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

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     #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));
             setAutoFillBackground(true);
             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(), (qreal(m_shade.width() - 1)))),
                                      qRound(qMin(l.y2(), qreal(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);

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

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

         QGroupBox *typeGroup = new QGroupBox(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);

         QGroupBox *spreadGroup = new QGroupBox(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);

         QGroupBox *defaultsGroup = new QGroupBox(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");
     #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);

         // 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);
     #ifdef QT_OPENGL_SUPPORT
         mainGroupLayout->addWidget(enableOpenGLButton);
     #endif
         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()));
     #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(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) {
             QLineF line(pts.at(0), pts.at(1));
             if (line.length() > 132)
                 line.setLength(132);
             g = QRadialGradient(line.p1(), qMin(width(), height()) / 3.0, line.p2());
         } 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());

     }