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Tk_CreateGenericHandler(3tk) Tk Library Procedures Tk_CreateGenericHandler(3tk) 





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.

  
void *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 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 Tcl_DoOneEvent or
  Tk_MainLoop).


Proc should have arguments and result that match the type
    Tk_GenericProc:




typedef int Tk_GenericProc(


        void *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







  

    
    Tk