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Tk_DeleteGenericHandler






Prepared by Ready-to-Run Software, Inc. 

Tk_CreateGenericHandleTk3Library Procedures




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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 display. ClientData clientData (in) Arbitrary one-word value to pass to proc. _________________________________________________________________

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 origi- nally 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 struc- ture containing application-specific information about how to handle events. EventPtr is a pointer to the X event. Tk 1 Prepared by Ready-to-Run Software, Inc.

Tk_CreateGenericHandleTk3Library Procedures




     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 han-
     dled  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 esta-
     blished.

     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  argu-
     ments.      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 2 Prepared by Ready-to-Run Software, Inc.

 

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