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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                                         │
       ├──────────────────┼─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┬─────┤
       │Function2.02.13.03.13.23.34.04.14.24.34.44.5 │
       │/                 │     │     │     │     │     │     │     │     │     │     │     │     │
       │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)