Dialog boxes are a convenient way to prompt the user for a small amount of input, e.g. to display a message, ask a question, or anything else that does not require extensive effort on the user’s part.

GTK+ treats a dialog as a window split vertically. The top section is a #GtkVBox, and is where widgets such as a #GtkLabel or a #GtkEntry should be packed. The bottom area is known as the “action area”. This is generally used for packing buttons into the dialog which may perform functions such as cancel, ok, or apply.

#GtkDialog boxes are created with a call to [gtk.dialog.Dialog.new_] or [gtk.dialog.Dialog.newWithButtons]. [gtk.dialog.Dialog.newWithButtons] is recommended; it allows you to set the dialog title, some convenient flags, and add simple buttons.

If “dialog” is a newly created dialog, the two primary areas of the window can be accessed through [gtk.dialog.Dialog.getContentArea] and [gtk.dialog.Dialog.getActionArea], as can be seen from the example below.

A “modal” dialog (that is, one which freezes the rest of the application from user input), can be created by calling [gtk.window.Window.setModal] on the dialog. Use the GTK_WINDOW() macro to cast the widget returned from [gtk.dialog.Dialog.new_] into a #GtkWindow. When using [gtk.dialog.Dialog.newWithButtons] you can also pass the #GTK_DIALOG_MODAL flag to make a dialog modal.

If you add buttons to #GtkDialog using [gtk.dialog.Dialog.newWithButtons], [gtk.dialog.Dialog.addButton], [gtk.dialog.Dialog.addButtons], or [gtk.dialog.Dialog.addActionWidget], clicking the button will emit a signal called #GtkDialog::response with a response ID that you specified. GTK+ will never assign a meaning to positive response IDs; these are entirely user-defined. But for convenience, you can use the response IDs in the #GtkResponseType enumeration (these all have values less than zero). If a dialog receives a delete event, the #GtkDialog::response signal will be emitted with a response ID of #GTK_RESPONSE_DELETE_EVENT.

If you want to block waiting for a dialog to return before returning control flow to your code, you can call [gtk.dialog.Dialog.run]. This function enters a recursive main loop and waits for the user to respond to the dialog, returning the response ID corresponding to the button the user clicked.

For the simple dialog in the following example, in reality you’d probably use #GtkMessageDialog to save yourself some effort. But you’d need to create the dialog contents manually if you had more than a simple message in the dialog.

An example for simple GtkDialog usage:

// Function to open a dialog box with a message
void
quick_message (GtkWindow *parent, gchar *message)
{
GtkWidget *dialog, *label, *content_area;
GtkDialogFlags flags;

// Create the widgets
flags = GTK_DIALOG_DESTROY_WITH_PARENT;
dialog = gtk_dialog_new_with_buttons ("Message",
                                      parent,
                                      flags,
                                      _("_OK"),
                                      GTK_RESPONSE_NONE,
                                      NULL);
content_area = gtk_dialog_get_content_area (GTK_DIALOG (dialog));
label = gtk_label_new (message);

// Ensure that the dialog box is destroyed when the user responds

g_signal_connect_swapped (dialog,
                          "response",
                          G_CALLBACK (gtk_widget_destroy),
                          dialog);

// Add the label, and show everything we’ve added

gtk_container_add (GTK_CONTAINER (content_area), label);
gtk_widget_show_all (dialog);
}

GtkDialog as GtkBuildable

The GtkDialog implementation of the #GtkBuildable interface exposes the @vbox and @action_area as internal children with the names “vbox” and “action_area”.

GtkDialog supports a custom <action-widgets> element, which can contain multiple <action-widget> elements. The “response” attribute specifies a numeric response, and the content of the element is the id of widget (which should be a child of the dialogs @action_area). To mark a response as default, set the “default“ attribute of the <action-widget> element to true.

GtkDialog supports adding action widgets by specifying “action“ as the “type“ attribute of a <child> element. The widget will be added either to the action area or the headerbar of the dialog, depending on the “use-header-bar“ property. The response id has to be associated with the action widget using the <action-widgets> element.

An example of a #GtkDialog UI definition fragment:

<object class="GtkDialog" id="dialog1">
 <child type="action">
   <object class="GtkButton" id="button_cancel"/>
 </child>
 <child type="action">
   <object class="GtkButton" id="button_ok">
     <property name="can-default">True</property>
   </object>
 </child>
 <action-widgets>
   <action-widget response="cancel">button_cancel</action-widget>
   <action-widget response="ok" default="true">button_ok</action-widget>
 </action-widgets>
</object>

Fluent builder for [gtk.dialog.Dialog]