MercuryConverter/src/UI/MainWindow.axaml.cs

using System;
using System.Threading.Tasks;
using Avalonia.Controls;
using Avalonia.Styling;
using Avalonia.Threading;
using MercuryConverter.UI.Dialogs;
using MercuryConverter.UI.Views;

namespace MercuryConverter.UI;

public partial class MainWindow : Window
{
    public static MainWindow? Instance { get; private set; }
    private bool initialShown = false;

    public MainWindow()
    {
        Instance = this;
        InitializeComponent();
        DataContext = this;

        // Force dark mode in designer
        if (Design.IsDesignMode)
        {
            RequestedThemeVariant = ThemeVariant.Dark;
        }

        // Setup tab views
        SelectionControl.Content = new Selection();

        // Show dialog on startup
        Activated += OnActivated;
    }

    private void OnActivated(object? sender, EventArgs e)
    {
        if (initialShown) return;
        initialShown = true;

        Dialog.DialogContent = new Welcome().Content;
        Dialog.IsOpen = true;
    }

    public void OpenDataHandler()
    {
        Dialog.IsOpen = true;
        Dialog.DialogContent = new DataScanning().Content;
    }

    public void OpenDataHOWTO()
    {
        var launcher = GetTopLevel(this)?.Launcher;
        if (launcher != null)
        {
            launcher.LaunchUriAsync(new Uri("https://github.com/muskit/MercuryConverter/blob/main/HOWTO.md"));
        }
    }
}