mainwindow.cpp Example File | Qt Widgets 5.12.11

- Qt 5.12
- Qt Widgets
- MDI Example
- mainwindow.cpp Example File
- Qt 5.12.11 Reference Documentation

# mainwindow.cpp Example File

mainwindows/mdi/mainwindow.cpp

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     #include <QtWidgets>

     #include "mainwindow.h"
     #include "mdichild.h"

     MainWindow::MainWindow()
         : mdiArea(new QMdiArea)
     {
         mdiArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAsNeeded);
         mdiArea->setVerticalScrollBarPolicy(Qt::ScrollBarAsNeeded);
         setCentralWidget(mdiArea);
         connect(mdiArea, &QMdiArea::subWindowActivated,
                 this, &MainWindow::updateMenus);

         createActions();
         createStatusBar();
         updateMenus();

         readSettings();

         setWindowTitle(tr("MDI"));
         setUnifiedTitleAndToolBarOnMac(true);
     }

     void MainWindow::closeEvent(QCloseEvent *event)
     {
         mdiArea->closeAllSubWindows();
         if (mdiArea->currentSubWindow()) {
             event->ignore();
         } else {
             writeSettings();
             event->accept();
         }
     }

     void MainWindow::newFile()
     {
         MdiChild *child = createMdiChild();
         child->newFile();
         child->show();
     }

     void MainWindow::open()
     {
         const QString fileName = QFileDialog::getOpenFileName(this);
         if (!fileName.isEmpty())
             openFile(fileName);
     }

     bool MainWindow::openFile(const QString &fileName)
     {
         if (QMdiSubWindow *existing = findMdiChild(fileName)) {
             mdiArea->setActiveSubWindow(existing);
             return true;
         }
         const bool succeeded = loadFile(fileName);
         if (succeeded)
             statusBar()->showMessage(tr("File loaded"), 2000);
         return succeeded;
     }

     bool MainWindow::loadFile(const QString &fileName)
     {
         MdiChild *child = createMdiChild();
         const bool succeeded = child->loadFile(fileName);
         if (succeeded)
             child->show();
         else
             child->close();
         MainWindow::prependToRecentFiles(fileName);
         return succeeded;
     }

     static inline QString recentFilesKey() { return QStringLiteral("recentFileList"); }
     static inline QString fileKey() { return QStringLiteral("file"); }

     static QStringList readRecentFiles(QSettings &settings)
     {
         QStringList result;
         const int count = settings.beginReadArray(recentFilesKey());
         for (int i = 0; i < count; ++i) {
             settings.setArrayIndex(i);
             result.append(settings.value(fileKey()).toString());
         }
         settings.endArray();
         return result;
     }

     static void writeRecentFiles(const QStringList &files, QSettings &settings)
     {
         const int count = files.size();
         settings.beginWriteArray(recentFilesKey());
         for (int i = 0; i < count; ++i) {
             settings.setArrayIndex(i);
             settings.setValue(fileKey(), files.at(i));
         }
         settings.endArray();
     }

     bool MainWindow::hasRecentFiles()
     {
         QSettings settings(QCoreApplication::organizationName(), QCoreApplication::applicationName());
         const int count = settings.beginReadArray(recentFilesKey());
         settings.endArray();
         return count > 0;
     }

     void MainWindow::prependToRecentFiles(const QString &fileName)
     {
         QSettings settings(QCoreApplication::organizationName(), QCoreApplication::applicationName());

         const QStringList oldRecentFiles = readRecentFiles(settings);
         QStringList recentFiles = oldRecentFiles;
         recentFiles.removeAll(fileName);
         recentFiles.prepend(fileName);
         if (oldRecentFiles != recentFiles)
             writeRecentFiles(recentFiles, settings);

         setRecentFilesVisible(!recentFiles.isEmpty());
     }

     void MainWindow::setRecentFilesVisible(bool visible)
     {
         recentFileSubMenuAct->setVisible(visible);
         recentFileSeparator->setVisible(visible);
     }

     void MainWindow::updateRecentFileActions()
     {
         QSettings settings(QCoreApplication::organizationName(), QCoreApplication::applicationName());

         const QStringList recentFiles = readRecentFiles(settings);
         const int count = qMin(int(MaxRecentFiles), recentFiles.size());
         int i = 0;
         for ( ; i < count; ++i) {
             const QString fileName = QFileInfo(recentFiles.at(i)).fileName();
             recentFileActs[i]->setText(tr("&%1 %2").arg(i + 1).arg(fileName));
             recentFileActs[i]->setData(recentFiles.at(i));
             recentFileActs[i]->setVisible(true);
         }
         for ( ; i < MaxRecentFiles; ++i)
             recentFileActs[i]->setVisible(false);
     }

     void MainWindow::openRecentFile()
     {
         if (const QAction *action = qobject_cast<const QAction *>(sender()))
             openFile(action->data().toString());
     }

     void MainWindow::save()
     {
         if (activeMdiChild() && activeMdiChild()->save())
             statusBar()->showMessage(tr("File saved"), 2000);
     }

     void MainWindow::saveAs()
     {
         MdiChild *child = activeMdiChild();
         if (child && child->saveAs()) {
             statusBar()->showMessage(tr("File saved"), 2000);
             MainWindow::prependToRecentFiles(child->currentFile());
         }
     }

     #ifndef QT_NO_CLIPBOARD
     void MainWindow::cut()
     {
         if (activeMdiChild())
             activeMdiChild()->cut();
     }

     void MainWindow::copy()
     {
         if (activeMdiChild())
             activeMdiChild()->copy();
     }

     void MainWindow::paste()
     {
         if (activeMdiChild())
             activeMdiChild()->paste();
     }
     #endif

     void MainWindow::about()
     {
        QMessageBox::about(this, tr("About MDI"),
                 tr("The <b>MDI</b> example demonstrates how to write multiple "
                    "document interface applications using Qt."));
     }

     void MainWindow::updateMenus()
     {
         bool hasMdiChild = (activeMdiChild() != 0);
         saveAct->setEnabled(hasMdiChild);
         saveAsAct->setEnabled(hasMdiChild);
     #ifndef QT_NO_CLIPBOARD
         pasteAct->setEnabled(hasMdiChild);
     #endif
         closeAct->setEnabled(hasMdiChild);
         closeAllAct->setEnabled(hasMdiChild);
         tileAct->setEnabled(hasMdiChild);
         cascadeAct->setEnabled(hasMdiChild);
         nextAct->setEnabled(hasMdiChild);
         previousAct->setEnabled(hasMdiChild);
         windowMenuSeparatorAct->setVisible(hasMdiChild);

     #ifndef QT_NO_CLIPBOARD
         bool hasSelection = (activeMdiChild() &&
                              activeMdiChild()->textCursor().hasSelection());
         cutAct->setEnabled(hasSelection);
         copyAct->setEnabled(hasSelection);
     #endif
     }

     void MainWindow::updateWindowMenu()
     {
         windowMenu->clear();
         windowMenu->addAction(closeAct);
         windowMenu->addAction(closeAllAct);
         windowMenu->addSeparator();
         windowMenu->addAction(tileAct);
         windowMenu->addAction(cascadeAct);
         windowMenu->addSeparator();
         windowMenu->addAction(nextAct);
         windowMenu->addAction(previousAct);
         windowMenu->addAction(windowMenuSeparatorAct);

         QList<QMdiSubWindow *> windows = mdiArea->subWindowList();
         windowMenuSeparatorAct->setVisible(!windows.isEmpty());

         for (int i = 0; i < windows.size(); ++i) {
             QMdiSubWindow *mdiSubWindow = windows.at(i);
             MdiChild *child = qobject_cast<MdiChild *>(mdiSubWindow->widget());

             QString text;
             if (i < 9) {
                 text = tr("&%1 %2").arg(i + 1)
                                    .arg(child->userFriendlyCurrentFile());
             } else {
                 text = tr("%1 %2").arg(i + 1)
                                   .arg(child->userFriendlyCurrentFile());
             }
             QAction *action = windowMenu->addAction(text, mdiSubWindow, [this, mdiSubWindow]() {
                 mdiArea->setActiveSubWindow(mdiSubWindow);
             });
             action->setCheckable(true);
             action ->setChecked(child == activeMdiChild());
         }
     }

     MdiChild *MainWindow::createMdiChild()
     {
         MdiChild *child = new MdiChild;
         mdiArea->addSubWindow(child);

     #ifndef QT_NO_CLIPBOARD
         connect(child, &QTextEdit::copyAvailable, cutAct, &QAction::setEnabled);
         connect(child, &QTextEdit::copyAvailable, copyAct, &QAction::setEnabled);
     #endif

         return child;
     }

     void MainWindow::createActions()
     {
         QMenu *fileMenu = menuBar()->addMenu(tr("&File"));
         QToolBar *fileToolBar = addToolBar(tr("File"));

         const QIcon newIcon = QIcon::fromTheme("document-new", QIcon(":/images/new.png"));
         newAct = new QAction(newIcon, tr("&New"), this);
         newAct->setShortcuts(QKeySequence::New);
         newAct->setStatusTip(tr("Create a new file"));
         connect(newAct, &QAction::triggered, this, &MainWindow::newFile);
         fileMenu->addAction(newAct);
         fileToolBar->addAction(newAct);

         const QIcon openIcon = QIcon::fromTheme("document-open", QIcon(":/images/open.png"));
         QAction *openAct = new QAction(openIcon, tr("&Open..."), this);
         openAct->setShortcuts(QKeySequence::Open);
         openAct->setStatusTip(tr("Open an existing file"));
         connect(openAct, &QAction::triggered, this, &MainWindow::open);
         fileMenu->addAction(openAct);
         fileToolBar->addAction(openAct);

         const QIcon saveIcon = QIcon::fromTheme("document-save", QIcon(":/images/save.png"));
         saveAct = new QAction(saveIcon, tr("&Save"), this);
         saveAct->setShortcuts(QKeySequence::Save);
         saveAct->setStatusTip(tr("Save the document to disk"));
         connect(saveAct, &QAction::triggered, this, &MainWindow::save);
         fileToolBar->addAction(saveAct);

         const QIcon saveAsIcon = QIcon::fromTheme("document-save-as");
         saveAsAct = new QAction(saveAsIcon, tr("Save &As..."), this);
         saveAsAct->setShortcuts(QKeySequence::SaveAs);
         saveAsAct->setStatusTip(tr("Save the document under a new name"));
         connect(saveAsAct, &QAction::triggered, this, &MainWindow::saveAs);
         fileMenu->addAction(saveAsAct);

         fileMenu->addSeparator();

         QMenu *recentMenu = fileMenu->addMenu(tr("Recent..."));
         connect(recentMenu, &QMenu::aboutToShow, this, &MainWindow::updateRecentFileActions);
         recentFileSubMenuAct = recentMenu->menuAction();

         for (int i = 0; i < MaxRecentFiles; ++i) {
             recentFileActs[i] = recentMenu->addAction(QString(), this, &MainWindow::openRecentFile);
             recentFileActs[i]->setVisible(false);
         }

         recentFileSeparator = fileMenu->addSeparator();

         setRecentFilesVisible(MainWindow::hasRecentFiles());

         fileMenu->addAction(tr("Switch layout direction"), this, &MainWindow::switchLayoutDirection);

         fileMenu->addSeparator();

         const QIcon exitIcon = QIcon::fromTheme("application-exit");
         QAction *exitAct = fileMenu->addAction(exitIcon, tr("E&xit"), qApp, &QApplication::closeAllWindows);
         exitAct->setShortcuts(QKeySequence::Quit);
         exitAct->setStatusTip(tr("Exit the application"));
         fileMenu->addAction(exitAct);

     #ifndef QT_NO_CLIPBOARD
         QMenu *editMenu = menuBar()->addMenu(tr("&Edit"));
         QToolBar *editToolBar = addToolBar(tr("Edit"));

         const QIcon cutIcon = QIcon::fromTheme("edit-cut", QIcon(":/images/cut.png"));
         cutAct = new QAction(cutIcon, tr("Cu&t"), this);
         cutAct->setShortcuts(QKeySequence::Cut);
         cutAct->setStatusTip(tr("Cut the current selection's contents to the "
                                 "clipboard"));
         connect(cutAct, &QAction::triggered, this, &MainWindow::cut);
         editMenu->addAction(cutAct);
         editToolBar->addAction(cutAct);

         const QIcon copyIcon = QIcon::fromTheme("edit-copy", QIcon(":/images/copy.png"));
         copyAct = new QAction(copyIcon, tr("&Copy"), this);
         copyAct->setShortcuts(QKeySequence::Copy);
         copyAct->setStatusTip(tr("Copy the current selection's contents to the "
                                  "clipboard"));
         connect(copyAct, &QAction::triggered, this, &MainWindow::copy);
         editMenu->addAction(copyAct);
         editToolBar->addAction(copyAct);

         const QIcon pasteIcon = QIcon::fromTheme("edit-paste", QIcon(":/images/paste.png"));
         pasteAct = new QAction(pasteIcon, tr("&Paste"), this);
         pasteAct->setShortcuts(QKeySequence::Paste);
         pasteAct->setStatusTip(tr("Paste the clipboard's contents into the current "
                                   "selection"));
         connect(pasteAct, &QAction::triggered, this, &MainWindow::paste);
         editMenu->addAction(pasteAct);
         editToolBar->addAction(pasteAct);
     #endif

         windowMenu = menuBar()->addMenu(tr("&Window"));
         connect(windowMenu, &QMenu::aboutToShow, this, &MainWindow::updateWindowMenu);

         closeAct = new QAction(tr("Cl&ose"), this);
         closeAct->setStatusTip(tr("Close the active window"));
         connect(closeAct, &QAction::triggered,
                 mdiArea, &QMdiArea::closeActiveSubWindow);

         closeAllAct = new QAction(tr("Close &All"), this);
         closeAllAct->setStatusTip(tr("Close all the windows"));
         connect(closeAllAct, &QAction::triggered, mdiArea, &QMdiArea::closeAllSubWindows);

         tileAct = new QAction(tr("&Tile"), this);
         tileAct->setStatusTip(tr("Tile the windows"));
         connect(tileAct, &QAction::triggered, mdiArea, &QMdiArea::tileSubWindows);

         cascadeAct = new QAction(tr("&Cascade"), this);
         cascadeAct->setStatusTip(tr("Cascade the windows"));
         connect(cascadeAct, &QAction::triggered, mdiArea, &QMdiArea::cascadeSubWindows);

         nextAct = new QAction(tr("Ne&xt"), this);
         nextAct->setShortcuts(QKeySequence::NextChild);
         nextAct->setStatusTip(tr("Move the focus to the next window"));
         connect(nextAct, &QAction::triggered, mdiArea, &QMdiArea::activateNextSubWindow);

         previousAct = new QAction(tr("Pre&vious"), this);
         previousAct->setShortcuts(QKeySequence::PreviousChild);
         previousAct->setStatusTip(tr("Move the focus to the previous "
                                      "window"));
         connect(previousAct, &QAction::triggered, mdiArea, &QMdiArea::activatePreviousSubWindow);

         windowMenuSeparatorAct = new QAction(this);
         windowMenuSeparatorAct->setSeparator(true);

         updateWindowMenu();

         menuBar()->addSeparator();

         QMenu *helpMenu = menuBar()->addMenu(tr("&Help"));

         QAction *aboutAct = helpMenu->addAction(tr("&About"), this, &MainWindow::about);
         aboutAct->setStatusTip(tr("Show the application's About box"));

         QAction *aboutQtAct = helpMenu->addAction(tr("About &Qt"), qApp, &QApplication::aboutQt);
         aboutQtAct->setStatusTip(tr("Show the Qt library's About box"));
     }

     void MainWindow::createStatusBar()
     {
         statusBar()->showMessage(tr("Ready"));
     }

     void MainWindow::readSettings()
     {
         QSettings settings(QCoreApplication::organizationName(), QCoreApplication::applicationName());
         const QByteArray geometry = settings.value("geometry", QByteArray()).toByteArray();
         if (geometry.isEmpty()) {
             const QRect availableGeometry = QApplication::desktop()->availableGeometry(this);
             resize(availableGeometry.width() / 3, availableGeometry.height() / 2);
             move((availableGeometry.width() - width()) / 2,
                  (availableGeometry.height() - height()) / 2);
         } else {
             restoreGeometry(geometry);
         }
     }

     void MainWindow::writeSettings()
     {
         QSettings settings(QCoreApplication::organizationName(), QCoreApplication::applicationName());
         settings.setValue("geometry", saveGeometry());
     }

     MdiChild *MainWindow::activeMdiChild() const
     {
         if (QMdiSubWindow *activeSubWindow = mdiArea->activeSubWindow())
             return qobject_cast<MdiChild *>(activeSubWindow->widget());
         return 0;
     }

     QMdiSubWindow *MainWindow::findMdiChild(const QString &fileName) const
     {
         QString canonicalFilePath = QFileInfo(fileName).canonicalFilePath();

         foreach (QMdiSubWindow *window, mdiArea->subWindowList()) {
             MdiChild *mdiChild = qobject_cast<MdiChild *>(window->widget());
             if (mdiChild->currentFile() == canonicalFilePath)
                 return window;
         }
         return 0;
     }

     void MainWindow::switchLayoutDirection()
     {
         if (layoutDirection() == Qt::LeftToRight)
             QGuiApplication::setLayoutDirection(Qt::RightToLeft);
         else
             QGuiApplication::setLayoutDirection(Qt::LeftToRight);
     }