svgview.cpp Example File

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 #include "svgview.h"

 #include <QSvgRenderer>

 #include <QWheelEvent>
 #include <QMouseEvent>
 #include <QGraphicsRectItem>
 #include <QGraphicsSvgItem>
 #include <QPaintEvent>
 #include <qmath.h>

 #ifndef QT_NO_OPENGL
 #include <QGLWidget>
 #endif

 SvgView::SvgView(QWidget *parent)
     : QGraphicsView(parent)
     , m_renderer(Native)
     , m_svgItem(nullptr)
     , m_backgroundItem(nullptr)
     , m_outlineItem(nullptr)
 {
     setScene(new QGraphicsScene(this));
     setTransformationAnchor(AnchorUnderMouse);
     setDragMode(ScrollHandDrag);
     setViewportUpdateMode(FullViewportUpdate);

     // Prepare background check-board pattern
     QPixmap tilePixmap(64, 64);
     tilePixmap.fill(Qt::white);
     QPainter tilePainter(&tilePixmap);
     QColor color(220, 220, 220);
     tilePainter.fillRect(0, 0, 32, 32, color);
     tilePainter.fillRect(32, 32, 32, 32, color);
     tilePainter.end();

     setBackgroundBrush(tilePixmap);
 }

 void SvgView::drawBackground(QPainter *p, const QRectF &)
 {
     p->save();
     p->resetTransform();
     p->drawTiledPixmap(viewport()->rect(), backgroundBrush().texture());
     p->restore();
 }

 QSize SvgView::svgSize() const
 {
     return m_svgItem ? m_svgItem->boundingRect().size().toSize() : QSize();
 }

 bool SvgView::openFile(const QString &fileName)
 {
     QGraphicsScene *s = scene();

     const bool drawBackground = (m_backgroundItem ? m_backgroundItem->isVisible() : false);
     const bool drawOutline = (m_outlineItem ? m_outlineItem->isVisible() : true);

     QScopedPointer<QGraphicsSvgItem> svgItem(new QGraphicsSvgItem(fileName));
     if (!svgItem->renderer()->isValid())
         return false;

     s->clear();
     resetTransform();

     m_svgItem = svgItem.take();
     m_svgItem->setFlags(QGraphicsItem::ItemClipsToShape);
     m_svgItem->setCacheMode(QGraphicsItem::NoCache);
     m_svgItem->setZValue(0);

     m_backgroundItem = new QGraphicsRectItem(m_svgItem->boundingRect());
     m_backgroundItem->setBrush(Qt::white);
     m_backgroundItem->setPen(Qt::NoPen);
     m_backgroundItem->setVisible(drawBackground);
     m_backgroundItem->setZValue(-1);

     m_outlineItem = new QGraphicsRectItem(m_svgItem->boundingRect());
     QPen outline(Qt::black, 2, Qt::DashLine);
     outline.setCosmetic(true);
     m_outlineItem->setPen(outline);
     m_outlineItem->setBrush(Qt::NoBrush);
     m_outlineItem->setVisible(drawOutline);
     m_outlineItem->setZValue(1);

     s->addItem(m_backgroundItem);
     s->addItem(m_svgItem);
     s->addItem(m_outlineItem);

     s->setSceneRect(m_outlineItem->boundingRect().adjusted(-10, -10, 10, 10));
     return true;
 }

 void SvgView::setRenderer(RendererType type)
 {
     m_renderer = type;

     if (m_renderer == OpenGL) {
 #ifndef QT_NO_OPENGL
         setViewport(new QGLWidget(QGLFormat(QGL::SampleBuffers)));
 #endif
     } else {
         setViewport(new QWidget);
     }
 }

 void SvgView::setHighQualityAntialiasing(bool highQualityAntialiasing)
 {
 #ifndef QT_NO_OPENGL
     setRenderHint(QPainter::HighQualityAntialiasing, highQualityAntialiasing);
 #else
     Q_UNUSED(highQualityAntialiasing);
 #endif
 }

 void SvgView::setViewBackground(bool enable)
 {
     if (!m_backgroundItem)
           return;

     m_backgroundItem->setVisible(enable);
 }

 void SvgView::setViewOutline(bool enable)
 {
     if (!m_outlineItem)
         return;

     m_outlineItem->setVisible(enable);
 }

 qreal SvgView::zoomFactor() const
 {
     return transform().m11();
 }

 void SvgView::zoomIn()
 {
     zoomBy(2);
 }

 void SvgView::zoomOut()
 {
     zoomBy(0.5);
 }

 void SvgView::resetZoom()
 {
     if (!qFuzzyCompare(zoomFactor(), qreal(1))) {
         resetTransform();
         emit zoomChanged();
     }
 }

 void SvgView::paintEvent(QPaintEvent *event)
 {
     if (m_renderer == Image) {
         if (m_image.size() != viewport()->size()) {
             m_image = QImage(viewport()->size(), QImage::Format_ARGB32_Premultiplied);
         }

         QPainter imagePainter(&m_image);
         QGraphicsView::render(&imagePainter);
         imagePainter.end();

         QPainter p(viewport());
         p.drawImage(0, 0, m_image);

     } else {
         QGraphicsView::paintEvent(event);
     }
 }

 void SvgView::wheelEvent(QWheelEvent *event)
 {
     zoomBy(qPow(1.2, event->delta() / 240.0));
 }

 void SvgView::zoomBy(qreal factor)
 {
     const qreal currentZoom = zoomFactor();
     if ((factor < 1 && currentZoom < 0.1) || (factor > 1 && currentZoom > 10))
         return;
     scale(factor, factor);
     emit zoomChanged();
 }

 QSvgRenderer *SvgView::renderer() const
 {
     if (m_svgItem)
         return m_svgItem->renderer();
     return nullptr;
 }