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 dis-play. display.
play.
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 dis-patch dispatch
patch 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_CreateGenericHan-dler Tk_CreateGenericHandler
dler 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)
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