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EvmCallback(5)

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NAME    [Toc]    [Back]

       EvmCallback - Event Management callback function

SYNOPSIS    [Toc]    [Back]

       void EventCB(
               EvmConnection_t connection,
               EvmCallbackArg_t callbackArg,
               EvmCallbackData_t *callbackData)

DESCRIPTION    [Toc]    [Back]

       An EVM callback function is a function that you provide to
       allow your program to handle messages arriving on  an  EVM
       connection.   Most  messages  will  be  incoming events or
       responses to requests you have made to the EVM daemon, but
       you may also get a callback for other reasons.

       You specify the name (EventCB) of the callback function in
       the callback parameter when you create an  EVM  connection
       with a response mode of callback.

       Your  callback  function  is invoked by EvmConnDispatch(),
       which you must call whenever you detect  activity  pending
       on the connection.

       An  EVM  callback  function  must conform to the prototype
       shown.

   Callback function parameters:
       The connection parameter contains the  connection  context
       pertaining  to  this callback.  This value was returned by
       EvmConnCreate() when the connection was  created.  If  you
       have one callback function servicing multiple connections,
       you might test this to determine which connection  a  particular
 invocation is handling.  The callbackArg parameter
       contains the value you specified as the callbackArg parameter
  to  EvmConnCreate() when you created the connection.
       For example, you might use it to hold a  pointer  to  your
       own  context  data  for  the connection.  The callbackData
       parameter points to a structure containing the details  of
       the  callback.   The  structure includes a callback reason
       code, an event, and a union containing  data  specific  to
       each  possible  reason.  The event member may contain NULL
       if it is not applicable to the reason.  You may get  these
       reasons:  This  callback  reason indicates that the daemon
       was unable to deliver one or more events, probably because
       the  client  process  had  not finished processing earlier
       events, causing the connection  buffer  to  overflow.   If
       necessary,  you  can use EvmConnControl(3) to increase the
       size of the receive buffer.  This  callback  reason  indicates
 that an EVM event has been received from the daemon.
       The event is available in the callbackData structure.  You
       must  use  EvmEventDestroy(3)  to  free the event when you
       have finished with it.   This  callback  reason  indicates
       that  a  prior  EvmEventPost() call has completed, usually
       with a response from the daemon if  the  responseMode  was
       specified  as EvmRESPONSE_CALLBACK when the connection was
       created. The posting status is available in the  callbackData
  structure.   This  callback  reason indicates that a
       requested template has been delivered in  response  to  an
       EvmConnRegistrationGet() request. You must use EvmEventDestroy(3) to free the template when you have finished  with
       it.    This   callback   reason  indicates  that  a  prior
       EvmEventSubscribe() call has  completed,  usually  with  a
       response  from the daemon.  This callback reason indicates
       that event template  information  has  been  delivered  in
       response  to  an  EvmConnTemplateScan() request.  The template
 is available in the callbackData structure. You must
       use  EvmEventDestroy(3) to free the template when you have
       finished with it.

       See the Common Desktop Environment: Programmer's Guide for
       examples of callback functions.

FILES    [Toc]    [Back]

       Header  file  that  contains the event declaration, structures,
 and prototype for the callback function

SEE ALSO    [Toc]    [Back]

      
      
       Routines: EvmConnCreate(3),  EvmConnCheck(3),  EvmConnSubscribe(3), EvmEventPost(3)

       Event Management: EVM(5)

       Event Connection: EvmConnection(5)

       EVM Events: EvmEvent(5)

       Programmer's Guide



                                                   EvmCallback(5)
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