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update(n)                                   Tcl Built-In Commands                                  update(n)



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NAME
       update - Process pending events and idle callbacks

SYNOPSIS
       update ?idletasks?
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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 processed.

       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 display 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  com-putation computation
       putation  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.

EXAMPLE
       Run computations for about a second and then finish:
              set x 1000
              set done 0
              after 1000 set done 1
              while {!$done} {
                  # A very silly example!
                  set x [expr {log($x) ** 2.8}]

                  # Test to see if our time-limit has been hit.  This would
                  # also give a chance for serving network sockets and, if
                  # the Tk package is loaded, updating a user interface.
                  update
              }


SEE ALSO
       after(n), interp(n)


KEYWORDS
       event, flush, handler, idle, update



Tcl                                                  7.5                                           update(n)