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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="glActiveTexture">
  <refmeta>
    <refentrytitle>glActiveTexture</refentrytitle>
    <manvolnum>3G</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>glActiveTexture</refname>
    <refpurpose>select server-side active texture unit</refpurpose>
  </refnamediv>

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

    <funcsynopsis>
      <funcprototype>
        <funcdef>void <function>glActiveTexture</function></funcdef>
        <paramdef>GLenum <parameter>texture</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Parameters</title>

    <variablelist>
      <varlistentry>
        <term>
          <parameter>texture</parameter>
        </term>

        <listitem>
          <para>
            Specifies which texture unit to make active. The
            number of texture units is implementation dependent, but
            must be at least one. 
            <parameter>texture</parameter> must be one of 
            <constant>GL_TEXTURE</constant><replaceable>i</replaceable>,
            where
            <inlineequation><math>
              <mn>0</mn>
              <mo>&lt;=</mo>
              <mi>i</mi>
              <mo>&lt;</mo>
              <mi>GL_MAX_TEXTURE_UNITS</mi>
            </math></inlineequation>,
            which is an implementation-dependent value. The intial value is 
            <constant>GL_TEXTURE0</constant>.
          </para>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>

    <para>
    <function>glActiveTexture</function>
    selects which texture unit subsequent texture state calls will
    affect. The number of texture units an implementation supports
    is implementation dependent, it must be at least 1.</para>
  </refsect1>

  <refsect1>
    <title>Errors</title>

    <para>
      <constant>GL_INVALID_ENUM</constant> is generated if 
      <parameter>texture</parameter> is not one of 
      <constant>GL_TEXTURE</constant><replaceable>i</replaceable>,
      where
      <inlineequation><math>
        <mn>0</mn>
        <mo>&lt;=</mo>
        <mi>i</mi>
        <mo>&lt;</mo>
        <mi>GL_MAX_TEXTURE_UNITS</mi>
      </math></inlineequation>.
    </para>
  </refsect1>

  <refsect1>
    <title>Notes</title>

    <para>It is always the case that
    <inlineequation><math>
      <mi>GL_TEXTURE</mi><mi>i</mi> <mo>=</mo>
      <mi>GL_TEXTURE0</mi><mo>+</mo><mi>i</mi>
    </math></inlineequation>.</para>

    <para>A texture unit consists of the texture enable state,
      texture matrix stack, texture environment and currently bound
      texture. Modifying any of these states has an effect only on
      the active texture unit.
    </para>

    <para>Vertex arrays are client-side GL resources, which are
    selected by the 
    <citerefentry><refentrytitle>glClientActiveTexture</refentrytitle></citerefentry>
    routine.</para>
  </refsect1>

  <refsect1>
    <title>Associated Gets</title>

    <para>
      <citerefentry><refentrytitle>glGetInteger</refentrytitle></citerefentry>
      with argument <constant>GL_MAX_TEXTURE_UNITS</constant>
    </para>
  </refsect1>

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

    <para>
      <citerefentry><refentrytitle>glBindTexture</refentrytitle></citerefentry>, 
      <citerefentry><refentrytitle>glClientActiveTexture</refentrytitle></citerefentry>, 
      <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>, 
      <citerefentry><refentrytitle>glGetInteger</refentrytitle></citerefentry>, 
      <citerefentry><refentrytitle>glMatrixMode</refentrytitle></citerefentry>, 
      <citerefentry><refentrytitle>glMultiTexCoord</refentrytitle></citerefentry>, 
      <citerefentry><refentrytitle>glTexEnv</refentrytitle></citerefentry>
    </para>
  </refsect1>
</refentry>