NAME
       update - Process pending events and idle callbacks

SYNOPSIS
       update ?idletasks?


DESCRIPTION
       This  command  is  used  to  bring the application ``up to
       date'' by entering the event  loop  repeatedly  until  all
       pending  events  (including idle callbacks) have been pro-
       cessed.

       If the idletasks keyword is specified as  an  argument  to
       the  command,  then no new events or errors are processed;
       only idle callbacks are invoked.  This  causes  operations
       that  are  normally  deferred, such as display updates and
       window layout calculations, to be performed immediately.

       The update idletasks command is useful  in  scripts  where
       changes  have been made to the application's state and you
       want those changes to appear on the  display  immediately,
       rather than waiting for the script to complete.  Most dis-
       play updates are performed as idle  callbacks,  so  update
       idletasks will cause them to run.  However, there are some
       kinds of updates that only happen in response  to  events,
       such  as  those  triggered  by  window size changes; these
       updates will not occur in update idletasks.

       The update command with no options is  useful  in  scripts
       where  you  are  performing a long-running computation but
       you still want the application to respond to  events  such
       as  user  interactions;   if  you occasionally call update
       then user input will be processed during the next call  to
       update.


KEYWORDS
       event, flush, handler, idle, update
