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update(n) Tcl Built-In Commands update(n)
update - Process pending events and idle callbacks
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
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.
event, flush, handler, idle, update
Tcl 7.5 update(n)
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