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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="glBindFragDataLocation">
<refentryinfo>
<copyright>
<year>2010-2013</year>
<holder>Khronos Group</holder>
</copyright>
</refentryinfo>
<refmeta>
<refentrytitle>glBindFragDataLocation</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>glBindFragDataLocation</refname>
<refpurpose>bind a user-defined varying out variable to a fragment shader color number</refpurpose>
</refnamediv>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glBindFragDataLocation</function></funcdef>
<paramdef>GLuint <parameter>program</parameter></paramdef>
<paramdef>GLuint <parameter>colorNumber</parameter></paramdef>
<paramdef>const char * <parameter>name</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 id="parameters"><title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>program</parameter></term>
<listitem>
<para>
The name of the program containing varying out variable whose binding to modify
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>colorNumber</parameter></term>
<listitem>
<para>
The color number to bind the user-defined varying out variable to
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>name</parameter></term>
<listitem>
<para>
The name of the user-defined varying out variable whose binding to modify
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="description"><title>Description</title>
<para>
<function>glBindFragDataLocation</function> explicitly specifies the binding of the user-defined varying out variable
<parameter>name</parameter> to fragment shader color number <parameter>colorNumber</parameter> for program
<parameter>program</parameter>. If <parameter>name</parameter> was bound previously, its assigned binding is replaced
with <parameter>colorNumber</parameter>. <parameter>name</parameter> must be a null-terminated string. <parameter>colorNumber</parameter>
must be less than <constant>GL_MAX_DRAW_BUFFERS</constant>.
</para>
<para>
The bindings specified by <function>glBindFragDataLocation</function> have no effect until <parameter>program</parameter>
is next linked. Bindings may be specified at any time after <parameter>program</parameter> has been created. Specifically,
they may be specified before shader objects are attached to the program. Therefore, any name may be specified in <parameter>name</parameter>,
including a name that is never used as a varying out variable in any fragment shader object. Names beginning with <constant>gl_</constant> are
reserved by the GL.
</para>
<para>
In addition to the errors generated by <function>glBindFragDataLocation</function>, the
program <parameter>program</parameter> will fail to link if:
<itemizedlist>
<listitem>
<para>
The number of active outputs is greater than the value <constant>GL_MAX_DRAW_BUFFERS</constant>.
</para>
</listitem>
<listitem>
<para>
More than one varying out variable is bound to the same color number.
</para>
</listitem>
</itemizedlist>
</para>
</refsect1>
<refsect1 id="notes"><title>Notes</title>
<para>
Varying out varyings may have indexed locations assigned explicitly in the shader text using a <code>location</code>
layout qualifier. If a shader statically assigns a location to a varying out variable in the shader text,
that location is used and any location assigned with <function>glBindFragDataLocation</function> is ignored.
</para>
</refsect1>
<refsect1 id="errors"><title>Errors</title>
<para>
<constant>GL_INVALID_VALUE</constant> is generated if <parameter>colorNumber</parameter> is greater than or equal to <constant>GL_MAX_DRAW_BUFFERS</constant>.
</para>
<para>
<constant>GL_INVALID_OPERATION</constant> is generated if <parameter>name</parameter> starts with the reserved <constant>gl_</constant> prefix.
</para>
<para>
<constant>GL_INVALID_OPERATION</constant> is generated if <function>program</function> is not the name of a program object.
</para>
</refsect1>
<refsect1 id="associatedgets"><title>Associated Gets</title>
<para>
<citerefentry><refentrytitle>glGetFragDataLocation</refentrytitle></citerefentry> with a valid program object
and the the name of a user-defined varying out variable
</para>
</refsect1>
<refsect1 id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>glCreateProgram</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glGetFragDataLocation</refentrytitle></citerefentry>
</para>
</refsect1>
<refsect1 id="Copyright"><title>Copyright</title>
<para>
Copyright <trademark class="copyright"></trademark> 2010-2013 Khronos Group.
This material may be distributed subject to the terms and conditions set forth in
the Open Publication License, v 1.0, 8 June 1999.
<ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
</para>
</refsect1>
</refentry>
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