Tk_CreateEventHandler, Tk_DeleteEventHandler - associate procedure
callback with an X event
Tk_CreateEventHandler(tkwin, mask, proc, clientData)
Tk_DeleteEventHandler(tkwin, mask, proc, clientData)
Tk_Window tkwin (in) Token for window in which events
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
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(
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 application-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 arguments. If no such
handler exists, then Tk_EventHandler 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 mutliple 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
bind, callback, event, handler
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