Provided by: tcl8.6-doc_8.6.10+dfsg-1_all bug


       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

       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.


       after(3tcl), interp(3tcl)


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