Program.cs

using Avalonia;
using Avalonia.OpenGL;

namespace StudioCCS;

internal sealed class Program
{
    // The CCS shaders are desktop GLSL #version 330 and use geometry shaders,
    // so every platform must hand us a desktop OpenGL 3.3 (or newer) core
    // context rather than the GLES/ANGLE default. Listed newest-first; the
    // backend negotiates the first one the driver can provide. We ask for 4.6
    // (the highest GL version) so capable drivers also light up the KHR_debug
    // output we register in debug builds (core in 4.3); 3.3 is the floor the
    // shaders actually require, used when the driver cannot grant anything newer.
    private static List<GlVersion> DesktopGlProfiles()
    {
        return new List<GlVersion>
    {
        new GlVersion(GlProfileType.OpenGL, 4, 6),
        new GlVersion(GlProfileType.OpenGL, 3, 3),
    };
    }

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

    public static AppBuilder BuildAvaloniaApp()
    {
        var builder = AppBuilder.Configure<App>()
            .UsePlatformDetect();

        if (OperatingSystem.IsWindows())
        {
            // Windows defaults to ANGLE, which only exposes OpenGL ES and so
            // cannot compile our desktop #version 330 / geometry shaders.
            // Switch the backend to native WGL and request a desktop profile.
            // (This routes Avalonia's own compositor through WGL too; that is
            // the supported way to get a desktop GL context here.)
            builder = builder.With(new Win32PlatformOptions
            {
                RenderingMode = new[] { Win32RenderingMode.Wgl },
                WglProfiles = DesktopGlProfiles(),
            });
        }
        else if (OperatingSystem.IsLinux())
        {
            builder = builder.With(new X11PlatformOptions
            {
                GlProfiles = DesktopGlProfiles(),
            });
        }
        // macOS (AvaloniaNative) exposes no GL-version selector: the OS hands
        // back an OpenGL 3.2 or 4.1 Core context of its choosing. Geometry
        // shaders work on both, but #version 330 compiles only on the 4.1 Core
        // context (3.2 Core caps GLSL at 1.50). This must be verified on real
        // Mac hardware; if it lands on a 3.2 context the shaders need a
        // #version 150 variant. Apple has deprecated OpenGL, so macOS is the
        // least certain target here.

        return builder
            .WithInterFont()
            .LogToTrace();
    }
}