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clCreateEventFromGLsyncKHR.adoc

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clCreateEventFromGLsyncKHR

Creates an event object linked to an OpenGL sync object.

cl_event clCreateEventFromGLsyncKHR(cl_context context,
                                    GLsync sync,
                                    cl_int *errcode_ret)

Parameters

context

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

sync

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

Description

An event object may be created by linking to an OpenGL sync object. Completion of such an event object is equivalent to waiting for completion of the fence command associated with the linked GL sync object.

Notes

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.

Errors

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.