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 xml:base="" id="eglQueryContext"> 5 <refentryinfo> 6 <copyright> 7 <year>2003-2014</year> 8 <holder>The Khronos Group Inc.</holder> 9 </copyright> 10 </refentryinfo> 11 <refmeta> 12 <refentrytitle>eglQueryContext</refentrytitle> 13 <manvolnum>3G</manvolnum> 14 </refmeta> 15 <refnamediv> 16 <refname>eglQueryContext</refname> 17 <refpurpose> 18 return <acronym>EGL</acronym> rendering context information 19 </refpurpose> 20 </refnamediv> 21 <refsynopsisdiv> 22 <title>C Specification</title> 23 <funcsynopsis> 24 <funcprototype> 25 <funcdef>EGLBoolean <function>eglQueryContext</function></funcdef> 26 <paramdef>EGLDisplay <parameter>display</parameter></paramdef> 27 <paramdef>EGLContext <parameter>context</parameter></paramdef> 28 <paramdef>EGLint <parameter>attribute</parameter></paramdef> 29 <paramdef>EGLint * <parameter>value</parameter></paramdef> 30 </funcprototype> 31 </funcsynopsis> 32 </refsynopsisdiv> 33 <refsect1 id="parameters"><title>Parameters</title> 34 <variablelist> 35 <varlistentry> 36 <term><parameter>display</parameter></term> 37 <listitem> 38 <para> 39 Specifies the EGL display connection. 40 </para> 41 </listitem> 42 </varlistentry> 43 <varlistentry> 44 <term><parameter>context</parameter></term> 45 <listitem> 46 <para> 47 Specifies the EGL rendering context to query. 48 </para> 49 </listitem> 50 </varlistentry> 51 <varlistentry> 52 <term><parameter>attribute</parameter></term> 53 <listitem> 54 <para> 55 Specifies the EGL rendering context attribute to be returned. 56 </para> 57 </listitem> 58 </varlistentry> 59 <varlistentry> 60 <term><parameter>value</parameter></term> 61 <listitem> 62 <para> 63 Returns the requested value. 64 </para> 65 </listitem> 66 </varlistentry> 67 </variablelist> 68 </refsect1> 69 <refsect1 id="description"><title>Description</title> 70 <para> 71 <function>eglQueryContext</function> returns in 72 <parameter>value</parameter> the value of 73 <parameter>attribute</parameter> for <parameter>context</parameter>. 74 <parameter>attribute</parameter> can be one of the following: 75 </para> 76 <variablelist> 77 <varlistentry> 78 <term><constant>EGL_CONFIG_ID</constant></term> 79 <listitem><para> 80 Returns the ID of the EGL frame buffer configuration 81 with respect to which the context was created. 82 </para></listitem> 83 </varlistentry> 84 <varlistentry> 85 <term><constant>EGL_CONTEXT_CLIENT_TYPE</constant></term> 86 <listitem><para> 87 Returns the type of client API which the context 88 supports (one of 89 <constant>EGL_OPENGL_API</constant>, 90 <constant>EGL_OPENGL_ES_API</constant>, or 91 <constant>EGL_OPENVG_API</constant>). 92 </para></listitem> 93 </varlistentry> 94 <varlistentry> 95 <term><constant>EGL_CONTEXT_CLIENT_VERSION</constant></term> 96 <listitem><para> 97 Returns the version of the client API which the 98 context supports, as specified at context creation 99 time. The resulting value is only meaningful for an 100 OpenGL ES context. 101 </para></listitem> 102 </varlistentry> 103 <varlistentry> 104 <term><constant>EGL_RENDER_BUFFER</constant></term> 105 <listitem> 106 <para> 107 Returns the buffer which client API rendering 108 via the context will use. The value returned 109 depends on properties of both the context, and 110 the surface to which the context is bound: 111 </para> 112 <itemizedlist> 113 <listitem><para> 114 If the context is bound to a pixmap surface, 115 then <constant>EGL_SINGLE_BUFFER</constant> will 116 be returned. 117 </para></listitem> 118 <listitem><para> 119 If the context is bound to a pbuffer surface, 120 then <constant>EGL_BACK_BUFFER</constant> will 121 be returned. 122 </para></listitem> 123 <listitem><para> 124 If the context is bound to a window surface, 125 then either <constant>EGL_BACK_BUFFER</constant> 126 or <constant>EGL_SINGLE_BUFFER</constant> may be 127 returned. The value returned depends on both the 128 buffer requested by the setting of the 129 <constant>EGL_RENDER_BUFFER</constant> property 130 of the surface (which may be queried by calling 131 <function>eglQuerySurface</function>), and on 132 the client API (not all client APIs support 133 single-buffer rendering to window surfaces). 134 </para></listitem> 135 <listitem><para> 136 If the context is not bound to a surface, such 137 as an OpenGL ES context bound to a framebuffer 138 object, then <constant>EGL_NONE</constant> will 139 be returned. 140 </para></listitem> 141 </itemizedlist> 142 </listitem> 143 </varlistentry> 144 </variablelist> 145 </refsect1> 146 <refsect1 id="notes"><title>Notes</title> 147 <para> 148 Attributes <constant>EGL_CONTEXT_CLIENT_TYPE</constant> and 149 <constant>EGL_RENDER_BUFFER</constant> are supported only if 150 the EGL version is 1.2 or greater. 151 </para> 152 <para> 153 Attribute <constant>EGL_CONTEXT_CLIENT_VERSION</constant> is 154 supported only if the EGL version is 1.3 or greater. 155 </para> 156 </refsect1> 157 <refsect1 id="errors"><title>Errors</title> 158 <para> 159 <constant>EGL_FALSE</constant> is returned on failure, 160 <constant>EGL_TRUE</constant> otherwise. 161 <parameter>value</parameter> is not modified when 162 <constant>EGL_FALSE</constant> is returned. 163 </para> 164 <para> 165 <constant>EGL_BAD_DISPLAY</constant> is generated if 166 <parameter>display</parameter> is not an EGL display connection. 167 </para> 168 <para> 169 <constant>EGL_NOT_INITIALIZED</constant> is generated if 170 <parameter>display</parameter> has not been initialized. 171 </para> 172 <para> 173 <constant>EGL_BAD_CONTEXT</constant> is generated if 174 <parameter>context</parameter> is not an EGL rendering context. 175 </para> 176 <para> 177 <constant>EGL_BAD_ATTRIBUTE</constant> is generated if 178 <parameter>attribute</parameter> is not a valid context attribute. 179 </para> 180 </refsect1> 181 <refsect1 id="seealso"><title>See Also</title> 182 <para> 183 <citerefentry><refentrytitle>eglCreateContext</refentrytitle></citerefentry> 184 </para> 185 </refsect1> 186 <refsect3 id="Copyright"><title></title> 187 <!-- Content included from copyright.inc.xsl --> 188 <imageobject> 189 <imagedata fileref="KhronosLogo.jpg" format="jpg" /> 190 </imageobject> 191 <para /> 192 </refsect3> 193</refentry> 194
