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;
 }