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Tk_CreateEventHandler(3)                    Tk Library Procedures                   Tk_CreateEventHandler(3)



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NAME
       Tk_CreateEventHandler, Tk_DeleteEventHandler - associate procedure callback with an X event

SYNOPSIS
       #include <tk.h>

       Tk_CreateEventHandler(tkwin, mask, proc, clientData)

       Tk_DeleteEventHandler(tkwin, mask, proc, clientData)

ARGUMENTS
       Tk_Window       tkwin        (in)      Token for window in which events may occur.

       unsigned long   mask         (in)      Bit-mask  of  events  (such as ButtonPressMask) for which proc
                                              should be called.

       Tk_EventProc    *proc        (in)      Procedure to invoke whenever an event in mask  occurs  in  the
                                              window given by tkwin.

       ClientData      clientData   (in)      Arbitrary one-word value to pass to proc.
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DESCRIPTION
       Tk_CreateEventHandler  arranges  for proc to be invoked in the future whenever one of the event types
       specified by mask occurs in the window specified by tkwin.  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_EventProc:
              typedef void Tk_EventProc(
                ClientData clientData,
                XEvent *eventPtr);
       The clientData parameter to proc is a copy of the clientData argument given to  Tk_CreateEventHandler
       when  the callback was created.  Typically, clientData points to a data structure containing applica-tion-specific application-specific
       tion-specific information about the window in which the event occurred.  EventPtr is a pointer to the
       X event, which will be one of the ones specified in the mask argument to Tk_CreateEventHandler.

       Tk_DeleteEventHandler  may  be  called  to delete a previously-created event handler:  it deletes the
       first handler it finds that is associated with tkwin and matches the mask, proc, and clientData argu-ments. arguments.
       ments.   If  no such handler exists, then Tk_HandleEvent returns without doing anything.  Although Tk
       supports it, it's probably a bad idea to have more than one callback with the same  mask,  proc,  and
       clientData  arguments.   When  a window is deleted all of its handlers will be deleted automatically;
       in this case there is no need to call Tk_DeleteEventHandler.

       If multiple handlers are declared for the same type of X event on the same window, then the  handlers
       will be invoked in the order they were created.


KEYWORDS
       bind, callback, event, handler



Tk                                                                                  Tk_CreateEventHandler(3)