204 /*!---------------------------------------------------------------------------

   205  *  Register stream content observer (append to chain). The observer will

   206  *  receive buffer modification event from the stream whenever a buffer is

   207  *  committed.

   208  *

   209  *  \param stream           Stream handle

   210  *  \param observer         Stream observer

   211  *  \param data             Optional data to pass to observer callback

   212  *                          function when event is dispatched.

   213  *----------------------------------------------------------------------------*/

   214  OWF_PUBLIC OWF_STREAM_ERROR

   215 owfNativeStreamAddObserver(OWFNativeStreamType stream,

   216                            OWFStreamCallback observer,

   217                            void* data);

   218 

   219 /*!---------------------------------------------------------------------------

   220  *  Remove stream content observer.

   221  *

   222  *  \param stream           Stream handle

   223  *  \param observer         Observer to remove

   224  *

   225  *  \param Zero if the observer was removed successfully, otherwise non-zero

   226  *  (OWF_STREAM_ERROR_INVALID_STREAM if the stream is invalid;

   227  *   OWF_STREAM_ERROR_INVALID_OBSERVER if the observer is invalid.)

   228  *

   229  *   NOTE (khronos bugzilla #5188): "Because the parameter is the observer

   230  *   function, it is likely that the wrong context could be removed if

   231  *   two contexts sharing the same implementation code are observing the

   232  *   same stream, and then one removes its observer. Ideally, both the

   233  *   function and the client void* should be passed as parameters

   234  *   to uniquely identify the observer."

   235  *

   236  *   The issue can be fixed by adding sync object handle into the interface

   237  *   of this function. Sync object must be passed to the static comparison

   238  *   function (ObserversEqual). Implementator must take into account that

   239  *   when the stream is destroyed, all observers of that stream must be destroyed.

   240  *

   241  *----------------------------------------------------------------------------*/

   242  OWF_API_CALL OWF_STREAM_ERROR

   243 owfNativeStreamRemoveObserver(OWFNativeStreamType stream,

   244                               OWFStreamCallback observer,

   245                               void* data);