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<refentry id="glGetProgramResourceIndex">
    <refmeta>
        <refmetainfo>
            <copyright>
                <year>2012</year>
                <holder>Khronos Group</holder>
            </copyright>
        </refmetainfo>
        <refentrytitle>glGetProgramResourceIndex</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glGetProgramResourceIndex</refname>
        <refpurpose>query the index of a named resource within a program</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>GLuint <function>glGetProgramResourceIndex</function></funcdef>
                <paramdef>GLuint <parameter>program</parameter></paramdef>
                <paramdef>GLenum <parameter>programInterface</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 a program object whose resources to query.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>programInterface</parameter></term>
            <listitem>
                <para>
                    A token identifying the interface within <parameter>program</parameter> containing the resource named <parameter>name</parameter>.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>name</parameter></term>
            <listitem>
                <para>
                    The name of the resource to query the index of.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
        <para>
            <function>glGetProgramResourceIndex</function> returns the unsigned
            integer index assigned to a resource named <parameter>name</parameter> in
            the interface type <parameter>programInterface</parameter> of program object <parameter>program</parameter>.
        </para>
        <para>
            <parameter>program</parameter> must be the name of an existing program object. <parameter>programInterface</parameter>
            is the name of the interface within <parameter>program</parameter> which contains the resource named
            <parameter>name</parameter>and must be one of the following
            values:
        </para>
        <variablelist>
            <varlistentry>
                <term><constant>GL_UNIFORM</constant></term>
                <listitem>
                    <para>
                        The query is targeted at the set of active uniforms within <parameter>program</parameter>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_UNIFORM_BLOCK</constant></term>
                <listitem>
                    <para>
                        The query is targeted at the set of active uniform blocks within <parameter>program</parameter>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_PROGRAM_INPUT</constant></term>
                <listitem>
                    <para>
                        The query is targeted at the set of active input variables used by the first shader stage of <parameter>program</parameter>.
                        If <parameter>program</parameter> contains multiple shader stages then input variables from any stage other than the first
                        will not be enumerated.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_PROGRAM_OUTPUT</constant></term>
                <listitem>
                    <para>
                        The query is targeted at the set of active output variables produced by the last shader stage of <parameter>program</parameter>.
                        If <parameter>program</parameter> contains multiple shader stages then output variables from any stage other than the last
                        will not be enumerated.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_VERTEX_SUBROUTINE</constant></term>,
                <term><constant>GL_TESS_CONTROL_SUBROUTINE</constant></term>,
                <term><constant>GL_TESS_EVALUATION_SUBROUTINE</constant></term>,
                <term><constant>GL_GEOMETRY_SUBROUTINE</constant></term>,
                <term><constant>GL_FRAGMENT_SUBROUTINE</constant></term>,
                <term><constant>GL_COMPUTE_SUBROUTINE</constant></term>
                <listitem>
                    <para>
                        The query is targeted at the set of active subroutines for the vertex, tessellation control, tessellation evaluation,
                        geometry, fragment and compute shader stages of <parameter>program</parameter>, respectively.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_VERTEX_SUBROUTINE_UNIFORM</constant></term>,
                <term><constant>GL_TESS_CONTROL_SUBROUTINE_UNIFORM</constant></term>,
                <term><constant>GL_TESS_EVALUATION_SUBROUTINE_UNIFORM</constant></term>,
                <term><constant>GL_GEOMETRY_SUBROUTINE_UNIFORM</constant></term>,
                <term><constant>GL_FRAGMENT_SUBROUTINE_UNIFORM</constant></term>,
                <term><constant>GL_COMPUTE_SUBROUTINE_UNIFORM</constant></term>
                <listitem>
                    <para>
                        The query is targeted at the set of active subroutine uniform variables used by the vertex, tessellation control, tessellation evaluation,
                        geometry, fragment and compute shader stages of <parameter>program</parameter>, respectively.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_TRANSFORM_FEEDBACK_VARYING</constant></term>
                <listitem>
                    <para>
                        The query is targeted at the set of output variables from the last non-fragment stage of <parameter>program</parameter> that would be
                        captured if transform feedback were active.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_TRANSFORM_FEEDBACK_BUFFER</constant></term>
                <listitem>
                    <para>
                        The query is targeted at the set of active buffer binding points to which output variables in the
                        <constant>GL_TRANSFORM_FEEDBACK_VARYING</constant> interface are written.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_BUFFER_VARIABLE</constant></term>
                <listitem>
                    <para>
                        The query is targeted at the set of active buffer variables used by <parameter>program</parameter>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_SHADER_STORAGE_BLOCK</constant></term>
                <listitem>
                    <para>
                        The query is targeted at the set of active shader storage blocks used by <parameter>program</parameter>.
                    </para>
                </listitem>
            </varlistentry>
        </variablelist>
        <para>
            If <parameter>name</parameter> exactly matches the name string of one of the active resources
            for <parameter>programInterface</parameter>, the index of the matched resource is returned.
            Additionally, if <parameter>name</parameter> would exactly match the name string of an active
            resource if "[0]" were appended to <parameter>name</parameter>, the index of the matched
            resource is returned.  Otherwise, <parameter>name</parameter> is considered not to be the name
            of an active resource, and <constant>GL_INVALID_INDEX</constant> is returned.
        </para>
        <para>
            For the interface <constant>GL_TRANSFORM_FEEDBACK_VARYING</constant>, the value <constant>GL_INVALID_INDEX</constant>
            should be returned when querying the index assigned to the special names
            <code>gl_NextBuffer</code>, <code>gl_SkipComponents1</code>, <code>gl_SkipComponents2</code>,
            <code>gl_SkipComponents3</code>, or <code>gl_SkipComponents4</code>.
        </para>
    </refsect1>
    <refsect1 id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>programInterface</parameter>
            is not one of the accepted interface types.
        </para>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>programInterface</parameter> is
            <constant>GL_ATOMIC_COUNTER_BUFFER</constant> or <constant>GL_TRANSFORM_FEEDBACK_BUFFER</constant>, since active atomic
            counter and transform feedback buffer resources are not assigned name strings.
        </para>
        <para>
            Although not an error, <constant>GL_INVALID_INDEX</constant> is returned if <parameter>name</parameter>
            is not the name of a resource within the interface identified by <parameter>programInterface</parameter>.
        </para>
    </refsect1>
    <refsect1 id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glGetProgramResourceName</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glGetGetProgramResource</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glGetProgramResourceLocation</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glGetProgramResourceLocationIndex</refentrytitle></citerefentry>.
        </para>
    </refsect1>
    <refsect1 id="Copyright"><title>Copyright</title>
        <para>
            Copyright <trademark class="copyright"></trademark> 2012 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>
