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 But‐
tonPressMask) for which proc
should be called.
Tk_EventProc *proc (in) Procedure to invoke whenever an
event in mask occurs in the win‐
dow 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
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_Han‐
dleEvent; 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. Typi‐
cally, 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 associ‐
ated 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 argu‐
ments. When a window is deleted all of its handlers will be deleted
automatically; in this case there is no need to call Tk_DeleteEven‐
tHandler.
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
TkTk_CreateEventHandler(3)
