1Tk_CreateGenericHandler(3)   Tk Library Procedures  Tk_CreateGenericHandler(3)
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NAME

8       Tk_CreateGenericHandler,  Tk_DeleteGenericHandler - associate procedure
9       callback with all X events
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SYNOPSIS

12       #include <tk.h>
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14       Tk_CreateGenericHandler(proc, clientData)
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16       Tk_DeleteGenericHandler(proc, clientData)
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ARGUMENTS

19       Tk_GenericProc *proc (in)               Procedure  to  invoke  whenever
20                                               any  X event occurs on any dis‐
21                                               play.
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23       ClientData clientData (in)              Arbitrary  one-word  value   to
24                                               pass to proc.
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DESCRIPTION

28       Tk_CreateGenericHandler  arranges  for proc to be invoked in the future
29       whenever any X event occurs.  This mechanism is not intended  for  dis‐
30       patching  X  events  on  windows  managed by Tk (you should use Tk_Cre‐
31       ateEventHandler for this purpose).  Tk_CreateGenericHandler is intended
32       for other purposes, such as tracing X events, monitoring events on win‐
33       dows not owned by Tk, accessing X-related libraries that were not orig‐
34       inally designed for use with Tk, and so on.
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36       The  callback  to  proc  will be made by Tk_HandleEvent; this mechanism
37       only works in programs that dispatch events through Tk_HandleEvent  (or
38       through   other   Tk  procedures  that  call  Tk_HandleEvent,  such  as
39       Tk_DoOneEvent or Tk_MainLoop).
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41       Proc should have arguments and result that  match  the  type  Tk_Gener‐
42       icProc:
43              typedef int Tk_GenericProc(
44                      ClientData clientData,
45                      XEvent *eventPtr);
46       The  clientData  parameter to proc is a copy of the clientData argument
47       given to Tk_CreateGenericHandler when the callback was created.   Typi‐
48       cally,  clientData  points  to a data structure containing application-
49       specific information about how to handle events.  EventPtr is a pointer
50       to the X event.
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52       Whenever  an  X  event  is processed by Tk_HandleEvent, proc is called.
53       The return value from proc is normally  0.   A  non-zero  return  value
54       indicates  that  the  event is not to be handled further; that is, proc
55       has done all processing that is to be allowed for the event.
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57       If there are multiple generic event handlers, each one  is  called  for
58       each event, in the order in which they were established.
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60       Tk_DeleteGenericHandler  may  be  called to delete a previously-created
61       generic event handler:  it deletes each handler it finds  that  matches
62       the  proc  and  clientData  arguments.  If no such handler exists, then
63       Tk_DeleteGenericHandler returns without doing  anything.   Although  Tk
64       supports  it,  it's  probably a bad idea to have more than one callback
65       with the same proc and clientData arguments.
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67       Establishing a generic event handler does nothing to  ensure  that  the
68       process  will  actually  receive the X events that the handler wants to
69       process.  For example, it is the caller's responsibility to invoke XSe‐
70       lectInput to select the desired events, if that is necessary.
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KEYWORDS

73       bind, callback, event, handler
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77Tk                                                  Tk_CreateGenericHandler(3)
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