Tk_CreateGenericHandler (3)
associate procedure callback with all X events
SYNOPSIS
#include <tk.h>
Tk_CreateGenericHandler(proc, clientData)
Tk_DeleteGenericHandler(proc, clientData)
ARGUMENTS
"Tk_GenericProc" clientData
Tk_GenericProc *proc in
Procedure to invoke whenever any X event occurs on any display.
ClientData clientData in
Arbitrary one-word value to pass to proc.
DESCRIPTION
Tk_CreateGenericHandler arranges for proc to be
invoked in the future whenever any X event occurs. This mechanism is
not intended for dispatching X events on windows managed by Tk
(you should use Tk_CreateEventHandler for this purpose).
Tk_CreateGenericHandler is intended for other purposes, such
as tracing X events, monitoring events on windows not owned by Tk,
accessing X-related libraries that were not originally designed for
use with Tk, and so on.
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_GenericProc:
typedef int Tk_GenericProc(
ClientData clientData,
XEvent *eventPtr);
The clientData parameter to proc is a copy of the clientData
argument given to Tk_CreateGenericHandler when the callback
was created. Typically, clientData points to a data
structure containing application-specific information about
how to handle events.
EventPtr is a pointer to the X event.
Whenever an X event is processed by Tk_HandleEvent, proc
is called. The return value from proc is normally 0.
A non-zero return value indicates that the event is not to be handled
further; that is, proc has done all processing that is to be
allowed for the event.
If there are multiple generic event handlers, each one is called
for each event, in the order in which they were established.
Tk_DeleteGenericHandler may be called to delete a
previously-created generic event handler: it deletes each handler
it finds that matches the proc and clientData arguments. If
no such handler exists, then Tk_DeleteGenericHandler returns
without doing anything. Although Tk supports it, it's probably
a bad idea to have more than one callback with the same
proc and clientData arguments.
Establishing a generic event handler does nothing to ensure that the
process will actually receive the X events that the handler wants to
process.
For example, it is the caller's responsibility to invoke
XSelectInput to select the desired events, if that is necessary.
KEYWORDS
bind, callback, event, handler
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