Tk_CreateEventHandler(3) Tk 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
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Tk_CreateEventHandler(3) Tk Tk_CreateEventHandler(3)
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 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
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