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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. _________________________________________________________________

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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