update(n) Tcl Built-In Commands update(n)
NAME
update - Process pending events and idle callbacks
SYNOPSIS
update ?idletasks?
DESCRIPTION
This command is used to bring the application 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 immedi-
ately.
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 trig-
gered 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 occasion-
ally 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
asynchronous I/O, event, flush, handler, idle, update
Tcl 7.5 update(n)
tcl 8.6.0 - Generated Sat Jan 12 16:21:51 CST 2013