- Qt 5.5
- Qt Widgets
- Gradients
- gradients.cpp Example File
- Qt 5.5.1 Reference Documentation

# gradients.cpp Example File

painting/gradients/gradients.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the demonstration applications of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:LGPL21$
    ** Commercial License Usage
    ** Licensees holding valid commercial Qt licenses may use this file in
    ** accordance with the commercial license agreement provided with the
    ** Software or, alternatively, in accordance with the terms contained in
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    ** information use the contact form at http://www.qt.io/contact-us.
    **
    ** GNU Lesser General Public License Usage
    ** Alternatively, this file may be used under the terms of the GNU Lesser
    ** General Public License version 2.1 or version 3 as published by the Free
    ** Software Foundation and appearing in the file LICENSE.LGPLv21 and
    ** LICENSE.LGPLv3 included in the packaging of this file. Please review the
    ** following information to ensure the GNU Lesser General Public License
    ** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
    ** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
    **
    ** As a special exception, The Qt Company gives you certain additional
    ** rights. These rights are described in The Qt Company LGPL Exception
    ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
    **
    ** $QT_END_LICENSE$
    **
    ****************************************************************************/

    #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, SIGNAL(pointsChanged(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()
    {
        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 *defaultsGroup = new QGroupBox(mainGroup);
        defaultsGroup->setTitle(tr("Defaults"));
        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(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(QGradientStops)),
                m_renderer, SLOT(setGradientStops(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/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);
    }

    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());

    }