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

  <refnamediv>
    <refname>glLogicOp</refname>
    <refpurpose>specify a logical pixel operation</refpurpose>
  </refnamediv>

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

    <funcsynopsis>
      <funcprototype>
        <funcdef>void <function>glLogicOp</function></funcdef>
        <paramdef>GLenum <parameter>opcode</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Parameters</title>

    <variablelist>
      <varlistentry>
        <term>
          <parameter>opcode</parameter>
        </term>

        <listitem>
          <para>Specifies a symbolic constant that selects a
          logical operation. The following symbols are accepted: 
          <constant>GL_CLEAR</constant>, 
          <constant>GL_SET</constant>, 
          <constant>GL_COPY</constant>, 
          <constant>GL_COPY_INVERTED</constant>, 
          <constant>GL_NOOP</constant>, 
          <constant>GL_INVERT</constant>, 
          <constant>GL_AND</constant>, 
          <constant>GL_NAND</constant>, 
          <constant>GL_OR</constant>, 
          <constant>GL_NOR</constant>, 
          <constant>GL_XOR</constant>, 
          <constant>GL_EQUIV</constant>, 
          <constant>GL_AND_REVERSE</constant>, 
          <constant>GL_AND_INVERTED</constant>, 
          <constant>GL_OR_REVERSE</constant>, and 
          <constant>GL_OR_INVERTED</constant>.  The initial value is 
          <constant>GL_COPY</constant>.</para>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>

    <para><function>glLogicOp</function>
    specifies a logical operation that, when enabled, is applied
    between the incoming color and the color at the corresponding
    location in the frame buffer.
    To enable or disable the logical operation, call 
    <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and 
    <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry>
    with argument <constant>GL_COLOR_LOGIC_OP</constant>.
    Logical operation is initially disabled.
    </para>

    <informaltable frame="none">
      <tgroup cols="2" align="center">
        <colspec align="left"/>
        <colspec align="center"/>

        <thead>
          <row>
            <entry align="left">Opcode</entry>
            <entry>Resulting Operation</entry>
          </row>
        </thead>

        <tbody>
          <row>
            <entry><constant>GL_CLEAR</constant></entry> 
            <entry>0</entry>
          </row>

          <row>
            <entry><constant>GL_SET</constant></entry>
            <entry>1</entry>
          </row>

          <row>
            <entry><constant>GL_COPY</constant></entry>
            <entry><replaceable>s</replaceable></entry>
          </row>

          <row>
            <entry><constant>GL_COPY_INVERTED</constant></entry>
            <entry>
              <inlineequation><math>
                <mo>~</mo><mi>s</mi>
              </math></inlineequation>
            </entry>
          </row>

          <row>
            <entry><constant>GL_NOOP</constant></entry>
            <entry><replaceable>d</replaceable></entry>
          </row>

          <row>
            <entry><constant>GL_INVERT</constant></entry>
            <entry>
              <inlineequation><math>
                <mo>~</mo><mi>d</mi>
              </math></inlineequation>
            </entry>
          </row>

          <row>
            <entry><constant>GL_AND</constant></entry>
            <entry>
              <inlineequation><math>
                <mi>s</mi><mo>&amp;</mo><mi>d</mi>
              </math></inlineequation>
            </entry>
          </row>

          <row>
            <entry><constant>GL_NAND</constant></entry>
            <entry>
              <inlineequation><math>
                <mo>~</mo><mfenced><mrow><mi>s</mi><mo>&amp;</mo><mi>d</mi></mrow></mfenced>
              </math></inlineequation>
            </entry>
          </row>

          <row>
            <entry><constant>GL_OR</constant></entry>
            <entry>
              <inlineequation><math>
                <mi>s</mi><mo>|</mo><mi>d</mi>
              </math></inlineequation>
            </entry>
          </row>

          <row>
            <entry><constant>GL_NOR</constant></entry>
            <entry>
              <inlineequation><math>
                <mo>~</mo><mfenced><mrow><mi>s</mi><mo>|</mo><mi>d</mi></mrow></mfenced>
              </math></inlineequation>
            </entry>
          </row>

          <row>
            <entry><constant>GL_XOR</constant></entry>
            <entry>
              <inlineequation><math>
                <mi>s</mi><mo>^</mo><mi>d</mi>
              </math></inlineequation>
            </entry>
          </row>

          <row>
            <entry><constant>GL_EQUIV</constant></entry>
            <entry>
              <inlineequation><math>
                <mo>~</mo><mfenced><mrow><mi>s</mi><mo>^</mo><mi>d</mi></mrow></mfenced>
              </math></inlineequation>
            </entry>
          </row>

          <row>
            <entry><constant>GL_AND_REVERSE</constant></entry>
            <entry>
              <inlineequation><math>
                <mi>s</mi><mo>&amp;</mo><mo>~</mo><mi>d</mi>
              </math></inlineequation>
            </entry>
          </row>

          <row>
            <entry><constant>GL_AND_INVERTED</constant></entry>
            <entry>
              <inlineequation><math>
                <mo>~</mo><mi>s</mi><mo>&amp;</mo><mi>d</mi>
              </math></inlineequation>
            </entry>
          </row>

          <row>
            <entry><constant>GL_OR_REVERSE</constant></entry>
            <entry>
              <inlineequation><math>
                <mi>s</mi><mo>|</mo><mo>~</mo><mi>d</mi>
              </math></inlineequation>
            </entry>
          </row>

          <row>
            <entry><constant>GL_OR_INVERTED</constant></entry>
            <entry>
              <inlineequation><math>
                <mo>~</mo><mi>s</mi><mo>|</mo><mi>d</mi>
              </math></inlineequation>
            </entry>
          </row>
        </tbody>
      </tgroup>
    </informaltable>

    <para>
    <parameter>opcode</parameter>
    is a symbolic constant chosen from the list above. In the
    explanation of the logical operations, <parameter>s</parameter>
    represents the incoming color and <parameter>d</parameter>
    represents the color in the frame buffer. Standard C-language
    operators are used. As these bitwise operators suggest, the
    logical operation is applied independently to each bit pair of
    the source and destination indices or colors.</para>
  </refsect1>

  <refsect1>
    <title>Errors</title>

    <para><constant>GL_INVALID_ENUM</constant> is generated if 
    <parameter>opcode</parameter> is not an accepted value.</para>
  </refsect1>

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

    <para>
    <citerefentry><refentrytitle>glAlphaFunc</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>, 
    <citerefentry><refentrytitle>glStencilOp</refentrytitle></citerefentry>
    </para>
  </refsect1>
</refentry>