sbox-public/game/addons/base/code/UI/MenuPanel.razor

@using System
@namespace Sandbox.UI
@inherits Panel

<root>

    <div class="background" onmousedown="@Close" onclick="@Close"></div>

    <div class="inner">

        @foreach ( var option in options )
        {
            if ( option.icon == "__spacer__" )
            {
                <div class="spacer"></div>
                continue;
            }

            <div class="option" onclick=@( () => SelectOption( option ) )>
                <div class="icon">@option.icon</div>
                <div class="text">@option.text</div>
            </div>
        }

    </div>

</root>

@code
{
    record struct MenuOption( string icon, string text, Action action );
    List<MenuOption> options = new List<MenuOption>();

    public static MenuPanel Open( Panel source )
    {
        var root = source.FindRootPanel();
        var menu = root.AddChild<MenuPanel>();

        menu.Style.Left = root.MousePosition.x * root.ScaleFromScreen;
        menu.Style.Top = root.MousePosition.y * root.ScaleFromScreen;

        // Todo - constrain to screen

        menu.PlaySound( "sounds/kenney/ui/ui.navigate.forward.sound" );

        return menu;
    }

    public void AddOption( string icon, string text, Action action )
    {
        options.Add( new( icon, text, action ) );
    }    

    public void AddSpacer()
    {
        options.Add( new( "__spacer__", "", null ) );
    }

    public void Close()
    {
        Panel root = FindRootPanel();
        foreach (var c in root.Children.OfType<MenuPanel>() )
        {
            c.Delete(false);
        }
    }

    void SelectOption( MenuOption option )
    {
        Close();
        option.action?.Invoke();
    }

    public override void OnLayout(ref Rect layoutRect)
    {
        var padding = 10;
        var h = Screen.Height - padding;
        var w = Screen.Width - padding;

        if (layoutRect.Bottom > h)
        {
            layoutRect.Top -= layoutRect.Bottom - h;
            layoutRect.Bottom -= layoutRect.Bottom - h;
        }

        if (layoutRect.Right > w)
        {
            layoutRect.Left -= layoutRect.Right - w;
            layoutRect.Right -= layoutRect.Right - w;
        }
    }
}