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235 lines
10 KiB
XML
235 lines
10 KiB
XML
<!DOCTYPE refentry [ <!ENTITY % mathent SYSTEM "math.ent"> %mathent; ]>
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<!-- Converted by db4-upgrade version 1.1 -->
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<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="glGetActiveAttrib">
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<info>
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<copyright>
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<year>2003-2005</year>
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<holder>3Dlabs Inc. Ltd.</holder>
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</copyright>
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<copyright>
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<year>2010-2014</year>
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<holder>Khronos Group</holder>
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</copyright>
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</info>
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<refmeta>
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<refentrytitle>glGetActiveAttrib</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>glGetActiveAttrib</refname>
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<refpurpose>Returns information about an active attribute variable for the specified program object</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<title>C Specification</title>
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<funcsynopsis>
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<funcprototype>
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<funcdef>void <function>glGetActiveAttrib</function></funcdef>
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<paramdef>GLuint <parameter>program</parameter></paramdef>
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<paramdef>GLuint <parameter>index</parameter></paramdef>
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<paramdef>GLsizei <parameter>bufSize</parameter></paramdef>
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<paramdef>GLsizei *<parameter>length</parameter></paramdef>
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<paramdef>GLint *<parameter>size</parameter></paramdef>
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<paramdef>GLenum *<parameter>type</parameter></paramdef>
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<paramdef>GLchar *<parameter>name</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1 xml:id="parameters"><title>Parameters</title>
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<variablelist>
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<varlistentry>
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<term><parameter>program</parameter></term>
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<listitem>
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<para>Specifies the program object to be
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queried.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>index</parameter></term>
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<listitem>
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<para>Specifies the index of the attribute variable
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to be queried.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>bufSize</parameter></term>
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<listitem>
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<para>Specifies the maximum number of characters
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OpenGL is allowed to write in the character buffer
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indicated by <parameter>name</parameter>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>length</parameter></term>
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<listitem>
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<para>Returns the number of characters actually
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written by OpenGL in the string indicated by
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<parameter>name</parameter> (excluding the null
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terminator) if a value other than
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<constant>NULL</constant> is passed.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>size</parameter></term>
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<listitem>
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<para>Returns the size of the attribute
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variable.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>type</parameter></term>
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<listitem>
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<para>Returns the data type of the attribute
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variable.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>name</parameter></term>
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<listitem>
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<para>Returns a null terminated string containing
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the name of the attribute variable.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1 xml:id="description"><title>Description</title>
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<para><function>glGetActiveAttrib</function> returns information
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about an active attribute variable in the program object
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specified by <parameter>program</parameter>. The number of
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active attributes can be obtained by calling
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<citerefentry><refentrytitle>glGetProgramiv</refentrytitle></citerefentry>
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with the value <constant>GL_ACTIVE_ATTRIBUTES</constant>. A
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value of zero for <parameter>index</parameter> selects the first
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active attribute variable. Permissible values for
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<parameter>index</parameter> range from zero to the number of
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active attribute variables minus one.</para>
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<para>Attribute variables have arbitrary names and obtain their values
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through numbered generic vertex attributes. An attribute
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variable is considered active
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if it is determined during the link operation that it may be
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accessed during program execution. Therefore,
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<parameter>program</parameter> should have previously been the
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target of a call to
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<citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry>,
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but it is not necessary for it to have been linked
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successfully.</para>
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<para>The size of the character buffer required to store the
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longest attribute variable name in
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<parameter>program</parameter> can be obtained by calling
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<citerefentry><refentrytitle>glGetProgramiv</refentrytitle></citerefentry>
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with the value
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<constant>GL_ACTIVE_ATTRIBUTE_MAX_LENGTH</constant>. This value
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should be used to allocate a buffer of sufficient size to store
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the returned attribute name. The size of this character buffer
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is passed in <parameter>bufSize</parameter>, and a pointer to
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this character buffer is passed in
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<parameter>name</parameter>.</para>
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<para><function>glGetActiveAttrib</function> returns the name of
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the attribute variable indicated by
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<parameter>index</parameter>, storing it in the character buffer
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specified by <parameter>name</parameter>. The string returned
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will be null terminated. The actual number of characters written
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into this buffer is returned in <parameter>length</parameter>,
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and this count does not include the null termination character.
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If the length of the returned string is not required, a value of
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<constant>NULL</constant> can be passed in the
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<parameter>length</parameter> argument.</para>
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<para>The <parameter>type</parameter> argument will return a
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pointer to the attribute variable's data type. The symbolic
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constants <constant>GL_FLOAT</constant>,
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<constant>GL_FLOAT_VEC2</constant>,
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<constant>GL_FLOAT_VEC3</constant>,
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<constant>GL_FLOAT_VEC4</constant>,
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<constant>GL_FLOAT_MAT2</constant>,
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<constant>GL_FLOAT_MAT3</constant>,
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<constant>GL_FLOAT_MAT4</constant>,
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<constant>GL_FLOAT_MAT2x3</constant>,
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<constant>GL_FLOAT_MAT2x4</constant>,
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<constant>GL_FLOAT_MAT3x2</constant>,
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<constant>GL_FLOAT_MAT3x4</constant>,
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<constant>GL_FLOAT_MAT4x2</constant>,
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<constant>GL_FLOAT_MAT4x3</constant>,
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<constant>GL_INT</constant>,
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<constant>GL_INT_VEC2</constant>,
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<constant>GL_INT_VEC3</constant>,
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<constant>GL_INT_VEC4</constant>,
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<constant>GL_UNSIGNED_INT</constant>,
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<constant>GL_UNSIGNED_INT_VEC2</constant>,
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<constant>GL_UNSIGNED_INT_VEC3</constant>, or
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<constant>GL_UNSIGNED_INT_VEC4</constant> may be returned. The
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<parameter>size</parameter> argument will return the size of the
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attribute, in units of the type returned in
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<parameter>type</parameter>.</para>
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<para>This function will return as much information as it can
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about the specified active attribute variable. If no information
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is available, <parameter>length</parameter> will be 0, and
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<parameter>name</parameter> will be an empty string. This
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situation could occur if this function is called after a link
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operation that failed. If an error occurs, the return values
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<parameter>length</parameter>, <parameter>size</parameter>,
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<parameter>type</parameter>, and <parameter>name</parameter>
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will be unmodified.</para>
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</refsect1>
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<refsect1 xml:id="errors"><title>Errors</title>
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<para><constant>GL_INVALID_VALUE</constant> is generated if
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<parameter>program</parameter> is not a value generated by
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OpenGL.</para>
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<para><constant>GL_INVALID_OPERATION</constant> is generated if
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<parameter>program</parameter> is not a program object.</para>
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<para><constant>GL_INVALID_VALUE</constant> is generated if
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<parameter>index</parameter> is greater than or equal to the
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number of active attribute variables in
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<parameter>program</parameter>.</para>
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<para><constant>GL_INVALID_VALUE</constant> is generated if
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<parameter>bufSize</parameter> is less than 0.</para>
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</refsect1>
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<refsect1 xml:id="associatedgets"><title>Associated Gets</title>
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<para><citerefentry><refentrytitle>glGet</refentrytitle></citerefentry>
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with argument <constant>GL_MAX_VERTEX_ATTRIBS</constant>.</para>
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<para><citerefentry><refentrytitle>glGetProgramiv</refentrytitle></citerefentry>
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with argument <constant>GL_ACTIVE_ATTRIBUTES</constant> or
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<constant>GL_ACTIVE_ATTRIBUTE_MAX_LENGTH</constant>.</para>
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<para><citerefentry><refentrytitle>glIsProgram</refentrytitle></citerefentry></para>
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</refsect1>
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<refsect1 xml:id="versions">
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<title>API Version Support</title>
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<informaltable>
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<tgroup cols="4" align="left">
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<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apifunchead.xml" xpointer="xpointer(/*/*)"/>
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<tbody>
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<row>
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<entry>glGetActiveAttrib</entry>
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<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='es20']/*)"/>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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</refsect1>
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<refsect1 xml:id="seealso"><title>See Also</title>
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<para><citerefentry><refentrytitle>glBindAttribLocation</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glVertexAttrib</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glVertexAttribPointer</refentrytitle></citerefentry></para>
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</refsect1>
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<refsect1 xml:id="Copyright"><title>Copyright</title>
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<para>
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Copyright <trademark class="copyright"/> 2003-2005 3Dlabs Inc. Ltd.
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Copyright <trademark class="copyright"/> 2010-2014 Khronos Group.
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This material may be distributed subject to the terms and conditions set forth in
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the Open Publication License, v 1.0, 8 June 1999.
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<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://opencontent.org/openpub/">http://opencontent.org/openpub/</link>.
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</para>
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</refsect1>
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</refentry>
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