Lua binding

gerrykwok7 · January 3, 2019, 3:38am

Is there any lua binding solutions that can bind a C++ class to lua? Including lua function callback.

AGulev · January 3, 2019, 8:41pm

Yes, you can write your own Native Extension (NE) and communicate between C/Cpp code and Lua code.
There is native extensions manual:

Example Extensions:

C API functions:
http://pgl.yoyo.org/luai/i/3.7+Functions+and+Types

Regarding Lua function callback.
Example of callback registration:

github.com

defold/extension-admob/blob/c9f0f5758426db41a0d0b7c64fa60945e57baf03/admob/src/googlemobileads.cpp#L224


}
if(adrequest.extras != 0)
{
    free((void*)adrequest.extras);
    adrequest.extras = 0;
}
memset(&adrequest, 0, sizeof(adrequest));
}


// http://www.defold.com/ref/dmScript/#dmScript::GetMainThread
static void RegisterCallback(lua_State* L, int index, LuaCallbackInfo* cbk)
{
if(cbk->m_Callback != LUA_NOREF)
{
    dmScript::Unref(cbk->m_L, LUA_REGISTRYINDEX, cbk->m_Callback);
    dmScript::Unref(cbk->m_L, LUA_REGISTRYINDEX, cbk->m_Self);
}


cbk->m_L = dmScript::GetMainThread(L);
luaL_checktype(L, index, LUA_TFUNCTION);

Invoke Callback:

github.com

defold/extension-admob/blob/c9f0f5758426db41a0d0b7c64fa60945e57baf03/admob/src/googlemobileads.cpp#L252


static void UnregisterCallback(LuaCallbackInfo* cbk)
{
if(cbk->m_Callback != LUA_NOREF)
{
    dmScript::Unref(cbk->m_L, LUA_REGISTRYINDEX, cbk->m_Callback);
    dmScript::Unref(cbk->m_L, LUA_REGISTRYINDEX, cbk->m_Self);
    cbk->m_Callback = LUA_NOREF;
}
}


static void InvokeCallback(LuaCallbackInfo* cbk, MessageCommand* cmd)
{
if(cbk->m_Callback == LUA_NOREF)
{
    return;
}


lua_State* L = cbk->m_L;
DM_LUA_STACK_CHECK(L, 0);


lua_rawgeti(L, LUA_REGISTRYINDEX, cbk->m_Callback);

gerrykwok7 · January 4, 2019, 2:04am

I know this, but I found If I want to bind a C++ class to lua, it has a lot of glue codes, Is there some solutions like tolua?

AGulev · January 4, 2019, 7:36am

Sorry for my misunderstanding.
Maybe @Mathias_Westerdahl could help with your question.

britzl · January 4, 2019, 9:41am

There are several tools for generating Lua bindings from header files etc I haven’t tried any of them myself though.

http://lua-users.org/wiki/BindingCodeToLua

I’ve heard of sol and sol2 in the list above and it is supposedly a very good solution.

Mathias_Westerdahl · January 8, 2019, 9:09am

No, I haven’t heard of anything like this. @britzl’s suggestions are probably a good approach though, if necessary.