opendarwin man page for update

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 imme-
       diately.

       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 computation but you still want the applica-
       tion 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.

SEE ALSO
       after(n), bgerror(n)

KEYWORDS
       event, flush, handler, idle, update

Tcl									7.5								 update(n)