Desktop Platform Support

using Avalonia;
using Avalonia.Controls.ApplicationLifetimes;

class Program
{
    public static void Main(string[] args)
    {
        BuildAvaloniaApp()
            .StartWithClassicDesktopLifetime(args);
    }

    public static AppBuilder BuildAvaloniaApp()
        => AppBuilder.Configure<App>()
            .UsePlatformDetect()  // Automatically selects platform
            .LogToTrace();
}

using Avalonia.Win32;

AppBuilder.Configure<App>()
    .With(new Win32PlatformOptions
    {
        // Render on UI thread (default: false)
        ShouldRenderOnUIThread = false,
        
        // Use overlay popups (default: true)
        OverlayPopups = true,
        
        // Enable Windows composition APIs
        UseWgl = false,
        
        // DPI awareness
        RenderingMode = new[]
        {
            Win32RenderingMode.Wgl,
            Win32RenderingMode.Software
        }
    })
    .UseWin32()
    .UseSkia();

using Avalonia.Controls.ApplicationLifetimes;

public override void OnFrameworkInitializationCompleted()
{
    if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
    {
        desktop.MainWindow = new MainWindow();
        
        // Configure shutdown mode
        desktop.ShutdownMode = ShutdownMode.OnMainWindowClose;
        
        // Handle application exit
        desktop.Exit += (sender, args) =>
        {
            // Cleanup code
        };
    }

    base.OnFrameworkInitializationCompleted();
}

using Avalonia.Controls;

public class MainWindow : Window
{
    public MainWindow()
    {
        Title = "My Application";
        Width = 800;
        Height = 600;
        
        // Window state
        WindowState = WindowState.Normal;
        WindowStartupLocation = WindowStartupLocation.CenterScreen;
        
        // Window features
        CanResize = true;
        ShowInTaskbar = true;
        SystemDecorations = SystemDecorations.Full;
        
        // Transparency (platform-dependent)
        TransparencyLevelHint = WindowTransparencyLevel.AcrylicBlur;
    }
}

using Avalonia.Controls;

var menu = new NativeMenu();
var fileMenu = new NativeMenuItem("File");
fileMenu.Menu = new NativeMenu
{
    new NativeMenuItem("Open...") { Command = OpenCommand },
    new NativeMenuItem("Save") { Command = SaveCommand },
    new NativeMenuItemSeparator(),
    new NativeMenuItem("Exit") { Command = ExitCommand }
};
menu.Add(fileMenu);

NativeMenu.SetMenu(this, menu);

using Avalonia.Controls;

var trayIcon = new TrayIcon
{
    Icon = new WindowIcon("/Assets/icon.ico"),
    ToolTipText = "My Application",
    Menu = new NativeMenu
    {
        new NativeMenuItem("Show") { Command = ShowCommand },
        new NativeMenuItemSeparator(),
        new NativeMenuItem("Exit") { Command = ExitCommand }
    }
};

trayIcon.Clicked += (s, e) => ShowMainWindow();
TrayIcon.SetIcons(Application.Current, new[] { trayIcon });

using Avalonia.Platform.Storage;

public async Task OpenFileAsync()
{
    var topLevel = TopLevel.GetTopLevel(this);
    var files = await topLevel.StorageProvider.OpenFilePickerAsync(
        new FilePickerOpenOptions
        {
            Title = "Select a file",
            AllowMultiple = false,
            FileTypeFilter = new[]
            {
                new FilePickerFileType("Text Files")
                {
                    Patterns = new[] { "*.txt" },
                    MimeTypes = new[] { "text/plain" }
                }
            }
        });
    
    if (files.Count > 0)
    {
        await using var stream = await files[0].OpenReadAsync();
        // Process file
    }
}

// Enable GPU acceleration
AppBuilder.Configure<App>()
    .UseSkia()
    .With(new SkiaOptions
    {
        // Use GPU rendering when available
        CustomGpuFactory = null,
        
        // Maximum FPS
        MaxFrameRate = 60
    });

// Configure for desktop memory profile
AvaloniaLocator.CurrentMutable
    .Bind<IPlatformSettings>()
    .ToConstant(new DefaultPlatformSettings
    {
        // Desktop defaults
    });