mainwindow.cpp Example File

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  #include <QtWidgets>

  #include "mainwindow.h"
  #include "previewform.h"

  MainWindow::MainWindow()
  {
      textEdit = new QPlainTextEdit;
      textEdit->setLineWrapMode(QPlainTextEdit::NoWrap);
      setCentralWidget(textEdit);

      findCodecs();

      previewForm = new PreviewForm(this);
      previewForm->setCodecList(codecs);

      createMenus();

      setWindowTitle(tr("Codecs"));

      const QRect screenGeometry = QApplication::desktop()->screenGeometry(this);
      resize(screenGeometry.width() / 2, screenGeometry.height() * 2 / 3);
  }

  void MainWindow::open()
  {
      const QString fileName = QFileDialog::getOpenFileName(this);
      if (fileName.isEmpty())
          return;
      QFile file(fileName);
      if (!file.open(QFile::ReadOnly)) {
          QMessageBox::warning(this, tr("Codecs"),
                               tr("Cannot read file %1:\n%2")
                               .arg(QDir::toNativeSeparators(fileName),
                                    file.errorString()));
          return;
      }

      const QByteArray data = file.readAll();

      previewForm->setWindowTitle(tr("Choose Encoding for %1").arg(QFileInfo(fileName).fileName()));
      previewForm->setEncodedData(data);
      if (previewForm->exec())
          textEdit->setPlainText(previewForm->decodedString());
  }

  void MainWindow::save()
  {
      const QAction *action = qobject_cast<const QAction *>(sender());
      const QByteArray codecName = action->data().toByteArray();
      const QString title = tr("Save As (%1)").arg(QLatin1String(codecName));

      QString fileName = QFileDialog::getSaveFileName(this, title);
      if (fileName.isEmpty())
          return;
      QFile file(fileName);
      if (!file.open(QFile::WriteOnly | QFile::Text)) {
          QMessageBox::warning(this, tr("Codecs"),
                               tr("Cannot write file %1:\n%2")
                               .arg(QDir::toNativeSeparators(fileName),
                                    file.errorString()));
          return;
      }

      QTextStream out(&file);
      out.setCodec(codecName.constData());
      out << textEdit->toPlainText();
  }

  void MainWindow::about()
  {
      QMessageBox::about(this, tr("About Codecs"),
              tr("The <b>Codecs</b> example demonstrates how to read and write "
                 "files using various encodings."));
  }

  void MainWindow::aboutToShowSaveAsMenu()
  {
      QString currentText = textEdit->toPlainText();

      foreach (QAction *action, saveAsActs) {
          QByteArray codecName = action->data().toByteArray();
          QTextCodec *codec = QTextCodec::codecForName(codecName);
          action->setVisible(codec && codec->canEncode(currentText));
      }
  }

  void MainWindow::findCodecs()
  {
      QMap<QString, QTextCodec *> codecMap;
      QRegularExpression iso8859RegExp("^ISO[- ]8859-([0-9]+).*$");
      QRegularExpressionMatch match;

      foreach (int mib, QTextCodec::availableMibs()) {
          QTextCodec *codec = QTextCodec::codecForMib(mib);

          QString sortKey = codec->name().toUpper();
          int rank;

          if (sortKey.startsWith(QLatin1String("UTF-8"))) {
              rank = 1;
          } else if (sortKey.startsWith(QLatin1String("UTF-16"))) {
              rank = 2;
          } else if ((match = iso8859RegExp.match(sortKey)).hasMatch()) {
              if (match.captured(1).size() == 1)
                  rank = 3;
              else
                  rank = 4;
          } else {
              rank = 5;
          }
          sortKey.prepend(QLatin1Char('0' + rank));

          codecMap.insert(sortKey, codec);
      }
      codecs = codecMap.values();
  }

  void MainWindow::createMenus()
  {
      QMenu *fileMenu = menuBar()->addMenu(tr("&File"));
      QAction *openAct =
          fileMenu->addAction(tr("&Open..."), this, &MainWindow::open);
      openAct->setShortcuts(QKeySequence::Open);

      QMenu *saveAsMenu = fileMenu->addMenu(tr("&Save As"));
      connect(saveAsMenu, &QMenu::aboutToShow,
              this, &MainWindow::aboutToShowSaveAsMenu);
      foreach (const QTextCodec *codec, codecs) {
          const QByteArray name = codec->name();
          QAction *action = saveAsMenu->addAction(tr("%1...").arg(QLatin1String(name)));
          action->setData(QVariant(name));
          connect(action, &QAction::triggered, this, &MainWindow::save);
          saveAsActs.append(action);
      }

      fileMenu->addSeparator();
      QAction *exitAct = fileMenu->addAction(tr("E&xit"), this, &QWidget::close);
      exitAct->setShortcuts(QKeySequence::Quit);

      menuBar()->addSeparator();

      QMenu *helpMenu = menuBar()->addMenu(tr("&Help"));
      helpMenu->addAction(tr("&About"), this, &MainWindow::about);
      helpMenu->addAction(tr("About &Qt"), qApp, &QApplication::aboutQt);
  }