Tk_CreateGenericHandler(3) Tk Library Procedures Tk_CreateGenericHandler(3)

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NAME

Tk_CreateGenericHandler, Tk_DeleteGenericHandler - associate
procedure callback with all X events

SYNOPSIS

#include <tk.h>

Tk_CreateGenericHandler(proc, clientData)

Tk_DeleteGenericHandler(proc, clientData)

ARGUMENTS

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.
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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
Tcl_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

Tk Tk_CreateGenericHandler(3)