mainwindow.cpp Example File | Qt Widgets 5.12.12

- Qt 5.12
- Qt Widgets
- SDI Example
- mainwindow.cpp Example File
- Qt 5.12.12 Reference Documentation

# mainwindow.cpp Example File

mainwindows/sdi/mainwindow.cpp

     /****************************************************************************
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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;
     }