update - Process pending events and/or when-idle handlers
This command 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 keyword is specified as an argument to the command, 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
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 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 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 user interactions; if you occasionally call update then
user input will be processed during the next call to update.
event, flush, handler, idle, update
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