- Qt 5.5
- Qt Widgets
- Text Codecs Example
- mainwindow.cpp Example File
- Qt 5.5.1 Reference Documentation

# mainwindow.cpp Example File

tools/codecs/mainwindow.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** You may use this file under the terms of the BSD license as follows:
    **
    ** "Redistribution and use in source and binary forms, with or without
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    **     contributors may be used to endorse or promote products derived
    **     from this software without specific prior written permission.
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    #include <QtWidgets>

    #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.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;
        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);
    }