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

  <refnamediv>
    <refdescriptor>glLineWidth</refdescriptor>
    <refname>glLineWidth</refname>
    <refname>glLineWidthx</refname>
    <refpurpose>specify the width of rasterized lines</refpurpose>
  </refnamediv>

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

    <funcsynopsis>
      <funcprototype>
        <funcdef>void <function>glLineWidth</function></funcdef>
        <paramdef>GLfloat <parameter>width</parameter></paramdef>
      </funcprototype>
      <funcprototype>
        <funcdef>void <function>glLineWidthx</function></funcdef>
        <paramdef>GLfixed <parameter>width</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Parameters</title>

    <variablelist>
      <varlistentry>
        <term>
          <parameter>width</parameter>
        </term>

        <listitem>
          <para>Specifies the width of rasterized lines. The
          initial value is 1.</para>
        </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>

    <para>
    <function>glLineWidth</function>
    specifies the rasterized width of both aliased and antialiased
    lines. Using a line width other than 1 has different effects,
    depending on whether line antialiasing is enabled. To enable
    and disable line antialiasing, call 
    <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and 
    <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry>
    with argument <constant>GL_LINE_SMOOTH</constant>.
    Line antialiasing is initially disabled.</para>

    <para>If line antialiasing is disabled, the actual width is
    determined by rounding the supplied width to the nearest
    integer. (If the rounding results in the value 0, it is as if
    the line width were 1.) If 
    <inlineequation><math>
      <mrow>
      <mo>|</mo>
        <mrow><mo>&#x394;</mo><mi>x</mi></mrow>
      <mo>|</mo>
      </mrow>
      <mo>&gt;=</mo>
      <mrow>
      <mo>|</mo>
        <mrow><mo>&#x394;</mo><mi>y</mi></mrow>
      <mo>|</mo>
      </mrow>
    </math></inlineequation>,
    <parameter>i</parameter>
    pixels are filled in each column that is rasterized, where 
    <parameter>i</parameter> is the rounded value of 
    <parameter>width</parameter>. Otherwise, <parameter>i</parameter>
    pixels are filled in each row that is rasterized.</para>

    <para>If antialiasing is enabled, line rasterization produces a
    fragment for each pixel square that intersects the region lying
    within the rectangle having width equal to the current line
    width, length equal to the actual length of the line, and
    centered on the mathematical line segment. The coverage value
    for each fragment is the window coordinate area of the
    intersection of the rectangular region with the corresponding
    pixel square. This value is saved and used in the final
    rasterization step.</para>

    <para>Not all widths can be supported when line antialiasing is
    enabled. If an unsupported width is requested, the nearest
    supported width is used. Only width 1 is guaranteed to be
    supported; others depend on the implementation. Likewise, there
    is a range for aliased line widths as well. To query the range
    of supported widths and the size difference between supported
    widths within the range, call 
    <citerefentry><refentrytitle>glGetInteger</refentrytitle></citerefentry>
    with arguments 
    <constant>GL_ALIASED_LINE_WIDTH_RANGE</constant>, 
    <constant>GL_SMOOTH_LINE_WIDTH_RANGE</constant>, 
    <constant>GL_SMOOTH_LINE_WIDTH_GRANULARITY</constant>.</para>
  </refsect1>

  <refsect1>
    <title>Notes</title>

    <para>Nonantialiased line width may be clamped to an
    implementation-dependent maximum. Call 
    <citerefentry><refentrytitle>glGetInteger</refentrytitle></citerefentry>
    with <constant>GL_ALIASED_LINE_WIDTH_RANGE</constant>
    to determine the maximum width.</para>
  </refsect1>

  <refsect1>
    <title>Errors</title>

    <para><constant>GL_INVALID_VALUE</constant> is generated if 
    <parameter>width</parameter> is less than or equal to 0.</para>
  </refsect1>

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

    <para>
    <citerefentry><refentrytitle>glGetInteger</refentrytitle></citerefentry>
    with argument <constant>GL_ALIASED_LINE_WIDTH_RANGE</constant></para>

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

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

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