'\" t
.\"     Title: glGetActiveUniformBlock
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 01/03/2018
.\"    Manual: [FIXME: manual]
.\"    Source: [FIXME: source]
.\"  Language: English
.\"
.TH "GLGETACTIVEUNIFORMBL" "3G" "01/03/2018" "[FIXME: source]" "[FIXME: manual]"
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.SH "NAME"
glGetActiveUniformBlock \- query information about an active uniform block
.SH "C SPECIFICATION"
.HP \w'void\ glGetActiveUniformBlockiv('u
.BI "void glGetActiveUniformBlockiv(GLuint\ " "program" ", GLuint\ " "uniformBlockIndex" ", GLenum\ " "pname" ", GLint\ *" "params" ");"
.SH "PARAMETERS"
.PP
\fIprogram\fR
.RS 4
Specifies the name of a program containing the uniform block\&.
.RE
.PP
\fIuniformBlockIndex\fR
.RS 4
Specifies the index of the uniform block within
\fIprogram\fR\&.
.RE
.PP
\fIpname\fR
.RS 4
Specifies the name of the parameter to query\&.
.RE
.PP
\fIparams\fR
.RS 4
Specifies the address of a variable to receive the result of the query\&.
.RE
.SH "DESCRIPTION"
.PP
\fBglGetActiveUniformBlockiv\fR
retrieves information about an active uniform block within
\fIprogram\fR\&.
.PP
\fIprogram\fR
must be the name of a program object for which the command
\fBglLinkProgram\fR()
must have been called in the past, although it is not required that
\fBglLinkProgram\fR()
must have succeeded\&. The link could have failed because the number of active uniforms exceeded the limit\&.
.PP
\fIuniformBlockIndex\fR
is an active uniform block index of
\fIprogram\fR, and must be less than the value of
\fBGL_ACTIVE_UNIFORM_BLOCKS\fR\&.
.PP
Upon success, the uniform block parameter(s) specified by
\fIpname\fR
are returned in
\fIparams\fR\&. If an error occurs, nothing will be written to
\fIparams\fR\&.
.PP
If
\fIpname\fR
is
\fBGL_UNIFORM_BLOCK_BINDING\fR, then the index of the uniform buffer binding point last selected by the uniform block specified by
\fIuniformBlockIndex\fR
for
\fIprogram\fR
is returned\&. If no uniform block has been previously specified, zero is returned\&.
.PP
If
\fIpname\fR
is
\fBGL_UNIFORM_BLOCK_DATA_SIZE\fR, then the implementation\-dependent minimum total buffer object size, in basic machine units, required to hold all active uniforms in the uniform block identified by
\fIuniformBlockIndex\fR
is returned\&. It is neither guaranteed nor expected that a given implementation will arrange uniform values as tightly packed in a buffer object\&. The exception to this is the
\fIstd140 uniform block layout\fR, which guarantees specific packing behavior and does not require the application to query for offsets and strides\&. In this case the minimum size may still be queried, even though it is determined in advance based only on the uniform block declaration\&.
.PP
If
\fIpname\fR
is
\fBGL_UNIFORM_BLOCK_NAME_LENGTH\fR, then the total length (including the nul terminator) of the name of the uniform block identified by
\fIuniformBlockIndex\fR
is returned\&.
.PP
If
\fIpname\fR
is
\fBGL_UNIFORM_BLOCK_ACTIVE_UNIFORMS\fR, then the number of active uniforms in the uniform block identified by
\fIuniformBlockIndex\fR
is returned\&.
.PP
If
\fIpname\fR
is
\fBGL_UNIFORM_BLOCK_ACTIVE_UNIFORM_INDICES\fR, then a list of the active uniform indices for the uniform block identified by
\fIuniformBlockIndex\fR
is returned\&. The number of elements that will be written to
\fIparams\fR
is the value of
\fBGL_UNIFORM_BLOCK_ACTIVE_UNIFORMS\fR
for
\fIuniformBlockIndex\fR\&.
.PP
If
\fIpname\fR
is
\fBGL_UNIFORM_BLOCK_REFERENCED_BY_VERTEX_SHADER\fR,
\fBGL_UNIFORM_BLOCK_REFERENCED_BY_TESS_CONTROL_SHADER\fR,
\fBGL_UNIFORM_BLOCK_REFERENCED_BY_TESS_EVALUATION_SHADER\fR,
\fBGL_UNIFORM_BLOCK_REFERENCED_BY_GEOMETRY_SHADER\fR,
\fBGL_UNIFORM_BLOCK_REFERENCED_BY_FRAGMENT_SHADER\fR, or
\fBGL_UNIFORM_BLOCK_REFERENCED_BY_COMPUTE_SHADER\fR
then a boolean value indicating whether the uniform block identified by
\fIuniformBlockIndex\fR
is referenced by the vertex, tessellation control, tessellation evaluation, geometry, fragment or compute programming stages of program, respectively, is returned\&.
.SH "ERRORS"
.PP
\fBGL_INVALID_VALUE\fR
is generated if
\fIuniformBlockIndex\fR
is greater than or equal to the value of
\fBGL_ACTIVE_UNIFORM_BLOCKS\fR
or is not the index of an active uniform block in
\fIprogram\fR\&.
.PP
\fBGL_INVALID_ENUM\fR
is generated if
\fIpname\fR
is not one of the accepted tokens\&.
.PP
\fBGL_INVALID_OPERATION\fR
is generated if
\fIprogram\fR
is not the name of a program object for which
\fBglLinkProgram\fR()
has been called in the past\&.
.SH "NOTES"
.PP
\fBglGetActiveUniformBlockiv\fR
is available only if the GL version is 3\&.1 or greater\&.
.PP
\fBGL_UNIFORM_BLOCK_REFERENCED_BY_COMPUTE_SHADER\fR
is accepted only if the GL version is 4\&.3 or greater\&.
.SH "VERSION SUPPORT"
.TS
allbox tab(:);
lB cB s s s s s s s s s s s
lB cB cB cB cB cB cB cB cB cB cB cB cB.
T{

T}:T{
\fBOpenGL Version\fR
T}
T{
\fBFunction / Feature Name\fR
T}:T{
\fB2\&.0\fR
T}:T{
\fB2\&.1\fR
T}:T{
\fB3\&.0\fR
T}:T{
\fB3\&.1\fR
T}:T{
\fB3\&.2\fR
T}:T{
\fB3\&.3\fR
T}:T{
\fB4\&.0\fR
T}:T{
\fB4\&.1\fR
T}:T{
\fB4\&.2\fR
T}:T{
\fB4\&.3\fR
T}:T{
\fB4\&.4\fR
T}:T{
\fB4\&.5\fR
T}
.T&
l c c c c c c c c c c c c.
T{
\fBglGetActiveUniformBlockiv\fR
T}:T{
\-
T}:T{
\-
T}:T{
\-
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}:T{
✔
T}
.TE
.sp 1
.SH "SEE ALSO"
.PP
\fBglGetActiveUniformBlockName\fR(),
\fBglGetUniformBlockIndex\fR(),
\fBglLinkProgram\fR()
.SH "COPYRIGHT"
.PP
Copyright
\(co
2010\-2014 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\&.
\m[blue]\fBhttp://opencontent\&.org/openpub/\fR\m[]\&.
.SH "COPYRIGHT"
.br
Copyright \(co 2010-2014 Khronos Group
.br