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<html>
<head>
<meta http-equiv="Content-Language" content="en-us">
<title>Lua Binding</title>
<link rel="stylesheet" type="text/css" href="../style.css">
</head>
<body>
<h2>Lua Binding</h2>
<h3><a name="Overview">Overview</a></h3>
<p>
All the CD functions are available in Lua, with a few exceptions. We call it <strong>
CDLua</strong>. To use them the
general application will do require"cdlua", and require"cdluaxxxx" to all other
secondary libraries that are needed. The functions and definitions will be available
under the table "cd" using the following name rules:</p>
<pre>cdXxx -> cd.Xxx (for functions)<br />wdXxx -> cd.wXxx (for WD functions)<br />CD_XXX -> cd.XXX (for definitions)<br />cdCanvasXXX(canvas,... => canvas:XXX(... (for methods)<br /></pre>
<p>
New functions (without equivalents in C) were implemented to create and
destroy objects that do not exist in C. For instance functions were developed
to create and destroy images, pattern, stipple and palette. All the
metatables have the "tostring" metamethod implemented to help debuging. Some functions were modified to receive those objects as parameters.</p>
<p>
Also the functions which receive values by reference in C were modified. Generally, the values of
parameters that would have their values modified are now returned by the function in the same order.</p>
<p>
Notice that, as opposed to C,
in which enumeration flags are<i> </i>combined with the bitwise operator OR, in Lua the flags are added arithmetically.</p>
<p>
In Lua all parameters are checked and a Lua error is emitted when the check fails.</p>
<p>
All the objects are garbage collected by the Lua garbage collector, except
the canvas because there can be different Lua canvases pointing to the same
C canvas. The "tostring"
metamethod of the Lua canvas will print both values, Lua
and C. The equal method will compare the C canvas value.</p>
<h3>
Initialization</h3>
<p>
<strong>Lua</strong> 5.1 "require" can be used for all the <strong>
CDLua</strong>
libraries. You can use <b>require</b>"<b>cdlua</b>" and so on, but the LUA_CPATH
must also contains the following:
</p>
<pre>"./lib?51.so;" [in UNIX]
".\\?51.dll;" [in Windows]
</pre>
<p>The <a href="http://luabinaries.luaforge.net/">LuaBinaries</a> distribution already includes these modifications on the
default search path.</p>
<p>The simplest form <b>require</b>"<b>cd</b>"
and so on, can not be used because there are CD dynamic libraries with names
that will conflict with the names used by <b>require</b> during search.</p>
<p>
Additionally you can statically link the <strong>CDLua</strong> libraries, but you must call the initialization functions manually. The <strong>
<font face="Courier New">cdlua_open</font></strong> function is declared in the header file <strong><font face="Courier New">cdlua</font><font size="2" face="Courier New">.</font><font face="Courier New">h</font></strong>,
see the example below:</p>
<div align="center">
<center>
<table border="1" cellpadding="10" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" id="AutoNumber1">
<tr>
<td>
<pre>#include <lua.h>
#include <lualib.h>
#include <lauxlib.h>
<b><font color="#FF0000">#include <cdlua.h></font></b></pre>
<pre>void main(void)
{
lua_State *L = lua_open();
luaopen_string(L);
luaopen_math(L);
luaopen_io(L);
<b> <font color="#FF0000">cdlua_open(L);</font>
</b>
lua_dofile("myprog.lua");
lua_close(L);
}</pre>
</td>
</tr>
</table>
</center>
</div>
<h3>Exchanging Values between C and Lua</h3>
<p>Because of some applications that interchange the use of CD canvases in Lua and C, we build a
few C functions that are available in "cdlua.h":</p>
<pre>cdCanvas* cdlua_checkcanvas(lua_State* L, int pos);
void cdlua_pushcanvas(lua_State* L, cdCanvas* canvas);</pre>
</body>
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