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pathstroke.cpp Example File
^{demos/pathstroke/pathstroke.cpp}

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 #include "pathstroke.h"
 #include "arthurstyle.h"
 #include "arthurwidgets.h"

 extern void draw_round_rect(QPainter *p, const QRect &bounds, int radius);

 PathStrokeWidget::PathStrokeWidget()
 {
     setWindowTitle(tr("Path Stroking"));

     // Setting up palette.
     QPalette pal = palette();
 //     pal.setBrush(QPalette::Background, Qt::white);
 //     pal.setBrush(QPalette::Foreground, QColor("aquamarine"));
 //     pal.setBrush(QPalette::Background, QPixmap("background.png"));
     setPalette(pal);

     // Widget construction and property setting
     m_renderer = new PathStrokeRenderer(this);

     QGroupBox *mainGroup = new QGroupBox(this);
 //     QWidget *mainGroup = new QWidget(this);
     mainGroup->setFixedWidth(180);
     mainGroup->setTitle("Path Stroking");

     QGroupBox *capGroup = new QGroupBox(mainGroup);
     capGroup->setAttribute(Qt::WA_ContentsPropagated);
     QRadioButton *flatCap = new QRadioButton(capGroup);
     QRadioButton *squareCap = new QRadioButton(capGroup);
     QRadioButton *roundCap = new QRadioButton(capGroup);
     capGroup->setTitle("Cap Style");
     flatCap->setText("Flat Cap");
     squareCap->setText("Square Cap");
     roundCap->setText("Round Cap");

     QGroupBox *joinGroup = new QGroupBox(mainGroup);
     joinGroup->setAttribute(Qt::WA_ContentsPropagated);
     QRadioButton *bevelJoin = new QRadioButton(joinGroup);
     QRadioButton *miterJoin = new QRadioButton(joinGroup);
     QRadioButton *roundJoin = new QRadioButton(joinGroup);
     joinGroup->setTitle("Join Style");
     bevelJoin->setText("Bevel Join");
     miterJoin->setText("Miter Join");
     roundJoin->setText("Round Join");

     QGroupBox *styleGroup = new QGroupBox(mainGroup);
     styleGroup->setAttribute(Qt::WA_ContentsPropagated);
     QRadioButton *solidLine = new QRadioButton(styleGroup);
     QRadioButton *dashLine = new QRadioButton(styleGroup);
     QRadioButton *dotLine = new QRadioButton(styleGroup);
     QRadioButton *dashDotLine = new QRadioButton(styleGroup);
     QRadioButton *dashDotDotLine = new QRadioButton(styleGroup);
     QRadioButton *customDashLine = new QRadioButton(styleGroup);
     styleGroup->setTitle("Pen Style");
 #if 0
     solidLine->setText("Solid Line");
     dashLine->setText("Dash Line");
     dotLine->setText("Dot Line");
     dashDotLine->setText("Dash Dot Line");
     dashDotDotLine->setText("Dash Dot Dot Line");
 #else
     QPixmap line_solid(":res/images/line_solid.png");
     solidLine->setIcon(line_solid);
     solidLine->setIconSize(line_solid.size());
     QPixmap line_dashed(":res/images/line_dashed.png");
     dashLine->setIcon(line_dashed);
     dashLine->setIconSize(line_dashed.size());
     QPixmap line_dotted(":res/images/line_dotted.png");
     dotLine->setIcon(line_dotted);
     dotLine->setIconSize(line_dotted.size());
     QPixmap line_dash_dot(":res/images/line_dash_dot.png");
     dashDotLine->setIcon(line_dash_dot);
     dashDotLine->setIconSize(line_dash_dot.size());
     QPixmap line_dash_dot_dot(":res/images/line_dash_dot_dot.png");
     dashDotDotLine->setIcon(line_dash_dot_dot);
     dashDotDotLine->setIconSize(line_dash_dot_dot.size());
     customDashLine->setText("Custom Style");

     int fixedHeight = bevelJoin->sizeHint().height();
     solidLine->setFixedHeight(fixedHeight);
     dashLine->setFixedHeight(fixedHeight);
     dotLine->setFixedHeight(fixedHeight);
     dashDotLine->setFixedHeight(fixedHeight);
     dashDotDotLine->setFixedHeight(fixedHeight);
 #endif

     QGroupBox *pathModeGroup = new QGroupBox(mainGroup);
     pathModeGroup->setAttribute(Qt::WA_ContentsPropagated);
     QRadioButton *curveMode = new QRadioButton(pathModeGroup);
     QRadioButton *lineMode = new QRadioButton(pathModeGroup);
     pathModeGroup->setTitle("Path composed of");
     curveMode->setText("Curves");
     lineMode->setText("Lines");

     QGroupBox *penWidthGroup = new QGroupBox(mainGroup);
     penWidthGroup->setAttribute(Qt::WA_ContentsPropagated);
     QSlider *penWidth = new QSlider(Qt::Horizontal, penWidthGroup);
     penWidth->setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Fixed);
     penWidthGroup->setTitle("Pen Width");
     penWidth->setRange(0, 500);

 #if 0
     QCheckBox *animated = new QCheckBox(mainGroup);
     animated->setText("Animated");
 #else
     QPushButton *animated = new QPushButton(mainGroup);
     animated->setText("Animate");
     animated->setCheckable(true);
 #endif

     QPushButton *showSourceButton = new QPushButton(mainGroup);
     showSourceButton->setText("Show Source");
 #ifdef QT_OPENGL_SUPPORT
     QPushButton *enableOpenGLButton = new QPushButton(mainGroup);
     enableOpenGLButton->setText("Use OpenGL");
     enableOpenGLButton->setCheckable(true);
     enableOpenGLButton->setChecked(m_renderer->usesOpenGL());
     if (!QGLFormat::hasOpenGL())
         enableOpenGLButton->hide();
 #endif
     QPushButton *whatsThisButton = new QPushButton(mainGroup);
     whatsThisButton->setText("What's This?");
     whatsThisButton->setCheckable(true);

     // Layouting
     QHBoxLayout *viewLayout = new QHBoxLayout(this);
     viewLayout->addWidget(m_renderer);
     viewLayout->addWidget(mainGroup);

     QVBoxLayout *mainGroupLayout = new QVBoxLayout(mainGroup);
     mainGroupLayout->setMargin(3);
     mainGroupLayout->addWidget(capGroup);
     mainGroupLayout->addWidget(joinGroup);
     mainGroupLayout->addWidget(styleGroup);
     mainGroupLayout->addWidget(penWidthGroup);
     mainGroupLayout->addWidget(pathModeGroup);
     mainGroupLayout->addWidget(animated);
     mainGroupLayout->addStretch(1);
     mainGroupLayout->addWidget(showSourceButton);
 #ifdef QT_OPENGL_SUPPORT
     mainGroupLayout->addWidget(enableOpenGLButton);
 #endif
     mainGroupLayout->addWidget(whatsThisButton);

     QVBoxLayout *capGroupLayout = new QVBoxLayout(capGroup);
     capGroupLayout->addWidget(flatCap);
     capGroupLayout->addWidget(squareCap);
     capGroupLayout->addWidget(roundCap);

     QVBoxLayout *joinGroupLayout = new QVBoxLayout(joinGroup);
     joinGroupLayout->addWidget(bevelJoin);
     joinGroupLayout->addWidget(miterJoin);
     joinGroupLayout->addWidget(roundJoin);

     QVBoxLayout *styleGroupLayout = new QVBoxLayout(styleGroup);
     styleGroupLayout->addWidget(solidLine);
     styleGroupLayout->addWidget(dashLine);
     styleGroupLayout->addWidget(dotLine);
     styleGroupLayout->addWidget(dashDotLine);
     styleGroupLayout->addWidget(dashDotDotLine);
     styleGroupLayout->addWidget(customDashLine);

     QVBoxLayout *pathModeGroupLayout = new QVBoxLayout(pathModeGroup);
     pathModeGroupLayout->addWidget(curveMode);
     pathModeGroupLayout->addWidget(lineMode);

     QVBoxLayout *penWidthLayout = new QVBoxLayout(penWidthGroup);
     penWidthLayout->addWidget(penWidth);

     // Set up connections
     connect(penWidth, SIGNAL(valueChanged(int)),
             m_renderer, SLOT(setPenWidth(int)));
     connect(animated, SIGNAL(toggled(bool)),
             m_renderer, SLOT(setAnimation(bool)));

     connect(flatCap, SIGNAL(clicked()), m_renderer, SLOT(setFlatCap()));
     connect(squareCap, SIGNAL(clicked()), m_renderer, SLOT(setSquareCap()));
     connect(roundCap, SIGNAL(clicked()), m_renderer, SLOT(setRoundCap()));

     connect(bevelJoin, SIGNAL(clicked()), m_renderer, SLOT(setBevelJoin()));
     connect(miterJoin, SIGNAL(clicked()), m_renderer, SLOT(setMiterJoin()));
     connect(roundJoin, SIGNAL(clicked()), m_renderer, SLOT(setRoundJoin()));

     connect(curveMode, SIGNAL(clicked()), m_renderer, SLOT(setCurveMode()));
     connect(lineMode, SIGNAL(clicked()), m_renderer, SLOT(setLineMode()));

     connect(solidLine, SIGNAL(clicked()), m_renderer, SLOT(setSolidLine()));
     connect(dashLine, SIGNAL(clicked()), m_renderer, SLOT(setDashLine()));
     connect(dotLine, SIGNAL(clicked()), m_renderer, SLOT(setDotLine()));
     connect(dashDotLine, SIGNAL(clicked()), m_renderer, SLOT(setDashDotLine()));
     connect(dashDotDotLine, SIGNAL(clicked()), m_renderer, SLOT(setDashDotDotLine()));
     connect(customDashLine, SIGNAL(clicked()), m_renderer, SLOT(setCustomDashLine()));

     connect(showSourceButton, SIGNAL(clicked()), m_renderer, SLOT(showSource()));
 #ifdef QT_OPENGL_SUPPORT
     connect(enableOpenGLButton, SIGNAL(clicked(bool)), m_renderer, SLOT(enableOpenGL(bool)));
 #endif
     connect(whatsThisButton, SIGNAL(clicked(bool)), m_renderer, SLOT(setDescriptionEnabled(bool)));
     connect(m_renderer, SIGNAL(descriptionEnabledChanged(bool)),
             whatsThisButton, SLOT(setChecked(bool)));

     // Set the defaults
     animated->setChecked(true);
     flatCap->setChecked(true);
     bevelJoin->setChecked(true);
     penWidth->setValue(50);
     curveMode->setChecked(true);
     solidLine->setChecked(true);

     m_renderer->loadSourceFile(":res/pathstroke.cpp");
     m_renderer->loadDescription(":res/pathstroke.html");
 }

 PathStrokeRenderer::PathStrokeRenderer(QWidget *parent)
     : ArthurFrame(parent)
 {
     m_pointSize = 10;
     m_activePoint = -1;
     m_capStyle = Qt::FlatCap;
     m_joinStyle = Qt::BevelJoin;
     m_pathMode = CurveMode;
     m_penWidth = 1;
     m_penStyle = Qt::SolidLine;
     m_wasAnimated = true;
     setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
 }

 void PathStrokeRenderer::paint(QPainter *painter)
 {
     if (m_points.isEmpty())
         initializePoints();

     painter->setRenderHint(QPainter::Antialiasing);

     QPalette pal = palette();
     painter->setPen(Qt::NoPen);

     // Construct the path
     QPainterPath path;
     path.moveTo(m_points.at(0));

     if (m_pathMode == LineMode) {
         for (int i=1; i<m_points.size(); ++i) {
             path.lineTo(m_points.at(i));
         }
     } else {
         int i=1;
         while (i + 2 < m_points.size()) {
             path.cubicTo(m_points.at(i), m_points.at(i+1), m_points.at(i+2));
             i += 3;
         }
         while (i < m_points.size()) {
             path.lineTo(m_points.at(i));
             ++i;
         }
     }

     // Draw the path
     {
         QColor lg = Qt::red;

         // The "custom" pen
         if (m_penStyle == Qt::NoPen) {
             QPainterPathStroker stroker;
             stroker.setWidth(m_penWidth);
             stroker.setJoinStyle(m_joinStyle);
             stroker.setCapStyle(m_capStyle);

             QVector<qreal> dashes;
             qreal space = 4;
             dashes << 1 << space
                    << 3 << space
                    << 9 << space
                    << 27 << space
                    << 9 << space
                    << 3 << space;
             stroker.setDashPattern(dashes);
             QPainterPath stroke = stroker.createStroke(path);
             painter->fillPath(stroke, lg);

         } else {
             QPen pen(lg, m_penWidth, m_penStyle, m_capStyle, m_joinStyle);
             painter->strokePath(path, pen);
         }
     }

     if (1) {
         // Draw the control points
         painter->setPen(QColor(50, 100, 120, 200));
         painter->setBrush(QColor(200, 200, 210, 120));
         for (int i=0; i<m_points.size(); ++i) {
             QPointF pos = m_points.at(i);
             painter->drawEllipse(QRectF(pos.x() - m_pointSize,
                                        pos.y() - m_pointSize,
                                        m_pointSize*2, m_pointSize*2));
         }
         painter->setPen(QPen(Qt::lightGray, 0, Qt::SolidLine));
         painter->setBrush(Qt::NoBrush);
         painter->drawPolyline(m_points);
     }

 }

 void PathStrokeRenderer::initializePoints()
 {
     const int count = 7;
     m_points.clear();
     m_vectors.clear();

     QMatrix m;
     double rot = 360 / count;
     QPointF center(width() / 2, height() / 2);
     QMatrix vm;
     vm.shear(2, -1);
     vm.scale(3, 3);

     for (int i=0; i<count; ++i) {
         m_vectors << QPointF(.1f, .25f) * (m * vm);
         m_points << QPointF(0, 100) * m + center;
         m.rotate(rot);
     }
 }

 void PathStrokeRenderer::updatePoints()
 {
     double pad = 10;
     double left = pad;
     double right = width() - pad;
     double top = pad;
     double bottom = height() - pad;

     Q_ASSERT(m_points.size() == m_vectors.size());
     for (int i=0; i<m_points.size(); ++i) {

         if (i == m_activePoint)
             continue;

         QPointF pos = m_points.at(i);
         QPointF vec = m_vectors.at(i);
         pos += vec;
         if (pos.x() < left || pos.x() > right) {
             vec.setX(-vec.x());
             pos.setX(pos.x() < left ? left : right);
         } if (pos.y() < top || pos.y() > bottom) {
             vec.setY(-vec.y());
             pos.setY(pos.y() < top ? top : bottom);
         }
         m_points[i] = pos;
         m_vectors[i] = vec;
     }
     update();
 }

 void PathStrokeRenderer::mousePressEvent(QMouseEvent *e)
 {
     setDescriptionEnabled(false);
     m_activePoint = -1;
     qreal distance = -1;
     for (int i=0; i<m_points.size(); ++i) {
         qreal d = QLineF(e->pos(), m_points.at(i)).length();
         if ((distance < 0 && d < 8 * m_pointSize) || d < distance) {
             distance = d;
             m_activePoint = i;
         }
     }

     if (m_activePoint != -1) {
         m_wasAnimated = m_timer.isActive();
         setAnimation(false);
         mouseMoveEvent(e);
     }
 }

 void PathStrokeRenderer::mouseMoveEvent(QMouseEvent *e)
 {
     if (m_activePoint >= 0 && m_activePoint < m_points.size()) {
         m_points[m_activePoint] = e->pos();
         update();
     }
 }

 void PathStrokeRenderer::mouseReleaseEvent(QMouseEvent *)
 {
     m_activePoint = -1;
     setAnimation(m_wasAnimated);
 }

 void PathStrokeRenderer::timerEvent(QTimerEvent *e)
 {
     if (e->timerId() == m_timer.timerId()) {
         updatePoints();
         QApplication::syncX();
     } // else if (e->timerId() == m_fpsTimer.timerId()) {
 //         emit frameRate(m_frameCount);
 //         m_frameCount = 0;
 //     }
 }

 void PathStrokeRenderer::setAnimation(bool animation)
 {
     m_timer.stop();
 //     m_fpsTimer.stop();

     if (animation) {
         m_timer.start(25, this);
 //         m_fpsTimer.start(1000, this);
 //         m_frameCount = 0;
     }
 }