Tk_CreateEventHandler

Prepared by Ready-to-Run Software, Inc. 

Tk_CreateEventHandler(Tk Library Procedures

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NAME
     Tk_CreateEventHandler,  Tk_DeleteEventHandler  -   associate
     procedure callback with an X event

SYNOPSIS
     #include <tk.h>

     Tk_CreateEventHandler(tkwin, mask, proc, clientData)

     Tk_DeleteEventHandler(tkwin, mask, proc, clientData)

ARGUMENTS
     Tk_Window       tkwin        (in)      Token for  window  in
                                            which    events   may
                                            occur.

     unsigned long   mask         (in)      Bit-mask  of   events
                                            (such     as     But-
                                            tonPressMask)     for
                                            which  proc should be
                                            called.

     Tk_EventProc    *proc        (in)      Procedure  to  invoke
                                            whenever  an event in
                                            mask  occurs  in  the
                                            window    given    by
                                            tkwin.

     ClientData      clientData   (in)      Arbitrary    one-word
                                            value   to   pass  to
                                            proc.
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DESCRIPTION
     Tk_CreateEventHandler arranges for proc to be invoked in the
     future  whenever  one  of  the event types specified by mask
     occurs in the window specified by tkwin.   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_EventProc:
          typedef void Tk_EventProc(
            ClientData clientData,
            XEvent *eventPtr);
     The clientData parameter to proc is a copy of the clientData
     argument  given  to  Tk_CreateEventHandler when the callback



Tk                                                              1







Prepared by Ready-to-Run Software, Inc. 

Tk_CreateEventHandler(Tk Library Procedures

     was created.  Typically, clientData points to a data  struc-
     ture  containing  application-specific information about the
     window in which the event occurred.  EventPtr is  a  pointer
     to  the  X event, which will be one of the ones specified in
     the mask argument to Tk_CreateEventHandler.

     Tk_DeleteEventHandler may be called to delete a  previously-
     created  event  handler:   it  deletes  the first handler it
     finds that is associated with tkwin and  matches  the  mask,
     proc,  and clientData arguments.  If no such handler exists,
     then  Tk_EventHandler  returns   without   doing   anything.
     Although  Tk  supports  it, it's probably a bad idea to have
     more than one callback with the same mask, proc, and client-
     Data  arguments.   When  a  window  is  deleted  all  of its
     handlers will be deleted automatically;  in this case  there
     is no need to call Tk_DeleteEventHandler.

     If multiple handlers are declared for the  same  type  of  X
     event  on the same window, then the handlers will be invoked
     in the order they were created.


KEYWORDS
     bind, callback, event, handler































Tk                                                              2



Prepared by Ready-to-Run Software, Inc. 

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