tcl7.6 User Commands - vwait






NAME

     vwait - Process events until a variable is written


SYNOPSIS

     vwait ?varName?





DESCRIPTION

     This command enters the Tcl event loop  to  process  events,
     blocking the application if no events are ready.  It contin-
     ues processing events until  some  event  handler  sets  the
     value  of  variable varName.  Once varName has been set, the
     vwait command will return as soon as the event handler  that
     modified varName completes.

     In some cases the vwait command may not  return  immediately
     after  varName is set.  This can happen if the event handler
     that sets varName does not complete immediately.  For  exam-
     ple,  if an event handler sets varName and then itself calls
     vwait to wait for a different  variable,  then  it  may  not
     return  for  a  long  time.   During this time the top-level
     vwait is blocked waiting for the event handler to  complete,
     so it cannot return either.



KEYWORDS

     event, variable, wait