qt5base-lts/examples/widgets/painting/gradients/gradients.cpp

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

#include <algorithm>

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, &HoverPoints::pointsChanged,
            this, &ShadeWidget::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, &ShadeWidget::colorsChanged,
            this, &GradientEditor::pointsUpdated);
    connect(m_green_shade, &ShadeWidget::colorsChanged,
           this, &GradientEditor::pointsUpdated);
    connect(m_blue_shade, &ShadeWidget::colorsChanged,
            this, &GradientEditor::pointsUpdated);
    connect(m_alpha_shade, &ShadeWidget::colorsChanged,
            this, &GradientEditor::pointsUpdated);
}

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

void GradientEditor::pointsUpdated()
{
    qreal 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();

    std::sort(points.begin(), points.end(), x_less_than);

    for (int i = 0; i < points.size(); ++i) {
        qreal x = int(points.at(i).x());
        if (i + 1 < points.size() && 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;

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

    for (int i = 0; i < stops.size(); ++i) {
        qreal 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(tr("Gradients"));

    m_renderer = new GradientRenderer(this);

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

    QGroupBox *editorGroup = new QGroupBox(mainGroup);
    editorGroup->setTitle(tr("Color Editor"));
    m_editor = new GradientEditor(editorGroup);

    QGroupBox *typeGroup = new QGroupBox(mainGroup);
    typeGroup->setTitle(tr("Gradient Type"));
    m_linearButton = new QRadioButton(tr("Linear Gradient"), typeGroup);
    m_radialButton = new QRadioButton(tr("Radial Gradient"), typeGroup);
    m_conicalButton = new QRadioButton(tr("Conical Gradient"), typeGroup);

    QGroupBox *spreadGroup = new QGroupBox(mainGroup);
    spreadGroup->setTitle(tr("Spread Method"));
    m_padSpreadButton = new QRadioButton(tr("Pad Spread"), spreadGroup);
    m_reflectSpreadButton = new QRadioButton(tr("Reflect Spread"), spreadGroup);
    m_repeatSpreadButton = new QRadioButton(tr("Repeat Spread"), spreadGroup);

    QGroupBox *presetsGroup = new QGroupBox(mainGroup);
    presetsGroup->setTitle(tr("Presets"));
    QPushButton *prevPresetButton = new QPushButton(tr("<"), presetsGroup);
    m_presetButton = new QPushButton(tr("(unset)"), presetsGroup);
    QPushButton *nextPresetButton = new QPushButton(tr(">"), presetsGroup);
    updatePresetName();

    QGroupBox *defaultsGroup = new QGroupBox(mainGroup);
    defaultsGroup->setTitle(tr("Examples"));
    QPushButton *default1Button = new QPushButton(tr("1"), defaultsGroup);
    QPushButton *default2Button = new QPushButton(tr("2"), defaultsGroup);
    QPushButton *default3Button = new QPushButton(tr("3"), defaultsGroup);
    QPushButton *default4Button = new QPushButton(tr("Reset"), editorGroup);

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

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

    mainGroup->setFixedWidth(200);
    QVBoxLayout *mainGroupLayout = new QVBoxLayout(mainGroup);
    mainGroupLayout->addWidget(editorGroup);
    mainGroupLayout->addWidget(typeGroup);
    mainGroupLayout->addWidget(spreadGroup);
    mainGroupLayout->addWidget(presetsGroup);
    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 *presetsGroupLayout = new QHBoxLayout(presetsGroup);
    presetsGroupLayout->addWidget(prevPresetButton);
    presetsGroupLayout->addWidget(m_presetButton, 1);
    presetsGroupLayout->addWidget(nextPresetButton);

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

    connect(m_editor, &GradientEditor::gradientStopsChanged,
            m_renderer, &GradientRenderer::setGradientStops);
    connect(m_linearButton, &QRadioButton::clicked,
            m_renderer, &GradientRenderer::setLinearGradient);
    connect(m_radialButton, &QRadioButton::clicked,
            m_renderer, &GradientRenderer::setRadialGradient);
    connect(m_conicalButton,&QRadioButton::clicked,
            m_renderer, &GradientRenderer::setConicalGradient);

    connect(m_padSpreadButton, &QRadioButton::clicked,
            m_renderer, &GradientRenderer::setPadSpread);
    connect(m_reflectSpreadButton, &QRadioButton::clicked,
            m_renderer, &GradientRenderer::setReflectSpread);
    connect(m_repeatSpreadButton, &QRadioButton::clicked,
            m_renderer, &GradientRenderer::setRepeatSpread);

    connect(prevPresetButton, &QPushButton::clicked,
            this, &GradientWidget::setPrevPreset);
    connect(m_presetButton, &QPushButton::clicked,
            this, &GradientWidget::setPreset);
    connect(nextPresetButton, &QPushButton::clicked,
            this, &GradientWidget::setNextPreset);

    connect(default1Button, &QPushButton::clicked,
            this, &GradientWidget::setDefault1);
    connect(default2Button, &QPushButton::clicked,
            this, &GradientWidget::setDefault2);
    connect(default3Button, &QPushButton::clicked,
            this, &GradientWidget::setDefault3);
    connect(default4Button, &QPushButton::clicked,
            this, &GradientWidget::setDefault4);

    connect(showSourceButton, &QPushButton::clicked,
            m_renderer, &GradientRenderer::showSource);
#ifdef QT_OPENGL_SUPPORT
    connect(enableOpenGLButton, QOverload<bool>::of(&QPushButton::clicked),
            m_renderer, &ArthurFrame::enableOpenGL);
#endif

    connect(whatsThisButton, QOverload<bool>::of(&QPushButton::clicked),
            m_renderer, &ArthurFrame::setDescriptionEnabled);
    connect(whatsThisButton, QOverload<bool>::of(&QPushButton::clicked),
            m_renderer->hoverPoints(), &HoverPoints::setDisabled);
    connect(m_renderer, QOverload<bool>::of(&ArthurFrame::descriptionEnabledChanged),
            whatsThisButton, &QPushButton::setChecked);
    connect(m_renderer, QOverload<bool>::of(&ArthurFrame::descriptionEnabledChanged),
            m_renderer->hoverPoints(), &HoverPoints::setDisabled);

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

void GradientWidget::updatePresetName()
{
    QMetaEnum presetEnum = QMetaEnum::fromType<QGradient::Preset>();
    m_presetButton->setText(QLatin1String(presetEnum.key(m_presetIndex)));
}

void GradientWidget::changePresetBy(int indexOffset)
{
    QMetaEnum presetEnum = QMetaEnum::fromType<QGradient::Preset>();
    m_presetIndex = qBound(0, m_presetIndex + indexOffset, presetEnum.keyCount() - 1);

    QGradient::Preset preset = static_cast<QGradient::Preset>(presetEnum.value(m_presetIndex));
    QGradient gradient(preset);
    if (gradient.type() != QGradient::LinearGradient)
        return;

    QLinearGradient *linearGradientPointer = static_cast<QLinearGradient *>(&gradient);
    QLineF objectStopsLine(linearGradientPointer->start(), linearGradientPointer->finalStop());
    qreal scaleX = qFuzzyIsNull(objectStopsLine.dx()) ? 1.0 : (0.8 * m_renderer->width() / qAbs(objectStopsLine.dx()));
    qreal scaleY = qFuzzyIsNull(objectStopsLine.dy()) ? 1.0 : (0.8 * m_renderer->height() / qAbs(objectStopsLine.dy()));
    QLineF logicalStopsLine = QTransform::fromScale(scaleX, scaleY).map(objectStopsLine);
    logicalStopsLine.translate(m_renderer->rect().center() - logicalStopsLine.center());
    QPolygonF logicalStops;
    logicalStops << logicalStopsLine.p1() << logicalStopsLine.p2();

    m_linearButton->animateClick();
    m_padSpreadButton->animateClick();
    m_editor->setGradientStops(gradient.stops());
    m_renderer->hoverPoints()->setPoints(logicalStops);
    m_renderer->setGradientStops(gradient.stops());

    updatePresetName();
}

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));
        qreal 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());

}