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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title xmlns:xlink="http://www.w3.org/1999/xlink">eglQueryContext - EGL Reference Pages</title>
<link rel="stylesheet" type="text/css" href="khronos-man.css"/>
<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"/>
</head>
<body>
<header/>
<div class="refentry" id="eglQueryContext">
<div class="titlepage"/>
<div class="refnamediv">
<h2>Name</h2>
<p>eglQueryContext —
return <abbr class="acronym">EGL</abbr> rendering context information
</p>
</div>
<div class="refsynopsisdiv">
<h2>C Specification</h2>
<div class="funcsynopsis">
<table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
<tr>
<td>
<code class="funcdef">EGLBoolean <strong class="fsfunc">eglQueryContext</strong>(</code>
</td>
<td>EGLDisplay <var class="pdparam">display</var>, </td>
</tr>
<tr>
<td> </td>
<td>EGLContext <var class="pdparam">context</var>, </td>
</tr>
<tr>
<td> </td>
<td>EGLint <var class="pdparam">attribute</var>, </td>
</tr>
<tr>
<td> </td>
<td>EGLint * <var class="pdparam">value</var><code>)</code>;</td>
</tr>
</table>
<div class="funcprototype-spacer"> </div>
</div>
</div>
<div class="refsect1" id="parameters">
<h2>Parameters</h2>
<div class="variablelist">
<dl class="variablelist">
<dt>
<span class="term">
<em class="parameter">
<code>display</code>
</em>
</span>
</dt>
<dd>
<p>
Specifies the EGL display connection.
</p>
</dd>
<dt>
<span class="term">
<em class="parameter">
<code>context</code>
</em>
</span>
</dt>
<dd>
<p>
Specifies the EGL rendering context to query.
</p>
</dd>
<dt>
<span class="term">
<em class="parameter">
<code>attribute</code>
</em>
</span>
</dt>
<dd>
<p>
Specifies the EGL rendering context attribute to be returned.
</p>
</dd>
<dt>
<span class="term">
<em class="parameter">
<code>value</code>
</em>
</span>
</dt>
<dd>
<p>
Returns the requested value.
</p>
</dd>
</dl>
</div>
</div>
<div class="refsect1" id="description">
<h2>Description</h2>
<p>
<code class="function">eglQueryContext</code> returns in
<em class="parameter"><code>value</code></em> the value of
<em class="parameter"><code>attribute</code></em> for <em class="parameter"><code>context</code></em>.
<em class="parameter"><code>attribute</code></em> can be one of the following:
</p>
<div class="variablelist">
<dl class="variablelist">
<dt>
<span class="term">
<code class="constant">EGL_CONFIG_ID</code>
</span>
</dt>
<dd>
<p>
Returns the ID of the EGL frame buffer configuration
with respect to which the context was created.
</p>
</dd>
<dt>
<span class="term">
<code class="constant">EGL_CONTEXT_CLIENT_TYPE</code>
</span>
</dt>
<dd>
<p>
Returns the type of client API which the context
supports (one of
<code class="constant">EGL_OPENGL_API</code>,
<code class="constant">EGL_OPENGL_ES_API</code>, or
<code class="constant">EGL_OPENVG_API</code>).
</p>
</dd>
<dt>
<span class="term">
<code class="constant">EGL_CONTEXT_CLIENT_VERSION</code>
</span>
</dt>
<dd>
<p>
Returns the version of the client API which the
context supports, as specified at context creation
time. The resulting value is only meaningful for an
OpenGL ES context.
</p>
</dd>
<dt>
<span class="term">
<code class="constant">EGL_RENDER_BUFFER</code>
</span>
</dt>
<dd>
<p>
Returns the buffer which client API rendering
via the context will use. The value returned
depends on properties of both the context, and
the surface to which the context is bound:
</p>
<div class="itemizedlist">
<ul style="list-style-type: disc; " class="itemizedlist">
<li class="listitem">
<p>
If the context is bound to a pixmap surface,
then <code class="constant">EGL_SINGLE_BUFFER</code> will
be returned.
</p>
</li>
<li class="listitem">
<p>
If the context is bound to a pbuffer surface,
then <code class="constant">EGL_BACK_BUFFER</code> will
be returned.
</p>
</li>
<li class="listitem">
<p>
If the context is bound to a window surface,
then either <code class="constant">EGL_BACK_BUFFER</code>
or <code class="constant">EGL_SINGLE_BUFFER</code> may be
returned. The value returned depends on both the
buffer requested by the setting of the
<code class="constant">EGL_RENDER_BUFFER</code> property
of the surface (which may be queried by calling
<code class="function">eglQuerySurface</code>), and on
the client API (not all client APIs support
single-buffer rendering to window surfaces).
</p>
</li>
<li class="listitem">
<p>
If the context is not bound to a surface, such
as an OpenGL ES context bound to a framebuffer
object, then <code class="constant">EGL_NONE</code> will
be returned.
</p>
</li>
</ul>
</div>
</dd>
</dl>
</div>
</div>
<div class="refsect1" id="notes">
<h2>Notes</h2>
<p>
Attributes <code class="constant">EGL_CONTEXT_CLIENT_TYPE</code> and
<code class="constant">EGL_RENDER_BUFFER</code> are supported only if
the EGL version is 1.2 or greater.
</p>
<p>
Attribute <code class="constant">EGL_CONTEXT_CLIENT_VERSION</code> is
supported only if the EGL version is 1.3 or greater.
</p>
</div>
<div class="refsect1" id="errors">
<h2>Errors</h2>
<p>
<code class="constant">EGL_FALSE</code> is returned on failure,
<code class="constant">EGL_TRUE</code> otherwise.
<em class="parameter"><code>value</code></em> is not modified when
<code class="constant">EGL_FALSE</code> is returned.
</p>
<p>
<code class="constant">EGL_BAD_DISPLAY</code> is generated if
<em class="parameter"><code>display</code></em> is not an EGL display connection.
</p>
<p>
<code class="constant">EGL_NOT_INITIALIZED</code> is generated if
<em class="parameter"><code>display</code></em> has not been initialized.
</p>
<p>
<code class="constant">EGL_BAD_CONTEXT</code> is generated if
<em class="parameter"><code>context</code></em> is not an EGL rendering context.
</p>
<p>
<code class="constant">EGL_BAD_ATTRIBUTE</code> is generated if
<em class="parameter"><code>attribute</code></em> is not a valid context attribute.
</p>
</div>
<div class="refsect1" id="seealso">
<h2>See Also</h2>
<p>
<a class="citerefentry" href="eglCreateContext.xhtml"><span class="citerefentry"><span class="refentrytitle">eglCreateContext</span></span></a>
</p>
</div>
<p>
</p>
<div class="refsect3" id="copyright">
<img src="KhronosLogo.jpg"/>
<p>
Copyright © 2003-2014 The Khronos Group Inc.
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and/or associated documentation files (the
"Materials"), to deal in the Materials without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Materials, and to
permit persons to whom the Materials are furnished to do so, subject to
the condition that this copyright notice and permission notice shall be included
in all copies or substantial portions of the Materials.
</p>
</div>
<p>
</p>
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