Re: Dialog system : pausing script and resume on player's answer

I usually try not to call lua code from C++ so I think I will stick
with my way.I agree with the use of 2 distinct functions "showMessage"
and "getUserReply" embedded into a single lua function : I had seen a
similar answer during my researches on the internet.

> However, in order for this to work, your Lua script needs to be in a
> coroutine. That's what they're for.
My question would be how to create the coroutine (I am not that
familiar with scripting) ?
I would like to yield/resume from C++ so do I need to use
lua_newthread()  + lua_resume() / lua_yield ? is it equivalent to
creating a coroutine from lua ( thread = coroutine.create( fn) ).

What bothers me in both cases is that I need to embed the script into
a function (well I could do it) to start the coroutine. Isn't there
some kind of a global coroutine ? I mean when one does luaL_dofile(),
it executes many lua instructions sequentially like a coroutine would,
so why the need to give an initial function ?

Thx for your answer, it does clarify things for a beginner like me.



On Mon, Jan 17, 2011 at 9:59 PM, Jason McKesson <[email protected]> wrote:
>
> On 1/17/2011 7:45 AM, Teto wrote:
> > Hi,
> >
> > I'm trying to create a dialog system for a game with the possibility
> > of choosing between different answers (there might be more than 2
> > answers)
> >
> > =========================
> > local speech = createSpeech("Welcome to the tutorial ! Do you want to
> > skip it ?");
> > speech:addAnswer('Yes',1);
> > speech:addAnswer('No',0);
> >
> > -- answerValue could be either 1 or 0
> > local answerValue = MainState:showMessage(speech);
> > if(answerValue == 1) then
> >        -- Player wants to skip tutorial
> > else
> >        -- we create new dialogs ....
> > end
> > =========================
> >
> > showMessage() is a C++ function that changes my C++ state machine to
> > the dialog system. I would like showMessage() to pause the script when
> > called. I would like the script to resume when the player answers the
> > question and return his answer (an integer, retrieved in the example
> > in "answerValue") possibly from a different function than
> > showMessage() (C++ function onAnswer() for example).
> >
> > Then on the lua side, I will create  matching dialogs.
> >
> > What is the best way to achieve this (if possible with luabind) ? I've
> > tried using the yield policy:
> >      luabind::class_<CSinglePlayerState>("CSinglePlayerState")
> >          .def("showMessage",&CSinglePlayerState::showMessage, yield)
> >          ,
> >
> > but I get the error "Attempt to yield across metamethod". Do I
> > absolutely need to create a thread ? (I would like to keep things
> > simple).
> >
> >
> > Let me know if things are unclear or if this would be best asked on a lua forum.
> >
> > Matt
> To me, it's all a matter of what your answer to this question is: who's
> supposed to be in charge?
>
> When using Lua as an embedded scripting language, I generally prefer
> that C++ is in charge. So, if I were doing something like this, each
> line of text in the dialog would be a Lua script. C++ would call that
> Lua script, and the script would tell it what string to show, what the
> possible answers are, and what dialog script to show for each choice. If
> the Lua script needs to be called after the player answers, then there
> would be a place for such hooks.
>
> So rather than the Lua script telling C++ to show some text, the C++
> system ask Lua what the current text and such are. The Lua script would
> return an object containing the text to show, the options to display,
> and what to do for each option. It would be up to C++ to do the
> equivalent to "MainState::showMessage()" call.
>
> This coding style makes it highly unlikely to ever need to yield in the
> fashion you're needing to.
>
> However, if you're adamant about doing things this way, then you should
> have a two-phase version of "MainState::showMessage()" There should be
> two C++ functions: showMessage and getUserReply. When you use them in
> Lua, you yield between them, with the understanding that C++ will not
> resume the Lua thread until the reply is ready:
>
> ======
> MainState:showMessage(...);
> thread.yield();
> local answerValue = MainState:getUserReply();
> ======
>
> You can even encapsulate this into a single Lua function.
>
> However, in order for this to work, your Lua script needs to be in a
> coroutine. That's what they're for.
>
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