DOKK / manpages / debian 10 / tcl8.6-doc / update.3tcl.en
update(3tcl) Tcl Built-In Commands update(3tcl) 







update - Process pending events and idle callbacks








update ?idletasks?










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 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.








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
}










after(3tcl), interp(3tcl)








asynchronous I/O, event, flush, handler, idle, update







  

    7.5
    Tcl