mainwindow.cpp Example File
tools/codecs/mainwindow.cpp

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 #include <QtGui>

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

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

     findCodecs();

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

     createActions();
     createMenus();

     setWindowTitle(tr("Codecs"));
     resize(500, 400);
 }

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

         QByteArray data = file.readAll();

         previewForm->setEncodedData(data);
         if (previewForm->exec())
             textEdit->setPlainText(previewForm->decodedString());
     }
 }

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

         QAction *action = qobject_cast<QAction *>(sender());
         QByteArray codecName = action->data().toByteArray();

         QTextStream out(&file);
         out.setCodec(codecName);
         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;
     QRegExp iso8859RegExp("ISO[- ]8859-([0-9]+).*");

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

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

         if (sortKey.startsWith("UTF-8")) {
             rank = 1;
         } else if (sortKey.startsWith("UTF-16")) {
             rank = 2;
         } else if (iso8859RegExp.exactMatch(sortKey)) {
             if (iso8859RegExp.cap(1).size() == 1)
                 rank = 3;
             else
                 rank = 4;
         } else {
             rank = 5;
         }
         sortKey.prepend(QChar('0' + rank));

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

 void MainWindow::createActions()
 {
     openAct = new QAction(tr("&Open..."), this);
     openAct->setShortcuts(QKeySequence::Open);
     connect(openAct, SIGNAL(triggered()), this, SLOT(open()));

     foreach (QTextCodec *codec, codecs) {
         QString text = tr("%1...").arg(QString(codec->name()));

         QAction *action = new QAction(text, this);
         action->setData(codec->name());
         connect(action, SIGNAL(triggered()), this, SLOT(save()));
         saveAsActs.append(action);
     }

     exitAct = new QAction(tr("E&xit"), this);
     exitAct->setShortcuts(QKeySequence::Quit);
     connect(exitAct, SIGNAL(triggered()), this, SLOT(close()));

     aboutAct = new QAction(tr("&About"), this);
     connect(aboutAct, SIGNAL(triggered()), this, SLOT(about()));

     aboutQtAct = new QAction(tr("About &Qt"), this);
     connect(aboutQtAct, SIGNAL(triggered()), qApp, SLOT(aboutQt()));
 }

 void MainWindow::createMenus()
 {
     saveAsMenu = new QMenu(tr("&Save As"), this);
     foreach (QAction *action, saveAsActs)
         saveAsMenu->addAction(action);
     connect(saveAsMenu, SIGNAL(aboutToShow()),
             this, SLOT(aboutToShowSaveAsMenu()));

     fileMenu = new QMenu(tr("&File"), this);
     fileMenu->addAction(openAct);
     fileMenu->addMenu(saveAsMenu);
     fileMenu->addSeparator();
     fileMenu->addAction(exitAct);

     helpMenu = new QMenu(tr("&Help"), this);
     helpMenu->addAction(aboutAct);
     helpMenu->addAction(aboutQtAct);

     menuBar()->addMenu(fileMenu);
     menuBar()->addSeparator();
     menuBar()->addMenu(helpMenu);
 }