GPU synchronisation fences

## GPU synchronisation fences GPU synchronisation fences — Functions for notification of command completion |

## Synopsis

                        CoglFence;
    void                (*CoglFenceCallback)                (CoglFence *fence,
                                                             void *user_data);
                        CoglFenceClosure;
    void *              cogl_fence_closure_get_user_data    (CoglFenceClosure *closure);
    CoglFenceClosure *  cogl_framebuffer_add_fence_callback (CoglFramebuffer *framebuffer,
                                                             CoglFenceCallback callback,
                                                             void *user_data);
    void                cogl_framebuffer_cancel_fence_callback
                                                            (CoglFramebuffer *framebuffer,
                                                             CoglFenceClosure *closure);

## Description

Cogl allows notification of GPU command completion; users may mark points in the GPU command stream and receive notification when the GPU has executed to that point.

## Details

### CoglFence

    typedef struct _CoglFence CoglFence;

An opaque object representing a fence. This type is currently unused but in the future may be used to pass extra information about the fence completion.

Since 2.0

Stability Level: Unstable

### CoglFenceCallback ()

    void                (*CoglFenceCallback)                (CoglFence *fence,
                                                             void *user_data);

The callback prototype used with `cogl_framebuffer_add_fence_callback()` for notification of GPU command completion.

`fence` : | Unused. In the future this parameter may be used to pass extra information about the fence completion but for now it should be ignored.
`user_data` : | The private data passed to `cogl_framebuffer_add_fence_callback()`

Since 2.0

Stability Level: Unstable

### CoglFenceClosure

    typedef struct _CoglFenceClosure CoglFenceClosure;

An opaque type representing one future callback to be made when the GPU command stream has passed a certain point.

Since 2.0

Stability Level: Unstable

### cogl_fence_closure_get_user_data ()

    void *              cogl_fence_closure_get_user_data    (CoglFenceClosure *closure);

### cogl_framebuffer_add_fence_callback ()

    CoglFenceClosure *  cogl_framebuffer_add_fence_callback (CoglFramebuffer *framebuffer,
                                                             CoglFenceCallback callback,
                                                             void *user_data);

Calls the provided callback when all previously-submitted commands have been executed by the GPU.

`framebuffer` : | The CoglFramebuffer the commands have been submitted to
`callback` : | A CoglFenceCallback to be called when all commands submitted to Cogl have been executed. [scope notified]
`user_data` : | Private data that will be passed to the callback. [closure]
Returns : | non-NULL if the fence succeeded, or `NULL` if it was unable to be inserted and the callback will never be called. The user does not need to free the closure; it will be freed automatically when the callback is called, or cancelled.

Since 2.0

Stability Level: Unstable

### cogl_framebuffer_cancel_fence_callback ()

    void                cogl_framebuffer_cancel_fence_callback
                                                            (CoglFramebuffer *framebuffer,
                                                             CoglFenceClosure *closure);

Removes a fence previously submitted with `cogl_framebuffer_add_fence_callback()`; the callback will not be called.

`framebuffer` : | The CoglFramebuffer the commands were submitted to
`closure` : | The CoglFenceClosure returned from `cogl_framebuffer_add_fence_callback()`

Since 2.0

Stability Level: Unstable