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;
  }