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

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     ** Alternatively, this file may be used under the terms of the GNU
     ** General Public License version 3.0 as published by the Free Software
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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);
     }