PhEventPeek()

Check to see if an event is pending

Synopsis:

int PhEventPeek( void *buffer,
                 unsigned size );

Library:

ph

Description:

This function lets you check if an event is pending on the current Photon channel:

• When there's an event pending, Photon replies immediately with that event, and this function returns Ph_EVENT_MSG.
• If no message is available, this function returns 0.

Since this function is nonblocking, you should find it useful for applications that need to run continuously and still interact with Photon.

For asynchronous event notification, see PhEventRead() and PhEventArm().

---

If your application uses widgets, don't try to write your own event-handling loop; use PtMainLoop() or PtProcessEvent() instead.

---

Returns:

Ph_EVENT_MSG

Successful completion.

Ph_RESIZE_MSG

The Ph_DYNAMIC_BUFFER flag was set in PhAttach(), and there's a pending Photon event that's larger than the client's event buffer. This event that indicates how large the client's buffer needs to be to receive the entire event message.

0

No message was available.

-1

An error occurred.

Examples:

#define EVENT_SIZE    sizeof( PhEvent_t ) + 1000

main( int argc, char *argv[] )
{
     int go = 1, count = 0;
     PhEvent_t *event;

     if( initialize() == -1 )
          exit( EXIT_FAILURE );
     
     if( NULL == ( event = malloc( EVENT_SIZE ) ) )
          exit( EXIT_FAILURE );
     
     while( go ) {
          if(( ++count & 15) == 0) {
               PgFlush();
               switch( PhEventPeek( event, EVENT_SIZE ) {
                    case Ph_EVENT_MSG:
                       PtEventHandler( event );
                       break;
                    case -1:
                       perror( "PhEventPeek failed" );
                       break;
               }
          }
          iterate_graphics_process();
     }
     exit( 0 );
}

Classification:

Photon

See also:

PhAttach(), PhEvent_t, PhEventNext(), PhEventRead(), PtEventHandler()

“Collecting events” in the Events chapter of the Photon Programmer's Guide