Tk_CreateEventHandler(3Tk)			    Tk_CreateEventHandler(3Tk)

NAME    [Toc]    [Back]

     Tk_CreateEventHandler, Tk_DeleteEventHandler - associate procedure
     callback with an X	event

SYNOPSIS    [Toc]    [Back]

     #include <tk.h>

     Tk_CreateEventHandler(tkwin, mask,	proc, clientData)

     Tk_DeleteEventHandler(tkwin, mask,	proc, clientData)

ARGUMENTS    [Toc]    [Back]

     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    [Toc]    [Back]

     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 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_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 clientData arguments.  When	a



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Tk_CreateEventHandler(3Tk)			    Tk_CreateEventHandler(3Tk)



     window is deleted all of its handlers will	be deleted automatically;  in
     this case there is	no need	to call	Tk_DeleteEventHandler.

     If	mutliple 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    [Toc]    [Back]

     bind, callback, event, handler


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