RE: Register Lua callback functions from within Lua to C++

["Jan de Vos" <Jan.de.Vos@...>]

You need the correct metatable to be set on you userdata object.

If you are not using any binding framework (such as tolua++ or luabind),
you might be able to take a look at how the Button:new() function is
implemented. Do the same in your code, and it will work :-)

If you have no idea of how the Button:new() function was implemented,
chances are that its programmer used some binding framework or other.
The answer to your question greatly depends on that, so please try to
find out.


Jan

> -----Original Message-----
> From: lua-bounces@bazar2.conectiva.com.br 
> [mailto:lua-bounces@bazar2.conectiva.com.br] On Behalf Of 
> Michael Bauroth
> Sent: maandag 10 november 2008 15:35
> To: Lua list
> Subject: Re: Register Lua callback functions from within Lua to C++
> 
> Unfortunately this doesn't do the trick :(
> 
> Let us reduce the complexity of the problem even more ...
> 
> Primary I create an C++ object Button in Lua:
> 
> btn = Button:new()
> btn.RegisterCallback( callback )
> 
> In C++ I store the reference ...
> 
> m_CbOnMouseDown = luaL_ref( L, LUA_REGISTRYINDEX );
> 
> 
> Later on I want to call a function from C++ in Lua like this:
> 
> callback( btn )
> 
> where btn should be of type Button again, so that I can call 
> additonal 
> C++ methods on it. I don't use any binding framework at the moment.
> 
> 
> // push function
> lua_rawgeti( L, LUA_REGISTRYINDEX, m_CbOnMouseDown );
> 
> //push parameter(s)
> //lua_pushlightuserdata( L, this );
> //lua_pushvalue(L, 1);
> 			
> // call function
> if ( lua_pcall( L, 1, LUA_MULTRET, 0 ) != 0 )
> {
>      // error
> }
> 
> pushlightuserdata has the disadvantage to give me only type free data.
> Were should I embed the call to pushvalue instead?
> 
> Best Regards
> Micha
> 
> 
> 
> Peter Cawley schrieb:
> > It depends on which Lua/C++ binding framework you're using, but I'd 
> > guess that a copy of the Lua-ized 'this' pointer will be at 
> stack index 
> > 1, and so you could use lua_pushvalue(L, 1); to push a copy 
> of it to the 
> > top of the stack.
> 
>