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NAME
glGetActiveAttrib - Returns information about an active attribute variable for the specified program
object
C SPECIFICATION
void glGetActiveAttrib(GLuint program, GLuint index, GLsizei bufSize, GLsizei *length, GLint *size,
GLenum *type, GLchar *name);
PARAMETERS
program
Specifies the program object to be queried.
index
Specifies the index of the attribute variable to be queried.
bufSize
Specifies the maximum number of characters OpenGL is allowed to write in the character buffer
indicated by name.
length
Returns the number of characters actually written by OpenGL in the string indicated by name
(excluding the null terminator) if a value other than NULL is passed.
size
Returns the size of the attribute variable.
type
Returns the data type of the attribute variable.
name
Returns a null terminated string containing the name of the attribute variable.
DESCRIPTION
glGetActiveAttrib returns information about an active attribute variable in the program object specified
by program. The number of active attributes can be obtained by calling glGetProgram() with the value
GL_ACTIVE_ATTRIBUTES. A value of 0 for index selects the first active attribute variable. Permissible
values for index range from zero to the number of active attribute variables minus one.
A vertex shader may use either built-in attribute variables, user-defined attribute variables, or both.
Built-in attribute variables have a prefix of "gl_" and reference conventional OpenGL vertex attribtes
(e.g., gl_Vertex, gl_Normal, etc., see the OpenGL Shading Language specification for a complete list.)
User-defined attribute variables have arbitrary names and obtain their values through numbered generic
vertex attributes. An attribute variable (either built-in or user-defined) is considered active if it is
determined during the link operation that it may be accessed during program execution. Therefore, program
should have previously been the target of a call to glLinkProgram(), but it is not necessary for it to
have been linked successfully.
The size of the character buffer required to store the longest attribute variable name in program can be
obtained by calling glGetProgram() with the value GL_ACTIVE_ATTRIBUTE_MAX_LENGTH. This value should be
used to allocate a buffer of sufficient size to store the returned attribute name. The size of this
character buffer is passed in bufSize, and a pointer to this character buffer is passed in name.
glGetActiveAttrib returns the name of the attribute variable indicated by index, storing it in the
character buffer specified by name. The string returned will be null terminated. The actual number of
characters written into this buffer is returned in length, and this count does not include the null
termination character. If the length of the returned string is not required, a value of NULL can be
passed in the length argument.
The type argument specifies a pointer to a variable into which the attribute variable's data type will be
written. The symbolic constants GL_FLOAT, GL_FLOAT_VEC2, GL_FLOAT_VEC3, GL_FLOAT_VEC4, GL_FLOAT_MAT2,
GL_FLOAT_MAT3, GL_FLOAT_MAT4, GL_FLOAT_MAT2x3, GL_FLOAT_MAT2x4, GL_FLOAT_MAT3x2, GL_FLOAT_MAT3x4,
GL_FLOAT_MAT4x2, GL_FLOAT_MAT4x3, GL_INT, GL_INT_VEC2, GL_INT_VEC3, GL_INT_VEC4, GL_UNSIGNED_INT,
GL_UNSIGNED_INT_VEC2, GL_UNSIGNED_INT_VEC3, GL_UNSIGNED_INT_VEC4, GL_DOUBLE, GL_DOUBLE_VEC2,
GL_DOUBLE_VEC3, GL_DOUBLE_VEC4, GL_DOUBLE_MAT2, GL_DOUBLE_MAT3, GL_DOUBLE_MAT4, GL_DOUBLE_MAT2x3,
GL_DOUBLE_MAT2x4, GL_DOUBLE_MAT3x2, GL_DOUBLE_MAT3x4, GL_DOUBLE_MAT4x2, or GL_DOUBLE_MAT4x3 may be
returned. The size argument will return the size of the attribute, in units of the type returned in type.
The list of active attribute variables may include both built-in attribute variables (which begin with
the prefix "gl_") as well as user-defined attribute variable names.
This function will return as much information as it can about the specified active attribute variable. If
no information is available, length will be 0, and name will be an empty string. This situation could
occur if this function is called after a link operation that failed. If an error occurs, the return
values length, size, type, and name will be unmodified.
ERRORS
GL_INVALID_VALUE is generated if program is not a value generated by OpenGL.
GL_INVALID_OPERATION is generated if program is not a program object.
GL_INVALID_VALUE is generated if index is greater than or equal to the number of active attribute
variables in program.
GL_INVALID_VALUE is generated if bufSize is less than 0.
ASSOCIATED GETS
glGet() with argument GL_MAX_VERTEX_ATTRIBS.
glGetProgram() with argument GL_ACTIVE_ATTRIBUTES or GL_ACTIVE_ATTRIBUTE_MAX_LENGTH.
glIsProgram()
VERSION SUPPORT
┌──────────────────┬───────────────────────────────────────────────────────────────────────┐
│ │ OpenGL Version │
├──────────────────┼─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┤
│Function │ 2.0 │ 2.1 │ 3.0 │ 3.1 │ 3.2 │ 3.3 │ 4.0 │ 4.1 │ 4.2 │ 4.3 │ 4.4 │ 4.5 │
│/ │ │ │ │ │ │ │ │ │ │ │ │ │
│Feature │ │ │ │ │ │ │ │ │ │ │ │ │
│Name │ │ │ │ │ │ │ │ │ │ │ │ │
├──────────────────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┼─────┤
│glGetActiveAttrib │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │ ✔ │
└──────────────────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┴─────┘
SEE ALSO
glBindAttribLocation(), glLinkProgram(), glVertexAttrib(), glVertexAttribPointer()
COPYRIGHT
Copyright © 2003-2005 3Dlabs Inc. Ltd. Copyright © 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. http://opencontent.org/openpub/.
COPYRIGHT
Copyright © 2003-2005 3Dlabs Inc. Ltd.
Copyright © 2010-2014 Khronos Group
[FIXME: source] 01/03/2018 GLGETACTIVEATTRIB(3G)