windowsGetPreferredColorScheme

pub fn windowsGetPreferredColorScheme() ?dvui.enums.ColorScheme {
    const winapi = struct {
        pub extern "advapi32" fn RegGetValueW(
            hkey: std.os.windows.HKEY,
            lpSubKey: std.os.windows.LPCWSTR,
            lpValue: std.os.windows.LPCWSTR,
            dwFlags: std.os.windows.DWORD,
            pdwType: ?*std.os.windows.DWORD,
            pvData: ?*anyopaque,
            pcbData: ?*std.os.windows.DWORD,
        ) callconv(.winapi) std.os.windows.LSTATUS;
    };

    var out: [4]u8 = undefined;
    var len: u32 = 4;
    const res = winapi.RegGetValueW(
        std.os.windows.HKEY_CURRENT_USER,
        std.unicode.utf8ToUtf16LeStringLiteral("SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize"),
        std.unicode.utf8ToUtf16LeStringLiteral("AppsUseLightTheme"),
        0x10, //advapi32.RRF.RT_REG_DWORD,
        null,
        &out,
        &len,
    );
    if (res != 0) return null;

    const val = std.mem.littleToNative(i32, @bitCast(out));
    return if (val > 0) .light else .dark;
}