Tk_RestrictEvents - filter and selectively delay X events
#include <tk.h>
Tk_RestrictProc *
Tk_RestrictEvents(proc, arg, prevArgPtr)
- Tk_RestrictProc *proc (in)
-
Predicate procedure to call to filter incoming X events.
NULL means do not restrict events at all.
- char *arg (in)
-
Arbitrary argument to pass to proc.
- char **prevArgPtr (in/out)
-
Pointer to place to save argument to previous restrict procedure.
This procedure is useful in certain situations where applications
are only prepared to receive certain X events. After
Tk_RestrictEvents is called, Tk_DoOneEvent (and
hence Tk_MainLoop) will filter X input events through
proc. Proc indicates whether a
given event is to be processed immediately or deferred until some
later time (e.g. when the event restriction is lifted). Proc
is a standard X predicate procedure, of the sort passed to
XCheckIfEvent. It must have arguments and result that match
the type Tk_RestrictProc:
typedef Bool Tk_RestrictProc(
Display *display,
XEvent *eventPtr,
char *arg);
The display argument to proc is the display from which
eventPtr was received, and eventPtr points to an event
under consideration. The arg argument is a copy of the arg
passed to Tk_RestrictEvents; it may be used to provide
proc with information it needs to filter events. Proc
must return True or False. True means the event
should be processed immediately and False means the event
should not be processed now, but should be saved for some later
time.
Tk_RestrictEvents uses its return value and prevArgPtr
to return information about the current event restriction procedure
(a NULL return value means there are currently no restrictions).
These values may be used to restore the previous restriction state
when there is no longer any need for the current restriction.
There are very few places where Tk_RestrictEvents is needed.
Please use it only where it is absolutely necessary.
If only a local restriction is needed, it can probably
be achieved more cleanly by changing event-to-Tcl bindings or by
calling Tk_DeleteEventHandler.
delay, event, filter, restriction
Copyright © 1990 The Regents of the University of California.
Copyright © 1994 Sun Microsystems, Inc.
Copyright © 1995 Roger E. Critchlow Jr.