[ fromfile: menus.xml id: menus ]

A QAction is a QObject that is a base class for user-selected actions. It provides a rich interface that can be used for a wide variety of actions, as we will soon see. The QWidget interface enables each widget to maintain a QList<QAction*>.

A QMenu is a QWidget that provides a particular kind of view for a collection of QActions. A QMenuBar is a collection of menus.

When the parent of a QMenu is a QMenuBar, the QMenu appears as a pull-down menu with a familiar interface. When its parent is not a QMenuBar it can pop up, like a dialog, in which case it is considered a context menu. ^[33] A QMenu can have another QMenu as its parent, in which case it becomes a submenu.

To help the user make the right choice, each action can have the following:

The Dialog in Example 11.4, earlier in this chapter, had a menubar with a single menu that gave two choices.

Example 11.18 shows the code that sets up that menubar.

[ . . . . ]
    
    /* Insert a menu into the menubar. */
    QMenu *menu = new QMenu("&Questions", this);

    QMainWindow::menuBar()->addMenu(menu);
    
    /* Add some choices to the menu. */
    menu->addAction("&Ask question",
                    this, SLOT(askQuestion()), tr("Alt+A"));
    menu->addAction("Ask a &dumb question",
                    this, SLOT(askDumbQuestion()), tr("Alt+D"));
}

The calls to QMenu::addAction(text, target, slot, shortcut) each create an unnamed QAction and call QWidget::addAction(QAction*) to install it in the menu. The latter call adds the new action to the menu's QList<QAction*>.