mainwindow.cpp Example File

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  #include <QtWidgets>

  #include "mainwindow.h"

  MainWindow::MainWindow()
      : textEdit(new QPlainTextEdit)
  {
      setCentralWidget(textEdit);

      createActions();
      createStatusBar();

      readSettings();

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

  #ifndef QT_NO_SESSIONMANAGER
      QGuiApplication::setFallbackSessionManagementEnabled(false);
      connect(qApp, &QGuiApplication::commitDataRequest,
              this, &MainWindow::commitData);
  #endif

      setCurrentFile(QString());
      setUnifiedTitleAndToolBarOnMac(true);
  }

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

  void MainWindow::newFile()
  {
      if (maybeSave()) {
          textEdit->clear();
          setCurrentFile(QString());
      }
  }

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

  bool MainWindow::save()
  {
      if (curFile.isEmpty()) {
          return saveAs();
      } else {
          return saveFile(curFile);
      }
  }

  bool MainWindow::saveAs()
  {
      QFileDialog dialog(this);
      dialog.setWindowModality(Qt::WindowModal);
      dialog.setAcceptMode(QFileDialog::AcceptSave);
      if (dialog.exec() != QDialog::Accepted)
          return false;
      return saveFile(dialog.selectedFiles().first());
  }

  void MainWindow::about()
  {
     QMessageBox::about(this, tr("About Application"),
              tr("The <b>Application</b> example demonstrates how to "
                 "write modern GUI applications using Qt, with a menu bar, "
                 "toolbars, and a status bar."));
  }

  void MainWindow::documentWasModified()
  {
      setWindowModified(textEdit->document()->isModified());
  }

  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();

      const QIcon exitIcon = QIcon::fromTheme("application-exit");
      QAction *exitAct = fileMenu->addAction(exitIcon, tr("E&xit"), this, &QWidget::close);
      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, &QPlainTextEdit::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, &QPlainTextEdit::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, &QPlainTextEdit::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, &QPlainTextEdit::copyAvailable, cutAct, &QAction::setEnabled);
      connect(textEdit, &QPlainTextEdit::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("Application"),
                                 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("Application"),
                               tr("Cannot read file %1:\n%2.")
                               .arg(QDir::toNativeSeparators(fileName), file.errorString()));
          return;
      }

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

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

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

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

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

  void MainWindow::setCurrentFile(const QString &fileName)
  {
      curFile = fileName;
      textEdit->document()->setModified(false);
      setWindowModified(false);

      QString shownName = curFile;
      if (curFile.isEmpty())
          shownName = "untitled.txt";
      setWindowFilePath(shownName);
  }

  QString MainWindow::strippedName(const QString &fullFileName)
  {
      return QFileInfo(fullFileName).fileName();
  }
  #ifndef QT_NO_SESSIONMANAGER
  void MainWindow::commitData(QSessionManager &manager)
  {
      if (manager.allowsInteraction()) {
          if (!maybeSave())
              manager.cancel();
      } else {
          // Non-interactive: save without asking
          if (textEdit->document()->isModified())
              save();
      }
  }
  #endif