-module(msgbox).
-compile([export_all]).

pause(X) ->
    receive after X -> ok end.

main() ->
    spawn(fun heartbeat/0),
    pause(1000),
    {ok, User32} = ffi:load_library_win("user32"),
    Answer = ffi:call_block(User32, "MessageBoxA",
                            [0,
                             "Erlang VM is now blocked by your call",
                             "Erlang",
                             4]),
    io:format("You have pressed '~p'\n", [msgbox(Answer)]),
    pause(1000),
    Answer2 = ffi:call(User32, "MessageBoxA",
                       [0,
                        "Erlang VM is not blocked now if you have "
                        "specified +A option to erl",
                        "Erlang",
                        4]),
    io:format("You have pressed '~s'\n", [msgbox(Answer2)]),
    pause(1000),
    erlang:halt().

msgbox(6) -> yes;
msgbox(7) -> no;
msgbox(X) -> X.

heartbeat() ->
    io:format("alive!~n", []),
    pause(500),
    heartbeat().