        };
        Add(lbl);

        Width = 100;
        Height = 10;
        Visible = false;

        MouseClick += ListViewSelection_MouseClick;
    }

    private void ListViewSelection_MouseClick(object? sender, MouseEventArgs e)
    {
        e.Handled = true;
    }

    public void MakeNotVisible()
    {
        if (Visible)
            Application.Popover?.Hide(this);
    }

    public void MakeVisible(Point? idealScreenPosition = null)
    {
        if (Visible)
            return;

        SetPosition(idealScreenPosition);
        Application.Popover?.Show(this);
    }
    public void SetPosition(Point? idealScreenPosition = null)
    {
        idealScreenPosition ??= Application.GetLastMousePosition();

        if (idealScreenPosition is null)
            return;

        Point pos = idealScreenPosition.Value;

        X = pos.X;
        Y = pos.Y;
    }

    private void ListView_SelectedItemChanged(object? sender, ListViewItemEventArgs e)
    {
        MakeNotVisible();
    }

    private void ListView_SameItemSelected(object? sender, EventArgs e)
    {
        MakeNotVisible();
    }

}

public class TestWindow: Window
{
    private Shortcut ShVersion;
    private MyPopover myPopover;
    public TestWindow()
    {
        BorderStyle = LineStyle.None;

        myPopover = new();
        myPopover.MouseClick += ContextMenu_MouseClick;

        Label lbl = new()
        {
            Width = Dim.Auto(),
            Height = Dim.Fill(),
            Text = "Click to display MyPopover"
        };
        lbl.MouseClick += Lbl_MouseClick;
        Add(lbl);

        // Create StatusBar
        StatusBar statusBar = new()
        {
            Visible = true,
            AlignmentModes = AlignmentModes.IgnoreFirstOrLast,
            CanFocus = false
        };

        ShVersion = new()
        {
            Title = "Version Info",
            CanFocus = false
        };
        statusBar.Add(ShVersion); // always add it as the last one
        Add(statusBar);

        Height = Dim.Fill();
        Width = Dim.Fill();

        // Need to manage Loaded event
        Loaded += LoadedHandler;
    }

    private void ContextMenu_MouseClick(object? sender, MouseEventArgs e)
    {
        e.Handled = true;
        myPopover.MakeNotVisible();
    }

    public void HideViewSelection()
    {
        myPopover.MakeNotVisible();
    }

    public void ShowViewSelection()
    {
        myPopover.MakeVisible();
    }

    private void Lbl_MouseClick(object? sender, MouseEventArgs e)
    {
        e.Handled = true;
        ShowViewSelection();
    }


    private void LoadedHandler(object? sender, EventArgs? args)
    {
        if (ShVersion is { })
        {
            ShVersion.Title = $"{RuntimeEnvironment.OperatingSystem} {RuntimeEnvironment.OperatingSystemVersion}, {Terminal.Gui.App.Application.Driver.GetVersionInfo()}";
        }
    }
}

What i'm doing wrong ?

[tig]

IPopover implementations need to have a command handler for Command.Quit.

The current implementation of RaiseMouseEvent has this code in it:

        // Dismiss the Popover if the user presses mouse outside of it
        if (mouseEvent.IsPressed
            && Popover?.GetActivePopover () as View is { Visible: true } visiblePopover
            && View.IsInHierarchy (visiblePopover, deepestViewUnderMouse, includeAdornments: true) is false)
        {
            // TODO: Build a use/test case for the popover not handling Quit
            if (visiblePopover.InvokeCommand (Command.Quit) is true && visiblePopover.Visible)
            {
                visiblePopover.Visible = false;
            }

            // Recurse once so the event can be handled below the popover
            RaiseMouseEvent (mouseEvent);

            return;

Note the TODO - LOL. I was anticipating this. My bad for not actually building such a test. Or even better a runtime check.

To fix this you can do either:

1. Don't implement IPopover yourself. Use PopoverBaseImpl (Recommended):

+public class MyPopover : View, PopoverBaseImpl
-public class MyPopover : View, IPopover

2. Register Command.Quit:

MouseClick += ListViewSelection_MouseClick;

+AddCommand (Command.Quit, Quit);
+KeyBindings.Add (Application.QuitKey, Command.Quit);

+return;

+bool? Quit (ICommandContext? ctx)
+{
+    if (!Visible)
+    {
+        return false;
+    }
+
+    Visible = false;
+
+    return true;
+}

Look at PopoverBaseImpl and you'll see you have other things missing, which is why I recommend you just use it:

#nullable enable

namespace Terminal.Gui.App;

/// <summary>
///     Abstract base class for Popover Views.
/// </summary>
/// <remarks>
///     <para>
///         To show a Popover, use <see cref="ApplicationPopover.Show"/>. To hide a popover,
///         call <see cref="ApplicationPopover.Show"/> with <see langword="null"/> set <see cref="View.Visible"/> to <see langword="false"/>.
///     </para>
///     <para>
///         If the user clicks anywhere not occluded by a SubView of the Popover, presses <see cref="Application.QuitKey"/>,
///         or causes another popover to show, the Popover will be hidden.
///     </para>
/// </remarks>
public abstract class PopoverBaseImpl : View, IPopover
{

    /// <summary>
    ///     Creates a new PopoverBaseImpl.
    /// </summary>
    protected PopoverBaseImpl ()
    {
        Id = "popoverBaseImpl";
        CanFocus = true;
        Width = Dim.Fill ();
        Height = Dim.Fill ();
        ViewportSettings = ViewportSettingsFlags.Transparent | ViewportSettingsFlags.TransparentMouse;

        // TODO: Add a diagnostic setting for this?
        //TextFormatter.VerticalAlignment = Alignment.End;
        //TextFormatter.Alignment = Alignment.End;
        //base.Text = "popover";

        AddCommand (Command.Quit, Quit);
        KeyBindings.Add (Application.QuitKey, Command.Quit);

        return;

        bool? Quit (ICommandContext? ctx)
        {
            if (!Visible)
            {
                return false;
            }

            Visible = false;

            return true;
        }
    }

    /// <inheritdoc />
    protected override bool OnVisibleChanging ()
    {
        bool ret = base.OnVisibleChanging ();
        if (ret is not true)
        {
            if (!Visible)
            {
                // Whenever visible is changing to true, we need to resize;
                // it's our only chance because we don't get laid out until we're visible
                Layout (Application.Screen.Size);
            }
            else
            {
                // Whenever visible is changing to false, we need to reset the focus
                if (ApplicationNavigation.IsInHierarchy(this, Application.Navigation?.GetFocused ()))
                {
                   Application.Navigation?.SetFocused (Application.Top?.MostFocused);
                }
            }
        }

        return ret;
    }

    /// <inheritdoc />
    public Toplevel? Toplevel { get; set; }

}

[ChristopheI]

Thanks. Using PopoverBaseImpl solved the crash. 👍

[ChristopheI]

Still digging with PopoverBaseImpl with some troubles :(
Mouse events are not available inside the View of the `PopoverBaseImpl'. It's automatically hidden thanks to the Command.Quit but I can't get info about the element clicked inside ...

NOTE: I don't use ListView. I add several Label objects

Below a full example code
Scenario:
TestWindow has a Label. A Click on it open a MyPopover which has 3 items (using a ComboBoxItem inherited from Label)
I expect to have event MouseClick of these labels when I use the mouse on them. But nothing ....
MyPopover is hidden

Full Code:

using System.Drawing;
using Terminal.Gui.App;
using Terminal.Gui.Drawing;
using Terminal.Gui.Input;
using Terminal.Gui.ViewBase;
using Terminal.Gui.Views;
using RuntimeEnvironment = Microsoft.DotNet.PlatformAbstractions.RuntimeEnvironment;


public class Item
{
    public String Id { get; set; }
    public string Text { get; set; }

    public Item()
    {
        Id = Text = "";
    }

    public Item(String id, String text)
    {
        Id = id;
        Text = text;
    }

    public override string ToString()
    {
        if (String.IsNullOrEmpty(Text))
            return Id;
        return Text;
    }
}

public class ComboBoxItem: Label
{
    public event EventHandler<Item>? ItemSelected;

    private Item Item;

    public ComboBoxItem(Item item)
    {
        this.Item = item;

        Width = Dim.Auto(DimAutoStyle.Text);
        Height = 1;
        Text = item.ToString();
        CanFocus = true;

        MouseClick += ComboBoxItem_MouseClick;
    }

    private void ComboBoxItem_MouseClick(object? sender, MouseEventArgs e)
    {
        ItemSelected?.Invoke(this, Item);
    }
}

public class MyPopover : PopoverBaseImpl
{
    List<ComboBoxItem> comboBoxItems;
    List<Item> items;
    int itemMaxLength;

    public Toplevel? Toplevel { get; set; }

    public MyPopover()
    {
        ////////////////////////////////////
        // CREATE items FOR TEST PURPOSE
        items = new List<Item>()
        {
            new() { Id = "id01", Text = "test01" },
            new() { Id = "id02", Text = "test02" },
            new() { Id = "id03", Text = "test03" },
        };

        var result = items.Select(i => i.Text).OrderByDescending(s => s.Length).First();
        if (String.IsNullOrEmpty(result))
            itemMaxLength = 0;
        else 
            itemMaxLength = result.Length;
        //
        ////////////////////////////////////

        comboBoxItems = new();
        View? previousComboBoxItem = null;
        foreach (var item in items)
        {
            var comboBoxItem = new ComboBoxItem(item)
            {
                Width = itemMaxLength,
                Y = (previousComboBoxItem is not null) ? Pos.Bottom(previousComboBoxItem) : 0,
            };
            comboBoxItem.ItemSelected += ComboBoxItem_ItemSelected;
            previousComboBoxItem = comboBoxItem;

            // Store / Display them
            comboBoxItems.Add(comboBoxItem);
            Add(comboBoxItem);
        }

        BorderStyle = LineStyle.Rounded;
        Width = Dim.Auto(DimAutoStyle.Content);
        Height = Dim.Auto(DimAutoStyle.Content);
        Visible = false;

        MouseClick += MyPopover_MouseClick;

        CanFocus = true;
    }

    private void ComboBoxItem_ItemSelected(object? sender, Item e)
    {
        MakeNotVisible();
        // TODO
    }

    private void MyPopover_MouseClick(object? sender, MouseEventArgs e)
    {
        e.Handled = true;
    }

    public void MakeNotVisible()
    {
        if (Visible)
            Application.Popover?.Hide(this);
    }

    public void MakeVisible(Point? idealScreenPosition = null)
    {
        if (Visible)
            return;

        SetPosition(idealScreenPosition);
        Application.Popover?.Show(this);
    }
 
    public void SetPosition(Point? idealScreenPosition = null)
    {
        idealScreenPosition ??= Application.GetLastMousePosition();

        if (idealScreenPosition is null)
            return;

        Point pos = idealScreenPosition.Value;

        X = pos.X;
        Y = pos.Y;
    }
}

public class TestWindow: Window
{
    private Shortcut ShVersion;
    private MyPopover myPopover;
    public TestWindow()
    {
        BorderStyle = LineStyle.None;

        myPopover = new();
        myPopover.MouseClick += ContextMenu_MouseClick;

        Label lbl = new()
        {
            Width = Dim.Auto(),
            Height = 1,
            Text = "Click to display MyPopover"
        };
        lbl.MouseClick += Lbl_MouseClick;
        Add(lbl);

        // Create StatusBar
        StatusBar statusBar = new()
        {
            Visible = true,
            AlignmentModes = AlignmentModes.IgnoreFirstOrLast,
            CanFocus = false
        };

        ShVersion = new()
        {
            Title = "Version Info",
            CanFocus = false
        };
        statusBar.Add(ShVersion); // always add it as the last one
        Add(statusBar);

        Height = Dim.Fill();
        Width = Dim.Fill();

        // Need to manage Loaded event
        Loaded += LoadedHandler;
    }

    private void ContextMenu_MouseClick(object? sender, MouseEventArgs e)
    {
        e.Handled = true;
        HideViewSelection();
    }

    public void HideViewSelection()
    {
        myPopover.MakeNotVisible();
    }

    public void ShowViewSelection()
    {
        myPopover.MakeVisible();
    }

    private void Lbl_MouseClick(object? sender, MouseEventArgs e)
    {
        //e.Handled = true;
        ShowViewSelection();
    }

    private void LoadedHandler(object? sender, EventArgs? args)
    {
        if (ShVersion is { })
        {
            ShVersion.Title = $"{RuntimeEnvironment.OperatingSystem} {RuntimeEnvironment.OperatingSystemVersion}, {Terminal.Gui.App.Application.Driver.GetVersionInfo()}";
        }
    }
}

[tig]

Popovers are ViewportSettingsFlags.TransparentToMouse and thus

        MouseClick += MyPopover_MouseClick;

       private void MyPopover_MouseClick (object? sender, MouseEventArgs e)
       {
         e.Handled = true;
        }

will never work.

In addition Label is not what you want to derive your ComboBoxitem from. This is because it is designed to be something that is a label for another control.

Just use View and CanFocus = true.

That say, you've found a bug.

In Veiew.Layout.cs:

    public static List<View?> GetViewsUnderLocation (in Point screenLocation, ViewportSettingsFlags excludeViewportSettingsFlags)
    {
        // PopoverHost - If visible, start with it instead of Top
        if (Application.Popover?.GetActivePopover () is View { Visible: true } visiblePopover)
        {
            // BUGBUG: We do not traverse all visible toplevels if there's an active popover. This may be a bug.
            List<View?> result = [];

            result.AddRange (GetViewsUnderLocation (visiblePopover, screenLocation, excludeViewportSettingsFlags));

-            if (result.Count > 1)
+            if (result.Count > 0)
            {
                return result;
            }
        }

Sorry about that.

Here's an update of your app that is simplified:

using System.Drawing;
using Terminal.Gui.App;
using Terminal.Gui.Drawing;
using Terminal.Gui.Input;
using Terminal.Gui.ViewBase;
using Terminal.Gui.Views;


Application.Init ();
Application.Run<TestWindow> ().Dispose ();
Application.Shutdown ();

public class Item
{
    public string Id { get; set; }
    public string Text { get; set; }

    public Item ()
    {
        Id = Text = "";
    }

    public Item (string id, string text)
    {
        Id = id;
        Text = text;
    }

    public override string ToString ()
    {
        if (string.IsNullOrEmpty (Text))
            return Id;
        return Text;
    }
}

public class ComboBoxItem : View
{
    public event EventHandler<Item>? ItemSelected;

    private Item Item;

    public ComboBoxItem (Item item)
    {
        this.Item = item;

        Width = Dim.Auto (DimAutoStyle.Text);
        Height = Dim.Auto (DimAutoStyle.Text);
        Text = item.ToString ();
        CanFocus = true;
    }

    protected override bool OnActivating (CommandEventArgs args)
    {
        ItemSelected?.Invoke (this, Item);

        return true;
    }
}

public class MyPopover : PopoverBaseImpl
{
    List<ComboBoxItem> comboBoxItems;
    List<Item> items;
    int itemMaxLength;

    public Toplevel? Toplevel { get; set; }

    public MyPopover ()
    {
        ////////////////////////////////////
        // CREATE items FOR TEST PURPOSE
        items = new List<Item> ()
        {
            new() { Id = "id01", Text = "test01" },
            new() { Id = "id02", Text = "test02" },
            new() { Id = "id03", Text = "test03" },
        };

        var result = items.Select (i => i.Text).OrderByDescending (s => s.Length).First ();
        if (String.IsNullOrEmpty (result))
            itemMaxLength = 0;
        else
            itemMaxLength = result.Length;
        //
        ////////////////////////////////////

        comboBoxItems = new ();
        View? previousComboBoxItem = null;
        foreach (var item in items)
        {
            var comboBoxItem = new ComboBoxItem (item)
            {
                Width = itemMaxLength,
                Y = (previousComboBoxItem is not null) ? Pos.Bottom (previousComboBoxItem) : 0,
            };

            comboBoxItem.Activating += (sender, args) =>
                                      {

                                      };
            comboBoxItem.ItemSelected += ComboBoxItem_ItemSelected;
            previousComboBoxItem = comboBoxItem;

            // Store / Display them
            comboBoxItems.Add (comboBoxItem);
            Add (comboBoxItem);
        }

        BorderStyle = LineStyle.Rounded;
        Width = Dim.Auto (DimAutoStyle.Content);
        Height = Dim.Auto (DimAutoStyle.Content);
        Visible = false;

        CanFocus = true;
    }

    private void ComboBoxItem_ItemSelected (object? sender, Item e)
    {
        MakeNotVisible ();

        // TODO
        MessageBox.Query ("Hello", $"Item {e.Text}", "ok");
    }

    public void MakeNotVisible ()
    {
        if (Visible)
            Application.Popover?.Hide (this);
    }

    public void MakeVisible (Point? idealScreenPosition = null)
    {
        if (Visible)
            return;

        SetPosition (idealScreenPosition);
        Application.Popover?.Show (this);
    }

    public void SetPosition (Point? idealScreenPosition = null)
    {
        idealScreenPosition ??= Application.GetLastMousePosition ();

        if (idealScreenPosition is null)
            return;

        Point pos = idealScreenPosition.Value;

        X = pos.X;
        Y = pos.Y;
    }
}

public class TestWindow : Toplevel
{
    private Shortcut ShVersion;
    private MyPopover myPopover;
    public TestWindow ()
    {
        myPopover = new ();

        View lbl = new ()
        {
            Width = Dim.Auto (),
            Height = 1,
            Text = "Click to display MyPopover"
        };
        lbl.MouseClick += Lbl_MouseClick;
        Add (lbl);

        // Create StatusBar
        StatusBar statusBar = new ()
        {
            Visible = true,
            AlignmentModes = AlignmentModes.IgnoreFirstOrLast,
            CanFocus = false
        };

        ShVersion = new ()
        {
            Title = "Version Info",
            CanFocus = false
        };
        statusBar.Add (ShVersion); // always add it as the last one
        Add (statusBar);

        Height = Dim.Fill ();
        Width = Dim.Fill ();

        // Need to manage Loaded event
        Loaded += LoadedHandler;
    }

    public void ShowViewSelection ()
    {
        myPopover.MakeVisible ();
    }

    private void Lbl_MouseClick (object? sender, MouseEventArgs e)
    {
        //e.Handled = true;
        ShowViewSelection ();
        e.Handled = true;
    }

    private void LoadedHandler (object? sender, EventArgs? args)
    {
        if (ShVersion is { })
        {
            ShVersion.Title = $"{Terminal.Gui.App.Application.Driver.GetVersionInfo ()}";
        }
    }
}

I'll get a PR in to fix the bug right away.