C Specification

To create an OpenCL event object linked to an OpenGL fence sync object, call the function

// Provided by cl_khr_gl_event
cl_event clCreateEventFromGLsyncKHR(
    cl_context context,
    cl_GLsync sync,
    cl_int* errcode_ret);
clCreateEventFromGLsyncKHR is provided by the cl_khr_gl_event extension.

Parameters

  • context is a valid OpenCL context created from an OpenGL context or share group, using the cl_khr_gl_sharing extension.

  • sync is the name of a sync object in the GL share group associated with context.

  • errcode_ret will return an appropriate error code. If errcode_ret is NULL, no error code is returned.

Description

Completion of such an event object is equivalent to waiting for completion of the fence command associated with the linked GL sync object.

clCreateEventFromGLsyncKHR returns a valid OpenCL event object and errcode_ret is set to CL_SUCCESS if the event object is created successfully. Otherwise, it returns a NULL value with one of the following error values returned in errcode_ret:

  • CL_INVALID_CONTEXT if context is not a valid context, or was not created from a GL context.

  • CL_INVALID_GL_OBJECT if sync is not the name of a sync object in the GL share group associated with context.

The parameters of an event object linked to a GL sync object will return the following values when queried with clGetEventInfo:

  • The CL_EVENT_COMMAND_QUEUE of a linked event is NULL, because the event is not associated with any OpenCL command-queue.

  • The CL_EVENT_COMMAND_TYPE of a linked event is CL_COMMAND_GL_FENCE_SYNC_OBJECT_KHR, indicating that the event is associated with a GL sync object, rather than an OpenCL command.

  • The CL_EVENT_COMMAND_EXECUTION_STATUS of a linked event is either CL_SUBMITTED, indicating that the fence command associated with the sync object has not yet completed, or CL_COMPLETE, indicating that the fence command has completed.

clCreateEventFromGLsyncKHR performs an implicit clRetainEvent on the returned event object. Creating a linked event object also places a reference on the linked GL sync object. When the event object is deleted, the reference will be removed from the GL sync object.

Events returned from clCreateEventFromGLsyncKHR can be used in the event_wait_list argument to clEnqueueAcquireGLObjects and CL APIs that take a cl_event as an argument but do not enqueue commands. Passing such events to any other CL API that enqueues commands will generate a CL_INVALID_EVENT error.

See Also

cl_GLsync, cl_context, cl_int, cl_khr_gl_event

Document Notes

For more information, see the OpenCL Specification

This page is extracted from the OpenCL Specification. Fixes and changes should be made to the Specification, not directly.

Copyright

Copyright 2014-2025 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0