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# context2d.cpp Example File
script/context2d/context2d.cpp

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     **
     ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
     ** All rights reserved.
     ** Contact: Nokia Corporation (qt-info@nokia.com)
     **
     ** This file is part of the examples of the Qt Toolkit.
     **
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     **
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     ** Alternatively, this file may be used under the terms of the GNU Lesser
     ** General Public License version 2.1 as published by the Free Software
     ** Foundation and appearing in the file LICENSE.LGPL included in the
     ** packaging of this file.  Please review the following information to
     ** ensure the GNU Lesser General Public License version 2.1 requirements
     ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
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     ** rights.  These rights are described in the Nokia Qt LGPL Exception
     ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
     **
     ** GNU General Public License Usage
     ** Alternatively, this file may be used under the terms of the GNU
     ** General Public License version 3.0 as published by the Free Software
     ** Foundation and appearing in the file LICENSE.GPL included in the
     ** packaging of this file.  Please review the following information to
     ** ensure the GNU General Public License version 3.0 requirements will be
     ** met: http://www.gnu.org/copyleft/gpl.html.
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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 (qVariantCanConvert<CanvasGradient>(style)) {
             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 (qVariantCanConvert<CanvasGradient>(style)) {
             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);
         }
     }