Re: lua/tolua 4 questions

[anon <anon@...>]

> First of all, it is great to see gllua being ported. I would like to
> coordinate the GL canvas of tklua with your port of gllua, so please
> get in touch with me when you feel that your port has reached an
> appropriate level of functionality. Also feel free to take a look at
> my partial gllua port. You can find the link at
> 
> http://www.cis.upenn.edu/~cvogler/lua/tklua.html
> 

ok will do.

> Now, to answer your question:
> 
> Getting the reference via tolua currently won't work without some
> hackery of the generated *.c file. I suggest that you do it the way I
> did it in tklua instead. This is how the idle function is written
> there, for example.
> 
> static int tkluaRegisterIdle (lua_State *tklua_S)
> {
> TkLua *tklua = tklua_tkinfo(tklua_S);
> DEBUG_BEGINFUNCTION;
> 
> if (tklua->idleLua)
> {
> lua_unref(tklua_S, tklua->idleLua);
> tklua->idleLua = LUA_NOREF;
> }
> if (lua_isnil(tklua_S, 1))
> Tk_CancelIdleCall(doLua,tklua_S);
> else
> {
> lua_pushvalue(tklua_S, 1);
> tklua->idleLua = lua_ref(tklua_S, 1);
> Tk_DoWhenIdle(doLua,tklua_S);
> }
> DEBUG_ENDFUNCTION(0);
> return 0;
> }
> 
> 
> and somewhere in the initialization function:
> 
> lua_register(tklua_S, "tkidle",tkluaRegisterIdle);
> 
> The crucial calls in the above function are
> 
> lua_pushvalue(tklua_S, 1);
> tklua->idleLua = lua_ref(tklua_S, 1);
> 
> The first one pushes the lua callback function on the top of the
> stack.  The second one creates a reference to it, so that it won't be
> garbage-collected, and so that it can later be accessed via this
> reference. This access is done in doLua, which dispatches the callback
> to the appropriate lua function. It is quite simple:
> 
> static void doLua (ClientData state)
> {
> lua_State *tklua_S = (lua_State *) state;
> TkLua *tklua = tklua_tkinfo(tklua_S);
> lua_getref(tklua_S, tklua->idleLua);
> lua_call(tklua_S, 0, 0);
> Tk_DoWhenIdle(doLua,tklua_S);
> }
> 
> As you can (hopefully) see, you can get the lua function with
> lua_getref(tklua->idleLua) here. This is the reference that previously
> was stored there by tkluaRegisterIdle().
> 
> 

thanks Christian, i was almost there, but not quite, and a wink is as
good as a nod to a blind man.


> Now, another thing: How are you obtaining the lua state for the
> callback functions? This was the most troublesome aspect of porting
> tklua. I solved this problem by passing the state in the ClientData
> field of the tk calls. How are you planning to solve this problem with
> OpenGL callbacks? IIRC, these callbacks don't allow you to pass extra
> data at all.
>

i store the lua_State within the DisplayTable list which the glut callback
wrappers pull out via the window ID. This may not be the best solution but
it seems to work so far.

i haven't done the non glut callbacks yet.. so i haven't solved that nor
thought about it. its probably possible to use the same method since
the only way so far to initialize a GL window is to use GLUT.

Most of it is working ok. Except for overloaded functions which so far
are failing since they are not able to tell how many arguments were passed,
at least i haven't figured out that part yet.

charlie