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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>CAIRO</title>
<link rel="stylesheet" type="text/css" href="../../style.css">
<style type="text/css">
.style1 {
font-family: Courier;
}
</style>
</head>
<body>
<h2>CAIRO Base Driver</h2>
<p>This driver represents a basic driver for all system-dependent drivers
implemented in the X-Windows and MS-Windows systems. The implementation uses the
<a href="http://library.gnome.org/devel/pango/">Cairo</a> API
functions and Pango functions to support Unicode text. This driver can be
compiled and used in all systems Cairo is supported. The drivers <b>Native Window</b>,
<b>Image</b>, <b>Printer</b> and <b>Double Buffer</b> were implemented.</p>
<p>The main motivation for the use of Cairo was transparency for all the
primitives. Beyond that we got other features like anti-aliasing, gradient
filling, transformations and back-ends (support to rendering: PDF, PS, SVG and
PNG surfaces).</p>
<p>This driver still does not completely replace the X-Windows and GDI Windows
base drivers, because Cairo does not have support for bitwise XOR operations and
for complex clipping regions.</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
Cairo for the available GDK, Win32 or 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 Cairo 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 Cairo 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 GD, Win32 or X-Windows canvas.</p>
<p>To enable the use of Cairo based drivers you must call the initialization function <font face="Courier"><strong>
cdInitContextPlus()</strong></font> once and link to the libraries "<strong>cdcairo</strong>" and "<strong>cairo</strong>".
When using the GDK base driver you do not need to link with the "<strong>cdcairo</strong>"
library. Also the Cairo library must be installed in your system.</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.</li>
</ul>
<h4>Primitives</h4>
<ul>
<li>Floating point primitives are supported.</li>
</ul>
<h4>Attributes </h4>
<ul>
<li>
<a href="http://www.tecgraf.puc-rio.br/cd/en/func/attributes.html#cdWriteMode">
<font face="Courier"><strong>WriteMode</strong></font></a>: does nothing.
There is no support for XOR or NOT_XOR.</li>
<li>
<a href="../func/text.html#cdNativeFont">
<font face="Courier"><strong>NativeFont</strong></font></a>: also accepts the
X-Windows font string format.</li>
<li><a href="../func/text.html#cdFont">
<font face="Courier"><strong>Font</strong></font></a>: "Courier" is mapped to
"Courier New", "Helvetica" is mapped to "Arial", and "Times" is mapped to
"Times New Roman". Underline and Strikeout are NOT supported.</li>
</ul>
<h4>Colors </h4>
<ul>
<li>
<a href="../func/color.html#cdPalette">
<font face="Courier"><strong>Palette</strong></font></a>: NOT supported.</li>
</ul>
<h4>Exclusive Attributes</h4>
<ul>
<li>"<b><font face="Courier">ANTIALIAS</font></b>": controls
the use of anti-aliasing for the text and drawing shapes. Assumes values "1"
(active) and "0" (inactive). Default value: "1".</li>
</ul>
<ul>
<li>"<b><font face="Courier">CAIRODC</font></b>": returns the
Cairo drawing context (get only). In Lua is returned as a user data.</li>
</ul>
<ul>
<li><b><font face="Courier">"CAIROVERSION": </font></b>returns a string with
the Cairo version number. It is empty if the Cairo is not available.</li>
</ul>
<ul>
<li><strong><span style="font-family: Courier">"HATCHBOXSIZE"</span></strong>:
defines the size of smallest hatch box pattern. This affects the spacing
between the hatch lines. The value passed must be a string containing an
integer ("%d"). If the value of the attribute passed is NULL, the value is
rest to the default. When consulted returns the current value ("%d"). Default:
"8".</li>
</ul>
<ul>
<li>"<b><font face="Courier">IMGINTERP</font></b>": changes how
interpolation is used in image scale. Can be "BEST" (highest-quality),
"BILINEAR" (linear interpolation), "GOOD" (quality similar to BILINEAR),
"NEAREST" (nearest-neighbor filtering) or "FAST" (quality similar to NEAREST).
Default: "GOOD".</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).</li>
</ul>
<ul>
<li>"<span class="style1"><strong>PATTERNIMAGE</strong></span>": defines
a filled interior style using a server image as pattern. Data must be a server
image handle created with he Cairo base driver.</li>
</ul>
<ul>
<li>"<b><font face="Courier">POLYHOLE</font></b>": defines the index of
the vertex where there is a hole in a closed polygon. It will affect the next
<strong>cdEnd</strong>. Can be called several times between <strong>cdBegin</strong>
and <strong>cdEnd</strong> to define holes. The value passed must be a string
containing an integer ("%d"). If the value of the attribute passed is NULL,
all holes will no longer be considered. When consulted returns the current
number of holes ("%d"). It can have a maximum of 500 holes. Default: NULL.</li>
</ul>
<ul>
<li>"<b><font face="Courier">RADIALGRADIENT</font></b>": defines
a filled interior style that uses a radial gradient between two colors. It
uses 2 points and 2 radius ("%d %d %g %d %d %g" = x1 y1 rad1 x2 y2 rad2), one
for the starting point using (using the foreground color), and another one for
the end point (using the background color).</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). Can not be set if a transformation is
already set.</li>
</ul>
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