2012 Khronos Group
glGetProgramInterface 3G
glGetProgramInterface query a property of an interface in a program

## C Specification

void `glGetProgramInterfaceiv` GLuint program GLenum programInterface GLenum pname GLint * params

## Parameters

program

  The name of a program object whose interface to query.

programInterface

  A token identifying the interface within program to query.

pname

  The name of the parameter within programInterface to query.

params

  The address of a variable to retrieve the value of pname for the program interface.

## Description

`glGetProgramInterfaceiv` queries the property of the interface identifed by programInterface in program, the property name of which is given by pname.

program must be the name of an existing program object. programInterface is the name of the interface within program to query and must be one of the following values:

`GL_UNIFORM`

  The query is targeted at the set of active uniforms within program.

`GL_UNIFORM_BLOCK`

  The query is targeted at the set of active uniform blocks within program.

`GL_ATOMIC_COUNTER_BUFFER`

  The query is targeted at the set of active atomic counter buffer binding points within program.

`GL_PROGRAM_INPUT`

  The query is targeted at the set of active input variables used by the first shader stage of program. If program contains multiple shader stages then input variables from any stage other than the first will not be enumerated.

`GL_PROGRAM_OUTPUT`

  The query is targeted at the set of active output variables produced by the last shader stage of program. If program contains multiple shader stages then output variables from any stage other than the last will not be enumerated.

`GL_VERTEX_SUBROUTINE`
,
`GL_TESS_CONTROL_SUBROUTINE`
,
`GL_TESS_EVALUATION_SUBROUTINE`
,
`GL_GEOMETRY_SUBROUTINE`
,
`GL_FRAGMENT_SUBROUTINE`
,
`GL_COMPUTE_SUBROUTINE`

  The query is targeted at the set of active subroutines for the vertex, tessellation control, tessellation evaluation, geometry, fragment and compute shader stages of program, respectively.

`GL_VERTEX_SUBROUTINE_UNIFORM`
,
`GL_TESS_CONTROL_SUBROUTINE_UNIFORM`
,
`GL_TESS_EVALUATION_SUBROUTINE_UNIFORM`
,
`GL_GEOMETRY_SUBROUTINE_UNIFORM`
,
`GL_FRAGMENT_SUBROUTINE_UNIFORM`
,
`GL_COMPUTE_SUBROUTINE_UNIFORM`

  The query is targeted at the set of active subroutine uniform variables used by the vertex, tessellation control, tessellation evaluation, geometry, fragment and compute shader stages of program, respectively.

`GL_TRANSFORM_FEEDBACK_VARYING`

  The query is targeted at the set of output variables from the last non-fragment stage of program that would be captured if transform feedback were active.

`GL_BUFFER_VARIABLE`

  The query is targeted at the set of active buffer variables used by program.

`GL_SHADER_STORAGE_BLOCK`

  The query is targeted at the set of active shader storage blocks used by program.

pname identifies the property of programInterface to return in params.

If pname is `GL_ACTIVE_RESOURCES`, the value returned is the number of resources in the active resource list for programInterface. If the list of active resources for programInterface is empty, zero is returned.

If pname is `GL_MAX_NAME_LENGTH`, the value returned is the length of the longest active name string for an active resource in programInterface. This length includes an extra character for the null terminator. If the list of active resources for programInterface is empty, zero is returned. It is an error to specify `GL_MAX_NAME_LENGTH` when programInterface is `GL_ATOMIC_COUNTER_BUFFER`, as active atomic counter buffer resources are not assigned name strings.

If pname is `GL_MAX_NUM_ACTIVE_VARIABLES`, the value returned is the number of active variables belonging to the interface block or atomic counter buffer resource in programInterface with the most active variables. If the list of active resources for programInterface is empty, zero is returned. When pname is `GL_MAX_NUM_ACTIVE_VARIABLES`, programInterface must be `GL_UNIFORM_BLOCK`, `GL_ATOMIC_COUNTER_BUFFER`, or `GL_SHADER_STORAGE_BLOCK`.

If pname is `GL_MAX_NUM_COMPATIBLE_SUBROUTINES`, the value returned is the number of compatible subroutines belonging to the active subroutine uniform in programInterface with the most compatible subroutines. If the list of active resources for programInterface is empty, zero is returned. When pname is `GL_MAX_NUM_COMPATIBLE_SUBROUTINES`, programInterface must be one of `GL_VERTEX_SUBROUTINE_UNIFORM`, `GL_TESS_CONTROL_SUBROUTINE_UNIFORM`, `GL_TESS_EVALUATION_SUBROUTINE_UNIFORM`, `GL_GEOMETRY_SUBROUTINE_UNIFORM`, `GL_FRAGMENT_SUBROUTINE_UNIFORM`, or `GL_COMPUTE_SUBROUTINE_UNIFORM`.

## Errors

`GL_INVALID_ENUM` is generated if identifier is not one of the accepted object types.

`GL_INVALID_VALUE` is generated if program is not the name of an existing sync object.

`GL_INVALID_VALUE` is generated if bufSize is zero.

If not NULL, length and label should be addresses to which the client has write access, otherwise undefined behavior, including process termination may occur.

## Associated Gets

glGet with argument `GL_MAX_LABEL_LENGTH`.

## See Also

glPushDebugGroup, glPopDebugGroup, glObjectLabel, glGetObjectLabel.

## Copyright

Copyright 2012 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/.