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# mainwindow.cpp Example File
mainwindows/application/mainwindow.cpp

        #include <QtGui>

        #include "mainwindow.h"

        MainWindow::MainWindow()
        {
            textEdit = new QTextEdit(this);
            setCentralWidget(textEdit);

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

            readSettings();

            connect(textEdit->document(), SIGNAL(contentsChanged()),
                    this, SLOT(documentWasModified()));

            setWindowTitle(tr("Application"));
        }

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

        void MainWindow::newFile()
        {
            if (maybeSave()) {
                textEdit->clear();
                setCurrentFile("");
            }
        }

        void MainWindow::open()
        {
            if (maybeSave()) {
                QString fileName = QFileDialog::getOpenFileName(this);
                if (!fileName.isEmpty())
                    loadFile(fileName);
            }
        }

        bool MainWindow::save()
        {
            if (curFile.isEmpty()) {
                return saveAs();
            } else {
                saveFile(curFile);
                return true;
            }
        }

        bool MainWindow::saveAs()
        {
            QString fileName = QFileDialog::getSaveFileName(this);
            if (fileName.isEmpty())
                return false;

            if (QFile::exists(fileName)) {
                int ret = QMessageBox::warning(this, tr("Application"),
                             tr("File %1 already exists.\n"
                                "Do you want to overwrite it?")
                             .arg(QDir::convertSeparators(fileName)),
                             QMessageBox::Yes | QMessageBox::Default,
                             QMessageBox::No | QMessageBox::Escape);
                if (ret == QMessageBox::No)
                    return true;
            }
            saveFile(fileName);
            return true;
        }

        void MainWindow::about()
        {
           QMessageBox::about(this, tr("About Application"),
                    tr("The <b>Application</b> example demonstrates how to "
                       "write modern GUI applications using Qt, with a menu bar, "
                       "toolbars, and a status bar."));
        }

        void MainWindow::documentWasModified()
        {
            modLabel->setText(tr("MOD"));
        }

        void MainWindow::createActions()
        {
            newAct = new QAction(QIcon(":/images/new.png"), tr("&New"), this);
            newAct->setShortcut(tr("Ctrl+N"));
            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->setShortcut(tr("Ctrl+O"));
            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->setShortcut(tr("Ctrl+S"));
            saveAct->setStatusTip(tr("Save the document to disk"));
            connect(saveAct, SIGNAL(triggered()), this, SLOT(save()));

            saveAsAct = new QAction(tr("Save &As..."), this);
            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->setShortcut(tr("Ctrl+Q"));
            exitAct->setStatusTip(tr("Exit the application"));
            connect(exitAct, SIGNAL(triggered()), this, SLOT(close()));

            cutAct = new QAction(QIcon(":/images/cut.png"), tr("Cu&t"), this);
            cutAct->setShortcut(tr("Ctrl+X"));
            cutAct->setStatusTip(tr("Cut the current selection's contents to the "
                                    "clipboard"));
            connect(cutAct, SIGNAL(triggered()), textEdit, SLOT(cut()));

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

            pasteAct = new QAction(QIcon(":/images/paste.png"), tr("&Paste"), this);
            pasteAct->setShortcut(tr("Ctrl+V"));
            pasteAct->setStatusTip(tr("Paste the clipboard's contents into the current "
                                      "selection"));
            connect(pasteAct, SIGNAL(triggered()), textEdit, SLOT(paste()));

            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();
            fileMenu->addAction(exitAct);

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

            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);

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

        void MainWindow::createStatusBar()
        {
            modLabel = new QLabel(tr(" MOD "));
            modLabel->setAlignment(Qt::AlignHCenter);
            modLabel->setMinimumSize(modLabel->sizeHint());
            modLabel->clear();

            statusBar()->addWidget(modLabel, 0, true);
        }

        void MainWindow::readSettings()
        {
            QSettings settings("doc.trolltech.com", "Application");
            QPoint pos = settings.value("pos", QPoint(200, 200)).toPoint();
            QSize size = settings.value("size", QSize(400, 400)).toSize();
            resize(size);
            move(pos);
        }

        void MainWindow::writeSettings()
        {
            QSettings settings("doc.trolltech.com", "Application");
            settings.setValue("pos", pos());
            settings.setValue("size", size());
        }

        bool MainWindow::maybeSave()
        {
            if (textEdit->document()->isModified()) {
                int ret = QMessageBox::warning(this, tr("Application"),
                             tr("The document has been modified.\n"
                                "Do you want to save your changes?"),
                             QMessageBox::Yes | QMessageBox::Default,
                             QMessageBox::No,
                             QMessageBox::Cancel | QMessageBox::Escape);
                if (ret == QMessageBox::Yes)
                    return save();
                else if (ret == QMessageBox::Cancel)
                    return false;
            }
            return true;
        }

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

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

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

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

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

            setCurrentFile(fileName);
            statusBar()->showMessage(tr("File saved"), 2000);
        }

        void MainWindow::setCurrentFile(const QString &fileName)
        {
            curFile = fileName;
            modLabel->clear();
            textEdit->document()->setModified(false);

            if (curFile.isEmpty())
                setWindowTitle(tr("Application"));
            else
                setWindowTitle(tr("%1 - %2").arg(strippedName(curFile))
                                            .arg(tr("Application")));
        }

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