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Tk_CreateGenericHandler(3)                  Tk Library Procedures                 Tk_CreateGenericHandler(3)



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NAME
       Tk_CreateGenericHandler, Tk_DeleteGenericHandler - associate procedure callback with all X events

SYNOPSIS
       #include <tk.h>

       Tk_CreateGenericHandler(proc, clientData)

       Tk_DeleteGenericHandler(proc, clientData)

ARGUMENTS
       Tk_GenericProc *proc (in)               Procedure  to  invoke whenever any X event occurs on any dis-play. display.
                                               play.

       ClientData clientData (in)              Arbitrary one-word value to pass to proc.
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DESCRIPTION
       Tk_CreateGenericHandler arranges for proc to be invoked in the future whenever any  X  event  occurs.
       This  mechanism  is  not  intended  for dispatching X events on windows managed by Tk (you should use
       Tk_CreateEventHandler for this purpose).  Tk_CreateGenericHandler is  intended  for  other  purposes,
       such as tracing X events, monitoring events on windows not owned by Tk, accessing X-related libraries
       that were not originally designed for use with Tk, and so on.

       The callback to proc will be made by Tk_HandleEvent; this mechanism only works in programs that  dis-patch dispatch
       patch 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_GenericProc:
              typedef int Tk_GenericProc(
                  ClientData clientData,
                  XEvent *eventPtr);
       The clientData parameter to proc is a copy of the clientData argument given  to  Tk_CreateGenericHan-dler Tk_CreateGenericHandler
       dler  when  the  callback  was  created.  Typically, clientData points to a data structure containing
       application-specific information about how to handle events.  EventPtr is a pointer to the X event.

       Whenever an X event is processed by Tk_HandleEvent, proc is called.  The return value  from  proc  is
       normally  0.  A non-zero return value indicates that the event is not to be handled further; that is,
       proc has done all processing that is to be allowed for the event.

       If there are multiple generic event handlers, each one is called for each  event,  in  the  order  in
       which they were established.

       Tk_DeleteGenericHandler  may  be  called  to  delete  a previously-created generic event handler:  it
       deletes each handler it finds that matches the proc and clientData arguments.   If  no  such  handler
       exists,  then  Tk_DeleteGenericHandler returns without doing anything.  Although Tk supports it, it's
       probably a bad idea to have more than one callback with the same proc and clientData arguments.

       Establishing a generic event handler does nothing to ensure that the process  will  actually  receive
       the  X  events  that the handler wants to process.  For example, it is the caller's responsibility to
       invoke XSelectInput to select the desired events, if that is necessary.

KEYWORDS
       bind, callback, event, handler



Tk                                                                                Tk_CreateGenericHandler(3)