context2d.cpp Example File
^{script/context2d/context2d.cpp}

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 #include "context2d.h"

 #include "qcontext2dcanvas.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;
 }

 static 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;
 }

 void CanvasGradientData::setup(QScriptEngine *e)
 {
     QScriptValue proto = e->newObject();
     proto.setProperty("addColorStop", e->newFunction(&CanvasGradientData::addColorStop, /*length=*/ 2));
     e->setDefaultPrototype(qRegisterMetaType<CanvasGradient>(), proto);
 }

 QScriptValue CanvasGradientData::addColorStop(QScriptContext *ctx, QScriptEngine *e)
 {
     QVariant self = ctx->thisObject().toVariant();

     if (qVariantCanConvert<CanvasGradient>(self)) {
         CanvasGradient g = qvariant_cast<CanvasGradient>(self);
         qsreal pos = ctx->argument(0).toNumber();
         QColor color = colorFromString(ctx->argument(1).toString());
         g->gradient.setColorAt(pos, color);
     }
     return e->undefinedValue();
 }

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

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

 void Context2D::scale(qreal x, qreal y)
 {
     if (m_state.creatingShape)
         m_state.matrix.scale(x, y);
     m_painter.scale(x, y);
 }

 void Context2D::rotate(qreal angle)
 {
     if (m_state.creatingShape)
         m_state.matrix.rotate(DEGREES(angle));
     m_painter.rotate(DEGREES(angle));
 }

 void Context2D::translate(qreal x, qreal y)
 {
     if (m_state.creatingShape)
         m_state.matrix.translate(x, y);
     m_painter.translate(x, y);
 }

 void Context2D::transform(qreal m11, qreal m12, qreal m21, qreal m22,
                           qreal dx, qreal dy)
 {
     QMatrix mat(m11, m12,
                 m21, m22,
                 dx, dy);
     if (m_state.creatingShape)
         m_state.matrix *= mat;
     m_painter.setMatrix(mat, true);
 }

 void Context2D::setTransform(qreal m11, qreal m12, qreal m21, qreal m22,
                              qreal dx, qreal dy)
 {
     QMatrix mat(m11, m12,
                 m21, m22,
                 dx, dy);
     if (m_state.creatingShape)
         m_state.matrix = mat;
     m_painter.setMatrix(mat, false);
 }

 void Context2D::setGlobalAlpha(qreal alpha)
 {
     m_painter.setOpacity(alpha);
 }

 void Context2D::setGlobalCompositeOperation(const QString &op)
 {
     QPainter::CompositionMode mode =
         compositeOperatorFromString(op);

     m_painter.setCompositionMode(mode);
 }

 void Context2D::setStrokeStyle(const QVariant &style)
 {
     QPen pen = m_painter.pen();
     if (qVariantCanConvert<CanvasGradient>(style)) {
         CanvasGradient cg = qvariant_cast<CanvasGradient>(style);
         pen.setBrush(cg->qgradient());
     } else {
         QColor clr = colorFromString(style.toString());
         pen.setColor(clr);
     }
     if (pen.style() == Qt::NoPen)
         pen.setStyle(Qt::SolidLine);
     m_painter.setPen(pen);
 }

 void Context2D::setFillStyle(const QVariant &style)
 {
     if (qVariantCanConvert<CanvasGradient>(style)) {
         CanvasGradient cg = qvariant_cast<CanvasGradient>(style);
         m_painter.setBrush(cg->qgradient());
     } else {
         QColor clr = colorFromString(style.toString());
         m_painter.setBrush(clr);
     }
 }

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

 QString Context2D::globalCompositeOperation() const
 {
     return 0;
 }

 QVariant Context2D::strokeStyle() const
 {
     return m_painter.pen().color().name();
 }

 QVariant Context2D::fillStyle() const
 {
     return m_painter.brush().color().name();
 }

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

 void Context2D::setLineWidth(qreal w)
 {
     QPen p = m_painter.pen();
     p.setWidthF(w);
     m_painter.setPen(p);
 }

 void Context2D::setLineCap(const QString &capString)
 {
     QPen pen = m_painter.pen();
     if (capString == "round")
         pen.setCapStyle(Qt::RoundCap);
     else if (capString == "square")
         pen.setCapStyle(Qt::SquareCap);
     else
         pen.setCapStyle(Qt::FlatCap);
     m_painter.setPen(pen);
 }

 void Context2D::setLineJoin(const QString &joinString)
 {
     QPen pen = m_painter.pen();
     if (joinString == "round")
         pen.setJoinStyle(Qt::RoundJoin);
     else if (joinString == "bevel")
         pen.setJoinStyle(Qt::BevelJoin);
     else
         pen.setJoinStyle(Qt::MiterJoin);
     m_painter.setPen(pen);
 }

 void Context2D::setMiterLimit(qreal m)
 {
     QPen pen = m_painter.pen();
     pen.setMiterLimit(m);
     m_painter.setPen(pen);
 }

 qreal Context2D::lineWidth() const
 {
     return m_painter.pen().widthF();
 }

 QString Context2D::lineCap() const
 {
     return QString();
 }

 QString Context2D::lineJoin() const
 {
     return QString();
 }

 qreal Context2D::miterLimit() const
 {
     return 0;
 }

 void Context2D::setShadowOffsetX(qreal x)
 {
     Q_UNUSED(x);
 }

 void Context2D::setShadowOffsetY(qreal y)
 {
     Q_UNUSED(y);
 }

 void Context2D::setShadowBlur(qreal b)
 {
     Q_UNUSED(b);
 }

 void Context2D::setShadowColor(const QColor &c)
 {
     Q_UNUSED(c);
 }

 qreal Context2D::shadowOffsetX() const
 {
     return 0;
 }

 qreal Context2D::shadowOffsetY() const
 {
     return 0;
 }

 qreal Context2D::shadowBlur() const
 {
     return 0;
 }

 QColor Context2D::shadowColor() const
 {
     return QColor();
 }

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

 void Context2D::fillRect(qreal x, qreal y, qreal w, qreal h)
 {
     m_painter.fillRect(QRectF(x, y, w, h), m_painter.brush());
 }

 void Context2D::strokeRect(qreal x, qreal y, qreal w, qreal h)
 {
     QPainterPath path; path.addRect(x, y, w, h);
     m_painter.strokePath(path, m_painter.pen());
 }

 void Context2D::beginPath()
 {
     m_path = QPainterPath();
     m_state.creatingShape = true;
 }

 void Context2D::closePath()
 {
     m_path.closeSubpath();
     m_state.creatingShape = false;
 }

 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), 0.0) &&
           qFuzzyCompare(qAbs(span), 360.0))) {
         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()
 {
     m_painter.fillPath(m_path, m_painter.brush());
     m_state.creatingShape = false;
 }

 void Context2D::stroke()
 {
     m_painter.strokePath(m_path, m_painter.pen());
     m_state.creatingShape = false;
 }

 void Context2D::clip()
 {
     m_painter.setClipPath(m_path);
 }

 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(QContext2DCanvas *parent)
     : QObject(parent),
       m_cache(parent->size(), QImage::Format_ARGB32_Premultiplied)
 {
     m_cache.fill(qRgba(0,0,0,0));
     CanvasGradientData::setup(parent->engine());

     begin();
 }

 const QImage &Context2D::end()
 {
     if (m_painter.isActive())
         m_painter.end();
     m_state.creatingShape = false;
     return m_cache;
 }

 void Context2D::begin()
 {
     if (!m_painter.isActive()) {
         m_painter.begin(&m_cache);
         m_painter.setRenderHint(QPainter::Antialiasing);
         m_painter.setBrush(Qt::black);
     }
 }

 void Context2D::clear()
 {
     m_cache.fill(qRgba(0,0,0,0));
 }

 void Context2D::setSize(int w, int h)
 {
     if (m_painter.isActive())
         end();
     QImage newi(w, h, QImage::Format_ARGB32_Premultiplied);
     newi.fill(qRgba(0,0,0,0));
     QPainter p(&newi);
     p.drawImage(0, 0, m_cache);
     p.end();
     m_cache = newi;
     begin();
 }

 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 {
         m_painter.drawImage(QPointF(dx, dy), image->image());
     }
 }

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

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