context2d.cpp Example File

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  ** Copyright (C) 2015 The Qt Company Ltd.
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  ** This file is part of the examples of the Qt Toolkit.
  **
  ** $QT_BEGIN_LICENSE:BSD$
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  #include "context2d.h"

  #include <QVariant>

  #include <math.h>
  static const double Q_PI   = 3.14159265358979323846;   // pi

  #define DEGREES(t) ((t) * 180.0 / Q_PI)

  #define qClamp(val, min, max) qMin(qMax(val, min), max)
  static QList<qreal> parseNumbersList(QString::const_iterator &itr)
  {
      QList<qreal> points;
      QString temp;
      while ((*itr).isSpace())
          ++itr;
      while ((*itr).isNumber() ||
             (*itr) == '-' || (*itr) == '+' || (*itr) == '.') {
          temp = QString();

          if ((*itr) == '-')
              temp += *itr++;
          else if ((*itr) == '+')
              temp += *itr++;
          while ((*itr).isDigit())
              temp += *itr++;
          if ((*itr) == '.')
              temp += *itr++;
          while ((*itr).isDigit())
              temp += *itr++;
          while ((*itr).isSpace())
              ++itr;
          if ((*itr) == ',')
              ++itr;
          points.append(temp.toDouble());
          //eat spaces
          while ((*itr).isSpace())
              ++itr;
      }

      return points;
  }

  QColor colorFromString(const QString &name)
  {
      QString::const_iterator itr = name.constBegin();
      QList<qreal> compo;
      if (name.startsWith("rgba(")) {
          ++itr; ++itr; ++itr; ++itr; ++itr;
          compo = parseNumbersList(itr);
          if (compo.size() != 4) {
              return QColor();
          }
          //alpha seems to be always between 0-1
          compo[3] *= 255;
          return QColor((int)compo[0], (int)compo[1],
                        (int)compo[2], (int)compo[3]);
      } else if (name.startsWith("rgb(")) {
          ++itr; ++itr; ++itr; ++itr;
          compo = parseNumbersList(itr);
          if (compo.size() != 3) {
              return QColor();
          }
          return QColor((int)qClamp(compo[0], qreal(0), qreal(255)),
                        (int)qClamp(compo[1], qreal(0), qreal(255)),
                        (int)qClamp(compo[2], qreal(0), qreal(255)));
      } else {
          //QRgb color;
          //CSSParser::parseColor(name, color);
          return QColor(name);
      }
  }

  static QPainter::CompositionMode compositeOperatorFromString(const QString &compositeOperator)
  {
      if ( compositeOperator == "source-over" ) {
          return QPainter::CompositionMode_SourceOver;
      } else if ( compositeOperator == "source-out" ) {
          return QPainter::CompositionMode_SourceOut;
      } else if ( compositeOperator == "source-in" ) {
          return QPainter::CompositionMode_SourceIn;
      } else if ( compositeOperator == "source-atop" ) {
          return QPainter::CompositionMode_SourceAtop;
      } else if ( compositeOperator == "destination-atop" ) {
          return QPainter::CompositionMode_DestinationAtop;
      } else if ( compositeOperator == "destination-in" ) {
          return QPainter::CompositionMode_DestinationIn;
      } else if ( compositeOperator == "destination-out" ) {
          return QPainter::CompositionMode_DestinationOut;
      } else if ( compositeOperator == "destination-over" ) {
          return QPainter::CompositionMode_DestinationOver;
      } else if ( compositeOperator == "darker" ) {
          return QPainter::CompositionMode_SourceOver;
      } else if ( compositeOperator == "lighter" ) {
          return QPainter::CompositionMode_SourceOver;
      } else if ( compositeOperator == "copy" ) {
          return QPainter::CompositionMode_Source;
      } else if ( compositeOperator == "xor" ) {
          return QPainter::CompositionMode_Xor;
      }

      return QPainter::CompositionMode_SourceOver;
  }

  static QString compositeOperatorToString(QPainter::CompositionMode op)
  {
      switch (op) {
      case QPainter::CompositionMode_SourceOver:
          return "source-over";
      case QPainter::CompositionMode_DestinationOver:
          return "destination-over";
      case QPainter::CompositionMode_Clear:
          return "clear";
      case QPainter::CompositionMode_Source:
          return "source";
      case QPainter::CompositionMode_Destination:
          return "destination";
      case QPainter::CompositionMode_SourceIn:
          return "source-in";
      case QPainter::CompositionMode_DestinationIn:
          return "destination-in";
      case QPainter::CompositionMode_SourceOut:
          return "source-out";
      case QPainter::CompositionMode_DestinationOut:
          return "destination-out";
      case QPainter::CompositionMode_SourceAtop:
          return "source-atop";
      case QPainter::CompositionMode_DestinationAtop:
          return "destination-atop";
      case QPainter::CompositionMode_Xor:
          return "xor";
      case QPainter::CompositionMode_Plus:
          return "plus";
      case QPainter::CompositionMode_Multiply:
          return "multiply";
      case QPainter::CompositionMode_Screen:
          return "screen";
      case QPainter::CompositionMode_Overlay:
          return "overlay";
      case QPainter::CompositionMode_Darken:
          return "darken";
      case QPainter::CompositionMode_Lighten:
          return "lighten";
      case QPainter::CompositionMode_ColorDodge:
          return "color-dodge";
      case QPainter::CompositionMode_ColorBurn:
          return "color-burn";
      case QPainter::CompositionMode_HardLight:
          return "hard-light";
      case QPainter::CompositionMode_SoftLight:
          return "soft-light";
      case QPainter::CompositionMode_Difference:
          return "difference";
      case QPainter::CompositionMode_Exclusion:
          return "exclusion";
      default:
          break;
      }
      return QString();
  }

  void Context2D::save()
  {
      m_stateStack.push(m_state);
  }

  void Context2D::restore()
  {
      if (!m_stateStack.isEmpty()) {
          m_state = m_stateStack.pop();
          m_state.flags = AllIsFullOfDirt;
      }
  }

  void Context2D::scale(qreal x, qreal y)
  {
      m_state.matrix.scale(x, y);
      m_state.flags |= DirtyTransformationMatrix;
  }

  void Context2D::rotate(qreal angle)
  {
      m_state.matrix.rotate(DEGREES(angle));
      m_state.flags |= DirtyTransformationMatrix;
  }

  void Context2D::translate(qreal x, qreal y)
  {
      m_state.matrix.translate(x, y);
      m_state.flags |= DirtyTransformationMatrix;
  }

  void Context2D::transform(qreal m11, qreal m12, qreal m21, qreal m22,
                            qreal dx, qreal dy)
  {
      QMatrix mat(m11, m12,
                  m21, m22,
                  dx, dy);
      m_state.matrix *= mat;
      m_state.flags |= DirtyTransformationMatrix;
  }

  void Context2D::setTransform(qreal m11, qreal m12, qreal m21, qreal m22,
                               qreal dx, qreal dy)
  {
      QMatrix mat(m11, m12,
                  m21, m22,
                  dx, dy);
      m_state.matrix = mat;
      m_state.flags |= DirtyTransformationMatrix;
  }

  QString Context2D::globalCompositeOperation() const
  {
      return compositeOperatorToString(m_state.globalCompositeOperation);
  }

  void Context2D::setGlobalCompositeOperation(const QString &op)
  {
      QPainter::CompositionMode mode =
          compositeOperatorFromString(op);
      m_state.globalCompositeOperation = mode;
      m_state.flags |= DirtyGlobalCompositeOperation;
  }

  QVariant Context2D::strokeStyle() const
  {
      return m_state.strokeStyle;
  }

  void Context2D::setStrokeStyle(const QVariant &style)
  {
      if (style.canConvert<CanvasGradient>()) {
          CanvasGradient cg = qvariant_cast<CanvasGradient>(style);
          m_state.strokeStyle = cg.value;
      } else {
          QColor color = colorFromString(style.toString());
          m_state.strokeStyle = color;
      }
      m_state.flags |= DirtyStrokeStyle;
  }

  QVariant Context2D::fillStyle() const
  {
      return m_state.fillStyle;
  }

  void Context2D::setFillStyle(const QVariant &style)
  {
      if (style.canConvert<CanvasGradient>()) {
          CanvasGradient cg = qvariant_cast<CanvasGradient>(style);
          m_state.fillStyle = cg.value;
      } else {
          QColor color = colorFromString(style.toString());
          m_state.fillStyle = color;
      }
      m_state.flags |= DirtyFillStyle;
  }

  qreal Context2D::globalAlpha() const
  {
      return m_state.globalAlpha;
  }

  void Context2D::setGlobalAlpha(qreal alpha)
  {
      m_state.globalAlpha = alpha;
      m_state.flags |= DirtyGlobalAlpha;
  }

  CanvasGradient Context2D::createLinearGradient(qreal x0, qreal y0,
                                                 qreal x1, qreal y1)
  {
      QLinearGradient g(x0, y0, x1, y1);
      return CanvasGradient(g);
  }

  CanvasGradient Context2D::createRadialGradient(qreal x0, qreal y0,
                                                 qreal r0, qreal x1,
                                                 qreal y1, qreal r1)
  {
      QRadialGradient g(QPointF(x1, y1), r0+r1, QPointF(x0, y0));
      return CanvasGradient(g);
  }

  qreal Context2D::lineWidth() const
  {
      return m_state.lineWidth;
  }

  void Context2D::setLineWidth(qreal w)
  {
      m_state.lineWidth = w;
      m_state.flags |= DirtyLineWidth;
  }

  QString Context2D::lineCap() const
  {
      switch (m_state.lineCap) {
      case Qt::FlatCap:
          return "butt";
      case Qt::SquareCap:
          return "square";
      case Qt::RoundCap:
          return "round";
      default: ;
      }
      return QString();
  }

  void Context2D::setLineCap(const QString &capString)
  {
      Qt::PenCapStyle style;
      if (capString == "round")
          style = Qt::RoundCap;
      else if (capString == "square")
          style = Qt::SquareCap;
      else //if (capString == "butt")
          style = Qt::FlatCap;
      m_state.lineCap = style;
      m_state.flags |= DirtyLineCap;
  }

  QString Context2D::lineJoin() const
  {
      switch (m_state.lineJoin) {
      case Qt::RoundJoin:
          return "round";
      case Qt::BevelJoin:
          return "bevel";
      case Qt::MiterJoin:
          return "miter";
      default: ;
      }
      return QString();
  }

  void Context2D::setLineJoin(const QString &joinString)
  {
      Qt::PenJoinStyle style;
      if (joinString == "round")
          style = Qt::RoundJoin;
      else if (joinString == "bevel")
          style = Qt::BevelJoin;
      else //if (joinString == "miter")
          style = Qt::MiterJoin;
      m_state.lineJoin = style;
      m_state.flags |= DirtyLineJoin;
  }

  qreal Context2D::miterLimit() const
  {
      return m_state.miterLimit;
  }

  void Context2D::setMiterLimit(qreal m)
  {
      m_state.miterLimit = m;
      m_state.flags |= DirtyMiterLimit;
  }

  void Context2D::setShadowOffsetX(qreal x)
  {
      m_state.shadowOffsetX = x;
      m_state.flags |= DirtyShadowOffsetX;
  }

  void Context2D::setShadowOffsetY(qreal y)
  {
      m_state.shadowOffsetY = y;
      m_state.flags |= DirtyShadowOffsetY;
  }

  void Context2D::setShadowBlur(qreal b)
  {
      m_state.shadowBlur = b;
      m_state.flags |= DirtyShadowBlur;
  }

  void Context2D::setShadowColor(const QString &str)
  {
      m_state.shadowColor = colorFromString(str);
      m_state.flags |= DirtyShadowColor;
  }

  qreal Context2D::shadowOffsetX() const
  {
      return m_state.shadowOffsetX;
  }

  qreal Context2D::shadowOffsetY() const
  {
      return m_state.shadowOffsetY;
  }

  qreal Context2D::shadowBlur() const
  {
      return m_state.shadowBlur;
  }

  QString Context2D::shadowColor() const
  {
      return m_state.shadowColor.name();
  }

  void Context2D::clearRect(qreal x, qreal y, qreal w, qreal h)
  {
      beginPainting();
      m_painter.save();
      m_painter.setMatrix(m_state.matrix, false);
      m_painter.setCompositionMode(QPainter::CompositionMode_Source);
      m_painter.fillRect(QRectF(x, y, w, h), QColor(0, 0, 0, 0));
      m_painter.restore();
      scheduleChange();
  }

  void Context2D::fillRect(qreal x, qreal y, qreal w, qreal h)
  {
      beginPainting();
      m_painter.save();
      m_painter.setMatrix(m_state.matrix, false);
      m_painter.fillRect(QRectF(x, y, w, h), m_painter.brush());
      m_painter.restore();
      scheduleChange();
  }

  void Context2D::strokeRect(qreal x, qreal y, qreal w, qreal h)
  {
      QPainterPath path;
      path.addRect(x, y, w, h);
      beginPainting();
      m_painter.save();
      m_painter.setMatrix(m_state.matrix, false);
      m_painter.strokePath(path, m_painter.pen());
      m_painter.restore();
      scheduleChange();
  }

  void Context2D::beginPath()
  {
      m_path = QPainterPath();
  }

  void Context2D::closePath()
  {
      m_path.closeSubpath();
  }

  void Context2D::moveTo(qreal x, qreal y)
  {
      QPointF pt = m_state.matrix.map(QPointF(x, y));
      m_path.moveTo(pt);
  }

  void Context2D::lineTo(qreal x, qreal y)
  {
      QPointF pt = m_state.matrix.map(QPointF(x, y));
      m_path.lineTo(pt);
  }

  void Context2D::quadraticCurveTo(qreal cpx, qreal cpy, qreal x, qreal y)
  {
      QPointF cp = m_state.matrix.map(QPointF(cpx, cpy));
      QPointF xy = m_state.matrix.map(QPointF(x, y));
      m_path.quadTo(cp, xy);
  }

  void Context2D::bezierCurveTo(qreal cp1x, qreal cp1y,
                                qreal cp2x, qreal cp2y, qreal x, qreal y)
  {
      QPointF cp1 = m_state.matrix.map(QPointF(cp1x, cp1y));
      QPointF cp2 = m_state.matrix.map(QPointF(cp2x, cp2y));
      QPointF end = m_state.matrix.map(QPointF(x, y));
      m_path.cubicTo(cp1, cp2, end);
  }

  void Context2D::arcTo(qreal x1, qreal y1, qreal x2, qreal y2, qreal radius)
  {
      //FIXME: this is surely busted
      QPointF st  = m_state.matrix.map(QPointF(x1, y1));
      QPointF end = m_state.matrix.map(QPointF(x2, y2));
      m_path.arcTo(st.x(), st.y(),
                   end.x()-st.x(), end.y()-st.y(),
                   radius, 90);
  }

  void Context2D::rect(qreal x, qreal y, qreal w, qreal h)
  {
      QPainterPath path; path.addRect(x, y, w, h);
      path = m_state.matrix.map(path);
      m_path.addPath(path);
  }

  void Context2D::arc(qreal xc, qreal yc, qreal radius,
                      qreal sar, qreal ear,
                      bool anticlockwise)
  {
      //### HACK
      // In Qt we don't switch the coordinate system for degrees
      // and still use the 0,0 as bottom left for degrees so we need
      // to switch
      sar = -sar;
      ear = -ear;
      anticlockwise = !anticlockwise;
      //end hack

      float sa = DEGREES(sar);
      float ea = DEGREES(ear);

      double span = 0;

      double xs     = xc - radius;
      double ys     = yc - radius;
      double width  = radius*2;
      double height = radius*2;

      if (!anticlockwise && (ea < sa)) {
          span += 360;
      } else if (anticlockwise && (sa < ea)) {
          span -= 360;
      }

      //### this is also due to switched coordinate system
      // we would end up with a 0 span instead of 360
      if (!(qFuzzyCompare(span + (ea - sa) + 1, 1) &&
            qFuzzyCompare(qAbs(span), 360))) {
          span   += ea - sa;
      }

      QPainterPath path;
      path.moveTo(QPointF(xc + radius  * cos(sar),
                                  yc - radius  * sin(sar)));

      path.arcTo(xs, ys, width, height, sa, span);
      path = m_state.matrix.map(path);
      m_path.addPath(path);
  }

  void Context2D::fill()
  {
      beginPainting();
      m_painter.fillPath(m_path, m_painter.brush());
      scheduleChange();
  }

  void Context2D::stroke()
  {
      beginPainting();
      m_painter.save();
      m_painter.setMatrix(m_state.matrix, false);
      QPainterPath tmp = m_state.matrix.inverted().map(m_path);
      m_painter.strokePath(tmp, m_painter.pen());
      m_painter.restore();
      scheduleChange();
  }

  void Context2D::clip()
  {
      m_state.clipPath = m_path;
      m_state.flags |= DirtyClippingRegion;
  }

  bool Context2D::isPointInPath(qreal x, qreal y) const
  {
      return m_path.contains(QPointF(x, y));
  }

  ImageData Context2D::getImageData(qreal sx, qreal sy, qreal sw, qreal sh)
  {
      Q_UNUSED(sx);
      Q_UNUSED(sy);
      Q_UNUSED(sw);
      Q_UNUSED(sh);
      return ImageData();
  }

  void Context2D::putImageData(ImageData image, qreal dx, qreal dy)
  {
      Q_UNUSED(image);
      Q_UNUSED(dx);
      Q_UNUSED(dy);
  }

  Context2D::Context2D(QObject *parent)
      : QObject(parent), m_changeTimerId(-1)
  {
      reset();
  }

  const QImage &Context2D::endPainting()
  {
      if (m_painter.isActive())
          m_painter.end();
      return m_image;
  }

  void Context2D::beginPainting()
  {
      if (!m_painter.isActive()) {
          m_painter.begin(&m_image);
          m_painter.setRenderHint(QPainter::Antialiasing);
          if (!m_state.clipPath.isEmpty())
              m_painter.setClipPath(m_state.clipPath);
          m_painter.setBrush(m_state.fillStyle);
          m_painter.setOpacity(m_state.globalAlpha);
          QPen pen;
          pen.setBrush(m_state.strokeStyle);
          if (pen.style() == Qt::NoPen)
              pen.setStyle(Qt::SolidLine);
          pen.setCapStyle(m_state.lineCap);
          pen.setJoinStyle(m_state.lineJoin);
          pen.setWidthF(m_state.lineWidth);
          pen.setMiterLimit(m_state.miterLimit);
          m_painter.setPen(pen);
      } else {
          if ((m_state.flags & DirtyClippingRegion) && !m_state.clipPath.isEmpty())
              m_painter.setClipPath(m_state.clipPath);
          if (m_state.flags & DirtyFillStyle)
              m_painter.setBrush(m_state.fillStyle);
          if (m_state.flags & DirtyGlobalAlpha)
              m_painter.setOpacity(m_state.globalAlpha);
          if (m_state.flags & DirtyGlobalCompositeOperation)
              m_painter.setCompositionMode(m_state.globalCompositeOperation);
          if (m_state.flags & MDirtyPen) {
              QPen pen = m_painter.pen();
              if (m_state.flags & DirtyStrokeStyle)
                  pen.setBrush(m_state.strokeStyle);
              if (m_state.flags & DirtyLineWidth)
                  pen.setWidthF(m_state.lineWidth);
              if (m_state.flags & DirtyLineCap)
                  pen.setCapStyle(m_state.lineCap);
              if (m_state.flags & DirtyLineJoin)
                  pen.setJoinStyle(m_state.lineJoin);
              if (m_state.flags & DirtyMiterLimit)
                  pen.setMiterLimit(m_state.miterLimit);
              m_painter.setPen(pen);
          }
          m_state.flags = 0;
      }
  }

  void Context2D::clear()
  {
      endPainting();
      m_image.fill(qRgba(0,0,0,0));
      scheduleChange();
  }

  void Context2D::reset()
  {
      m_stateStack.clear();
      m_state.matrix = QMatrix();
      m_state.clipPath = QPainterPath();
      m_state.globalAlpha = 1.0;
      m_state.globalCompositeOperation = QPainter::CompositionMode_SourceOver;
      m_state.strokeStyle = Qt::black;
      m_state.fillStyle = Qt::black;
      m_state.lineWidth = 1;
      m_state.lineCap = Qt::FlatCap;
      m_state.lineJoin = Qt::MiterJoin;
      m_state.miterLimit = 10;
      m_state.shadowOffsetX = 0;
      m_state.shadowOffsetY = 0;
      m_state.shadowBlur = 0;
      m_state.shadowColor = qRgba(0, 0, 0, 0);
      m_state.flags = AllIsFullOfDirt;
      clear();
  }

  void Context2D::setSize(int width, int height)
  {
      endPainting();
      QImage newi(width, height, QImage::Format_ARGB32_Premultiplied);
      newi.fill(qRgba(0,0,0,0));
      QPainter p(&newi);
      p.drawImage(0, 0, m_image);
      p.end();
      m_image = newi;
      scheduleChange();
  }

  void Context2D::setSize(const QSize &size)
  {
      setSize(size.width(), size.height());
  }

  QSize Context2D::size() const
  {
      return m_image.size();
  }

  void Context2D::drawImage(DomImage *image, qreal dx, qreal dy)
  {
      if (!image)
          return;
      if (dx < 0) {
          qreal sx = qAbs(dx);
          qreal sy = qAbs(dy);
          qreal sw = image->width() - sx;
          qreal sh = image->height() - sy;

          drawImage(image, sx, sy, sw, sh, 0, 0, sw, sh);
      } else {
          beginPainting();
          m_painter.drawImage(QPointF(dx, dy), image->image());
          scheduleChange();
      }
  }

  void Context2D::drawImage(DomImage *image, qreal dx, qreal dy,
                            qreal dw, qreal dh)
  {
      if (!image)
          return;
      beginPainting();
      m_painter.drawImage(QRectF(dx, dy, dw, dh).toRect(), image->image());
      scheduleChange();
  }

  void Context2D::drawImage(DomImage *image, qreal sx, qreal sy,
                            qreal sw, qreal sh, qreal dx, qreal dy,
                            qreal dw, qreal dh)
  {
      if (!image)
          return;
      beginPainting();
      m_painter.drawImage(QRectF(dx, dy, dw, dh), image->image(),
                          QRectF(sx, sy, sw, sh));
      scheduleChange();
  }

  void Context2D::scheduleChange()
  {
      if (m_changeTimerId == -1)
          m_changeTimerId = startTimer(0);
  }

  void Context2D::timerEvent(QTimerEvent *e)
  {
      if (e->timerId() == m_changeTimerId) {
          killTimer(m_changeTimerId);
          m_changeTimerId = -1;
          emit changed(endPainting());
      } else {
          QObject::timerEvent(e);
      }
  }