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<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="glViewportIndexed">
    <info>
        <copyright>
            <year>2010-2013</year>
            <holder>Khronos Group</holder>
        </copyright>
    </info>
    <refmeta>
        <refentrytitle>glViewportIndexed</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glViewportIndexed</refname>
        <refpurpose>set a specified viewport</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glViewportIndexedf</function></funcdef>
                <paramdef>GLuint <parameter>index</parameter></paramdef>
                <paramdef>GLfloat <parameter>x</parameter></paramdef>
                <paramdef>GLfloat <parameter>y</parameter></paramdef>
                <paramdef>GLfloat <parameter>w</parameter></paramdef>
                <paramdef>GLfloat <parameter>h</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glViewportIndexedfv</function></funcdef>
                <paramdef>GLuint <parameter>index</parameter></paramdef>
                <paramdef>const GLfloat *<parameter>v</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 xml:id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>index</parameter></term>
            <listitem>
                <para>
                   Specify the first viewport to set.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>x</parameter></term>
            <term><parameter>y</parameter></term>
            <listitem>
                <para>
                    For <function>glViewportIndexedf</function>, specifies the lower left corner of
                    the viewport rectangle, in pixels. The initial value is (0,0).
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>width</parameter></term>
            <term><parameter>height</parameter></term>
            <listitem>
                <para>
                    For <function>glViewportIndexedf</function>, specifies the width and height
                    of the viewport.
                    When a GL context is first attached to a window,
                    <parameter>width</parameter> and <parameter>height</parameter> are set to the dimensions of that
                    window.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>v</parameter></term>
            <listitem>
                <para>
                   For <function>glViewportIndexedfv</function>, specifies the address of an array containing the viewport parameters.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 xml:id="description"><title>Description</title>
        <para>
            <function>glViewportIndexedf</function> and <function>glViewportIndexedfv</function>
            specify the parameters for a single viewport.
            <parameter>index</parameter> specifies the index of the viewport
            to modify.
            <parameter>index</parameter> must be less than the value of <constant>GL_MAX_VIEWPORTS</constant>.
            For <function>glViewportIndexedf</function>, <parameter>x</parameter>, <parameter>y</parameter>,
            <parameter>w</parameter>, and <parameter>h</parameter> specify the left, bottom, width and height
            of the viewport in pixels, respectively.
            For <function>glViewportIndexedfv</function>, <parameter>v</parameter> contains the address of an array of floating
            point values specifying the
            left (<inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">x</mml:mi></mml:math></inlineequation>),
            bottom (<inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">y</mml:mi></mml:math></inlineequation>),
            width (<inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">w</mml:mi></mml:math></inlineequation>),
            and height (<inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">h</mml:mi></mml:math></inlineequation>)
            of each viewport, in that order. <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">x</mml:mi></mml:math></inlineequation>
            and <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">y</mml:mi></mml:math></inlineequation> give
            the location of the viewport's lower left corner, and
            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">w</mml:mi></mml:math></inlineequation>
            and <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">h</mml:mi></mml:math></inlineequation>
            give the width and height of the viewport, respectively.
            The viewport specifies the affine transformation of
            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">x</mml:mi></mml:math></inlineequation>
            and
            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">y</mml:mi></mml:math></inlineequation>
            from
            normalized device coordinates to window coordinates.
            Let
            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- eqn: (x sub nd, y sub nd): -->
                <mml:mfenced open="(" close=")">
                    <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
                    <mml:mi mathvariant="italic">nd</mml:mi>
                    </mml:msub>
                    <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
                    <mml:mi mathvariant="italic">nd</mml:mi>
                    </mml:msub>
                </mml:mfenced>
            </mml:math></inlineequation>
            be normalized device coordinates.
            Then the window coordinates
            <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- eqn: (x sub w, y sub w): -->
                <mml:mfenced open="(" close=")">
                    <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
                    <mml:mi mathvariant="italic">w</mml:mi>
                    </mml:msub>
                    <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
                    <mml:mi mathvariant="italic">w</mml:mi>
                    </mml:msub>
                </mml:mfenced>
            </mml:math></inlineequation>
            are computed as follows:
        </para>
        <para>
            <informalequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- eqn: x sub w  =  ( x sub nd  +  1 ) left ( width over 2 right )  +  x: -->
                <mml:mrow>
                    <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
                    <mml:mi mathvariant="italic">w</mml:mi>
                    </mml:msub>
                    <mml:mo>=</mml:mo>
                    <mml:mrow>
                        <mml:mfenced open="(" close=")">
                            <mml:mrow>
                                <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
                                <mml:mi mathvariant="italic">nd</mml:mi>
                                </mml:msub>
                                <mml:mo>+</mml:mo>
                                <mml:mn>1</mml:mn>
                            </mml:mrow>
                        </mml:mfenced>
                        <mml:mo>&it;</mml:mo>
                        <mml:mfenced open="(" close=")">
                            <mml:mfrac>
                                <mml:mi mathvariant="italic">width</mml:mi>
                                <mml:mn>2</mml:mn>
                            </mml:mfrac>
                        </mml:mfenced>
                        <mml:mo>+</mml:mo>
                        <mml:mi mathvariant="italic">x</mml:mi>
                    </mml:mrow>
                </mml:mrow>
            </mml:math></informalequation>
        </para>
        <para>
            <informalequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
                <!-- eqn: y sub w  =  ( y sub nd  +  1 ) left ( height over 2 right )  +  y: -->
                <mml:mrow>
                    <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
                    <mml:mi mathvariant="italic">w</mml:mi>
                    </mml:msub>
                    <mml:mo>=</mml:mo>
                    <mml:mrow>
                        <mml:mfenced open="(" close=")">
                            <mml:mrow>
                                <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
                                <mml:mi mathvariant="italic">nd</mml:mi>
                                </mml:msub>
                                <mml:mo>+</mml:mo>
                                <mml:mn>1</mml:mn>
                            </mml:mrow>
                        </mml:mfenced>
                        <mml:mo>&it;</mml:mo>
                        <mml:mfenced open="(" close=")">
                            <mml:mfrac>
                                <mml:mi mathvariant="italic">height</mml:mi>
                                <mml:mn>2</mml:mn>
                            </mml:mfrac>
                        </mml:mfenced>
                        <mml:mo>+</mml:mo>
                        <mml:mi mathvariant="italic">y</mml:mi>
                    </mml:mrow>
                </mml:mrow>
            </mml:math></informalequation>
        </para>
        <para>
            The location of the viewport's bottom left corner, given by
            (<inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">x</mml:mi></mml:math></inlineequation>, <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">y</mml:mi></mml:math></inlineequation>)
            is clamped to be within the implementaiton-dependent viewport bounds range.
            The viewport bounds range [<inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">min</mml:mi></mml:math></inlineequation>, <inlineequation><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">max</mml:mi></mml:math></inlineequation>]
            can be determined by calling <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument
            <constant>GL_VIEWPORT_BOUNDS_RANGE</constant>.
            Viewport width and height are silently clamped
            to a range that depends on the implementation.
            To query this range, call <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument
            <constant>GL_MAX_VIEWPORT_DIMS</constant>.
        </para>
        <para>
            The precision with which the GL interprets the floating point viewport bounds is implementation-dependent
            and may be determined by querying the impementation-defined constant <constant>GL_VIEWPORT_SUBPIXEL_BITS</constant>.
        </para>
        <para>
            Calling <function>glViewportIndexedfv</function> is equivalent to calling <citerefentry><refentrytitle>glViewportArray</refentrytitle></citerefentry>
            with <parameter>first</parameter> set to <parameter>index</parameter>, <parameter>count</parameter> set to
            1 and <parameter>v</parameter> passsed directly. <function>glViewportIndexedf</function> is equivalent
            to:
        </para>
<programlisting>    void glViewportIndexedf(GLuint index, GLfloat x, GLfloat y, GLfloat w, GLfloat h) {
        const float v[4]  = { x, y, w, h };
        glViewportArrayv(index, 1, v);
    }</programlisting>
    </refsect1>
    <refsect1 xml:id="errors"><title>Errors</title>
        <para>
            <constant>GL_INVALID_VALUE</constant> is generated if <parameter>index</parameter> is greater than or equal to
            the value of <constant>GL_MAX_VIEWPORTS</constant>.
        </para>
        <para>
            <constant>GL_INVALID_VALUE</constant> is generated if either <parameter>width</parameter> or <parameter>height</parameter> is negative.
        </para>
    </refsect1>
    <refsect1 xml:id="associatedgets"><title>Associated Gets</title>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_VIEWPORT</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_MAX_VIEWPORT_DIMS</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_VIEWPORT_BOUNDS_RANGE</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_VIEWPORT_SUBPIXEL_BITS</constant>
        </para>
    </refsect1>
    <refsect1 xml:id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glDepthRange</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glViewport</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glViewportArray</refentrytitle></citerefentry>
        </para>
    </refsect1>
    <refsect1 xml:id="Copyright"><title>Copyright</title>
        <para>
            Copyright <trademark class="copyright"/> 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.
            <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://opencontent.org/openpub/">http://opencontent.org/openpub/</link>.
        </para>
    </refsect1>
</refentry>
