Qt Reference Documentation

# sourcewidget.cpp Example File

draganddrop/delayedencoding/sourcewidget.cpp

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     #include <QtGui>
     #include <QtSvg>
     #include "mimedata.h"
     #include "sourcewidget.h"

     SourceWidget::SourceWidget(QWidget *parent)
         : QWidget(parent)
     {
         QFile imageFile(":/images/example.svg");
         imageFile.open(QIODevice::ReadOnly);
         imageData = imageFile.readAll();
         imageFile.close();

         QScrollArea *imageArea = new QScrollArea;
         imageLabel = new QSvgWidget;
         imageLabel->renderer()->load(imageData);
         imageArea->setWidget(imageLabel);
         //imageLabel->setMinimumSize(imageLabel->renderer()->viewBox().size());

         QLabel *instructTopLabel = new QLabel(tr("This is an SVG drawing:"));
         QLabel *instructBottomLabel = new QLabel(
             tr("Drag the icon to copy the drawing as a PNG file:"));
         QPushButton *dragIcon = new QPushButton(tr("Export"));
         dragIcon->setIcon(QIcon(":/images/drag.png"));

         connect(dragIcon, SIGNAL(pressed()), this, SLOT(startDrag()));

         QGridLayout *layout = new QGridLayout;
         layout->addWidget(instructTopLabel, 0, 0, 1, 2);
         layout->addWidget(imageArea, 1, 0, 2, 2);
         layout->addWidget(instructBottomLabel, 3, 0);
         layout->addWidget(dragIcon, 3, 1);
         setLayout(layout);
         setWindowTitle(tr("Delayed Encoding"));
     }

     void SourceWidget::createData(const QString &mimeType)
     {
         if (mimeType != "image/png")
             return;

         QImage image(imageLabel->size(), QImage::Format_RGB32);
         QPainter painter;
         painter.begin(&image);
         imageLabel->renderer()->render(&painter);
         painter.end();

         QByteArray data;
         QBuffer buffer(&data);
         buffer.open(QIODevice::WriteOnly);
         image.save(&buffer, "PNG");
         buffer.close();

         mimeData->setData("image/png", data);
     }

     void SourceWidget::startDrag()
     {
         mimeData = new MimeData;

         connect(mimeData, SIGNAL(dataRequested(QString)),
                 this, SLOT(createData(QString)), Qt::DirectConnection);

         QDrag *drag = new QDrag(this);
         drag->setMimeData(mimeData);
         drag->setPixmap(QPixmap(":/images/drag.png"));

         drag->exec(Qt::CopyAction);
     }