clGetGLContextInfoKHR
clGetGLContextInfoKHR
2007-2011 The Khronos Group Inc. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and/or associated documentation files (the "Materials"), to deal in the Materials without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Materials, and to permit persons to whom the Materials are furnished to do so, subject to the condition that this copyright notice and permission notice shall be included in all copies or substantial portions of the Materials.
3
clGetGLContextInfoKHR Get OpenGL context information.

##

cl_int `clGetGLContextInfoKHR` const cl_context_properties *properties cl_gl_context_info param_name size_t param_value_size void *param_value size_t *param_value_size_ret

## Parameters

`properties`

  Points to an attribute list whose format and valid contents are identical to the `properties` argument of clCreateContext. `properties` must identify a single valid GL context or GL share group object.

`param_name`

  A constant that specifies the GL context information to query, and must be one of the values shown in the table below.

`param_value_size`

  Specifies the size in bytes of memory pointed to by `param_value`. This size must be greater than or equal to the size of the return type described in the table below.

`param_value`

  A pointer to memory where the result of the query is returned as described in the table below. If `param_value` is NULL, it is ignored.

`param_value_size_ret`

  Returns the actual size in bytes of data being queried by `param_value`. If `param_value_size_ret` is NULL, it is ignored.

param_name | Return Type | Information returned in param_value
--- | --- | ---
`CL_CURRENT_DEVICE_FOR_GL_CONTEXT_KHR` | cl_device_id | Return the CL device currently associated with the specified OpenGL context.
`CL_DEVICES_FOR_GL_CONTEXT_KHR` | cl_device_id[] | List of all CL devices which may be associated with the specified OpenGL context.

## Description

The OpenGL object used to create the OpenCL memory object and information about the object type i.e. whether it is a texture, renderbuffer, or buffer object can be queried using this function.

## Notes

The OpenCL specification in section 9.7 defines how to share data with texture and buffer objects in a parallel OpenGL implementation, but does not define how the association between an OpenCL context and an OpenGL context or share group is established. This extension defines optional attributes to OpenCL context creation routines which associate a GL context or share group object with a newly created OpenCL context. If this extension is supported by an implementation, the string "cl_khr_gl_sharing" will be present in the `CL_PLATFORM_EXTENSIONS` or `CL_DEVICE_EXTENSIONS` string described in the table of allowed values for `param_name` for clGetDeviceInfo.

An OpenGL implementation supporting buffer objects and sharing of texture and buffer object images with OpenCL is required by this extension.

OpenCL device(s) corresponding to an OpenGL context may be queried. Such a device may not always exist (for example, if an OpenGL context is specified on a GPU not supporting OpenCL command queues, but which does support shared CL/GL objects), and if it does exist, may change over time. When such a device does exist, acquiring and releasing shared CL/GL objects may be faster on a command queue corresponding to this device than on command queues corresponding to other devices available to an OpenCL context.

## Errors

Returns CL_SUCCESS if the function is executed successfully. If no device(s) exist corresponding to `param_name`, the call will not fail, but the value of `param_value_size_ret` will be zero. Otherwise returns one of the following:

- CL_INVALID_GL_SHAREGROUP_REFERENCE_KHR when an invalid OpenGL context or share group object handle is specified in `properties`.

- CL_INVALID_GL_SHAREGROUP_REFERENCE_KHR if a context was specified by any of the following means:
  - A context was specified for an EGL-based OpenGL ES or OpenGL implementation by setting the attributes `CL_GL_CONTEXT_KHR` and `CL_EGL_DISPLAY_KHR`
  - A context was specified for a GLX-based OpenGL implementation by setting the attributes `CL_GL_CONTEXT_KHR` and `CL_GLX_DISPLAY_KHR`
  - A context was specified for a WGL-based OpenGL implementation by setting the attributes `CL_GL_CONTEXT_KHR` and `CL_WGL_HDC_KHR`

  and any of the following conditions hold:

  - The specified display and context attributes do not identify a valid OpenGL or OpenGL ES context.
  - The specified context does not support buffer and renderbuffer objects.
  - The specified context is not compatible with the OpenCL context being created (for example, it exists in a physically distinct address space, such as another hardware device; or it does not support sharing data with OpenCL due to implementation restrictions).

- CL_INVALID_GL_SHAREGROUP_REFERENCE_KHR if a share group was specified for a CGL-based OpenGL implementation by setting the attribute `CL_CGL_SHAREGROUP_KHR`, and the specified share group does not identify a valid CGL share group object.

- CL_INVALID_OPERATION if a context was specified as described above and any of the following conditions hold:

  - A context or share group object was specified for one of CGL, EGL, GLX, or WGL and the OpenGL implementation does not support that window-system binding API.
  - More than one of the attributes `CL_CGL_SHAREGROUP_KHR`, `CL_EGL_DISPLAY_KHR`, `CL_GLX_DISPLAY_KHR`, and `CL_WGL_HDC_KHR` is set to a non-default value.
  - Both of the attributes `CL_CGL_SHAREGROUP_KHR` and `CL_GL_CONTEXT_KHR` are set to non-default values.
  - Any of the devices specified in the `devices` argument cannot support OpenCL objects which share the data store of an OpenGL object.
- CL_INVALID_VALUE if an attribute name other than those specified in the table of supported `properties` for clCreateContext is specified in `properties`.
- CL_INVALID_VALUE if `param_name` is not `CL_CURRENT_DEVICE_FOR_GL_CONTEXT_KHR` or `CL_DEVICES_FOR_GL_CONTEXT_KHR`; or if the size in bytes specified by `param_value_size` is less than the size of the return type shown above for `CL_CURRENT_DEVICE_FOR_GL_CONTEXT_KHR` or `CL_DEVICES_FOR_GL_CONTEXT_KHR`; and `param_value` is not a NULL value.
- CL_OUT_OF_RESOURCES if there is a failure to allocate resources required by the OpenCL implementation on the device
- CL_OUT_OF_HOST_MEMORY if there is a failure to allocate resources required by the OpenCL implementation on the host.

## Specification

OpenCL Specification

## Also see

clCreateContext cl_khr_gl_sharing

##