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 display.

       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 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_GenericProc:
              typedef int Tk_GenericProc(
                      ClientData clientData,
                      XEvent *eventPtr);
       The  clientData  parameter  to proc is a copy of the clientData argument given to Tk_CreateGenericHandler
       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