update(n) Tcl (7.5) 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 repeated 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.
KEYWORDS
event, flush, handler, idle, update
Page 1 (printed 2/19/99)
