| 1 | <?xml version="1.0" encoding="UTF-8"?> |
| 2 | <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN" |
| 3 | "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd"> |
| 4 | <refentry id="glScissor"> |
| 5 | <refmeta> |
| 6 | <refmetainfo> |
| 7 | <copyright> |
| 8 | <year>1991-2006</year> |
| 9 | <holder>Silicon Graphics, Inc.</holder> |
| 10 | </copyright> |
| 11 | </refmetainfo> |
| 12 | <refentrytitle>glScissor</refentrytitle> |
| 13 | <manvolnum>3G</manvolnum> |
| 14 | </refmeta> |
| 15 | <refnamediv> |
| 16 | <refname>glScissor</refname> |
| 17 | <refpurpose>define the scissor box</refpurpose> |
| 18 | </refnamediv> |
| 19 | <refsynopsisdiv><title>C Specification</title> |
| 20 | <funcsynopsis> |
| 21 | <funcprototype> |
| 22 | <funcdef>void <function>glScissor</function></funcdef> |
| 23 | <paramdef>GLint <parameter>x</parameter></paramdef> |
| 24 | <paramdef>GLint <parameter>y</parameter></paramdef> |
| 25 | <paramdef>GLsizei <parameter>width</parameter></paramdef> |
| 26 | <paramdef>GLsizei <parameter>height</parameter></paramdef> |
| 27 | </funcprototype> |
| 28 | </funcsynopsis> |
| 29 | </refsynopsisdiv> |
| 30 | <refsect1 id="parameters"><title>Parameters</title> |
| 31 | <variablelist> |
| 32 | <varlistentry> |
| 33 | <term><parameter>x</parameter></term> |
| 34 | <term><parameter>y</parameter></term> |
| 35 | <listitem> |
| 36 | <para> |
| 37 | Specify the lower left corner of the scissor box. |
| 38 | Initially (0, 0). |
| 39 | </para> |
| 40 | </listitem> |
| 41 | </varlistentry> |
| 42 | <varlistentry> |
| 43 | <term><parameter>width</parameter></term> |
| 44 | <term><parameter>height</parameter></term> |
| 45 | <listitem> |
| 46 | <para> |
| 47 | Specify the width and height of the scissor box. |
| 48 | When a GL context is first attached to a window, |
| 49 | <parameter>width</parameter> and <parameter>height</parameter> are set to the dimensions of that |
| 50 | window. |
| 51 | </para> |
| 52 | </listitem> |
| 53 | </varlistentry> |
| 54 | </variablelist> |
| 55 | </refsect1> |
| 56 | <refsect1 id="description"><title>Description</title> |
| 57 | <para> |
| 58 | <function>glScissor</function> defines a rectangle, called the scissor box, |
| 59 | in window coordinates. |
| 60 | The first two arguments, |
| 61 | <parameter>x</parameter> and <parameter>y</parameter>, |
| 62 | specify the lower left corner of the box. |
| 63 | <parameter>width</parameter> and <parameter>height</parameter> specify the width and height of the box. |
| 64 | </para> |
| 65 | <para> |
| 66 | To enable and disable the scissor test, call |
| 67 | <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry> with argument |
| 68 | <constant>GL_SCISSOR_TEST</constant>. The test is initially disabled. |
| 69 | While the test is enabled, only pixels that lie within the scissor box |
| 70 | can be modified by drawing commands. |
| 71 | Window coordinates have integer values at the shared corners of |
| 72 | frame buffer pixels. |
| 73 | <code>glScissor(0,0,1,1)</code> allows modification of only the lower left |
| 74 | pixel in the window, and <code>glScissor(0,0,0,0)</code> doesn't allow |
| 75 | modification of any pixels in the window. |
| 76 | </para> |
| 77 | <para> |
| 78 | When the scissor test is disabled, |
| 79 | it is as though the scissor box includes the entire window. |
| 80 | </para> |
| 81 | </refsect1> |
| 82 | <refsect1 id="errors"><title>Errors</title> |
| 83 | <para> |
| 84 | <constant>GL_INVALID_VALUE</constant> is generated if either <parameter>width</parameter> or <parameter>height</parameter> is negative. |
| 85 | </para> |
| 86 | </refsect1> |
| 87 | <refsect1 id="associatedgets"><title>Associated Gets</title> |
| 88 | <para> |
| 89 | <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_SCISSOR_BOX</constant> |
| 90 | </para> |
| 91 | <para> |
| 92 | <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_SCISSOR_TEST</constant> |
| 93 | </para> |
| 94 | </refsect1> |
| 95 | <refsect1 id="seealso"><title>See Also</title> |
| 96 | <para> |
| 97 | <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>, |
| 98 | <citerefentry><refentrytitle>glViewport</refentrytitle></citerefentry> |
| 99 | </para> |
| 100 | </refsect1> |
| 101 | <refsect1 id="Copyright"><title>Copyright</title> |
| 102 | <para> |
| 103 | Copyright <trademark class="copyright"></trademark> 1991-2006 |
| 104 | Silicon Graphics, Inc. This document is licensed under the SGI |
| 105 | Free Software B License. For details, see |
| 106 | <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>. |
| 107 | </para> |
| 108 | </refsect1> |
| 109 | </refentry> |