Changes made via Tk commands do not become
visible until a call to
update.
Update
flushes any pending changes to the screen.
The following options are supported:
-disable
If this option is given, all updates are disabled.
This is useful to enable a program to
stop mouse movement causing
automatic updates while it is making changes to the window.
-enable
This reverses a previous update -enable invocation.
BUGS
Changes that affect window sizes are visible immediately.