call_wWinMain

fn call_wWinMain() std.os.windows.INT

File

Code

fn call_wWinMain() std.os.windows.INT {
    const peb = std.os.windows.peb();
    const MAIN_HINSTANCE = @typeInfo(@TypeOf(root.wWinMain)).@"fn".param_types[0].?;
    const hInstance: MAIN_HINSTANCE = @ptrCast(peb.ImageBaseAddress);
    const lpCmdLine: [*:0]u16 = @ptrCast(peb.ProcessParameters.CommandLine.Buffer);

    // There are various types used for the 'show window' variable through the Win32 APIs:
    // - u16 in STARTUPINFOA.wShowWindow / STARTUPINFOW.wShowWindow
    // - c_int in ShowWindow
    // - u32 in PEB.ProcessParameters.dwShowWindow
    // Since STARTUPINFO is the bottleneck for the allowed values, we use `u16` as the
    // type which can coerce into i32/c_int/u32 depending on how the user defines their wWinMain
    // (the Win32 docs show wWinMain with `int` as the type for nShowCmd).
    const nShowCmd: u16 = nShowCmd: {
        // This makes Zig match the nShowCmd behavior of a C program with a WinMain symbol:
        // - With STARTF_USESHOWWINDOW set in STARTUPINFO.dwFlags of the CreateProcess call:
        //   - nShowCmd is STARTUPINFO.wShowWindow from the parent CreateProcess call
        // - With STARTF_USESHOWWINDOW unset:
        //   - nShowCmd is always SW_SHOWDEFAULT
        const SW_SHOWDEFAULT = 10;
        if (peb.ProcessParameters.dwFlags & std.os.windows.STARTF_USESHOWWINDOW != 0) {
            break :nShowCmd @truncate(peb.ProcessParameters.dwShowWindow);
        }
        break :nShowCmd SW_SHOWDEFAULT;
    };

    // second parameter hPrevInstance, MSDN: "This parameter is always NULL"
    return root.wWinMain(hInstance, null, lpCmdLine, nShowCmd);
}