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<!doctype HTML PUBLIC "-//IETF//DTD HTML//EN">
<html>
<head>
<meta http-equiv="Content-Language" content="en-us">
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title>XRender</title>
<link rel="stylesheet" type="text/css" href="../../style.css">
</head>
<body>
<h2>XRender Base Driver</h2>
<p>This driver represents a basic driver for all system-dependent drivers
implemented in the X-Windows system using the XRender extension. The implementation uses the
XRender and Xft API functions.</p>
<p>The main motivation for the use of XRender was transparency for all the primitives. Beyond that we got other features
like anti-aliasing, gradient filling and transformations.</p>
<p>This driver still does not completely replace the X-Windows base driver, because
XRender does not have support for
XOR and for line styles.</p>
<p>So we let the programmer to choose what to use. We created the function <font face="Courier"><strong>
cdUseContextPlus</strong></font> that allows to activate or to deactivate the use of
X-Render for the available X-Windows based drivers.
This function affects only the <font face="Courier"><strong>cdCreateCanvas</strong></font> function call, once created
the canvas will be always a XRender canvas. In fact the function affects primary the definitions
<font face="Courier"><strong>CD_NATIVEWINDOW</strong></font>,
<strong><span style="font-family: Courier">CD_IMAGE</span></strong> and <strong>
<span style="font-family: Courier">CD_DBUFFER</span></strong>, because they are
function calls and not static defines.</p>
<p>Using XRender it is allowed to create more that one canvas at the same time for the same Window. And they can co-exist
with a standard X-Windows canvas.</p>
<p>To enable the use of XRender based drivers you must call the initialization function <font face="Courier"><strong>
cdInitContextPlus()</strong></font> once and link to the libraries "<strong>cdcontextplus</strong>", "<strong>Xrender</strong>" and "<strong>Xft</strong>".
Also the libraries "<strong>Xrender</strong>" and "<strong>Xft</strong>"
must be installed in your system. The XRender extension must be available in
the X-Windows server for the driver to work.</p>
<p>Currently, pre-compiled binaries are available for Linux, Darwin
and FreeBSD54. It is not available for the systems we have with AIX, SunOS and
IRIX.</p>
<p>In CDLua it is not necessary any additional initialization, but the
application must still be linked with the <strong>cdcontextplus.lib</strong>
library or a <strong>require"cdluacontextplus"</strong> can be used when
using dynamic libraries.</p>
<h3>Behavior of Functions</h3>
<h4>Control </h4>
<ul>
<li><a href="../func/other.html#cdPlay">
<font face="Courier"><strong>Play</strong></font></a>: does nothing, returns
<font face="Courier">CD_ERROR</font>. </li>
</ul>
<h4>Coordinate System and Clipping </h4>
<ul>
<li>
<a href="../func/coordinates.html#cdUpdateYAxis">
<font face="Courier"><strong>UpdateYAxis</strong></font></a>: the
orientation of axis Y is the opposite to its orientation in the CD library.
Except when using transformations.</li>
</ul>
<h4>Primitives</h4>
<ul>
<li><font face="Courier"><a href="../func/lines.html#cdLine"><b>Line</b></a></font>:
simulated using the client's <strong>Poly</strong>.</li>
<li><a href="../func/text.html#cdText"><font face="Courier"><strong>Text</strong></font></a>:
Generic transformation
matrix affects only the position of the text. Complex clipping regions can not
contain text regions.</li>
<li><a href="../func/lines.html#cdBegin">
<font face="Courier"><strong>Begin</strong></font></a>: <strong><tt>
CD_BEZIER</tt></strong> is simulated with lines.
<strong><tt>CD_PATH</tt></strong> is supported.</li>
<li><font face="Courier"><strong><a href="../func/lines.html#cdRect">Rect</a></strong></font>:
simulated using the client's <strong>Line</strong>.</li>
<li><font face="Courier"><a href="../func/lines.html#cdArc"><b>Arc</b></a></font>:
simulated using the client's <strong>Line</strong>. </li>
<li><font face="Courier"><a href="../func/filled.html#cdSector"><b>Sector</b></a></font>:
simulated using the client's <strong>Poly</strong>. </li>
<li><font face="Courier"><b><a href="../func/filled.html#cdChord">Chord</a></b></font>:
simulated using the client's <strong>Poly</strong></li>
<li><font face="Courier"><a href="../func/filled.html#cdBox"><b>Box</b></a></font>:
simulated using the client's <strong>Poly</strong>. </li>
</ul>
<h4>Attributes </h4>
<ul>
<li>
<a href="../func/lines.html#cdLineWidth">
<font face="Courier"><strong>LineWidth</strong></font></a>: the driver will
use a polygon that fits to the line extents, even when linewidth==1.</li>
<li>
<a href="../func/lines.html#cdLineStyle">
<font face="Courier"><strong>LineStyle</strong></font></a>: NOT supported.</li>
<li><a href="../func/filled.html#cdPattern"><font face="Courier"><strong>
Pattern</strong></font></a>: each pixel can contain transparency information.</li>
<li>
<a href="../func/text.html#cdNativeFont">
<font face="Courier"><strong>NativeFont</strong></font></a>: also accepts the
X-Windows font string format. You can use program <strong>xfontsel</strong> to select a font and obtain the string.
For ex: "-*-times-bold-r-*-*-24-*-*-*-*-*-*-*" (equivalent of <strong>Font</strong>("Times",
CD_BOLD, -24).</li>
<li><a href="../func/text.html#cdFont">
<font face="Courier"><strong>Font</strong></font></a>: font support is
implemented using the Xft library. Internally the Xft library uses the
Freetype library.</li>
</ul>
<h4>Colors </h4>
<ul>
<li>
Use the X-Windows base driver support for colors.</li>
</ul>
<h4>Client and Server Images</h4>
<ul>
<li>
All functions use the X-Windows base driver functions.</li>
</ul>
<h4>Exclusive Attributes</h4>
<ul>
<li>"<b><font face="Courier">GC</font></b>": returns the X11 graphics
context (get only). In Lua is returned as a user data.</li>
</ul>
<ul>
<li>"<b><font face="Courier">ROTATE</font></b>": allows the usage of 1
angle and 1 coordinate (x, y), that define a global rotation transformation
centered in the specified coordinate. Use 1 real and 2 integer values inside a
string ("%g %d %d" = angle x y). In this driver will change the
current transformation matrix, if removed will reset the current
transformation matrix.</li>
</ul>
<ul>
<li>"<b><font face="Courier">ANTIALIAS</font></b>": controls the use of anti-aliasing
for the text, image zoom and line
drawing primitives. Assumes values "1" (active) and "0" (inactive). Default value: "1". </li>
</ul>
<ul>
<li><b><font face="Courier">"LINEGRADIENT": </font></b>defines a filled interior style that uses a line gradient
between two colors. It uses 2 points ("%d %d %d %d" = x1 y1 x2 y2), one for the starting point using (using the
foreground color), and another one for the end point (using the background color).
(available only if Xrender version >= 0.10)</li>
</ul>
<ul>
<li><b><font face="Courier">"XRENDERVERSION": </font></b>returns a
string with the XRender version number. It is empty if the XRender extension
is not available in the X-Windows server.</li>
</ul>
</body>
</html>
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