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mainwindow.cpp Example File
itemviews/pixelator/mainwindow.cpp

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 #include <QtGui>

 #include "imagemodel.h"
 #include "mainwindow.h"
 #include "pixeldelegate.h"

 MainWindow::MainWindow()
 {
     currentPath = QDir::homePath();
     model = new ImageModel(this);

     QWidget *centralWidget = new QWidget;

     view = new QTableView;
     view->setShowGrid(false);
     view->horizontalHeader()->hide();
     view->verticalHeader()->hide();
     view->horizontalHeader()->setMinimumSectionSize(1);
     view->verticalHeader()->setMinimumSectionSize(1);
     view->setModel(model);

     PixelDelegate *delegate = new PixelDelegate(this);
     view->setItemDelegate(delegate);

     QLabel *pixelSizeLabel = new QLabel(tr("Pixel size:"));
     QSpinBox *pixelSizeSpinBox = new QSpinBox;
     pixelSizeSpinBox->setMinimum(4);
     pixelSizeSpinBox->setMaximum(32);
     pixelSizeSpinBox->setValue(12);

     QMenu *fileMenu = new QMenu(tr("&File"), this);
     QAction *openAction = fileMenu->addAction(tr("&Open..."));
     openAction->setShortcuts(QKeySequence::Open);

     printAction = fileMenu->addAction(tr("&Print..."));
     printAction->setEnabled(false);
     printAction->setShortcut(QKeySequence::Print);

     QAction *quitAction = fileMenu->addAction(tr("E&xit"));
     quitAction->setShortcuts(QKeySequence::Quit);

     QMenu *helpMenu = new QMenu(tr("&Help"), this);
     QAction *aboutAction = helpMenu->addAction(tr("&About"));

     menuBar()->addMenu(fileMenu);
     menuBar()->addSeparator();
     menuBar()->addMenu(helpMenu);

     connect(openAction, SIGNAL(triggered()), this, SLOT(chooseImage()));
     connect(printAction, SIGNAL(triggered()), this, SLOT(printImage()));
     connect(quitAction, SIGNAL(triggered()), qApp, SLOT(quit()));
     connect(aboutAction, SIGNAL(triggered()), this, SLOT(showAboutBox()));
     connect(pixelSizeSpinBox, SIGNAL(valueChanged(int)),
             delegate, SLOT(setPixelSize(int)));
     connect(pixelSizeSpinBox, SIGNAL(valueChanged(int)),
             this, SLOT(updateView()));

     QHBoxLayout *controlsLayout = new QHBoxLayout;
     controlsLayout->addWidget(pixelSizeLabel);
     controlsLayout->addWidget(pixelSizeSpinBox);
     controlsLayout->addStretch(1);

     QVBoxLayout *mainLayout = new QVBoxLayout;
     mainLayout->addWidget(view);
     mainLayout->addLayout(controlsLayout);
     centralWidget->setLayout(mainLayout);

     setCentralWidget(centralWidget);

     setWindowTitle(tr("Pixelator"));
     resize(640, 480);
 }

 void MainWindow::chooseImage()
 {
     QString fileName = QFileDialog::getOpenFileName(this,
         tr("Choose an image"), currentPath, "*");

     if (!fileName.isEmpty())
         openImage(fileName);
 }

 void MainWindow::openImage(const QString &fileName)
 {
     QImage image;

     if (image.load(fileName)) {
         model->setImage(image);
         if (!fileName.startsWith(":/")) {
             currentPath = fileName;
             setWindowTitle(tr("%1 - Pixelator").arg(currentPath));
         }

         printAction->setEnabled(true);
         updateView();
     }
 }

 void MainWindow::printImage()
 {
 #ifndef QT_NO_PRINTER
     if (model->rowCount(QModelIndex())*model->columnCount(QModelIndex())
         > 90000) {
             QMessageBox::StandardButton answer;
             answer = QMessageBox::question(this, tr("Large Image Size"),
             tr("The printed image may be very large. Are you sure that "
                "you want to print it?"),
             QMessageBox::Yes | QMessageBox::No);
         if (answer == QMessageBox::No)
             return;
     }

     QPrinter printer(QPrinter::HighResolution);

     QPrintDialog *dlg = new QPrintDialog(&printer, this);
     dlg->setWindowTitle(tr("Print Image"));

     if (dlg->exec() != QDialog::Accepted)
         return;

     QPainter painter;
     painter.begin(&printer);

     int rows = model->rowCount(QModelIndex());
     int columns = model->columnCount(QModelIndex());
     int sourceWidth = (columns+1) * ItemSize;
     int sourceHeight = (rows+1) * ItemSize;

     painter.save();

     double xscale = printer.pageRect().width()/double(sourceWidth);
     double yscale = printer.pageRect().height()/double(sourceHeight);
     double scale = qMin(xscale, yscale);

     painter.translate(printer.paperRect().x() + printer.pageRect().width()/2,
                       printer.paperRect().y() + printer.pageRect().height()/2);
     painter.scale(scale, scale);
     painter.translate(-sourceWidth/2, -sourceHeight/2);

     QStyleOptionViewItem option;
     QModelIndex parent = QModelIndex();

     QProgressDialog progress(tr("Printing..."), tr("Cancel"), 0, rows, this);
     progress.setWindowModality(Qt::ApplicationModal);
     float y = ItemSize/2;

     for (int row = 0; row < rows; ++row) {
         progress.setValue(row);
         qApp->processEvents();
         if (progress.wasCanceled())
             break;

         float x = ItemSize/2;

         for (int column = 0; column < columns; ++column) {
             option.rect = QRect(int(x), int(y), ItemSize, ItemSize);
             view->itemDelegate()->paint(&painter, option,
                                         model->index(row, column, parent));
             x = x + ItemSize;
         }
         y = y + ItemSize;
     }
     progress.setValue(rows);

     painter.restore();
     painter.end();

     if (progress.wasCanceled()) {
         QMessageBox::information(this, tr("Printing canceled"),
             tr("The printing process was canceled."), QMessageBox::Cancel);
     }
 #else
     QMessageBox::information(this, tr("Printing canceled"),
         tr("Printing is not supported on this Qt build"), QMessageBox::Cancel);
 #endif
 }

 void MainWindow::showAboutBox()
 {
     QMessageBox::about(this, tr("About the Pixelator example"),
         tr("This example demonstrates how a standard view and a custom\n"
            "delegate can be used to produce a specialized representation\n"
            "of data in a simple custom model."));
 }

 void MainWindow::updateView()
 {
     view->resizeColumnsToContents();
     view->resizeRowsToContents();
 }


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Qt 4.6.3