upstream-doc/man2/xhtml/glViewport.xml

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   3 <?xml-stylesheet type="text/xsl" href="mathml.xsl"?><html xmlns="http://www.w3.org/1999/xhtml" xmlns:pref="http://www.w3.org/2002/Math/preference" pref:renderer="mathplayer-dl"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>glViewport</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glViewport"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glViewport — set the viewport</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glViewport</b>(</code></td><td>GLint  </td><td><var class="pdparam">x</var>, </td></tr><tr><td> </td><td>GLint  </td><td><var class="pdparam">y</var>, </td></tr><tr><td> </td><td>GLsizei  </td><td><var class="pdparam">width</var>, </td></tr><tr><td> </td><td>GLsizei  </td><td><var class="pdparam">height</var><code>)</code>;</td></tr></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>x</code></em>, </span><span class="term"><em class="parameter"><code>y</code></em></span></dt><dd><p>
   4                     Specify the lower left corner of the viewport rectangle,
   5                     in pixels. The initial value is (0,0).
   6                 </p></dd><dt><span class="term"><em class="parameter"><code>width</code></em>, </span><span class="term"><em class="parameter"><code>height</code></em></span></dt><dd><p>
   7                     Specify the width and height
   8                     of the viewport.
   9                     When a GL context is first attached to a window,
  10                     <em class="parameter"><code>width</code></em> and <em class="parameter"><code>height</code></em> are set to the dimensions of that
  11                     window.
  12                 </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
  13             <code class="function">glViewport</code> specifies the affine transformation of
  14             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">x</mml:mi></mml:math>
  15             and
  16             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">y</mml:mi></mml:math>
  17             from
  18             normalized device coordinates to window coordinates.
  19             Let
  20             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  21
  22                 <mml:mfenced open="(" close=")">
  23                     <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
  24                     <mml:mi mathvariant="italic">nd</mml:mi>
  25                     </mml:msub>
  26                     <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
  27                     <mml:mi mathvariant="italic">nd</mml:mi>
  28                     </mml:msub>
  29                 </mml:mfenced>
  30             </mml:math>
  31             be normalized device coordinates.
  32             Then the window coordinates
  33             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  34
  35                 <mml:mfenced open="(" close=")">
  36                     <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
  37                     <mml:mi mathvariant="italic">w</mml:mi>
  38                     </mml:msub>
  39                     <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
  40                     <mml:mi mathvariant="italic">w</mml:mi>
  41                     </mml:msub>
  42                 </mml:mfenced>
  43             </mml:math>
  44             are computed as follows:
  45         </p><p>
  46             </p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  47
  48                 <mml:mrow>
  49                     <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
  50                     <mml:mi mathvariant="italic">w</mml:mi>
  51                     </mml:msub>
  52                     <mml:mo>=</mml:mo>
  53                     <mml:mrow>
  54                         <mml:mfenced open="(" close=")">
  55                             <mml:mrow>
  56                                 <mml:msub><mml:mi mathvariant="italic">x</mml:mi>
  57                                 <mml:mi mathvariant="italic">nd</mml:mi>
  58                                 </mml:msub>
  59                                 <mml:mo>+</mml:mo>
  60                                 <mml:mn>1</mml:mn>
  61                             </mml:mrow>
  62                         </mml:mfenced>
  63                         <mml:mo>⁢</mml:mo>
  64                         <mml:mfenced open="(" close=")">
  65                             <mml:mfrac>
  66                                 <mml:mi mathvariant="italic">width</mml:mi>
  67                                 <mml:mn>2</mml:mn>
  68                             </mml:mfrac>
  69                         </mml:mfenced>
  70                         <mml:mo>+</mml:mo>
  71                         <mml:mi mathvariant="italic">x</mml:mi>
  72                     </mml:mrow>
  73                 </mml:mrow>
  74             </mml:math></div><p>
  75         </p><p>
  76             </p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  77
  78                 <mml:mrow>
  79                     <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
  80                     <mml:mi mathvariant="italic">w</mml:mi>
  81                     </mml:msub>
  82                     <mml:mo>=</mml:mo>
  83                     <mml:mrow>
  84                         <mml:mfenced open="(" close=")">
  85                             <mml:mrow>
  86                                 <mml:msub><mml:mi mathvariant="italic">y</mml:mi>
  87                                 <mml:mi mathvariant="italic">nd</mml:mi>
  88                                 </mml:msub>
  89                                 <mml:mo>+</mml:mo>
  90                                 <mml:mn>1</mml:mn>
  91                             </mml:mrow>
  92                         </mml:mfenced>
  93                         <mml:mo>⁢</mml:mo>
  94                         <mml:mfenced open="(" close=")">
  95                             <mml:mfrac>
  96                                 <mml:mi mathvariant="italic">height</mml:mi>
  97                                 <mml:mn>2</mml:mn>
  98                             </mml:mfrac>
  99                         </mml:mfenced>
 100                         <mml:mo>+</mml:mo>
 101                         <mml:mi mathvariant="italic">y</mml:mi>
 102                     </mml:mrow>
 103                 </mml:mrow>
 104             </mml:math></div><p>
 105         </p><p>
 106             Viewport width and height are silently clamped
 107             to a range that depends on the implementation.
 108             To query this range, call <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument
 109             <code class="constant">GL_MAX_VIEWPORT_DIMS</code>.
 110         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
 111             <code class="constant">GL_INVALID_VALUE</code> is generated if either <em class="parameter"><code>width</code></em> or <em class="parameter"><code>height</code></em> is negative.
 112         </p><p>
 113             <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glViewport</code>
 114             is executed between the execution of <a class="citerefentry" href="glBegin.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a>
 115             and the corresponding execution of <a class="citerefentry" href="glEnd.xml"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>.
 116         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
 117             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_VIEWPORT</code>
 118         </p><p>
 119             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_MAX_VIEWPORT_DIMS</code>
 120         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
 121             <a class="citerefentry" href="glDepthRange.xml"><span class="citerefentry"><span class="refentrytitle">glDepthRange</span></span></a>
 122         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
 123             Copyright <span class="trademark"></span>© 1991-2006
 124             Silicon Graphics, Inc. This document is licensed under the SGI
 125             Free Software B License. For details, see
 126             <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
 127         </p></div></div></body></html>