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 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, 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_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)