[Date Prev][Date Next][Thread Prev][Thread Next]
- Subject: How do I manipulate C++ vectors of C structs in Lua?
- From: "Nolan Check" <nolancheck@...>
- Date: Sun, 10 Sep 2006 15:58:14 -0700
This may seem like a question that has been answered dozens of times with
"use metatables". However, I'm having trouble figuring out how to apply that
to the problem I have right now. I'll try to explain...
I need to manipulate sprites with Lua (I am embedding Lua in my own simple
video game engine). A sprite is just a graphic that can be placed anywhere
on the screen. I have this C structure for a sprite:
bool Enabled; // Should this sprite be drawn?
lua_Number X; // X position
lua_Number Y; // Y position
This structure can't specify which graphic to use. It doesn't need to
because there is only one graphic available at the moment.
My program keeps a C++ vector of sprites. On each frame, it goes through the
vector and draws all of the sprites in it:
A C function "Sprite_New" is exported to Lua. It adds a SPRITE_USERDATA to
the end of the vector. I'm not worried about any "Sprite_Delete" function
yet. I need to get this working first.
All I need is a way to access the elements of g_SpriteVector from Lua. Then,
I need to be able to manipulate the "Enabled", "X", and "Y" fields of the
structure. In other words, I want to be able to access g_SpriteVector in Lua
just like I can in my C++ code.
I hope this is all understandable. I was thinking of using Lua Userdata
objects to represent the sprite vector and each sprite. Then, I could give
them metatables which let me access g_SpriteVector like an array and the
SPRITE_USERDATA elements like tables. I need help figuring out how to do it,
if it is possible.