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<?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" /><link rel="stylesheet" type="text/css" href="opengl-man.css" /><title>glDebugMessageCallback - OpenGL 4 Reference Pages</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glDebugMessageCallback"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glDebugMessageCallback — specify a callback to receive debugging messages from the GL</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">glDebugMessageCallback</b>(</code></td><td>DEBUGPROC  </td><td><var class="pdparam">callback</var>, </td></tr><tr><td> </td><td>void *  </td><td><var class="pdparam">userParam</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>callback</code></em></span></dt><dd><p>
                    The address of a callback function that will be called when a debug message is generated.
                </p></dd><dt><span class="term"><em class="parameter"><code>userParam</code></em></span></dt><dd><p>
                    A user supplied pointer that will be passed on each invocation of <em class="parameter"><code>callback</code></em>.
                </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
            <code class="function">glDebugMessageInsert</code> sets the current debug output callback function to
            the function whose address is given in <em class="parameter"><code>callback</code></em>. The callback function
            should have the following prototype (in C), or be otherwise compatible with such a prototype:
        </p><pre class="programlisting">        typedef void (APIENTRY *DEBUGPROC)(GLenum source,
                                           GLenum type,
                                           GLuint id,
                                           GLenum severity,
                                           GLsizei length,
                                           const GLchar* message,
                                           void* userParam);</pre><p>
            This function is defined to have the same calling convention as the GL API functions. In
            most cases this is defined as <code class="code">APIENTRY</code>, although it will vary depending
            on platform, language and compiler.
        </p><p>
            Each time a debug message is generated the debug callback function will be invoked
            with <em class="parameter"><code>source</code></em>, <em class="parameter"><code>type</code></em>, <em class="parameter"><code>id</code></em>, and
            <em class="parameter"><code>severity</code></em> associated with the message, and <em class="parameter"><code>length</code></em> set to
            the length of debug message whose character string is in the array pointed to by <em class="parameter"><code>message</code></em>
            <em class="parameter"><code>userParam</code></em> will be set to the value passed in the
            <em class="parameter"><code>userParam</code></em> parameter to the most recent call to <code class="function">glDebugMessageInsert</code>.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p>
            When the GL is in use remotely, the server may not be able to call functions in the client's address space.
            In such cases, the callback function may not be invoked and the user should retrieve debug messages from
            the context's debug message log by calling <a href="glGetDebugMessageLog.xml"><span class="citerefentry"><span class="refentrytitle">glGetDebugMessageLog</span></span></a>.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
            <a href="glDebugMessageControl.xml"><span class="citerefentry"><span class="refentrytitle">glDebugMessageControl</span></span></a>,
            <a href="glDebugMessageInsert.xml"><span class="citerefentry"><span class="refentrytitle">glDebugMessageInsert</span></span></a>,
            <a href="glGetDebugMessageLog.xml"><span class="citerefentry"><span class="refentrytitle">glGetDebugMessageLog</span></span></a>.
        </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
            Copyright <span class="trademark"></span>© 2012 Khronos Group. 
            This material may be distributed subject to the terms and conditions set forth in 
            the Open Publication License, v 1.0, 8 June 1999.
            <a href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
        </p></div></div></body></html>
