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 ButtonPressMask) 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.
________________________________________________________________________________________________________________

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 Tcl_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  was  created.   Typically,  clientData  points to a data structure 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_HandleEvent 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  clientData
       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