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<html>
<head>
<meta http-equiv="Content-Language" content="en-us">
<title>Lua Binding</title>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<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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