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# gradients.cpp Example File
demos/gradients/gradients.cpp

        #include "gradients.h"
        #include "hoverpoints.h"

        ShadeWidget::ShadeWidget(ShadeType type, QWidget *parent)
            : QWidget(parent), m_shade_type(type), m_alpha_gradient(QLinearGradient(0, 0, 0, 0))
        {

            // Checkers background
            if (m_shade_type == ARGBShade) {
                QPixmap pm(20, 20);
                QPainter pmp(&pm);
                pmp.fillRect(0, 0, 10, 10, Qt::lightGray);
                pmp.fillRect(10, 10, 10, 10, Qt::lightGray);
                pmp.fillRect(0, 10, 10, 10, Qt::darkGray);
                pmp.fillRect(10, 0, 10, 10, Qt::darkGray);
                pmp.end();
                QPalette pal = palette();
                pal.setBrush(backgroundRole(), QBrush(pm));
                setPalette(pal);

            } else {
                setAttribute(Qt::WA_NoBackground);

            }

            QPolygonF points;
            points << QPointF(0, sizeHint().height())
                   << QPointF(sizeHint().width(), 0);

            m_hoverPoints = new HoverPoints(this, HoverPoints::CircleShape);
        //     m_hoverPoints->setConnectionType(HoverPoints::LineConnection);
            m_hoverPoints->setPoints(points);
            m_hoverPoints->setPointLock(0, HoverPoints::LockToLeft);
            m_hoverPoints->setPointLock(1, HoverPoints::LockToRight);
            m_hoverPoints->setSortType(HoverPoints::XSort);

            setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Fixed);

            connect(m_hoverPoints, SIGNAL(pointsChanged(const QPolygonF &)), this, SIGNAL(colorsChanged()));
        }

        QPolygonF ShadeWidget::points() const
        {
            return m_hoverPoints->points();
        }

        uint ShadeWidget::colorAt(int x)
        {
            generateShade();

            QPolygonF pts = m_hoverPoints->points();
            for (int i=1; i < pts.size(); ++i) {
                if (pts.at(i-1).x() <= x && pts.at(i).x() >= x) {
                    QLineF l(pts.at(i-1), pts.at(i));
                    l.setLength(l.length() * ((x - l.x1()) / l.dx()));
                    return m_shade.pixel(qRound(qMin(l.x2(), (double(m_shade.width() - 1)))),
                                         qRound(qMin(l.y2(), double(m_shade.height() - 1))));
                }
            }
            return 0;
        }

        void ShadeWidget::setGradientStops(const QGradientStops &stops)
        {
            if (m_shade_type == ARGBShade) {
                m_alpha_gradient = QLinearGradient(0, 0, width(), 0);

                for (int i=0; i<stops.size(); ++i) {
                    QColor c = stops.at(i).second;
                    m_alpha_gradient.setColorAt(stops.at(i).first, QColor(c.red(), c.green(), c.blue()));
                }

                m_shade = QImage();
                generateShade();
                update();
            }
        }

        void ShadeWidget::paintEvent(QPaintEvent *)
        {
            generateShade();

            QPainter p(this);
            p.drawImage(0, 0, m_shade);

            p.setPen(QColor(146, 146, 146));
            p.drawRect(0, 0, width() - 1, height() - 1);
        }

        void ShadeWidget::generateShade()
        {
            if (m_shade.isNull() || m_shade.size() != size()) {

                if (m_shade_type == ARGBShade) {
                    m_shade = QImage(size(), QImage::Format_ARGB32_Premultiplied);
                    m_shade.fill(0);

                    QPainter p(&m_shade);
                    p.fillRect(rect(), m_alpha_gradient);

                    p.setCompositionMode(QPainter::CompositionMode_DestinationIn);
                    QLinearGradient fade(0, 0, 0, height());
                    fade.setColorAt(0, QColor(0, 0, 0, 255));
                    fade.setColorAt(1, QColor(0, 0, 0, 0));
                    p.fillRect(rect(), fade);

                } else {
                    m_shade = QImage(size(), QImage::Format_RGB32);
                    QLinearGradient shade(0, 0, 0, height());
                    shade.setColorAt(1, Qt::black);

                    if (m_shade_type == RedShade)
                        shade.setColorAt(0, Qt::red);
                    else if (m_shade_type == GreenShade)
                        shade.setColorAt(0, Qt::green);
                    else
                        shade.setColorAt(0, Qt::blue);

                    QPainter p(&m_shade);
                    p.fillRect(rect(), shade);
                }
            }

        }

        GradientEditor::GradientEditor(QWidget *parent)
            : QWidget(parent)
        {
            QVBoxLayout *vbox = new QVBoxLayout(this);
            vbox->setSpacing(1);
            vbox->setMargin(1);

            m_red_shade = new ShadeWidget(ShadeWidget::RedShade, this);
            m_green_shade = new ShadeWidget(ShadeWidget::GreenShade, this);
            m_blue_shade = new ShadeWidget(ShadeWidget::BlueShade, this);
            m_alpha_shade = new ShadeWidget(ShadeWidget::ARGBShade, this);

            vbox->addWidget(m_red_shade);
            vbox->addWidget(m_green_shade);
            vbox->addWidget(m_blue_shade);
            vbox->addWidget(m_alpha_shade);

            connect(m_red_shade, SIGNAL(colorsChanged()), this, SLOT(pointsUpdated()));
            connect(m_green_shade, SIGNAL(colorsChanged()), this, SLOT(pointsUpdated()));
            connect(m_blue_shade, SIGNAL(colorsChanged()), this, SLOT(pointsUpdated()));
            connect(m_alpha_shade, SIGNAL(colorsChanged()), this, SLOT(pointsUpdated()));
        }

        inline static bool x_less_than(const QPointF &p1, const QPointF &p2)
        {
            return p1.x() < p2.x();
        }

        void GradientEditor::pointsUpdated()
        {
            double w = m_alpha_shade->width();

            QGradientStops stops;

            QPolygonF points;

            points += m_red_shade->points();
            points += m_green_shade->points();
            points += m_blue_shade->points();
            points += m_alpha_shade->points();

            qSort(points.begin(), points.end(), x_less_than);

            for (int i=0; i<points.size(); ++i) {
                double x = int(points.at(i).x());
                if (i < points.size() - 1 && x == points.at(i+1).x())
                    continue;
                QColor color((0x00ff0000 & m_red_shade->colorAt(int(x))) >> 16,
                             (0x0000ff00 & m_green_shade->colorAt(int(x))) >> 8,
                             (0x000000ff & m_blue_shade->colorAt(int(x))),
                             (0xff000000 & m_alpha_shade->colorAt(int(x))) >> 24);

                if (x / w > 1)
                    return;

                stops << QGradientStop(x / w, color);
            }

            m_alpha_shade->setGradientStops(stops);

            emit gradientStopsChanged(stops);
        }

        static void set_shade_points(const QPolygonF &points, ShadeWidget *shade)
        {
            shade->hoverPoints()->setPoints(points);
            shade->hoverPoints()->setPointLock(0, HoverPoints::LockToLeft);
            shade->hoverPoints()->setPointLock(points.size() - 1, HoverPoints::LockToRight);
            shade->update();
        }

        void GradientEditor::setGradientStops(const QGradientStops &stops)
        {
            QPolygonF pts_red, pts_green, pts_blue, pts_alpha;

            double h_red = m_red_shade->height();
            double h_green = m_green_shade->height();
            double h_blue = m_blue_shade->height();
            double h_alpha = m_alpha_shade->height();

            for (int i=0; i<stops.size(); ++i) {
                double pos = stops.at(i).first;
                QRgb color = stops.at(i).second.rgba();
                pts_red << QPointF(pos * m_red_shade->width(), h_red - qRed(color) * h_red / 255);
                pts_green << QPointF(pos * m_green_shade->width(), h_green - qGreen(color) * h_green / 255);
                pts_blue << QPointF(pos * m_blue_shade->width(), h_blue - qBlue(color) * h_blue / 255);
                pts_alpha << QPointF(pos * m_alpha_shade->width(), h_alpha - qAlpha(color) * h_alpha / 255);
            }

            set_shade_points(pts_red, m_red_shade);
            set_shade_points(pts_green, m_green_shade);
            set_shade_points(pts_blue, m_blue_shade);
            set_shade_points(pts_alpha, m_alpha_shade);

        }

        GradientWidget::GradientWidget(QWidget *parent)
            : QWidget(parent)
        {
            setWindowTitle("Gradients");

            m_renderer = new GradientRenderer(this);

            ArthurGroupBox *mainGroup = new ArthurGroupBox(this);
            mainGroup->setTitle("Gradients");

            ArthurGroupBox *editorGroup = new ArthurGroupBox(mainGroup);
            editorGroup->setAttribute(Qt::WA_ContentsPropagated);
            editorGroup->setTitle("Color Editor");
            m_editor = new GradientEditor(editorGroup);

            ArthurGroupBox *typeGroup = new ArthurGroupBox(mainGroup);
            typeGroup->setAttribute(Qt::WA_ContentsPropagated);
            typeGroup->setTitle("Gradient Type");
            m_linearButton = new QRadioButton("Linear Gradient", typeGroup);
            m_radialButton = new QRadioButton("Radial Gradient", typeGroup);
            m_conicalButton = new QRadioButton("Conical Gradient", typeGroup);

            ArthurGroupBox *spreadGroup = new ArthurGroupBox(mainGroup);
            spreadGroup->setAttribute(Qt::WA_ContentsPropagated);
            spreadGroup->setTitle("Spread Method");
            m_padSpreadButton = new QRadioButton("Pad Spread", spreadGroup);
            m_reflectSpreadButton = new QRadioButton("Reflect Spread", spreadGroup);
            m_repeatSpreadButton = new QRadioButton("Repeat Spread", spreadGroup);

            ArthurGroupBox *defaultsGroup = new ArthurGroupBox(mainGroup);
            defaultsGroup->setAttribute(Qt::WA_ContentsPropagated);
            defaultsGroup->setTitle("Defaults");
            QPushButton *default1Button = new QPushButton("1", defaultsGroup);
            QPushButton *default2Button = new QPushButton("2", defaultsGroup);
            QPushButton *default3Button = new QPushButton("3", defaultsGroup);
            QPushButton *default4Button = new QPushButton("Reset", editorGroup);

            QPushButton *showSourceButton = new QPushButton(mainGroup);
            showSourceButton->setText("Show Source");

            QPushButton *whatsThisButton = new QPushButton(mainGroup);
            whatsThisButton->setText("What's This?");
            whatsThisButton->setCheckable(true);

            // Layouts
            QHBoxLayout *mainLayout = new QHBoxLayout(this);
            mainLayout->addWidget(m_renderer);
            mainLayout->addWidget(mainGroup);

            mainGroup->setFixedWidth(180);
            QVBoxLayout *mainGroupLayout = new QVBoxLayout(mainGroup);
            mainGroupLayout->addWidget(editorGroup);
            mainGroupLayout->addWidget(typeGroup);
            mainGroupLayout->addWidget(spreadGroup);
            mainGroupLayout->addWidget(defaultsGroup);
            mainGroupLayout->addStretch(1);
            mainGroupLayout->addWidget(showSourceButton);
            mainGroupLayout->addWidget(whatsThisButton);

            QVBoxLayout *editorGroupLayout = new QVBoxLayout(editorGroup);
            editorGroupLayout->addWidget(m_editor);

            QVBoxLayout *typeGroupLayout = new QVBoxLayout(typeGroup);
            typeGroupLayout->addWidget(m_linearButton);
            typeGroupLayout->addWidget(m_radialButton);
            typeGroupLayout->addWidget(m_conicalButton);

            QVBoxLayout *spreadGroupLayout = new QVBoxLayout(spreadGroup);
            spreadGroupLayout->addWidget(m_padSpreadButton);
            spreadGroupLayout->addWidget(m_repeatSpreadButton);
            spreadGroupLayout->addWidget(m_reflectSpreadButton);

            QHBoxLayout *defaultsGroupLayout = new QHBoxLayout(defaultsGroup);
            defaultsGroupLayout->addWidget(default1Button);
            defaultsGroupLayout->addWidget(default2Button);
            defaultsGroupLayout->addWidget(default3Button);
            editorGroupLayout->addWidget(default4Button);

            connect(m_editor, SIGNAL(gradientStopsChanged(const QGradientStops &)),
                    m_renderer, SLOT(setGradientStops(const QGradientStops &)));

            connect(m_linearButton, SIGNAL(clicked()), m_renderer, SLOT(setLinearGradient()));
            connect(m_radialButton, SIGNAL(clicked()), m_renderer, SLOT(setRadialGradient()));
            connect(m_conicalButton, SIGNAL(clicked()), m_renderer, SLOT(setConicalGradient()));

            connect(m_padSpreadButton, SIGNAL(clicked()), m_renderer, SLOT(setPadSpread()));
            connect(m_reflectSpreadButton, SIGNAL(clicked()), m_renderer, SLOT(setReflectSpread()));
            connect(m_repeatSpreadButton, SIGNAL(clicked()), m_renderer, SLOT(setRepeatSpread()));

            connect(default1Button, SIGNAL(clicked()), this, SLOT(setDefault1()));
            connect(default2Button, SIGNAL(clicked()), this, SLOT(setDefault2()));
            connect(default3Button, SIGNAL(clicked()), this, SLOT(setDefault3()));
            connect(default4Button, SIGNAL(clicked()), this, SLOT(setDefault4()));

            connect(showSourceButton, SIGNAL(clicked()), m_renderer, SLOT(showSource()));

            connect(whatsThisButton, SIGNAL(clicked(bool)), m_renderer, SLOT(setDescriptionEnabled(bool)));
            connect(whatsThisButton, SIGNAL(clicked(bool)),
                    m_renderer->hoverPoints(), SLOT(setDisabled(bool)));
            connect(m_renderer, SIGNAL(descriptionEnabledChanged(bool)),
                    whatsThisButton, SLOT(setChecked(bool)));
            connect(m_renderer, SIGNAL(descriptionEnabledChanged(bool)),
                    m_renderer->hoverPoints(), SLOT(setDisabled(bool)));

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

            QTimer::singleShot(50, this, SLOT(setDefault1()));
        }

        void GradientWidget::setDefault(int config)
        {
            QGradientStops stops;
            QPolygonF points;
            switch (config) {
            case 1:
                stops << QGradientStop(0.00, QColor::fromRgba(0));
                stops << QGradientStop(0.04, QColor::fromRgba(0xff131360));
                stops << QGradientStop(0.08, QColor::fromRgba(0xff202ccc));
                stops << QGradientStop(0.42, QColor::fromRgba(0xff93d3f9));
                stops << QGradientStop(0.51, QColor::fromRgba(0xffb3e6ff));
                stops << QGradientStop(0.73, QColor::fromRgba(0xffffffec));
                stops << QGradientStop(0.92, QColor::fromRgba(0xff5353d9));
                stops << QGradientStop(0.96, QColor::fromRgba(0xff262666));
                stops << QGradientStop(1.00, QColor::fromRgba(0));
                m_linearButton->animateClick();
                m_repeatSpreadButton->animateClick();
                break;

            case 2:
                stops << QGradientStop(0.00, QColor::fromRgba(0xffffffff));
                stops << QGradientStop(0.11, QColor::fromRgba(0xfff9ffa0));
                stops << QGradientStop(0.13, QColor::fromRgba(0xfff9ff99));
                stops << QGradientStop(0.14, QColor::fromRgba(0xfff3ff86));
                stops << QGradientStop(0.49, QColor::fromRgba(0xff93b353));
                stops << QGradientStop(0.87, QColor::fromRgba(0xff264619));
                stops << QGradientStop(0.96, QColor::fromRgba(0xff0c1306));
                stops << QGradientStop(1.00, QColor::fromRgba(0));
                m_radialButton->animateClick();
                m_padSpreadButton->animateClick();
                break;

            case 3:
                stops << QGradientStop(0.00, QColor::fromRgba(0));
                stops << QGradientStop(0.10, QColor::fromRgba(0xffe0cc73));
                stops << QGradientStop(0.17, QColor::fromRgba(0xffc6a006));
                stops << QGradientStop(0.46, QColor::fromRgba(0xff600659));
                stops << QGradientStop(0.72, QColor::fromRgba(0xff0680ac));
                stops << QGradientStop(0.92, QColor::fromRgba(0xffb9d9e6));
                stops << QGradientStop(1.00, QColor::fromRgba(0));
                m_conicalButton->animateClick();
                m_padSpreadButton->animateClick();
                break;

            case 4:
                stops << QGradientStop(0.00, QColor::fromRgba(0xff000000));
                stops << QGradientStop(1.00, QColor::fromRgba(0xffffffff));
                break;

            default:
                qWarning("bad default: %d\n", config);
                break;
            }

            QPolygonF pts;
            int h_off = m_renderer->width() / 10;
            int v_off = m_renderer->height() / 8;
            pts << QPointF(m_renderer->width() / 2, m_renderer->height() / 2)
                << QPointF(m_renderer->width() / 2 - h_off, m_renderer->height() / 2 - v_off);

            m_editor->setGradientStops(stops);
            m_renderer->hoverPoints()->setPoints(pts);
            m_renderer->setGradientStops(stops);
        }

        GradientRenderer::GradientRenderer(QWidget *parent)
            : ArthurFrame(parent)
        {
            m_hoverPoints = new HoverPoints(this, HoverPoints::CircleShape);
            m_hoverPoints->setPointSize(QSize(20, 20));
            m_hoverPoints->setConnectionType(HoverPoints::NoConnection);
            m_hoverPoints->setEditable(false);

            QVector<QPointF> points;
            points << QPointF(100, 100) << QPointF(200, 200);
            m_hoverPoints->setPoints(points);

            m_spread = QGradient::PadSpread;
            m_gradientType = Qt::LinearGradientPattern;
        }

        void GradientRenderer::setGradientStops(const QGradientStops &stops)
        {
            m_stops = stops;
            update();
        }

        void GradientRenderer::mousePressEvent(QMouseEvent *)
        {
            setDescriptionEnabled(false);
        }

        void GradientRenderer::paint(QPainter *p)
        {
            QPolygonF pts = m_hoverPoints->points();

            QGradient g;

            if (m_gradientType == Qt::LinearGradientPattern) {
                g = QLinearGradient(pts.at(0), pts.at(1));

            } else if (m_gradientType == Qt::RadialGradientPattern) {
                g = QRadialGradient(pts.at(0), qMin(width(), height()) / 3.0, pts.at(1));

            } else {
                QLineF l(pts.at(0), pts.at(1));
                double angle = l.angle(QLineF(0, 0, 1, 0));
                if (l.dy() > 0)
                    angle = 360 - angle;
                g = QConicalGradient(pts.at(0), angle);
            }

            for (int i=0; i<m_stops.size(); ++i)
                g.setColorAt(m_stops.at(i).first, m_stops.at(i).second);

            g.setSpread(m_spread);

            p->setBrush(g);
            p->setPen(Qt::NoPen);

            p->drawRect(rect());

        }