SDI Example | Qt Widgets 5.13.0

Qt 5.13 | Qt Widgets | SDI Example

Qt 5.13.0 Reference Documentation

# SDI Example

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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);
          QGuiApplication::setOverrideCursor(Qt::WaitCursor);
          textEdit->setPlainText(in.readAll());
          QGuiApplication::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);
          QGuiApplication::setOverrideCursor(Qt::WaitCursor);
          out << textEdit->toPlainText();
          QGuiApplication::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();

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

          return nullptr;
      }