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



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

SYNOPSIS
       (update)

       (update 'idletasks)


DESCRIPTION
       This procedure 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 option is specified as an argument to the procedure,
       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 procedure 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 procedure 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.



STk                                   3.1                            update(n)
