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<refentry id="glBindFragDataLocation">
    <refmeta>
        <refmetainfo>
            <copyright>
                <year>2010</year>
                <holder>Khronos Group</holder>
            </copyright>
        </refmetainfo>
        <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 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>
