Re: lua_pushusertag - am I just confused?

["Matt Holmes" <kerion@...>]

Answered my own question :)

I have to push the user data, get a reference to and lua_getref it when I
need it :) Helps to read a bit closer sometimes ;)

Matt Holmes
Lead Developer
The Visual Lua Project
http://www.sourceforge.net/projects/visuallua/

----- Original Message -----
From: "Matt Holmes" <kerion@bellatlantic.net>
To: "Multiple recipients of list" <lua-l@tecgraf.puc-rio.br>
Sent: Thursday, August 23, 2001 9:20 PM
Subject: lua_pushusertag - am I just confused?


> Hello again everyone :)
>
> I am having some trouble with usertags/data, and I was wondering if
someone
> might clear some stuff up form. I have the following peice of code that
> creates a new global and pushes a user tag on the stack as its values:
>
> void VLLuaHandler::SetErrorHandler()
> {
>  if(m_cState)
>  {
>   lua_setglobal(m_cState, "_handler");
>   lua_pushusertag(m_cState, this, LUA_ANYTAG);
>
>   lua_register(m_cState, LUA_ERRORMESSAGE, HandleLuaError);
>  }
> }
>
> As you can see, I create the global "_handler" and push a piece of user
data
> (in this case "this", an instance of the VLLuaHandler class) on to the
> stack, using LUA_ANYTAG, because I want it to match by value rather then
tag
> (and to be quite honest, when I tried to use my own tag I kept getting a
> GPF, strange...)
>
> I then register my HandleLuaError function for the _ERRORMESSAGE lua
> function (using the LUA_ERRORMESSAGE define from lua.h).
>
> My HandleLuaError function looks as follows:
>
> int HandleLuaError(lua_State *cState)
> {
>  char *sBuffer = NULL;
>  VLLuaHandler *cHandler = NULL;
>
>  // I assumed that this would push my user data on to the stack, by
getting
> the global "_handler"  that I previously set
>  lua_getglobal(cState, "_handler");
>  int nArgs = lua_gettop(cState);
>
>  // Test code to figure out what was going on. This loop is supposed to
> MessageBox me the type of the data on the stack, and it works fine for
stack
> index 1,returns 'string'. It crashes the program when it it tries to get
the
> type of stack index 2....hmmmm
>
>  for(int i = 1; i <= nArgs; i++)
>   VLErrorNotifier::Ref().Notify(lua_typename(cState, lua_type(cState, i)),
> VLErrorNotifier::INFO);
>
>  // Not even sure of any of this is right, I figured that lua_getglobal
> would push my user data to index 2 on the stack, but 1 or 2, doesn't
matter,
> this returns false kills the function
>  if(!lua_isuserdata(cState, 2))
>   return 0;
>
>  if(!lua_isstring(cState, 1))
>   return 0;
>
>  // More stuff here, but it never gets that far
>  ...
> }
>
> Okay, so oviously I am doing something wrong here, or just missing a basic
> concept. Anyone care to make me look the fool and point it out? ;)
>
> Matt Holmes
> Lead Developer
> The Visual Lua Project
> http://www.sourceforge.net/projects/visuallua/
>
>
>