Volume 6A: Motif Programming Manual

* and the message to display.

*/

Widget

PostDialog(parent, dialog_type, msg)

Widget parent;

int dialog_type;

char *msg;

{

Widget dialog;

XmString text;

dialog = XmCreateMessageDialog (parent, "dialog", NULL, 0);

text = XmStringCreateLocalized (msg);

XtVaSetValues (dialog,

XmNdialogType, dialog_type,

XmNmessageString, text,

NULL);

XmStringFree (text);

XtManageChild (dialog);

XtPopup (XtParent (dialog), XtGrabNone);

return dialog;

}

This routine allows the programmer to specify several parameters: the parent widget, the type of dialog that is to be

used, and the message that is to be displayed. The function returns the new dialog widget, so that the calling routine

can modify it, unmanage it, or keep a handle to it. You may have additional requirements that this simplified example

does not satisfy. For instance, the routine does not allow you to specify callback functions for the buttons in the action

area and it does not handle the destruction of the widget when it is no longer needed. You could extend the routine to

handle these issues, or you could control them outside the context of the function. You may also want to extend the

routine so that it reuses the same dialog each time it is called and so that it allows you to disable the different action

area buttons. All of these issues are discussed again in Chapter 6, Selection Dialogs, and in Chapter 21, Advanced

Dialog Programming.

6.4 Dialog Resources

The following sections discuss resources that are specific to Motif dialogs. In most cases, these resources are

BulletinBoard widget resources, since all Motif dialogs are subclassed from this class. However, they are not intended

to be used by generic BulletinBoard widgets. The resources only apply when the widget is an immediate child of a

DialogShell widget; they are really intended to be used exclusively by the predefined Motif dialog classes. Remember

that the resources must be set on the dialog widget, not the DialogShell. See Chapter 8, Manager Widgets, for details

on the generic BulletinBoard resources.

6.4.1 The Default Button

All predefined Motif dialogs have a default button in their action area. The default button is activated when the user

presses the RETURN key in the dialog. The OK button is normally the default button, but once the dialog is

displayed, the user can change the default button by using the arrow keys to traverse the action buttons. The action

button with the keyboard focus is always the default button. Since the default button can be changed by the user, the

button that is the default is only important when the dialog is initially popped up. The importance of the default button

lies in its ability to influence the user's default response to the dialog.

6 Introduction to Dialogs 6.4 Dialog Resources

120

You can change the default button for a MessageDialog by setting the XmNdefaultButtonType resource on the

dialog widget. This resource is specific to MessageDialogs; it cannot be set for the various types of selection dialogs.

The resource can have one of the following values:

XmDIALOG_OK_BUTTON

This value specifies that the default button is the furthest button on the left of the dialog. By default, this

button is the OK button, although its label may have been changed to another string.

XmDIALOG_CANCEL_BUTTON

This value specifies that the Cancel button is the default button. This value is appropriate in situations where

the action of the dialog is destructive, such as for a WarningDialog that is posted in order to warn the user of a

possibly dangerous action.

XmDIALOG_HELP_BUTTON

This value specifies the Help button, which is always the furthest button on the right of a Motif dialog. This

button is rarely set as the default button.

XmDIALOG_NONE

This value specifies that there is no default button.

The values for XmNdefaultButtonType come up again later, when we discuss

XmMessageBoxGetChild() and again in Chapter 6, Selection Dialogs, for

XmSelectionBoxGetChild(). An example of how the default button type can be used is shown in the

source code XmStringCreateLocalized() is only available in Motif 1.2;

XmStringCreateSimple() is the corresponding function in Motif 1.1.

/*

* WarningMsg() −− Inform the user that she is about to embark on a

* dangerous mission and give her the opportunity to back out.

*/

void

WarningMsg(parent, client_data, call_data)

Widget parent;

XtPointer client_data;

XtPointer call_data;

{

static Widget dialog;

XmString text, ok_str, cancel_str;

char *msg = (char *) client_data;

if (!dialog)

dialog = XmCreateWarningDialog (parent, "warning", NULL, 0);

text = XmStringCreateLtoR (msg, XmFONTLIST_DEFAULT_TAG);

ok_str = XmStringCreateLocalized ("Yes");

cancel_str = XmStringCreateLocalized ("No");

XtVaSetValues (dialog,

XmNmessageString, text,

XmNokLabelString, ok_str,

XmNcancelLabelString, cancel_str,

XmNdefaultButtonType, XmDIALOG_CANCEL_BUTTON,

NULL);

XmStringFree (text);

XmStringFree (ok_str);

XmStringFree (cancel_str);

XtManageChild (dialog);

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121