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());

 }