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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>GDK</title>
<link rel="stylesheet" type="text/css" href="../../style.css">
</head>
<body>
<h2>GDK Base Driver</h2>
<p>This driver represents a basic driver for all system-dependent drivers
implemented in the X-Windows system. The implementation uses the
<a href="http://library.gnome.org/devel/gdk/">GDK</a> and
<a href="http://library.gnome.org/devel/cairo/">Cairo</a> API
functions. This driver was designed for the GTK+ version 2, and can be
compiled and used in all systems GDK is supported.</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>Attributes </h4>
<ul>
<li>
<a href="../func/lines.html#cdLineWidth">
<font face="Courier"><strong>LineWidth</strong></font></a>: if
<font face="Courier">width</font> is 1, the driver will use 0 for a better
performance.</li>
<li>
<a href="../func/lines.html#cdLineStyle">
<font face="Courier"><strong>LineStyle</strong></font></a>: thick lines have
style only in the line's direction. For example, you will see small rectangles
in a thick dotted line.</li>
<li>
<a href="../func/text.html#cdNativeFont">
<font face="Courier"><strong>NativeFont</strong></font></a>: also accepts the
X-Windows font string format. A scaled font is generated using the font size
and the font face.</li>
<li><a href="../func/text.html#cdFont">
<font face="Courier"><strong>Font</strong></font></a>: the old name "System"
is mapped to "fixed". A scaled font is generated using the font size
and the font face.</li>
</ul>
<h4>Colors </h4>
<ul>
<li>
<a href="../func/color.html#cdPalette">
<font face="Courier"><strong>Palette</strong></font></a>: When the number of
bits per pixel is smaller than or equal to 8, the driver will use the system
palette to solve colors passed as parameters to the canvas. The driver
allocates colors as they are requested - if a color cannot be allocated, the
closest color is used in the palette. For such, the driver sees all available
colors, in the current application and others. If one of the applications is
terminated, a color in the palette may become invalid and will only be updated
by the driver when it is requested again. For this reason, a call to <strong>
cdForeground </strong>or <strong>cdBackground</strong> or <strong>cdPalette</strong>
is recommended before drawing.<br>
When CD_FORCE is used, the driver forces color allocation.
This may imply changing colors in other applications when a cursor moves in
and out of the canvas. However, if the number of requested colors is smaller
than the maximum number of possible colors in the palette, then the first
colors in the default system palette will be preserved, minimizing this
problem.<br>
When CD_POLITE is used, all colors allocated by the driver are liberated, and
the requested colors are allocated. This is useful for the application to
prioritize the colors that will be allocated, causing other colors to be
mapped to their closest colors.<br>
Note that canvases in the same application interfere with one another, but
when a canvas is terminated it liberates all allocated colors.</li>
</ul>
<h4>Exclusive Attributes</h4>
<ul>
<li>"<b><font face="Courier">GC</font></b>": returns the GDK 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">"CAIROVERSION": </font></b>returns a string with
the Cairo version number. It is empty if the Cairo is not available.</li>
</ul>
</body>
</html>
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