Avalonia Docking with a Native Dock Manager

<Window xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:sgc="https://www.esegece.com/sgcui"
        x:Class="DockSample.MainWindow"
        Title="Avalonia docking" Width="1100" Height="720">
  <sgc:TsgcAvaloniaDockManager x:Name="dockManager"
                               DocumentShowNewButton="True"
                               SplitterSize="5"
                               AutoHideDelay="400"/>
</Window>

using System;
using System.IO;
using Avalonia.Controls;
using esegece.sgcNavigation;

namespace DockSample
{
    public partial class MainWindow : Window
    {
        private readonly string FLayoutFile = Path.Combine(AppContext.BaseDirectory, "layout.json");
        private int FUntitled;

        public MainWindow()
        {
            InitializeComponent();

            // three tool panels and two documents, placed once at EndUpdate
            dockManager.Panels.BeginUpdate();
            try
            {
                AddTool("Explorer", new TreeView(), TsgcDockPlacement.dplLeft, 240);
                AddTool("Properties", new StackPanel(), TsgcDockPlacement.dplRight, 260);
                AddTool("Output", new TextBox { IsReadOnly = true }, TsgcDockPlacement.dplBottom, 180);
                AddDocument("main.cs").Pinned = true;
                AddDocument("readme.md");
            }
            finally
            {
                dockManager.Panels.EndUpdate();
            }

            // the Output panel starts auto hidden at the bottom edge
            dockManager.Model.SetAutoHide(dockManager.Model.FindPanel("Output"), true);

            // the + button of the document area
            dockManager.OnNewDocument = (s, aPanel) => AddDocument("Untitled " + (++FUntitled));
            // a saved layout names a document this session has not opened yet
            dockManager.OnRestorePanel = DockRestorePanel;

            // floats show with the window, so load the layout once it is open
            Opened += (s, e) =>
            {
                if (File.Exists(FLayoutFile))
                    dockManager.LoadLayoutFromFile(FLayoutFile);
            };
            Closing += (s, e) => dockManager.SaveLayoutToFile(FLayoutFile);
        }

        private TsgcDockPanel AddTool(string aName, Control aControl, TsgcDockPlacement aPlacement, int aSize)
        {
            TsgcDockPanel oPanel = dockManager.Panels.Add();
            oPanel.Name = aName;
            oPanel.Caption = aName;
            oPanel.Control = aControl;
            oPanel.Placement = aPlacement;
            oPanel.DockSize = aSize;
            return oPanel;
        }

        private TsgcDockPanel AddDocument(string aName)
        {
            TsgcDockPanel oPanel = dockManager.Panels.Add();
            oPanel.Name = aName;
            oPanel.Caption = aName;
            oPanel.Kind = TsgcDockPanelKind.dpkDocument;
            oPanel.Control = new TextBox { AcceptsReturn = true };
            return oPanel;
        }

        private void DockRestorePanel(object Sender, TsgcDockPanel aPanel, ref bool aAccept)
        {
            aAccept = aPanel.Kind == TsgcDockPanelKind.dpkDocument;
            if (aAccept)
                aPanel.Control = new TextBox { AcceptsReturn = true };
        }
    }
}

public override void Initialize()
{
    AvaloniaXamlLoader.Load(this);
    // every sgcUI control, the dock manager included, paints with the Fluent preset
    sgcUIApplication.ThemePreset = sgcUICore_Theme.CS_UI_THEME_FLUENT;
}