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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
<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>