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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
<refentry id="glReadBuffer">
<refmeta>
<refmetainfo>
<copyright>
<year>1991-2006</year>
<holder>Silicon Graphics, Inc.</holder>
</copyright>
</refmetainfo>
<refentrytitle>glReadBuffer</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>glReadBuffer</refname>
<refpurpose>select a color buffer source for pixels</refpurpose>
</refnamediv>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glReadBuffer</function></funcdef>
<paramdef>GLenum <parameter>mode</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 id="parameters"><title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>mode</parameter></term>
<listitem>
<para>
Specifies a color buffer.
Accepted values are
<constant>GL_FRONT_LEFT</constant>,
<constant>GL_FRONT_RIGHT</constant>,
<constant>GL_BACK_LEFT</constant>,
<constant>GL_BACK_RIGHT</constant>,
<constant>GL_FRONT</constant>,
<constant>GL_BACK</constant>,
<constant>GL_LEFT</constant>,
<constant>GL_RIGHT</constant>, and
<constant>GL_AUX</constant><emphasis>i</emphasis>,
where <emphasis>i</emphasis> is between 0 and the value of <constant>GL_AUX_BUFFERS</constant> minus 1.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="description"><title>Description</title>
<para>
<function>glReadBuffer</function> specifies a color buffer as the source for subsequent
<citerefentry><refentrytitle>glReadPixels</refentrytitle></citerefentry>, <citerefentry><refentrytitle>glCopyTexImage1D</refentrytitle></citerefentry>, <citerefentry><refentrytitle>glCopyTexImage2D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexSubImage1D</refentrytitle></citerefentry>, <citerefentry><refentrytitle>glCopyTexSubImage2D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexSubImage3D</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glCopyPixels</refentrytitle></citerefentry> commands.
<parameter>mode</parameter> accepts one of twelve or more predefined values.
(<constant>GL_AUX0</constant> through <constant>GL_AUX3</constant> are always defined.)
In a fully configured system,
<constant>GL_FRONT</constant>,
<constant>GL_LEFT</constant>, and
<constant>GL_FRONT_LEFT</constant> all name the front left buffer,
<constant>GL_FRONT_RIGHT</constant> and
<constant>GL_RIGHT</constant> name the front right buffer, and
<constant>GL_BACK_LEFT</constant> and
<constant>GL_BACK</constant> name the back left buffer.
</para>
<para>
Nonstereo double-buffered configurations have only a front left and a
back left buffer.
Single-buffered configurations have a front left and a front right
buffer if stereo, and only a front left buffer if nonstereo.
It is an error to specify a nonexistent buffer to <function>glReadBuffer</function>.
</para>
<para>
<parameter>mode</parameter> is initially <constant>GL_FRONT</constant> in single-buffered configurations
and <constant>GL_BACK</constant> in double-buffered configurations.
</para>
</refsect1>
<refsect1 id="errors"><title>Errors</title>
<para>
<constant>GL_INVALID_ENUM</constant> is generated if <parameter>mode</parameter> is not one of the twelve
(or more) accepted values.
</para>
<para>
<constant>GL_INVALID_OPERATION</constant> is generated if <parameter>mode</parameter> specifies a buffer
that does not exist.
</para>
<para>
<constant>GL_INVALID_OPERATION</constant> is generated if <function>glReadBuffer</function>
is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
</para>
</refsect1>
<refsect1 id="associatedgets"><title>Associated Gets</title>
<para>
<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_READ_BUFFER</constant>
</para>
</refsect1>
<refsect1 id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>glCopyPixels</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexImage1D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexImage2D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexSubImage1D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexSubImage2D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexSubImage3D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glDrawBuffer</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glReadPixels</refentrytitle></citerefentry>
</para>
</refsect1>
<refsect1 id="Copyright"><title>Copyright</title>
<para>
Copyright <trademark class="copyright"></trademark> 1991-2006
Silicon Graphics, Inc. This document is licensed under the SGI
Free Software B License. For details, see
<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
</para>
</refsect1>
</refentry>