class Test_Class : private play_callback {

public:

    // play_callback methods
    virtual void on_playback_new_track(metadb_handle_ptr p_track) {Send_Message();}

    virtual void on_playback_stop(play_control::t_stop_reason reason) {}
    virtual void on_playback_dynamic_info_track(const file_info & p_info) {}
    virtual void on_playback_starting(play_control::t_track_command p_command, bool p_paused) {}
    virtual void on_playback_seek(double p_time) {}
    virtual void on_playback_pause(bool p_state) {}
    virtual void on_playback_edited(metadb_handle_ptr p_track) {}
    virtual void on_playback_dynamic_info(const file_info & p_info) {}
    virtual void on_playback_time(double p_time) {}
    virtual void on_volume_change(float p_new_val) {}

    void Send_Message();

    Test_Class() {

        // Register play callback.
            try {
                static_api_ptr_t<play_callback_manager> pcm;
                pcm->register_callback(this,
                    flag_on_playback_new_track, false);
            }
            catch (const exception_service_not_found &) {
                // play_callback_manager does not exist; something is very wrong.

            }

    }
};

void Test_Class::Send_Message()
{
    ShellExecute(NULL, _T("open"), _T("C:\\snarl_command.exe"), _T("/M \"Hello\" \"Hello World!\""), _T("C:\\"), SW_HIDE);
}

class snarl_play_callback : public play_callback_static {
public:
    /* play_callback methods go here */

    void Send_Message();

    /* The play_callback_manager enumerates play_callback_static services and registers them automatically. We only have to provide the flags indicating which callbacks we want. */
    virtual unsigned get_flags() {
        return flag_on_playback_new_track;
    }
};

static service_factory_single_t<snarl_play_callback> g_play_callback_static_factory;

class initquit_Snarl : public initquit {
public:
    virtual void on_init() {
            Test_Class snarl_Messenger;
            snarl_Messenger.Send_Message();
    }

    virtual void on_quit() {
        // Do nothing.
    }
};

Test_Class snarl_Messenger;
static_api_ptr_t<play_callback_manager> pcm;
                pcm->register_callback(snarl_Messenger,
                    flag_on_playback_new_track, false);

static service_factory_single_t<Test_Class> g_play_callback_static_factory;