- Qt 5.5
- Qt Widgets
- MDI Example
- mdichild.cpp Example File
- Qt 5.5.1 Reference Documentation

# mdichild.cpp Example File

mainwindows/mdi/mdichild.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
    ** modification, are permitted provided that the following conditions are
    ** met:
    **   * Redistributions of source code must retain the above copyright
    **     notice, this list of conditions and the following disclaimer.
    **   * Redistributions in binary form must reproduce the above copyright
    **     notice, this list of conditions and the following disclaimer in
    **     the documentation and/or other materials provided with the
    **     distribution.
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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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    **
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    ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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    #include <QtWidgets>

    #include "mdichild.h"

    MdiChild::MdiChild()
    {
        setAttribute(Qt::WA_DeleteOnClose);
        isUntitled = true;
    }

    void MdiChild::newFile()
    {
        static int sequenceNumber = 1;

        isUntitled = true;
        curFile = tr("document%1.txt").arg(sequenceNumber++);
        setWindowTitle(curFile + "[*]");

        connect(document(), SIGNAL(contentsChanged()),
                this, SLOT(documentWasModified()));
    }

    bool MdiChild::loadFile(const QString &fileName)
    {
        QFile file(fileName);
        if (!file.open(QFile::ReadOnly | QFile::Text)) {
            QMessageBox::warning(this, tr("MDI"),
                                 tr("Cannot read file %1:\n%2.")
                                 .arg(fileName)
                                 .arg(file.errorString()));
            return false;
        }

        QTextStream in(&file);
        QApplication::setOverrideCursor(Qt::WaitCursor);
        setPlainText(in.readAll());
        QApplication::restoreOverrideCursor();

        setCurrentFile(fileName);

        connect(document(), SIGNAL(contentsChanged()),
                this, SLOT(documentWasModified()));

        return true;
    }

    bool MdiChild::save()
    {
        if (isUntitled) {
            return saveAs();
        } else {
            return saveFile(curFile);
        }
    }

    bool MdiChild::saveAs()
    {
        QString fileName = QFileDialog::getSaveFileName(this, tr("Save As"),
                                                        curFile);
        if (fileName.isEmpty())
            return false;

        return saveFile(fileName);
    }

    bool MdiChild::saveFile(const QString &fileName)
    {
        QFile file(fileName);
        if (!file.open(QFile::WriteOnly | QFile::Text)) {
            QMessageBox::warning(this, tr("MDI"),
                                 tr("Cannot write file %1:\n%2.")
                                 .arg(fileName)
                                 .arg(file.errorString()));
            return false;
        }

        QTextStream out(&file);
        QApplication::setOverrideCursor(Qt::WaitCursor);
        out << toPlainText();
        QApplication::restoreOverrideCursor();

        setCurrentFile(fileName);
        return true;
    }

    QString MdiChild::userFriendlyCurrentFile()
    {
        return strippedName(curFile);
    }

    void MdiChild::closeEvent(QCloseEvent *event)
    {
        if (maybeSave()) {
            event->accept();
        } else {
            event->ignore();
        }
    }

    void MdiChild::documentWasModified()
    {
        setWindowModified(document()->isModified());
    }

    bool MdiChild::maybeSave()
    {
        if (document()->isModified()) {
            QMessageBox::StandardButton ret;
            ret = QMessageBox::warning(this, tr("MDI"),
                         tr("'%1' has been modified.\n"
                            "Do you want to save your changes?")
                         .arg(userFriendlyCurrentFile()),
                         QMessageBox::Save | QMessageBox::Discard
                         | QMessageBox::Cancel);
            if (ret == QMessageBox::Save)
                return save();
            else if (ret == QMessageBox::Cancel)
                return false;
        }
        return true;
    }

    void MdiChild::setCurrentFile(const QString &fileName)
    {
        curFile = QFileInfo(fileName).canonicalFilePath();
        isUntitled = false;
        document()->setModified(false);
        setWindowModified(false);
        setWindowTitle(userFriendlyCurrentFile() + "[*]");
    }

    QString MdiChild::strippedName(const QString &fullFileName)
    {
        return QFileInfo(fullFileName).fileName();
    }