mainwindow.cpp Example File

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  #include <QtWidgets>

  #include "mainwindow.h"

  MainWindow::MainWindow()
  {
      init();
      setCurrentFile(QString());
  }

  MainWindow::MainWindow(const QString &fileName)
  {
      init();
      loadFile(fileName);
  }

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

  void MainWindow::newFile()
  {
      MainWindow *other = new MainWindow;
      other->tile(this);
      other->show();
  }

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

  void MainWindow::openFile(const QString &fileName)
  {
      MainWindow *existing = findMainWindow(fileName);
      if (existing) {
          existing->show();
          existing->raise();
          existing->activateWindow();
          return;
      }

      if (isUntitled && textEdit->document()->isEmpty() && !isWindowModified()) {
          loadFile(fileName);
          return;
      }

      MainWindow *other = new MainWindow(fileName);
      if (other->isUntitled) {
          delete other;
          return;
      }
      other->tile(this);
      other->show();
  }

  bool MainWindow::save()
  {
      return isUntitled ? saveAs() : saveFile(curFile);
  }

  bool MainWindow::saveAs()
  {
      QString fileName = QFileDialog::getSaveFileName(this, tr("Save As"),
                                                      curFile);
      if (fileName.isEmpty())
          return false;

      return saveFile(fileName);
  }

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

  void MainWindow::documentWasModified()
  {
      setWindowModified(true);
  }

  void MainWindow::init()
  {
      setAttribute(Qt::WA_DeleteOnClose);

      isUntitled = true;

      textEdit = new QTextEdit;
      setCentralWidget(textEdit);

      createActions();
      createStatusBar();

      readSettings();

      connect(textEdit->document(), &QTextDocument::contentsChanged,
              this, &MainWindow::documentWasModified);

      setUnifiedTitleAndToolBarOnMac(true);
  }

  void MainWindow::tile(const QMainWindow *previous)
  {
      if (!previous)
          return;
      int topFrameWidth = previous->geometry().top() - previous->pos().y();
      if (!topFrameWidth)
          topFrameWidth = 40;
      const QPoint pos = previous->pos() + 2 * QPoint(topFrameWidth, topFrameWidth);
      if (QApplication::desktop()->availableGeometry(this).contains(rect().bottomRight() + pos))
          move(pos);
  }

  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"));
      QAction *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"));
      QAction *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);
      fileMenu->addAction(saveAct);
      fileToolBar->addAction(saveAct);

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

      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());

      QAction *closeAct = fileMenu->addAction(tr("&Close"), this, &QWidget::close);
      closeAct->setShortcut(tr("Ctrl+W"));
      closeAct->setStatusTip(tr("Close this window"));

      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"));

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

  #ifndef QT_NO_CLIPBOARD
      const QIcon cutIcon = QIcon::fromTheme("edit-cut", QIcon(":/images/cut.png"));
      QAction *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, textEdit, &QTextEdit::cut);
      editMenu->addAction(cutAct);
      editToolBar->addAction(cutAct);

      const QIcon copyIcon = QIcon::fromTheme("edit-copy", QIcon(":/images/copy.png"));
      QAction *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, textEdit, &QTextEdit::copy);
      editMenu->addAction(copyAct);
      editToolBar->addAction(copyAct);

      const QIcon pasteIcon = QIcon::fromTheme("edit-paste", QIcon(":/images/paste.png"));
      QAction *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, textEdit, &QTextEdit::paste);
      editMenu->addAction(pasteAct);
      editToolBar->addAction(pasteAct);

      menuBar()->addSeparator();
  #endif // !QT_NO_CLIPBOARD

      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"));

  #ifndef QT_NO_CLIPBOARD
      cutAct->setEnabled(false);
      copyAct->setEnabled(false);
      connect(textEdit, &QTextEdit::copyAvailable, cutAct, &QAction::setEnabled);
      connect(textEdit, &QTextEdit::copyAvailable, copyAct, &QAction::setEnabled);
  #endif // !QT_NO_CLIPBOARD
  }

  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());
  }

  bool MainWindow::maybeSave()
  {
      if (!textEdit->document()->isModified())
          return true;
      const QMessageBox::StandardButton ret
          = QMessageBox::warning(this, tr("SDI"),
                                 tr("The document has been modified.\n"
                                    "Do you want to save your changes?"),
                                 QMessageBox::Save | QMessageBox::Discard
                                 | QMessageBox::Cancel);
      switch (ret) {
      case QMessageBox::Save:
          return save();
      case QMessageBox::Cancel:
          return false;
      default:
          break;
      }
      return true;
  }

  void MainWindow::loadFile(const QString &fileName)
  {

      QFile file(fileName);
      if (!file.open(QFile::ReadOnly | QFile::Text)) {
          QMessageBox::warning(this, tr("SDI"),
                               tr("Cannot read file %1:\n%2.")
                               .arg(QDir::toNativeSeparators(fileName), file.errorString()));
          return;
      }

      QTextStream in(&file);
      QApplication::setOverrideCursor(Qt::WaitCursor);
      textEdit->setPlainText(in.readAll());
      QApplication::restoreOverrideCursor();

      setCurrentFile(fileName);
      statusBar()->showMessage(tr("File loaded"), 2000);
  }

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

  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::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 = MainWindow::strippedName(recentFiles.at(i));
          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());
  }

  bool MainWindow::saveFile(const QString &fileName)
  {
      QFile file(fileName);
      if (!file.open(QFile::WriteOnly | QFile::Text)) {
          QMessageBox::warning(this, tr("SDI"),
                               tr("Cannot write file %1:\n%2.")
                               .arg(QDir::toNativeSeparators(fileName), file.errorString()));
          return false;
      }

      QTextStream out(&file);
      QApplication::setOverrideCursor(Qt::WaitCursor);
      out << textEdit->toPlainText();
      QApplication::restoreOverrideCursor();

      setCurrentFile(fileName);
      statusBar()->showMessage(tr("File saved"), 2000);
      return true;
  }

  void MainWindow::setCurrentFile(const QString &fileName)
  {
      static int sequenceNumber = 1;

      isUntitled = fileName.isEmpty();
      if (isUntitled) {
          curFile = tr("document%1.txt").arg(sequenceNumber++);
      } else {
          curFile = QFileInfo(fileName).canonicalFilePath();
      }

      textEdit->document()->setModified(false);
      setWindowModified(false);

      if (!isUntitled && windowFilePath() != curFile)
          MainWindow::prependToRecentFiles(curFile);

      setWindowFilePath(curFile);
  }

  QString MainWindow::strippedName(const QString &fullFileName)
  {
      return QFileInfo(fullFileName).fileName();
  }

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

      foreach (QWidget *widget, QApplication::topLevelWidgets()) {
          MainWindow *mainWin = qobject_cast<MainWindow *>(widget);
          if (mainWin && mainWin->curFile == canonicalFilePath)
              return mainWin;
      }

      return 0;
  }