Tk_CreateGenericHandler

Prepared by Ready-to-Run Software, Inc. 

Tk_CreateGenericHandleTk3Library Procedures

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NAME
     Tk_CreateGenericHandler, Tk_DeleteGenericHandler - associate
     procedure callback with all X events

SYNOPSIS
     #include <tk.h>

     Tk_CreateGenericHandler(proc, clientData)

     Tk_DeleteGenericHandler(proc, clientData)

ARGUMENTS
     Tk_GenericProc   *proc        (in)      Procedure to  invoke
                                             whenever any X event
                                             occurs    on     any
                                             display.

     ClientData       clientData   (in)      Arbitrary   one-word
                                             value   to  pass  to
                                             proc.
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DESCRIPTION
     Tk_CreateGenericHandler arranges for proc to be  invoked  in
     the  future  whenever any X event occurs.  This mechanism is
     not intended for dispatching X events on windows managed  by
     Tk  (you should use Tk_CreateEventHandler for this purpose).
     Tk_CreateGenericHandler is intended for other purposes, such
     as  tracing X events, monitoring events on windows not owned
     by Tk, accessing X-related libraries that  were  not  origi-
     nally designed for use with Tk, and so on.

     The callback to proc will be made  by  Tk_HandleEvent;  this
     mechanism  only  works  in  programs  that  dispatch  events
     through Tk_HandleEvent (or through other Tk procedures  that
     call Tk_HandleEvent, such as Tk_DoOneEvent or Tk_MainLoop).

     Proc should have arguments and result that  match  the  type
     Tk_GenericProc:
          typedef int Tk_GenericProc(
            ClientData clientData,
            XEvent *eventPtr);
     The clientData parameter to proc is a copy of the clientData
     argument  given to Tk_CreateGenericHandler when the callback
     was created.  Typically, clientData points to a data  struc-
     ture  containing  application-specific information about how
     to handle events.  EventPtr is a pointer to the X event.





Tk                                                              1







Prepared by Ready-to-Run Software, Inc. 

Tk_CreateGenericHandleTk3Library Procedures

     Whenever an X event is processed by Tk_HandleEvent, proc  is
     called.   The  return value from proc is normally 0.  A non-
     zero return value indicates that the event is not to be han-
     dled  further; that is, proc has done all processing that is
     to be allowed for the event.

     If there are multiple generic event handlers,  each  one  is
     called for each event, in the order in which they were esta-
     blished.

     Tk_DeleteGenericHandler  may   be   called   to   delete   a
     previously-created  generic  event handler:  it deletes each
     handler it finds that matches the proc and clientData  argu-
     ments.      If     no     such    handler    exists,    then
     Tk_DeleteGenericHandler  returns  without  doing   anything.
     Although  Tk  supports  it, it's probably a bad idea to have
     more than one callback with the  same  proc  and  clientData
     arguments.

     Establishing a generic event handler does nothing to  ensure
     that the process will actually receive the X events that the
     handler wants to process.  For example, it is  the  caller's
     responsibility  to invoke XSelectInput to select the desired
     events, if that is necessary.

KEYWORDS
     bind, callback, event, handler




























Tk                                                              2



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