Avalonia/src/Avalonia.Desktop/AppBuilderDesktopExtensions.cs

using Avalonia.Controls;
using Avalonia.Platform;

namespace Avalonia
{
    public static class AppBuilderDesktopExtensions
    {
        public static TAppBuilder UsePlatformDetect<TAppBuilder>(this TAppBuilder builder)
            where TAppBuilder : AppBuilderBase<TAppBuilder>, new()
        {
            var os = builder.RuntimePlatform.GetRuntimeInfo().OperatingSystem;

            // We don't have the ability to load every assembly right now, so we are
            // stuck with manual configuration  here
            // Helpers are extracted to separate methods to take the advantage of the fact
            // that CLR doesn't try to load dependencies before referencing method is jitted
            // Additionally, by having a hard reference to each assembly,
            // we verify that the assemblies are in the final .deps.json file
            //  so .NET Core knows where to load the assemblies from,.
            if (os == OperatingSystemType.WinNT)
            {
                LoadWin32(builder);
                LoadSkia(builder);
            }
            else if(os==OperatingSystemType.OSX)
            {
                LoadAvaloniaNative(builder);
                LoadSkia(builder);
            }
            else
            {
                LoadGtk3(builder);
                LoadSkia(builder);
            }
            return builder;
        }

        static void LoadAvaloniaNative<TAppBuilder>(TAppBuilder builder)
            where TAppBuilder : AppBuilderBase<TAppBuilder>, new()
             => builder.UseAvaloniaNative();
        static void LoadWin32<TAppBuilder>(TAppBuilder builder)
            where TAppBuilder : AppBuilderBase<TAppBuilder>, new()
             => builder.UseWin32();

        static void LoadGtk3<TAppBuilder>(TAppBuilder builder)
            where TAppBuilder : AppBuilderBase<TAppBuilder>, new()
             => builder.UseGtk3();

        static void LoadDirect2D1<TAppBuilder>(TAppBuilder builder)
            where TAppBuilder : AppBuilderBase<TAppBuilder>, new()
             => builder.UseDirect2D1();

        static void LoadSkia<TAppBuilder>(TAppBuilder builder)
            where TAppBuilder : AppBuilderBase<TAppBuilder>, new()
             => builder.UseSkia();
    }
}