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<refentry id="glGetSubroutineUniformLocation">
    <refentryinfo>
        <copyright>
            <year>2010-2013</year>
            <holder>Khronos Group.</holder>
        </copyright>
    </refentryinfo>
    <refmeta>
        <refentrytitle>glGetSubroutineUniformLocation</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glGetSubroutineUniformLocation</refname>
        <refpurpose>retrieve the location of a subroutine uniform of a given shader stage within a program</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>GLint <function>glGetSubroutineUniformLocation</function></funcdef>
                <paramdef>GLuint <parameter>program</parameter></paramdef>
                <paramdef>GLenum <parameter>shadertype</parameter></paramdef>
                <paramdef>const GLchar *<parameter>name</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>program</parameter></term>
            <listitem>
                <para>
                    Specifies the name of the program containing shader stage.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>shadertype</parameter></term>
            <listitem>
                <para>
                    Specifies the shader stage from which to query for subroutine uniform index.
                    <parameter>shadertype</parameter>
                    must be one of <constant>GL_VERTEX_SHADER</constant>, <constant>GL_TESS_CONTROL_SHADER</constant>,
                    <constant>GL_TESS_EVALUATION_SHADER</constant>, <constant>GL_GEOMETRY_SHADER</constant> or
                    <constant>GL_FRAGMENT_SHADER</constant>.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>name</parameter></term>
            <listitem>
                <para>
                    Specifies the name of the subroutine uniform whose index to query.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
        <para>
            <function>glGetSubroutineUniformLocation</function> returns the location of the subroutine uniform variable
            <parameter>name</parameter> in the shader stage of type <parameter>shadertype</parameter> attached to
            <parameter>program</parameter>, with behavior otherwise identical to
            <citerefentry><refentrytitle>glGetUniformLocation</refentrytitle></citerefentry>.
        </para>
        <para>
            If <parameter>name</parameter> is not the name of a subroutine uniform in the shader stage, -1
            is returned, but no error is generated. If <parameter>name</parameter> is the name of a subroutine uniform in the shader stage,
            a value between zero and the value of <constant>GL_ACTIVE_SUBROUTINE_LOCATIONS</constant> minus one will be returned.
            Subroutine locations are assigned using consecutive integers in the range from zero to the value
            of <constant>GL_ACTIVE_SUBROUTINE_LOCATIONS</constant> minus one for the shader stage.  For active subroutine uniforms
            declared as arrays, the declared array elements are assigned consecutive locations.
        </para>
    </refsect1>
    <refsect1 id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>shadertype</parameter> or <parameter>pname</parameter>
            is not one of the accepted values.
        </para>
        <para>
            <constant>GL_INVALID_VALUE</constant> is generated if <parameter>program</parameter> is not the name of an
            existing program object.
        </para>
    </refsect1>
    <refsect1 id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glGetProgram</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glGetActiveSubroutineUniform</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glGetActiveSubroutineUniformName</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glGetUniformLocation</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>
