metin-launcher/src/Metin2Launcher/Bootstrap/NativeLibraryBootstrap.cs

using System.Diagnostics;
using System.Runtime.InteropServices;

namespace Metin2Launcher.Bootstrap;

/// <summary>
/// Pre-resolves the native DLL search path so LoadLibrary calls from
/// Avalonia / SkiaSharp find their deps when running as a .NET 8
/// single-file self-contained executable under Wine.
///
/// Why this exists:
///
/// - .NET 8 single-file bundles the native libs (libSkiaSharp.dll,
///   libHarfBuzzSharp.dll, libsodium.dll, av_libglesv2.dll) inside the
///   exe and extracts them at startup to
///   <c>$DOTNET_BUNDLE_EXTRACT_BASE_DIR/&lt;app&gt;/&lt;hash&gt;/</c>
///   (default: <c>%TEMP%/.net/&lt;app&gt;/&lt;hash&gt;/</c>).
/// - On native Windows, the CLR calls AddDllDirectory on the extract
///   dir so LoadLibrary picks them up.
/// - Under Wine, either wine's %TEMP% mapping trips over tmpfs during
///   extract (we observed a thread stack overflow in virtual_setup_exception
///   before Main even runs, with the default %TEMP%), or the DLL
///   search path never learns about the extract dir, and Avalonia's
///   P/Invoke hits DllNotFoundException when SkiaSharp tries to load.
///
/// The fix is two-part:
///
/// 1. Externally: set <c>DOTNET_BUNDLE_EXTRACT_BASE_DIR</c> to a path
///    under the exe's own directory, so the extract writes onto the
///    real filesystem (not wine's tmpfs).
/// 2. Here: once the CLR is up and Main has been reached, iterate
///    <see cref="Process.GetCurrentProcess"/>.Modules, find a loaded
///    module that lives inside the extract dir, and call
///    <c>SetDllDirectoryW</c> with that directory so subsequent
///    LoadLibrary calls (from Avalonia, SkiaSharp, NSec, etc.)
///    resolve their native deps.
///
/// The bootstrap is a no-op if we cannot identify an extract dir
/// (e.g. on native Windows where the default resolver already works,
/// or when the launcher is not running as a single-file bundle).
/// </summary>
internal static class NativeLibraryBootstrap
{
    [DllImport("kernel32", CharSet = CharSet.Unicode, SetLastError = true)]
    private static extern bool SetDllDirectoryW(string? lpPathName);

    public static void Apply()
    {
        try
        {
            var extractDir = FindExtractDir();
            if (string.IsNullOrEmpty(extractDir))
                return;
            SetDllDirectoryW(extractDir);
        }
        catch
        {
            // Intentionally swallow — bootstrap is best-effort. If it
            // fails the launcher will surface the real DllNotFoundException
            // from Avalonia later with a stack trace.
        }
    }

    // Strategy: look at DOTNET_BUNDLE_EXTRACT_BASE_DIR + app name and
    // pick the single hash-suffixed subdirectory that contains a file
    // with a name like libSkiaSharp.dll. Avoids depending on which
    // native libs are already loaded at Main() entry (they usually are
    // not).
    private static string? FindExtractDir()
    {
        var baseDir = Environment.GetEnvironmentVariable("DOTNET_BUNDLE_EXTRACT_BASE_DIR");
        if (string.IsNullOrEmpty(baseDir))
            return null;
        var appName = Path.GetFileNameWithoutExtension(Environment.ProcessPath ?? "Metin2Launcher");
        var appBase = Path.Combine(baseDir, appName);
        if (!Directory.Exists(appBase))
            return null;
        // There should be exactly one hash-suffixed subdir per binary.
        // Pick whichever one contains the Skia native lib.
        foreach (var candidate in Directory.EnumerateDirectories(appBase))
        {
            if (File.Exists(Path.Combine(candidate, "libSkiaSharp.dll")))
                return candidate;
        }
        // Fall back to whichever subdir exists first — better than nothing.
        return Directory.EnumerateDirectories(appBase).FirstOrDefault();
    }
}