Qt 5.11 | Qt Widgets | MDI Example | mainwindow.cpp Example File

Qt 5.11.3 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);
      }