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

# mainwindow.cpp Example File

mainwindows/mdi/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:
    **
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    ** modification, are permitted provided that the following conditions are
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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 "mdichild.h"

    MainWindow::MainWindow()
    {
        mdiArea = new QMdiArea;
        mdiArea->setHorizontalScrollBarPolicy(Qt::ScrollBarAsNeeded);
        mdiArea->setVerticalScrollBarPolicy(Qt::ScrollBarAsNeeded);
        setCentralWidget(mdiArea);
        connect(mdiArea, SIGNAL(subWindowActivated(QMdiSubWindow*)),
                this, SLOT(updateMenus()));
        windowMapper = new QSignalMapper(this);
        connect(windowMapper, SIGNAL(mapped(QWidget*)),
                this, SLOT(setActiveSubWindow(QWidget*)));

        createActions();
        createMenus();
        createToolBars();
        createStatusBar();
        updateMenus();

        readSettings();

        setWindowTitle(tr("MDI"));
        setUnifiedTitleAndToolBarOnMac(true);
    }

    void MainWindow::closeEvent(QCloseEvent *event)
    {
        mdiArea->closeAllSubWindows();
        if (mdiArea->currentSubWindow()) {
            event->ignore();
        } else {
            writeSettings();
            event->accept();
        }
    }

    void MainWindow::newFile()
    {
        MdiChild *child = createMdiChild();
        child->newFile();
        child->show();
    }

    void MainWindow::open()
    {
        QString fileName = QFileDialog::getOpenFileName(this);
        if (!fileName.isEmpty()) {
            QMdiSubWindow *existing = findMdiChild(fileName);
            if (existing) {
                mdiArea->setActiveSubWindow(existing);
                return;
            }

            if (openFile(fileName))
                statusBar()->showMessage(tr("File loaded"), 2000);
        }
    }

    bool MainWindow::openFile(const QString &fileName)
    {
        MdiChild *child = createMdiChild();
        const bool succeeded = child->loadFile(fileName);
        if (succeeded)
            child->show();
        else
            child->close();
        return succeeded;
    }

    void MainWindow::save()
    {
        if (activeMdiChild() && activeMdiChild()->save())
            statusBar()->showMessage(tr("File saved"), 2000);
    }

    void MainWindow::saveAs()
    {
        if (activeMdiChild() && activeMdiChild()->saveAs())
            statusBar()->showMessage(tr("File saved"), 2000);
    }

    #ifndef QT_NO_CLIPBOARD
    void MainWindow::cut()
    {
        if (activeMdiChild())
            activeMdiChild()->cut();
    }

    void MainWindow::copy()
    {
        if (activeMdiChild())
            activeMdiChild()->copy();
    }

    void MainWindow::paste()
    {
        if (activeMdiChild())
            activeMdiChild()->paste();
    }
    #endif

    void MainWindow::about()
    {
       QMessageBox::about(this, tr("About MDI"),
                tr("The <b>MDI</b> example demonstrates how to write multiple "
                   "document interface applications using Qt."));
    }

    void MainWindow::updateMenus()
    {
        bool hasMdiChild = (activeMdiChild() != 0);
        saveAct->setEnabled(hasMdiChild);
        saveAsAct->setEnabled(hasMdiChild);
    #ifndef QT_NO_CLIPBOARD
        pasteAct->setEnabled(hasMdiChild);
    #endif
        closeAct->setEnabled(hasMdiChild);
        closeAllAct->setEnabled(hasMdiChild);
        tileAct->setEnabled(hasMdiChild);
        cascadeAct->setEnabled(hasMdiChild);
        nextAct->setEnabled(hasMdiChild);
        previousAct->setEnabled(hasMdiChild);
        separatorAct->setVisible(hasMdiChild);

    #ifndef QT_NO_CLIPBOARD
        bool hasSelection = (activeMdiChild() &&
                             activeMdiChild()->textCursor().hasSelection());
        cutAct->setEnabled(hasSelection);
        copyAct->setEnabled(hasSelection);
    #endif
    }

    void MainWindow::updateWindowMenu()
    {
        windowMenu->clear();
        windowMenu->addAction(closeAct);
        windowMenu->addAction(closeAllAct);
        windowMenu->addSeparator();
        windowMenu->addAction(tileAct);
        windowMenu->addAction(cascadeAct);
        windowMenu->addSeparator();
        windowMenu->addAction(nextAct);
        windowMenu->addAction(previousAct);
        windowMenu->addAction(separatorAct);

        QList<QMdiSubWindow *> windows = mdiArea->subWindowList();
        separatorAct->setVisible(!windows.isEmpty());

        for (int i = 0; i < windows.size(); ++i) {
            MdiChild *child = qobject_cast<MdiChild *>(windows.at(i)->widget());

            QString text;
            if (i < 9) {
                text = tr("&%1 %2").arg(i + 1)
                                   .arg(child->userFriendlyCurrentFile());
            } else {
                text = tr("%1 %2").arg(i + 1)
                                  .arg(child->userFriendlyCurrentFile());
            }
            QAction *action  = windowMenu->addAction(text);
            action->setCheckable(true);
            action ->setChecked(child == activeMdiChild());
            connect(action, SIGNAL(triggered()), windowMapper, SLOT(map()));
            windowMapper->setMapping(action, windows.at(i));
        }
    }

    MdiChild *MainWindow::createMdiChild()
    {
        MdiChild *child = new MdiChild;
        mdiArea->addSubWindow(child);

    #ifndef QT_NO_CLIPBOARD
        connect(child, SIGNAL(copyAvailable(bool)),
                cutAct, SLOT(setEnabled(bool)));
        connect(child, SIGNAL(copyAvailable(bool)),
                copyAct, SLOT(setEnabled(bool)));
    #endif

        return child;
    }

    void MainWindow::createActions()
    {
        newAct = new QAction(QIcon(":/images/new.png"), tr("&New"), this);
        newAct->setShortcuts(QKeySequence::New);
        newAct->setStatusTip(tr("Create a new file"));
        connect(newAct, SIGNAL(triggered()), this, SLOT(newFile()));

        openAct = new QAction(QIcon(":/images/open.png"), tr("&Open..."), this);
        openAct->setShortcuts(QKeySequence::Open);
        openAct->setStatusTip(tr("Open an existing file"));
        connect(openAct, SIGNAL(triggered()), this, SLOT(open()));

        saveAct = new QAction(QIcon(":/images/save.png"), tr("&Save"), this);
        saveAct->setShortcuts(QKeySequence::Save);
        saveAct->setStatusTip(tr("Save the document to disk"));
        connect(saveAct, SIGNAL(triggered()), this, SLOT(save()));

        saveAsAct = new QAction(tr("Save &As..."), this);
        saveAsAct->setShortcuts(QKeySequence::SaveAs);
        saveAsAct->setStatusTip(tr("Save the document under a new name"));
        connect(saveAsAct, SIGNAL(triggered()), this, SLOT(saveAs()));

        exitAct = new QAction(tr("E&xit"), this);
        exitAct->setShortcuts(QKeySequence::Quit);
        exitAct->setStatusTip(tr("Exit the application"));
        connect(exitAct, SIGNAL(triggered()), qApp, SLOT(closeAllWindows()));

    #ifndef QT_NO_CLIPBOARD
        cutAct = new QAction(QIcon(":/images/cut.png"), tr("Cu&t"), this);
        cutAct->setShortcuts(QKeySequence::Cut);
        cutAct->setStatusTip(tr("Cut the current selection's contents to the "
                                "clipboard"));
        connect(cutAct, SIGNAL(triggered()), this, SLOT(cut()));

        copyAct = new QAction(QIcon(":/images/copy.png"), tr("&Copy"), this);
        copyAct->setShortcuts(QKeySequence::Copy);
        copyAct->setStatusTip(tr("Copy the current selection's contents to the "
                                 "clipboard"));
        connect(copyAct, SIGNAL(triggered()), this, SLOT(copy()));

        pasteAct = new QAction(QIcon(":/images/paste.png"), tr("&Paste"), this);
        pasteAct->setShortcuts(QKeySequence::Paste);
        pasteAct->setStatusTip(tr("Paste the clipboard's contents into the current "
                                  "selection"));
        connect(pasteAct, SIGNAL(triggered()), this, SLOT(paste()));
    #endif

        closeAct = new QAction(tr("Cl&ose"), this);
        closeAct->setStatusTip(tr("Close the active window"));
        connect(closeAct, SIGNAL(triggered()),
                mdiArea, SLOT(closeActiveSubWindow()));

        closeAllAct = new QAction(tr("Close &All"), this);
        closeAllAct->setStatusTip(tr("Close all the windows"));
        connect(closeAllAct, SIGNAL(triggered()),
                mdiArea, SLOT(closeAllSubWindows()));

        tileAct = new QAction(tr("&Tile"), this);
        tileAct->setStatusTip(tr("Tile the windows"));
        connect(tileAct, SIGNAL(triggered()), mdiArea, SLOT(tileSubWindows()));

        cascadeAct = new QAction(tr("&Cascade"), this);
        cascadeAct->setStatusTip(tr("Cascade the windows"));
        connect(cascadeAct, SIGNAL(triggered()), mdiArea, SLOT(cascadeSubWindows()));

        nextAct = new QAction(tr("Ne&xt"), this);
        nextAct->setShortcuts(QKeySequence::NextChild);
        nextAct->setStatusTip(tr("Move the focus to the next window"));
        connect(nextAct, SIGNAL(triggered()),
                mdiArea, SLOT(activateNextSubWindow()));

        previousAct = new QAction(tr("Pre&vious"), this);
        previousAct->setShortcuts(QKeySequence::PreviousChild);
        previousAct->setStatusTip(tr("Move the focus to the previous "
                                     "window"));
        connect(previousAct, SIGNAL(triggered()),
                mdiArea, SLOT(activatePreviousSubWindow()));

        separatorAct = new QAction(this);
        separatorAct->setSeparator(true);

        aboutAct = new QAction(tr("&About"), this);
        aboutAct->setStatusTip(tr("Show the application's About box"));
        connect(aboutAct, SIGNAL(triggered()), this, SLOT(about()));

        aboutQtAct = new QAction(tr("About &Qt"), this);
        aboutQtAct->setStatusTip(tr("Show the Qt library's About box"));
        connect(aboutQtAct, SIGNAL(triggered()), qApp, SLOT(aboutQt()));
    }

    void MainWindow::createMenus()
    {
        fileMenu = menuBar()->addMenu(tr("&File"));
        fileMenu->addAction(newAct);
        fileMenu->addAction(openAct);
        fileMenu->addAction(saveAct);
        fileMenu->addAction(saveAsAct);
        fileMenu->addSeparator();
        QAction *action = fileMenu->addAction(tr("Switch layout direction"));
        connect(action, SIGNAL(triggered()), this, SLOT(switchLayoutDirection()));
        fileMenu->addAction(exitAct);

        editMenu = menuBar()->addMenu(tr("&Edit"));
    #ifndef QT_NO_CLIPBOARD
        editMenu->addAction(cutAct);
        editMenu->addAction(copyAct);
        editMenu->addAction(pasteAct);
    #endif

        windowMenu = menuBar()->addMenu(tr("&Window"));
        updateWindowMenu();
        connect(windowMenu, SIGNAL(aboutToShow()), this, SLOT(updateWindowMenu()));

        menuBar()->addSeparator();

        helpMenu = menuBar()->addMenu(tr("&Help"));
        helpMenu->addAction(aboutAct);
        helpMenu->addAction(aboutQtAct);
    }

    void MainWindow::createToolBars()
    {
        fileToolBar = addToolBar(tr("File"));
        fileToolBar->addAction(newAct);
        fileToolBar->addAction(openAct);
        fileToolBar->addAction(saveAct);

    #ifndef QT_NO_CLIPBOARD
        editToolBar = addToolBar(tr("Edit"));
        editToolBar->addAction(cutAct);
        editToolBar->addAction(copyAct);
        editToolBar->addAction(pasteAct);
    #endif
    }

    void MainWindow::createStatusBar()
    {
        statusBar()->showMessage(tr("Ready"));
    }

    void MainWindow::readSettings()
    {
        QSettings settings("QtProject", "MDI Example");
        QPoint pos = settings.value("pos", QPoint(200, 200)).toPoint();
        QSize size = settings.value("size", QSize(400, 400)).toSize();
        move(pos);
        resize(size);
    }

    void MainWindow::writeSettings()
    {
        QSettings settings("QtProject", "MDI Example");
        settings.setValue("pos", pos());
        settings.setValue("size", size());
    }

    MdiChild *MainWindow::activeMdiChild()
    {
        if (QMdiSubWindow *activeSubWindow = mdiArea->activeSubWindow())
            return qobject_cast<MdiChild *>(activeSubWindow->widget());
        return 0;
    }

    QMdiSubWindow *MainWindow::findMdiChild(const QString &fileName)
    {
        QString canonicalFilePath = QFileInfo(fileName).canonicalFilePath();

        foreach (QMdiSubWindow *window, mdiArea->subWindowList()) {
            MdiChild *mdiChild = qobject_cast<MdiChild *>(window->widget());
            if (mdiChild->currentFile() == canonicalFilePath)
                return window;
        }
        return 0;
    }

    void MainWindow::switchLayoutDirection()
    {
        if (layoutDirection() == Qt::LeftToRight)
            qApp->setLayoutDirection(Qt::RightToLeft);
        else
            qApp->setLayoutDirection(Qt::LeftToRight);
    }

    void MainWindow::setActiveSubWindow(QWidget *window)
    {
        if (!window)
            return;
        mdiArea->setActiveSubWindow(qobject_cast<QMdiSubWindow *>(window));
    }