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DoOneEvent (3)
  • >> DoOneEvent (3) ( Solaris man: Библиотечные вызовы )
  • 
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    NAME
         Tcl_DoOneEvent - wait for events and invoke event handlers
    
    SYNOPSIS
         #include <tcl.h>
    
         int
         Tcl_DoOneEvent(flags)
    
    ARGUMENTS
         int   flags   (in)      This parameter is normally zero.  It
                                 may  be  an OR-ed combination of any
                                 of   the   following   flag    bits:
                                 TCL_WINDOW_EVENTS,  TCL_FILE_EVENTS,
                                 TCL_TIMER_EVENTS,   TCL_IDLE_EVENTS,
                                 TCL_ALL_EVENTS, or TCL_DONT_WAIT.
    _________________________________________________________________
    
    
    DESCRIPTION
         This procedure is the entry point to Tcl's event loop; it is
         responsible  for  waiting  for  events and dispatching event
         handlers     created     with     procedures     such     as
         Tk_CreateEventHandler,                Tcl_CreateFileHandler,
         Tcl_CreateTimerHandler, and Tcl_DoWhenIdle.   Tcl_DoOneEvent
         checks to see if events are already present on the Tcl event
         queue; if so, it calls the handler(s) for the first (oldest)
         event, removes it from the queue, and returns.  If there are
         no events ready to be handled,  then  Tcl_DoOneEvent  checks
         for new events from all possible sources.  If any are found,
         it puts all of them on Tcl's event queue, calls handlers for
         the first event on the queue, and returns.  If no events are
         found, Tcl_DoOneEvent checks for  Tcl_DoWhenIdle  callbacks;
         if  any  are  found,  it  invokes  all  of them and returns.
         Finally, if no events or idle  callbacks  have  been  found,
         then  Tcl_DoOneEvent  sleeps  until an event occurs; then it
         adds any new events to the Tcl event queue,  calls  handlers
         for  the  first event, and returns.  The normal return value
         is 1 to signify that some event was processed (see below for
         other alternatives).
    
         If the flags argument to Tcl_DoOneEvent is non-zero, it res-
         tricts  the  kinds  of  events  that  will  be  processed by
         Tcl_DoOneEvent.  Flags may be an OR-ed combination of any of
         the following bits:
    
         TCL_WINDOW_EVENTS -        Process window system events.
    
         TCL_FILE_EVENTS -          Process file events.
    
         TCL_TIMER_EVENTS -         Process timer events.
    
         TCL_IDLE_EVENTS -          Process idle callbacks.
    
         TCL_ALL_EVENTS -           Process  all  kinds  of   events:
                                    equivalent to OR-ing together all
                                    of the above flags or  specifying
                                    none of them.
    
         TCL_DONT_WAIT -            Don't sleep:  process only events
                                    that are ready at the time of the
                                    call.
    
         If any  of  the  flags  TCL_WINDOW_EVENTS,  TCL_FILE_EVENTS,
         TCL_TIMER_EVENTS,  or  TCL_IDLE_EVENTS is set, then the only
         events that will be considered are those for which flags are
         set.  Setting none of these flags is equivalent to the value
         TCL_ALL_EVENTS, which causes all  event  types  to  be  pro-
         cessed.   If  an  application  has  defined additional event
         sources with  Tcl_CreateEventSource,  then  additional  flag
         values may also be valid, depending on those event sources.
    
         The TCL_DONT_WAIT flag causes Tcl_DoOneEvent not to put  the
         process  to sleep:  it will check for events but if none are
         found then it returns immediately with a return value  of  0
         to indicate that no work was done.  Tcl_DoOneEvent will also
         return 0 without doing anything if the only  alternative  is
         to  block forever (this can happen, for example, if flags is
         TCL_IDLE_EVENTS and there are  no  Tcl_DoWhenIdle  callbacks
         pending, or if no event handlers or timer handlers exist).
    
         Tcl_DoOneEvent may be invoked recursively.  For example,  it
         is  possible  to  invoke  Tcl_DoOneEvent  recursively from a
         handler called by Tcl_DoOneEvent.  This sort of operation is
         useful in some modal situations, such as when a notification
         dialog has been popped up and an application wishes to  wait
         for  the  user  to click a button in the dialog before doing
         anything else.
    
    
    KEYWORDS
         callback, event, handler, idle, timer
    
    
    
    


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