mainwindow.cpp Example File

mainwindows/application/mainwindow.cpp 
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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

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