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Name Strings
Last Modifed Date: November 28, 2017
OpenGL ES 2.0 is required.
This extension supports cross-process GL context synchronization.
A "gpu fence" represents a synchronization point in a GL stream that can be
duplicated into an associated gpu fence in another unrelated GL stream. A
server wait on the duplicate ensures that the pre-fence commands on the
source stream have executed. The gpu fence is a reference to a
platform-dependent external GL fence object.
IPC transport is based on a "gpu fence handle" which can be converted to
and from a gpu fence, but the details of this are out of scope for this
See also the ANDROID_native_fence_sync extension which is used to
implement the GLFenceEGLNativeSync class on Android.
New Procedures and Functions
The command
GLuint CreateClientGpuFenceCHROMIUM(ClientGpuFence source)
creates a waitable service-side gpu fence that signals when the supplied
external gpu fence is signalled. It returns a gpu fence name.
The command
GLuint CreateGpuFenceCHROMIUM()
creates a new service side gpu fence backed by a new synchronization point
inserted into the command stream. It returns a gpu fence name. This
creation method is intended for use with a platform-specific mechanism that
supports extracting a client gpu fence for external use.
The command
void WaitGpuFenceCHROMIUM(GLuint gpu_fence_id)
issues a server wait. Use this on a gpu fence that was created from an
external gpu fence to ensure that operations are synchronized with the source
gpu fence that provided the gpu fence handle.
The command
void DestroyGpuFenceCHROMIUM(GLuint gpu_fence_id)
destroys the specified service side gpu fence and invalidates the gpu_fence
name. A gpu fence that was duplicated from it remains valid, and it is not
necessary to wait for the duplicated fence to be used before destroying the
service side gpu fence.
New Tokens
INVALID_VALUE is generated if the <source> parameter of
CreateClientGpuFenceCHROMIUM is not a valid ClientGpuFence.
INVALID_VALUE is generated if the <gpu_fence_id> parameter of
WaitGpuFenceCHROMIUM or DestroyGpuFenceCHROMIUM is not a valid gpu fence
New State
Q: Should there be a GetGpuFenceCHROMIUM GLES call to get a ClientGpuFence?
A: This was excluded and left as a platform-specific non-GLES mechanism for
flexibility. A synchronous call to get an externally-usable
ClientGpuFence would be counterproductive since the intent of this
extension is to sequence asynchronous operations. A callback-based
method is most natural, but would not be a good fit to the GLES API. A
sample implementation would be context_support->GetGpuFence(EGLint
gpu_fence, Callback<void(std::unique_ptr<GpuFence>)>), where the supplied
callback receives a client gpu fence that it can use to create an
external fence object for use with a local server wait.
Revision History
11/28/2017 Documented the extension