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# mainwindow.cpp Example File
multitouch/fingerpaint/mainwindow.cpp

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     #include <QtGui>

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

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

         createActions();
         createMenus();

         setWindowTitle(tr("Finger Paint"));
         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::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);
         }

         printAct = new QAction(tr("&Print..."), this);
         connect(printAct, SIGNAL(triggered()), scribbleArea, SLOT(print()));

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

         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->addAction(printAct);
         fileMenu->addSeparator();
         fileMenu->addAction(exitAct);

         optionMenu = new QMenu(tr("&Options"), this);
         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()) {
            QMessageBox::StandardButton ret;
            ret = QMessageBox::warning(this, tr("Scribble"),
                               tr("The image has been modified.\n"
                                  "Do you want to save your changes?"),
                               QMessageBox::Save | QMessageBox::Discard
                               | QMessageBox::Cancel);
             if (ret == QMessageBox::Save) {
                 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);
         }
     }