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Tk_CreateEventHandler(3) Tk Library Procedures Tk_CreateEventHandler(3) ________________________________________________________________________________ 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 Button- PressMask) 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. ________________________________________________________________________________ DESCRIPTION Tk_CreateEventHandler arranges for proc to be invoked in the future when- ever one of the event types specified by mask occurs in the window speci- fied by tkwin. The callback to proc will be made by Tk_HandleEvent; this mechanism only works in programs that dispatch events through Tk_Han- dleEvent (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_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, client- Data 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 tk- win and matches the mask, proc, and clientData arguments. If no such han- dler 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)
NAME | SYNOPSIS | ARGUMENTS | DESCRIPTION | KEYWORDS
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