update(3Tk)							   update(3Tk)

NAME    [Toc]    [Back]

     update - Process pending events and/or when-idle handlers

SYNOPSIS    [Toc]    [Back]

     update ?idletasks?

DESCRIPTION    [Toc]    [Back]

     This command is used to bring the entire application world	``up to
     date.''  It flushes all pending output to the display,  waits for the
     server to process that output and return errors or	events,	handles	all
     pending events of any sort	(including when-idle handlers),	and repeats
     this set of operations until there	are no pending events, no pending
     when-idle handlers, no pending output to the server, and no operations
     still outstanding at the server.

     If	the idletasks keyword is specified as an argument to the command, then
     no	new events or errors are processed;  only when-idle idlers 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	handlers, 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 user	interactions;  if you occasionally call	update then
     user input	will be	processed during the next call to update.

KEYWORDS    [Toc]    [Back]

     event, flush, handler, idle, update


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