Home > Articles > Programming > C/C++

This chapter is from the book

Creating Menus and Toolbars

Most modern GUI applications provide menus, context menus, and toolbars. The menus enable users to explore the application and learn how to do new things, while the context menus and toolbars provide quick access to frequently used functionality. Figure 3.3 shows the Spreadsheet application's menus.

03fig03.jpg

Figure 3.3 The Spreadsheet application's menus

Qt simplifies the programming of menus and toolbars through its action concept. An action is an item that can be added to any number of menus and toolbars. Creating menus and toolbars in Qt involves these steps:

  1. Create and set up the actions.
  2. Create menus and populate them with the actions.
  3. Create toolbars and populate them with the actions.

In the Spreadsheet application, actions are created in createActions():

void MainWindow::createActions()
{
    newAction = new QAction(tr("&New"), this);
    newAction->setIcon(QIcon(":/images/new.png"));
    newAction->setShortcut(QKeySequence::New);
    newAction->setStatusTip(tr("Create a new spreadsheet file"));
    connect(newAction, SIGNAL(triggered()), this, SLOT(newFile()));

The New action has an accelerator ( New), a parent (the main window), an icon, a shortcut key, and a status tip. Most window systems have standardized keyboard shortcuts for certain actions. For example, the New action has a shortcut of Ctrl+N on Windows, KDE, and GNOME, and Command+N on Mac OS X. By using the appropriate QKeySequence::StandardKey enum value, we ensure that Qt will provide the correct shortcuts for the platform on which the application is running.

We connect the action's triggered() signal to the main window's private newFile() slot, which we will implement in the next section. This connection ensures that when the user chooses the File|New menu item, clicks the New toolbar button, or presses Ctrl+N, the newFile() slot is called.

The Open, Save, and Save As actions are very similar to the New action, so we will skip directly to the "recently opened files" part of the File menu:

    ...
    for (int i = 0; i < MaxRecentFiles; ++i) {
        recentFileActions[i] = new QAction(this);
        recentFileActions[i]->setVisible(false);
        connect(recentFileActions[i], SIGNAL(triggered()),
                this, SLOT(openRecentFile()));
    }

We populate the recentFileActions array with actions. Each action is hidden and connected to the openRecentFile() slot. Later on, we will see how the recent file actions are made visible and used.

    exitAction = new QAction(tr("E&xit"), this);
    exitAction->setShortcut(tr("Ctrl+Q"));
    exitAction->setStatusTip(tr("Exit the application"));
    connect(exitAction, SIGNAL(triggered()), this, SLOT(close()));

The Exit action is slightly different from the ones we have seen so far. There is no standardized key sequence for terminating an application, so here we specify the key sequence explicitly. Another difference is that we connect to the window's close() slot, which is provided by Qt.

We can now skip to the Select All action:

    ...
    selectAllAction = new QAction(tr("&All"), this);
    selectAllAction->setShortcut(QKeySequence::SelectAll);
    selectAllAction->setStatusTip(tr("Select all the cells in the "
                                    "spreadsheet"));
    connect(selectAllAction, SIGNAL(triggered()),
            spreadsheet, SLOT(selectAll()));

The selectAll() slot is provided by one of QTableWidget's ancestors, QAbstractItemView, so we do not have to implement it ourselves.

Let's skip further to the Show Grid action in the Options menu:

    ...
    showGridAction = new QAction(tr("&Show Grid"), this);
    showGridAction->setCheckable(true);
    showGridAction->setChecked(spreadsheet->showGrid());
    showGridAction->setStatusTip(tr("Show or hide the spreadsheet's "
                                       "grid"));
    connect(showGridAction, SIGNAL(toggled(bool)),
            spreadsheet, SLOT(setShowGrid(bool)));

Show Grid is a checkable action. Checkable actions are rendered with a check-mark in the menu and implemented as toggle buttons in the toolbar. When the action is turned on, the Spreadsheet component displays a grid. We initialize the action with the default for the Spreadsheet component so that they are synchronized at startup. Then we connect the Show Grid action's toggled(bool) signal to the Spreadsheet component's setShowGrid(bool) slot, which it inherits from QTableWidget. Once this action is added to a menu or toolbar, the user can toggle the grid on and off.

The Show Grid and Auto-Recalculate actions are independent checkable actions. Qt also supports mutually exclusive actions through the QActionGroup class.

    ...
    aboutQtAction = new QAction(tr("About &Qt"), this);
    aboutQtAction->setStatusTip(tr("Show the Qt library's About box"));
    connect(aboutQtAction, SIGNAL(triggered()), qApp, SLOT(aboutQt()));
}

For the About Qt action, we use the QApplication object's aboutQt() slot, accessible through the qApp global variable. This pops up the dialog shown in Figure 3.4.

03fig04.jpg

Figure 3.4 About Qt

Now that we have created the actions, we can move on to building a menu system containing them:

void MainWindow::createMenus()
{
    fileMenu = menuBar()->addMenu(tr("&File"));
    fileMenu->addAction(newAction);
    fileMenu->addAction(openAction);
    fileMenu->addAction(saveAction);
    fileMenu->addAction(saveAsAction);
    separatorAction = fileMenu->addSeparator();
    for (int i = 0; i < MaxRecentFiles; ++i)
        fileMenu->addAction(recentFileActions[i]);
    fileMenu->addSeparator();
    fileMenu->addAction(exitAction);

In Qt, menus are instances of QMenu. The addMenu() function creates a QMenu widget with the specified text and adds it to the menu bar. The QMainWindow::menuBar() function returns a pointer to a QMenuBar. The menu bar is created the first time menuBar() is called.

We start by creating the File menu and then add the New, Open, Save, and Save As actions to it. We insert a separator to visually group closely related items together. We use a for loop to add the (initially hidden) actions from the recentFileActions array, and then add the exitAction action at the end.

We have kept a pointer to one of the separators. This will allow us to hide the separator (if there are no recent files) or to show it, since we do not want to show two separators with nothing in between.

    editMenu = menuBar()->addMenu(tr("&Edit"));
    editMenu->addAction(cutAction);
    editMenu->addAction(copyAction);
    editMenu->addAction(pasteAction);
    editMenu->addAction(deleteAction);

    selectSubMenu = editMenu->addMenu(tr("&Select"));
    selectSubMenu->addAction(selectRowAction);
    selectSubMenu->addAction(selectColumnAction);
    selectSubMenu->addAction(selectAllAction);

    editMenu->addSeparator();
    editMenu->addAction(findAction);
    editMenu->addAction(goToCellAction);

Now we create the Edit menu, adding actions with QMenu::addAction() as we did for the File menu, and adding the submenu with QMenu::addMenu() at the position where we want it to appear. The submenu, like the menu it belongs to, is a QMenu.

    toolsMenu = menuBar()->addMenu(tr("&Tools"));
    toolsMenu->addAction(recalculateAction);
    toolsMenu->addAction(sortAction);

    optionsMenu = menuBar()->addMenu(tr("&Options"));
    optionsMenu->addAction(showGridAction);
    optionsMenu->addAction(autoRecalcAction);

    menuBar()->addSeparator();

    helpMenu = menuBar()->addMenu(tr("&Help"));
    helpMenu->addAction(aboutAction);
    helpMenu->addAction(aboutQtAction);
}

We create the Tools, Options, and Help menus in a similar fashion. We insert a separator between the Options and Help menus. In Motif and CDE styles, the separator pushes the Help menu to the right; in other styles, the separator is ignored. Figure 3.5 shows both cases.

Figure 3.5 The menu bar in Motif and Windows styles

void MainWindow::createContextMenu()
{
    spreadsheet->addAction(cutAction);
    spreadsheet->addAction(copyAction);
    spreadsheet->addAction(pasteAction);
    spreadsheet->setContextMenuPolicy(Qt::ActionsContextMenu);
}

Any Qt widget can have a list of QActions associated with it. To provide a context menu for the application, we add the desired actions to the Spreadsheet widget and set that widget's context menu policy to show a context menu with these actions. Context menus are invoked by right-clicking a widget or by pressing a platform-specific key. The Spreadsheet's context menu is shown in Figure 3.6.

03fig06.jpg

Figure 3.6 The Spreadsheet application's context menu

A more sophisticated way of providing context menus is to reimplement the QWidget::contextMenuEvent() function, create a QMenu widget, populate it with the desired actions, and call exec() on it.

void MainWindow::createToolBars()
{
    fileToolBar = addToolBar(tr("&File"));
    fileToolBar->addAction(newAction);
    fileToolBar->addAction(openAction);
    fileToolBar->addAction(saveAction);

    editToolBar = addToolBar(tr("&Edit"));
    editToolBar->addAction(cutAction);
    editToolBar->addAction(copyAction);
    editToolBar->addAction(pasteAction);
    editToolBar->addSeparator();
    editToolBar->addAction(findAction);
    editToolBar->addAction(goToCellAction);
}

Creating toolbars is very similar to creating menus. We create a File toolbar and an Edit toolbar. Just like a menu, a toolbar can have separators, as Figure 3.7 shows.

Figure 3.7 The Spreadsheet application's toolbars

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020