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

# mainwindow.cpp Example File

itemviews/pixelator/mainwindow.cpp

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    ** This file is part of the examples of the Qt Toolkit.
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    #include "imagemodel.h"
    #include "mainwindow.h"
    #include "pixeldelegate.h"

    #include <QtWidgets>
    #ifndef QT_NO_PRINTER
    #include <QPrinter>
    #include <QPrintDialog>
    #endif

    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()
    {
    #if !defined(QT_NO_PRINTER) && !defined(QT_NO_PRINTDIALOG)
        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(&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();
    }