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<refentry id="glEnable">
    <refmeta>
        <refmetainfo>
            <copyright>
                <year>1991-2006</year>
                <holder>Silicon Graphics, Inc.</holder>
            </copyright>
        </refmetainfo>
        <refentrytitle>glEnable</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glEnable</refname>
        <refpurpose>enable or disable server-side GL capabilities</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glEnable</function></funcdef>
                <paramdef>GLenum <parameter>cap</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>cap</parameter></term>
            <listitem>
                <para>
                    Specifies a symbolic constant indicating a GL capability.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glDisable</function></funcdef>
                <paramdef>GLenum <parameter>cap</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 id="parameters2"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>cap</parameter></term>
            <listitem>
                <para>
                    Specifies a symbolic constant indicating a GL capability.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glEnablei</function></funcdef>
                <paramdef>GLenum <parameter>cap</parameter></paramdef>
                <paramdef>GLuint <parameter>index</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 id="parameters3"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>cap</parameter></term>
            <listitem>
                <para>
                    Specifies a symbolic constant indicating a GL capability.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>index</parameter></term>
            <listitem>
                <para>
                    Specifies the index of the swtich to enable.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glDisablei</function></funcdef>
                <paramdef>GLenum <parameter>cap</parameter></paramdef>
                <paramdef>GLuint <parameter>index</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 id="parameters4"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>cap</parameter></term>
            <listitem>
                <para>
                    Specifies a symbolic constant indicating a GL capability.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>index</parameter></term>
            <listitem>
                <para>
                    Specifies the index of the swtich to disable.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
        <para>
            <function>glEnable</function> and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry> enable and disable various capabilities.
            Use <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> or <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> to determine the current setting
            of any capability. The initial value for each capability with the
            exception of <constant>GL_DITHER</constant> and <constant>GL_MULTISAMPLE</constant> is
            <constant>GL_FALSE</constant>. The initial value for
            <constant>GL_DITHER</constant> and <constant>GL_MULTISAMPLE</constant> is <constant>GL_TRUE</constant>.
        </para>
        <para>
            Both <function>glEnable</function> and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry> take a single argument, <parameter>cap</parameter>,
            which can assume one of the following values:
        </para>
        <para>
            Some of the GL's capabilities are indicated. <function>glEnablei</function> and <function>glDisablei</function> enable and disable
            indexed capabilities.
        </para>
        <variablelist>
            <varlistentry>
                <term><constant>GL_BLEND</constant></term>
                <listitem>
                 <para>
                </para>
                    <para>
                        If enabled,
                        blend the computed fragment color values with the values in the color
                        buffers. See <citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_CLIP_DISTANCE</constant><emphasis>i</emphasis></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled, clip geometry against user-defined half space <emphasis>i</emphasis>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_COLOR_LOGIC_OP</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled,
                        apply the currently selected logical operation to the computed fragment
                        color and color buffer values. See <citerefentry><refentrytitle>glLogicOp</refentrytitle></citerefentry>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_CULL_FACE</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled,
                        cull polygons based on their winding in window coordinates.
                        See <citerefentry><refentrytitle>glCullFace</refentrytitle></citerefentry>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_DEPTH_CLAMP</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled,
                        the
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                        plane equation is ignored by view volume clipping (effectively, there is no near or
                        far plane clipping).
                        See <citerefentry><refentrytitle>glDepthRange</refentrytitle></citerefentry>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_DEPTH_TEST</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled,
                        do depth comparisons and update the depth buffer. Note that even if
                        the depth buffer exists and the depth mask is non-zero, the
                        depth buffer is not updated if the depth test is disabled. See
                        <citerefentry><refentrytitle>glDepthFunc</refentrytitle></citerefentry> and
                        <citerefentry><refentrytitle>glDepthRange</refentrytitle></citerefentry>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_DITHER</constant>    </term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled,
                        dither color components or indices before they are written to the
                        color buffer.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_LINE_SMOOTH</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled,
                        draw lines with correct filtering.
                        Otherwise,
                        draw aliased lines.
                        See <citerefentry><refentrytitle>glLineWidth</refentrytitle></citerefentry>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_MULTISAMPLE</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled,
                        use multiple fragment samples in computing the final color of a pixel.
                        See <citerefentry><refentrytitle>glSampleCoverage</refentrytitle></citerefentry>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_POLYGON_OFFSET_FILL</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled, and if the polygon is rendered in
                        <constant>GL_FILL</constant> mode, an offset is added to depth values of a polygon's
                        fragments before the depth comparison is performed.
                        See <citerefentry><refentrytitle>glPolygonOffset</refentrytitle></citerefentry>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_POLYGON_OFFSET_LINE</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled, and if the polygon is rendered in
                        <constant>GL_LINE</constant> mode, an offset is added to depth values of a polygon's
                        fragments before the depth comparison is performed.
                        See <citerefentry><refentrytitle>glPolygonOffset</refentrytitle></citerefentry>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_POLYGON_OFFSET_POINT</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled, an offset is added to depth values of a polygon's fragments
                        before the depth comparison is performed, if the polygon is rendered in
                        <constant>GL_POINT</constant> mode. See <citerefentry><refentrytitle>glPolygonOffset</refentrytitle></citerefentry>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_POLYGON_SMOOTH</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled, draw polygons with proper filtering.
                        Otherwise, draw aliased polygons. For correct antialiased polygons,
                        an alpha buffer is needed and the polygons must be sorted front to
                        back.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_PRIMITIVE_RESTART</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        Enables primitive restarting.  If enabled, any one of the draw commands 
                        which transfers a set of generic attribute array elements to the GL will restart 
                        the primitive when the index of the vertex is equal to the primitive restart index.
                        See <citerefentry><refentrytitle>glPrimitiveRestartIndex</refentrytitle></citerefentry>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_SAMPLE_ALPHA_TO_COVERAGE</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled,
                        compute a temporary coverage value where each bit is determined by the
                        alpha value at the corresponding sample location.  The temporary coverage
                        value is then ANDed with the fragment coverage value.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_SAMPLE_ALPHA_TO_ONE</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled,
                        each sample alpha value is replaced by the maximum representable alpha value.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_SAMPLE_COVERAGE</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled,
                        the fragment's coverage is ANDed with the temporary coverage value.  If
                        <constant>GL_SAMPLE_COVERAGE_INVERT</constant> is set to <constant>GL_TRUE</constant>, invert the coverage
                        value.
                        See <citerefentry><refentrytitle>glSampleCoverage</refentrytitle></citerefentry>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_SCISSOR_TEST</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled,
                        discard fragments that are outside the scissor rectangle.
                        See <citerefentry><refentrytitle>glScissor</refentrytitle></citerefentry>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_STENCIL_TEST</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled,
                        do stencil testing and update the stencil buffer.
                        See <citerefentry><refentrytitle>glStencilFunc</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glStencilOp</refentrytitle></citerefentry>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_TEXTURE_CUBE_MAP_SEAMLESS</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled, modifies the way sampling is performed on cube map textures.  See the spec for more information.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term><constant>GL_PROGRAM_POINT_SIZE</constant></term>
                <listitem>
                <para>
                </para>
                    <para>
                        If enabled
                        and a vertex or geometry shader is active, then the derived point size is taken from the (potentially clipped) shader builtin
                        <constant>gl_PointSize</constant> and clamped to the implementation-dependent point size range.
                    </para>
                </listitem>
            </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_ENUM</constant> is generated if <parameter>cap</parameter> is not one of the values
            listed previously.
        </para>
        <para>
            <constant>GL_INVALID_VALUE</constant> is generated by <function>glEnablei</function> and <function>glDisablei</function>
            if <parameter>index</parameter> is greater than or equal to the number of indexed capabilities for <parameter>cap</parameter>.
        </para>
    </refsect1>
    <refsect1 id="notes"><title>Notes</title>
        <para>
            <constant>GL_PRIMITIVE_RESTART</constant> is available only if the GL version is 3.1 or greater.
        </para>
        <para>
            <constant>GL_TEXTURE_CUBE_MAP_SEAMLESS</constant> is available only if the GL version is 3.2 or greater.
        </para>
        <para>
            Any token accepted by <function>glEnable</function> or <function>glDisable</function> is also accepted by
            <function>glEnablei</function> and <function>glDisablei</function>, but if the capability is not indexed,
            the maximum value that <parameter>index</parameter> may take is zero.
        </para>
        <para>
            In general, passing an indexed capability to <function>glEnable</function> or <function>glDisable</function>
            will enable or disable that capability for all indices, resepectively.
        </para>
    </refsect1>
    <refsect1 id="associatedgets"><title>Associated Gets</title>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry>
        </para>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry>
        </para>
    </refsect1>
    <refsect1 id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glActiveTexture</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glCullFace</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glDepthFunc</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glDepthRange</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glLineWidth</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glLogicOp</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glPointSize</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glPolygonMode</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glPolygonOffset</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glSampleCoverage</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glScissor</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glStencilFunc</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glStencilOp</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glTexImage1D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glTexImage3D</refentrytitle></citerefentry>
        </para>
    </refsect1>
    <refsect1 id="Copyright"><title>Copyright</title>
        <para>
            Copyright <trademark class="copyright"></trademark> 1991-2006
            Silicon Graphics, Inc. Copyright <trademark class="copyright"></trademark> 2010 Khronos Group.
            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>
