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

 /****************************************************************************
 **
 ** 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.
 **
 ** $QT_BEGIN_LICENSE:LGPL$
 ** Commercial Usage
 ** Licensees holding valid Qt Commercial licenses may use this file in
 ** accordance with the Qt Commercial License Agreement provided with the
 ** Software or, alternatively, in accordance with the terms contained in
 ** a written agreement between you and Nokia.
 **
 ** GNU Lesser General Public License Usage
 ** 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.
 **
 ** In addition, as a special exception, Nokia gives you certain additional
 ** 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.
 **
 ** If you have questions regarding the use of this file, please contact
 ** Nokia at qt-info@nokia.com.
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/

 #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);
     }
 }