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<refentry id="glValidateProgram">
    <refmeta>
	<refentrytitle>glValidateProgram</refentrytitle>
	<manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
	<refname>glValidateProgram</refname>
	<refpurpose>Validates a program object</refpurpose>
    </refnamediv>
    <refsynopsisdiv><title>C Specification</title>
	<funcsynopsis>
	    <funcprototype>
		<funcdef>void <function>glValidateProgram</function></funcdef>
		<paramdef>GLuint <parameter>program</parameter></paramdef>
	    </funcprototype>
	</funcsynopsis>
    </refsynopsisdiv>
    <refsect1 id="parameters"><title>Parameters</title>
	<variablelist>
	    <varlistentry>
		<term><parameter>program</parameter></term>
		<listitem>
		    <para>Specifies the handle of the program object to
		    be validated.</para>
		</listitem>
	    </varlistentry>
	</variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
	<para><function>glValidateProgram</function> checks to see
	whether the executables contained in
	<parameter>program</parameter> can execute given the current
	OpenGL state. The information generated by the validation
	process will be stored in <parameter>program</parameter>'s
	information log. The validation information may consist of an
	empty string, or it may be a string containing information about
	how the current program object interacts with the rest of
	current OpenGL state. This provides a way for OpenGL
	implementers to convey more information about why the current
	program is inefficient, suboptimal, failing to execute, and so
	on.</para>

	<para>The status of the validation operation will be stored as
	part of the program object's state. This value will be set to
	<constant>GL_TRUE</constant> if the validation succeeded, and
	<constant>GL_FALSE</constant> otherwise. It can be queried by
	calling
	<citerefentry><refentrytitle>glGetProgram</refentrytitle></citerefentry>
	with arguments <parameter>program</parameter> and
	<constant>GL_VALIDATE_STATUS</constant>. If validation is
	successful, <parameter>program</parameter> is guaranteed to
	execute given the current state. Otherwise,
	<parameter>program</parameter> is guaranteed to not execute.</para>

	<para>This function is typically useful only during application
	development. The informational string stored in the information
	log is completely implementation dependent; therefore, an
	application should not expect different OpenGL implementations
	to produce identical information strings.</para>
    </refsect1>
    <refsect1 id="notes"><title>Notes</title>
	<para><function>glValidateProgram</function> is available only
	if the GL version is 2.0 or greater.</para>

	<para>This function mimics the validation operation that OpenGL
	implementations must perform when rendering commands are issued
	while programmable shaders are part of current state. The error
	<constant>GL_INVALID_OPERATION</constant> will be generated by
	<citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>,
	<citerefentry><refentrytitle>glRasterPos</refentrytitle></citerefentry>,
	or any command that performs an implicit call to
	<citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
	if:</para>

	<itemizedlist>
	    <listitem>
		<para>any two active samplers in the current program
		object are of different types, but refer to the same
		texture image unit,</para>
	    </listitem>
	    <listitem>
		<para>any active sampler in the current program object
		refers to a texture image unit where fixed-function
		fragment processing accesses a texture target that does
		not match the sampler type, or</para>
	    </listitem>
	    <listitem>
		<para>the sum of the number of active samplers in the
		program and the number of texture image units enabled
		for fixed-function fragment processing exceeds the
		combined limit on the total number of texture image
		units allowed.</para>
	    </listitem>
	</itemizedlist>

	<para>It may be difficult or cause a performance degradation for
	applications to catch these errors when rendering commands are
	issued. Therefore, applications are advised to make calls to
	<function>glValidateProgram</function> to detect these issues
	during application development.</para>
    </refsect1>
    <refsect1 id="errors"><title>Errors</title>
	<para><constant>GL_INVALID_VALUE</constant> is generated if
	<parameter>program</parameter> is not a value generated by
	OpenGL.</para>

	<para><constant>GL_INVALID_OPERATION</constant> is generated if
	<parameter>program</parameter> is not a program object.</para>

	<para><constant>GL_INVALID_OPERATION</constant> is generated if
	<function>glValidateProgram</function> is executed between the
	execution of
	<citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
	and the corresponding execution of
	<citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.</para>
    </refsect1>
    <refsect1 id="associatedgets"><title>Associated Gets</title>
	<para><citerefentry><refentrytitle>glGetProgram</refentrytitle></citerefentry>
	with arguments <parameter>program</parameter> and
	<constant>GL_VALIDATE_STATUS</constant></para>

	<para><citerefentry><refentrytitle>glGetProgramInfoLog</refentrytitle></citerefentry>
	with argument <parameter>program</parameter></para>

	<para><citerefentry><refentrytitle>glIsProgram</refentrytitle></citerefentry></para>
    </refsect1>
    <refsect1 id="seealso"><title>See Also</title>
	<para><citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry>,
	<citerefentry><refentrytitle>glUseProgram</refentrytitle></citerefentry></para>
    </refsect1>
    <refsect1 id="Copyright"><title>Copyright</title>
        <para>
            Copyright <trademark class="copyright"></trademark> 2003-2005 3Dlabs Inc. Ltd. 
            This material may be distributed subject to the terms and conditions set forth in 
            the Open Publication License, v 1.0, 8 June 1999.
            <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
        </para>
    </refsect1>
</refentry>
