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NAME
     tttk_block_while - block while a  counter  is  greater  than
     zero

SYNOPSIS
     #include <Tt/tttk.h>
     Tt_status tttk_block_while(XtAppContext app2run,
                                const int *blocked,
                                int ms_timeout);

DESCRIPTION
     The tttk_block_while() function is used to process asynchro-
     nous  events,  such  as  ToolTalk  messages or window system
     events, while waiting for a condition or timeout.

     If app2run is not zero, then an event loop is run  for  that
     application      context,      by     repeatedly     calling
     XtAppProcessEvent(3X) with ms_timeout being  effected  using
     XtAppAddTimeOut(3X).   If  app2run  is  zero,  then the file
     descriptor (as returned by tt_fd(3)) of the  default  procid
     is    polled    (using    the    poll(2)    function)    and
     tttk_Xt_input_handler(3)  is  called   whenever   the   file
     descriptor is active.

     If blocked  is  zero,  then  tttk_block_while()  runs  until
     ms_timeout occurs.  If blocked is non-zero, then the loop is
     run until either ms_timeout occurs, or *blocked is less than
     1.

     If ms_timeout is zero, tttk_block_while()  checks  once  for
     events,  processes  the  first  one,  and  then returns.  If
     ms_timeout is negative, no timeout is in effect.

RETURN VALUE
     Upon successful completion, the tttk_block_while()  function
     returns  the status of the operation as one of the following
     Tt_status values:

        TT_OK   The operation completed successfully.

        TT_DESKTOP_ETIMEDOUT
                The  timeout  occurred  within  ms_timeout   mil-
                liseconds,  or  ms_timeout  was zero and no input
                was available.

        TT_DESKTOP_EINTR
                The app2run argument was zero,  and  poll(2)  was
                interrupted by a signal.

        TT_DESKTOP_EAGAIN
                The  app2run  argument  was  zero,  and   poll(2)
                returned EAGAIN.

     If app2run is not zero  and  ms_timeout  is  negative,  then
     tttk_block_while()  will  only  return when *blocked is less
     than 1, with TT_OK being returned.

     If app2run is not zero, ms_timeout is negative, and  blocked
     is  zero,  then  tttk_block_while()  behaves  equivalent  to
     XtAppMainLoop(3X), and will never return.

APPLICATION USAGE
     If app2run is zero,  then  only  messaging  events  for  the
     default  procid  will be serviced.  Events for other procids
     will be blocked, as will window system events, so  that  the
     graphical  user interface of the application will not update
     itself even, for example, after expose events.

     On the other hand, if the application passes its Xt  context
     in as app2run, then window system events will continue to be
     handled, as will message activity for all procids for  which
     an XtAppAddInput(3X) has been done.  Since the window system
     event loop is fully operational in this case,  the  applica-
     tion should take care to disable any user interface controls
     that the user should not operate while  the  application  is
     waiting for tttk_block_while() to return.

SEE ALSO
     tttk(5), tttk_Xt_input_handler(3); poll(2),
     XtAppPending(3X), XtAppAddTimeOut(3X), XtAppNextEvent(3X),
     XtDispatchEvent(3X).

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