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OpenGL ES 1.0 and EGL 1.0 reference manual and man pages (written by
Claude Knaus, based on OpenGL SI man pages).

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.2//EN" "DTD/docbook/docbookx.dtd">

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<refentry id="glScissor">
  <refmeta>
    <refentrytitle>glScissor</refentrytitle>
    <manvolnum>3G</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>glScissor</refname>
    <refpurpose>define the scissor box</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <title>C Specification</title>

    <funcsynopsis>
      <funcprototype>
        <funcdef>void <function>glScissor</function></funcdef>
        <paramdef>GLint <parameter>x</parameter></paramdef>
        <paramdef>GLint <parameter>y</parameter></paramdef>
        <paramdef>GLsizei <parameter>width</parameter></paramdef>
        <paramdef>GLsizei <parameter>height</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Parameters</title>

    <variablelist>
      <varlistentry>
        <term>
        <parameter>x</parameter>, <parameter>y</parameter>
        </term>

        <listitem>
          <para>Specify the lower left corner of the scissor box, in pixels.
          The initial value is (0, 0).</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
        <parameter>width</parameter>, <parameter>height</parameter>
        </term>

        <listitem>
          <para>Specify the width and height of the scissor box.
          When a GL context is first attached to a surface (e.g. window), 
          <parameter>width</parameter> and <parameter>height</parameter> 
          are set to the dimensions of that surface.</para>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>

    <para>
    <function>glScissor</function>
    defines a rectangle, called the scissor box, in window
    coordinates. The first two arguments, 
    <parameter>x</parameter> and 
    <parameter>y</parameter>, specify the lower left corner of the box. 
    <parameter>width</parameter> and <parameter>height</parameter>
    specify the width and height of the box.</para>

    <para>To enable and disable the scissor test, call 
    <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and 
    <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry>
    with argument <constant>GL_SCISSOR_TEST</constant>.
    The scissor test is initially disabled. While scissor test is enabled,
    only pixels that lie within the scissor box can be modified by
    drawing commands. Window coordinates have integer values at the
    shared corners of frame buffer pixels. 
    <function>glScissor</function>(0, 0, 1, 1)
    allows modification of only the lower left pixel in the window,
    and <function>glScissor</function>(0, 0, 0, 0)
    doesn't allow modification of any pixels in the window.</para>

    <para>When the scissor test is disabled, it is as though the
    scissor box includes the entire window.</para>
  </refsect1>

  <refsect1>
    <title>Errors</title>

    <para><constant>GL_INVALID_VALUE</constant> is generated if either 
    <parameter>width</parameter> or <parameter>height</parameter>
    is negative.</para>
  </refsect1>

  <refsect1>
    <title>See Also</title>

    <para>
      <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>, 
      <citerefentry><refentrytitle>glViewport</refentrytitle></citerefentry>
    </para>
  </refsect1>
</refentry>