1<?xml version="1.0" encoding="UTF-8" standalone="no"?> 2<!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml"> 3 <head> 4 <title xmlns:xlink="http://www.w3.org/1999/xlink">eglQueryContext - EGL Reference Pages</title> 5 <link rel="stylesheet" type="text/css" href="khronos-man.css"/> 6 <meta name="generator" content="DocBook XSL Stylesheets V1.79.1"/> 7 </head> 8 <body> 9 <header/> 10 <div class="refentry" id="eglQueryContext"> 11 <div class="titlepage"/> 12 <div class="refnamediv"> 13 <h2>Name</h2> 14 <p>eglQueryContext — 15 return <abbr class="acronym">EGL</abbr> rendering context information 16 </p> 17 </div> 18 <div class="refsynopsisdiv"> 19 <h2>C Specification</h2> 20 <div class="funcsynopsis"> 21 <table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table"> 22 <tr> 23 <td> 24 <code class="funcdef">EGLBoolean <strong class="fsfunc">eglQueryContext</strong>(</code> 25 </td> 26 <td>EGLDisplay <var class="pdparam">display</var>, </td> 27 </tr> 28 <tr> 29 <td> </td> 30 <td>EGLContext <var class="pdparam">context</var>, </td> 31 </tr> 32 <tr> 33 <td> </td> 34 <td>EGLint <var class="pdparam">attribute</var>, </td> 35 </tr> 36 <tr> 37 <td> </td> 38 <td>EGLint * <var class="pdparam">value</var><code>)</code>;</td> 39 </tr> 40 </table> 41 <div class="funcprototype-spacer"> </div> 42 </div> 43 </div> 44 <div class="refsect1" id="parameters"> 45 <h2>Parameters</h2> 46 <div class="variablelist"> 47 <dl class="variablelist"> 48 <dt> 49 <span class="term"> 50 <em class="parameter"> 51 <code>display</code> 52 </em> 53 </span> 54 </dt> 55 <dd> 56 <p> 57 Specifies the EGL display connection. 58 </p> 59 </dd> 60 <dt> 61 <span class="term"> 62 <em class="parameter"> 63 <code>context</code> 64 </em> 65 </span> 66 </dt> 67 <dd> 68 <p> 69 Specifies the EGL rendering context to query. 70 </p> 71 </dd> 72 <dt> 73 <span class="term"> 74 <em class="parameter"> 75 <code>attribute</code> 76 </em> 77 </span> 78 </dt> 79 <dd> 80 <p> 81 Specifies the EGL rendering context attribute to be returned. 82 </p> 83 </dd> 84 <dt> 85 <span class="term"> 86 <em class="parameter"> 87 <code>value</code> 88 </em> 89 </span> 90 </dt> 91 <dd> 92 <p> 93 Returns the requested value. 94 </p> 95 </dd> 96 </dl> 97 </div> 98 </div> 99 <div class="refsect1" id="description"> 100 <h2>Description</h2> 101 <p> 102 <code class="function">eglQueryContext</code> returns in 103 <em class="parameter"><code>value</code></em> the value of 104 <em class="parameter"><code>attribute</code></em> for <em class="parameter"><code>context</code></em>. 105 <em class="parameter"><code>attribute</code></em> can be one of the following: 106 </p> 107 <div class="variablelist"> 108 <dl class="variablelist"> 109 <dt> 110 <span class="term"> 111 <code class="constant">EGL_CONFIG_ID</code> 112 </span> 113 </dt> 114 <dd> 115 <p> 116 Returns the ID of the EGL frame buffer configuration 117 with respect to which the context was created. 118 </p> 119 </dd> 120 <dt> 121 <span class="term"> 122 <code class="constant">EGL_CONTEXT_CLIENT_TYPE</code> 123 </span> 124 </dt> 125 <dd> 126 <p> 127 Returns the type of client API which the context 128 supports (one of 129 <code class="constant">EGL_OPENGL_API</code>, 130 <code class="constant">EGL_OPENGL_ES_API</code>, or 131 <code class="constant">EGL_OPENVG_API</code>). 132 </p> 133 </dd> 134 <dt> 135 <span class="term"> 136 <code class="constant">EGL_CONTEXT_CLIENT_VERSION</code> 137 </span> 138 </dt> 139 <dd> 140 <p> 141 Returns the version of the client API which the 142 context supports, as specified at context creation 143 time. The resulting value is only meaningful for an 144 OpenGL ES context. 145 </p> 146 </dd> 147 <dt> 148 <span class="term"> 149 <code class="constant">EGL_RENDER_BUFFER</code> 150 </span> 151 </dt> 152 <dd> 153 <p> 154 Returns the buffer which client API rendering 155 via the context will use. The value returned 156 depends on properties of both the context, and 157 the surface to which the context is bound: 158 </p> 159 <div class="itemizedlist"> 160 <ul style="list-style-type: disc; " class="itemizedlist"> 161 <li class="listitem"> 162 <p> 163 If the context is bound to a pixmap surface, 164 then <code class="constant">EGL_SINGLE_BUFFER</code> will 165 be returned. 166 </p> 167 </li> 168 <li class="listitem"> 169 <p> 170 If the context is bound to a pbuffer surface, 171 then <code class="constant">EGL_BACK_BUFFER</code> will 172 be returned. 173 </p> 174 </li> 175 <li class="listitem"> 176 <p> 177 If the context is bound to a window surface, 178 then either <code class="constant">EGL_BACK_BUFFER</code> 179 or <code class="constant">EGL_SINGLE_BUFFER</code> may be 180 returned. The value returned depends on both the 181 buffer requested by the setting of the 182 <code class="constant">EGL_RENDER_BUFFER</code> property 183 of the surface (which may be queried by calling 184 <code class="function">eglQuerySurface</code>), and on 185 the client API (not all client APIs support 186 single-buffer rendering to window surfaces). 187 </p> 188 </li> 189 <li class="listitem"> 190 <p> 191 If the context is not bound to a surface, such 192 as an OpenGL ES context bound to a framebuffer 193 object, then <code class="constant">EGL_NONE</code> will 194 be returned. 195 </p> 196 </li> 197 </ul> 198 </div> 199 </dd> 200 </dl> 201 </div> 202 </div> 203 <div class="refsect1" id="notes"> 204 <h2>Notes</h2> 205 <p> 206 Attributes <code class="constant">EGL_CONTEXT_CLIENT_TYPE</code> and 207 <code class="constant">EGL_RENDER_BUFFER</code> are supported only if 208 the EGL version is 1.2 or greater. 209 </p> 210 <p> 211 Attribute <code class="constant">EGL_CONTEXT_CLIENT_VERSION</code> is 212 supported only if the EGL version is 1.3 or greater. 213 </p> 214 </div> 215 <div class="refsect1" id="errors"> 216 <h2>Errors</h2> 217 <p> 218 <code class="constant">EGL_FALSE</code> is returned on failure, 219 <code class="constant">EGL_TRUE</code> otherwise. 220 <em class="parameter"><code>value</code></em> is not modified when 221 <code class="constant">EGL_FALSE</code> is returned. 222 </p> 223 <p> 224 <code class="constant">EGL_BAD_DISPLAY</code> is generated if 225 <em class="parameter"><code>display</code></em> is not an EGL display connection. 226 </p> 227 <p> 228 <code class="constant">EGL_NOT_INITIALIZED</code> is generated if 229 <em class="parameter"><code>display</code></em> has not been initialized. 230 </p> 231 <p> 232 <code class="constant">EGL_BAD_CONTEXT</code> is generated if 233 <em class="parameter"><code>context</code></em> is not an EGL rendering context. 234 </p> 235 <p> 236 <code class="constant">EGL_BAD_ATTRIBUTE</code> is generated if 237 <em class="parameter"><code>attribute</code></em> is not a valid context attribute. 238 </p> 239 </div> 240 <div class="refsect1" id="seealso"> 241 <h2>See Also</h2> 242 <p> 243 <a class="citerefentry" href="eglCreateContext.xhtml"><span class="citerefentry"><span class="refentrytitle">eglCreateContext</span></span></a> 244 </p> 245 </div> 246 <p> 247 </p> 248 <div class="refsect3" id="copyright"> 249 <img src="KhronosLogo.jpg"/> 250 <p> 251 Copyright © 2003-2014 The Khronos Group Inc. 252 Permission is hereby granted, free of charge, to any person obtaining a 253 copy of this software and/or associated documentation files (the 254 "Materials"), to deal in the Materials without restriction, including 255 without limitation the rights to use, copy, modify, merge, publish, 256 distribute, sublicense, and/or sell copies of the Materials, and to 257 permit persons to whom the Materials are furnished to do so, subject to 258 the condition that this copyright notice and permission notice shall be included 259 in all copies or substantial portions of the Materials. 260 </p> 261 </div> 262 <p> 263</p> 264 </div> 265 <footer/> 266 </body> 267</html> 268
