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Tk_CreateEventHandler(3)	      Tk Library Procedures		 Tk_CreateEventHandler(3)

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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  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.
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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_Cre-
       ateEventHandler	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

Tk									 Tk_CreateEventHandler(3)
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