Specifications

Athena Widget Set libXaw 1.0.7

void XtAddCallback(w, callback_name,callback, client_data)

Widget w;

String callback_name;

XtCallbackProc callback;

XtPointer client_data;

w Speciﬁes the widget to add the callback to.

callback_name Speciﬁes the callback list within the widget to append to.

callback Speciﬁes the callback procedure to add.

client_data Speciﬁes the data to be passed to the callback when it is invoked.

XtAddCallback adds the speciﬁed callback to the list for the named widget.

All widgets provide a callback list named destroyCallback where clients can register procedures

that are to be executed when the widget is destroyed. The destroycallbacks are executed when

the widget or an ancestor is destroyed. The call_data argument is unused for destroycallbacks.

2.10. Programming Considerations

This section provides some guidelines on howtoset up an application program that uses the X

Toolkit.

2.10.1. Writing Applications

When writing an application that uses the X Toolkit, you should makesure that your application

performs the following:

1. Include <X11/Intrinsic.h>inyour application programs. This header ﬁle automatically

includes <X11/Xlib.h>, so all Xlib functions also are deﬁned. It may also be necessary to

include <X11/StringDefs.h > when setting up argument lists, as manyofthe XtNsome-

thing deﬁnitions are only deﬁned in this ﬁle.

2. Include the widget-speciﬁc header ﬁles for each widget type that you need to use. For

example, <X11/Xaw/Label.h>and <X11/Xaw/Command.h>.

3. Call the XtAppInitialize function before invoking anyother toolkit or Xlib functions. For

further information, see Section 2.1 and the XToolkit Intrinsics — C Language Interface.

4. Topass attributes to the widget creation routines that will override anysite or user cus-

tomizations, set up argument lists. In this document, a list of valid argument names is pro-

vided in the discussion of each widget. The names each have a global symbol deﬁned that

begins with XtN to help catch spelling errors. Forexample, XtNlabel is deﬁned for the

label resource of manywidgets.

Forfurther information, see Section 2.9.2.2.

5. When the argument list is set up, create the widget with the XtCreateManagedWidget

function. For further information, see Section 2.2 and the XToolkit Intrinsics — C Lan-

guage Interface.

6. If the widget has anycallback routines, set by the XtNcallback argument or the XtAdd-

Callback function, declare these routines within the application.

7. After creating the initial widget hierarchy, windows must be created for each widget by

calling XtRealizeWidget on the top levelwidget.

8. Most applications nowsit in a loop processing events using XtAppMainLoop,for exam-

ple:

XtCreateManagedWidget(name, class, parent, args, num_args);

XtRealizeWidget(shell);

XtAppMainLoop(app_context);