Qt 4.0: mainwindow.cpp Example File (widgets/scribble/mainwindow.cpp)

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# mainwindow.cpp Example File
widgets/scribble/mainwindow.cpp

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        ** This file is part of the documentation of the Qt Toolkit.
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    ** and appearing in the file LICENSE.GPL included in the packaging of
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        #include <QtGui>

        #include "mainwindow.h"
        #include "scribblearea.h"

        MainWindow::MainWindow()
        {
            scribbleArea = new ScribbleArea;
            setCentralWidget(scribbleArea);

            createActions();
            createMenus();

            setWindowTitle(tr("Scribble"));
            resize(500, 500);
        }

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

        void MainWindow::open()
        {
            if (maybeSave()) {
                QString fileName = QFileDialog::getOpenFileName(this,
                                           tr("Open File"), QDir::currentPath());
                if (!fileName.isEmpty())
                    scribbleArea->openImage(fileName);
            }
        }

        void MainWindow::save()
        {
            QAction *action = qobject_cast<QAction *>(sender());
            QByteArray fileFormat = action->data().toByteArray();
            saveFile(fileFormat);
        }

        void MainWindow::penColor()
        {
            QColor newColor = QColorDialog::getColor(scribbleArea->penColor());
            if (newColor.isValid())
                scribbleArea->setPenColor(newColor);
        }

        void MainWindow::penWidth()
        {
            bool ok;
            int newWidth = QInputDialog::getInteger(this, tr("Scribble"),
                                                    tr("Select pen width:"),
                                                    scribbleArea->penWidth(),
                                                    1, 50, 1, &ok);
            if (ok)
                scribbleArea->setPenWidth(newWidth);
        }

        void MainWindow::about()
        {
            QMessageBox::about(this, tr("About Scribble"),
                    tr("<p>The <b>Scribble</b> example shows how to use QMainWindow as the "
                       "base widget for an application, and how to reimplement some of "
                       "QWidget's event handlers to receive the events generated for "
                       "the application's widgets:</p><p> We reimplement the mouse event "
                       "handlers to facilitate drawing, the paint event handler to "
                       "update the application and the resize event handler to optimize "
                       "the application's appearance. In addition we reimplement the "
                       "close event handler to intercept the close events before "
                       "terminating the application.</p><p> The example also demonstrates "
                       "how to use QPainter to draw an image in real time, as well as "
                       "to repaint widgets.</p>"));
        }

        void MainWindow::createActions()
        {
            openAct = new QAction(tr("&Open..."), this);
            openAct->setShortcut(tr("Ctrl+O"));
            connect(openAct, SIGNAL(triggered()), this, SLOT(open()));

            foreach (QByteArray format, QImageWriter::supportedImageFormats()) {
                QString text = tr("%1...").arg(QString(format).toUpper());

                QAction *action = new QAction(text, this);
                action->setData(format);
                connect(action, SIGNAL(triggered()), this, SLOT(save()));
                saveAsActs.append(action);
            }

            exitAct = new QAction(tr("E&xit"), this);
            exitAct->setShortcut(tr("Ctrl+Q"));
            connect(exitAct, SIGNAL(triggered()), this, SLOT(close()));

            penColorAct = new QAction(tr("&Pen Color..."), this);
            connect(penColorAct, SIGNAL(triggered()), this, SLOT(penColor()));

            penWidthAct = new QAction(tr("Pen &Width..."), this);
            connect(penWidthAct, SIGNAL(triggered()), this, SLOT(penWidth()));

            clearScreenAct = new QAction(tr("&Clear Screen"), this);
            clearScreenAct->setShortcut(tr("Ctrl+L"));
            connect(clearScreenAct, SIGNAL(triggered()),
                    scribbleArea, SLOT(clearImage()));

            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);

            fileMenu = new QMenu(tr("&File"), this);
            fileMenu->addAction(openAct);
            fileMenu->addMenu(saveAsMenu);
            fileMenu->addSeparator();
            fileMenu->addAction(exitAct);

            optionMenu = new QMenu(tr("&Options"), this);
            optionMenu->addAction(penColorAct);
            optionMenu->addAction(penWidthAct);
            optionMenu->addSeparator();
            optionMenu->addAction(clearScreenAct);

            helpMenu = new QMenu(tr("&Help"), this);
            helpMenu->addAction(aboutAct);
            helpMenu->addAction(aboutQtAct);

            menuBar()->addMenu(fileMenu);
            menuBar()->addMenu(optionMenu);
            menuBar()->addMenu(helpMenu);
        }

        bool MainWindow::maybeSave()
        {
            if (scribbleArea->isModified()) {
                int ret = QMessageBox::warning(this, tr("Scribble"),
                                  tr("The image 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 saveFile("png");
                } else if (ret == QMessageBox::Cancel) {
                    return false;
                }
            }
            return true;
        }

        bool MainWindow::saveFile(const QByteArray &fileFormat)
        {
            QString initialPath = QDir::currentPath() + "/untitled." + fileFormat;

            QString fileName = QFileDialog::getSaveFileName(this, tr("Save As"),
                                       initialPath,
                                       tr("%1 Files (*.%2);;All Files (*)")
                                       .arg(QString(fileFormat.toUpper()))
                                       .arg(QString(fileFormat)));
            if (fileName.isEmpty()) {
                return false;
            } else {
                return scribbleArea->saveImage(fileName, fileFormat);
            }
        }