qt 6.5.1 original

examples/widgets/painting/gradients/CMakeLists.txt

@@ -0,0 +1,102 @@
+# Copyright (C) 2022 The Qt Company Ltd.
+# SPDX-License-Identifier: BSD-3-Clause
+
+cmake_minimum_required(VERSION 3.16)
+project(gradients LANGUAGES CXX)
+
+if(NOT DEFINED INSTALL_EXAMPLESDIR)
+    set(INSTALL_EXAMPLESDIR "examples")
+endif()
+
+set(INSTALL_EXAMPLEDIR "${INSTALL_EXAMPLESDIR}/widgets/painting/gradients")
+
+find_package(Qt6 REQUIRED COMPONENTS Core Gui Widgets)
+
+qt_standard_project_setup()
+
+qt_add_executable(gradients
+    gradients.cpp gradients.h
+    main.cpp
+)
+
+set_target_properties(gradients PROPERTIES
+    WIN32_EXECUTABLE TRUE
+    MACOSX_BUNDLE TRUE
+)
+
+if(NOT TARGET painting_shared::painting_shared)
+    include(../shared/use_lib.cmake)
+endif()
+
+target_link_libraries(gradients PRIVATE
+    Qt6::Core
+    Qt6::Gui
+    Qt6::Widgets
+    painting_shared::painting_shared
+)
+
+# Resources:
+set(shared_resource_files
+    "../shared/images/button_normal_cap_left.png"
+    "../shared/images/button_normal_cap_right.png"
+    "../shared/images/button_normal_stretch.png"
+    "../shared/images/button_pressed_cap_left.png"
+    "../shared/images/button_pressed_cap_right.png"
+    "../shared/images/button_pressed_stretch.png"
+    "../shared/images/frame_bottom.png"
+    "../shared/images/frame_bottomleft.png"
+    "../shared/images/frame_bottomright.png"
+    "../shared/images/frame_left.png"
+    "../shared/images/frame_right.png"
+    "../shared/images/frame_top.png"
+    "../shared/images/frame_topleft.png"
+    "../shared/images/frame_topright.png"
+    "../shared/images/groupframe_bottom_left.png"
+    "../shared/images/groupframe_bottom_right.png"
+    "../shared/images/groupframe_bottom_stretch.png"
+    "../shared/images/groupframe_left_stretch.png"
+    "../shared/images/groupframe_right_stretch.png"
+    "../shared/images/groupframe_top_stretch.png"
+    "../shared/images/groupframe_topleft.png"
+    "../shared/images/groupframe_topright.png"
+    "../shared/images/line_dash_dot.png"
+    "../shared/images/line_dash_dot_dot.png"
+    "../shared/images/line_dashed.png"
+    "../shared/images/line_dotted.png"
+    "../shared/images/line_solid.png"
+    "../shared/images/radiobutton-on.png"
+    "../shared/images/radiobutton_off.png"
+    "../shared/images/radiobutton_on.png"
+    "../shared/images/slider_bar.png"
+    "../shared/images/slider_thumb_on.png"
+    "../shared/images/title_cap_left.png"
+    "../shared/images/title_cap_right.png"
+    "../shared/images/title_stretch.png"
+)
+
+qt_add_resources(gradients "shared"
+    PREFIX
+        "/res"
+    BASE
+        "../shared"
+    FILES
+        ${shared_resource_files}
+)
+
+set(gradients_resource_files
+    "gradients.cpp"
+    "gradients.html"
+)
+
+qt_add_resources(gradients "gradients"
+    PREFIX
+        "/res/gradients"
+    FILES
+        ${gradients_resource_files}
+)
+
+install(TARGETS gradients
+    RUNTIME DESTINATION "${INSTALL_EXAMPLEDIR}"
+    BUNDLE DESTINATION "${INSTALL_EXAMPLEDIR}"
+    LIBRARY DESTINATION "${INSTALL_EXAMPLEDIR}"
+)

examples/widgets/painting/gradients/gradients.cpp

@@ -0,0 +1,547 @@
+// Copyright (C) 2016 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#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_OpaquePaintEvent);
+    }
+
+    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));
+            if (qIsNull(l.dx()))
+                continue;
+            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 (const auto &stop : stops) {
+            QColor c = stop.second;
+            m_alpha_gradient.setColorAt(stop.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->setContentsMargins(1, 1, 1, 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) {
+        const int x = int(points.at(i).x());
+        if (i + 1 < points.size() && x == int(points.at(i + 1).x()))
+            continue;
+        QColor color((0x00ff0000 & m_red_shade->colorAt(x)) >> 16,
+                     (0x0000ff00 & m_green_shade->colorAt(x)) >> 8,
+                     (0x000000ff & m_blue_shade->colorAt(x)),
+                     (0xff000000 & m_alpha_shade->colorAt(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);
+
+    QWidget *mainContentWidget = new QWidget();
+    QGroupBox *mainGroup = new QGroupBox(mainContentWidget);
+    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"));
+#if QT_CONFIG(opengl)
+    QPushButton *enableOpenGLButton = new QPushButton(mainGroup);
+    enableOpenGLButton->setText(tr("Use OpenGL"));
+    enableOpenGLButton->setCheckable(true);
+    enableOpenGLButton->setChecked(m_renderer->usesOpenGL());
+#endif
+    QPushButton *whatsThisButton = new QPushButton(mainGroup);
+    whatsThisButton->setText(tr("What's This?"));
+    whatsThisButton->setCheckable(true);
+
+    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);
+#if QT_CONFIG(opengl)
+    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);
+
+    mainGroup->setLayout(mainGroupLayout);
+
+    QVBoxLayout *mainContentLayout = new QVBoxLayout();
+    mainContentLayout->addWidget(mainGroup);
+    mainContentWidget->setLayout(mainContentLayout);
+
+    QScrollArea *mainScrollArea = new QScrollArea();
+    mainScrollArea->setWidget(mainContentWidget);
+    mainScrollArea->setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Preferred);
+
+    // Layouts
+    QHBoxLayout *mainLayout = new QHBoxLayout(this);
+    mainLayout->addWidget(m_renderer);
+    mainLayout->addWidget(mainScrollArea);
+
+    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);
+#if QT_CONFIG(opengl)
+    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, &GradientWidget::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);
+
+    QList<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 = QLineF(0, 0, 1, 0).angleTo(l);
+        g = QConicalGradient(pts.at(0), angle);
+    }
+
+    for (const auto &stop : std::as_const(m_stops))
+        g.setColorAt(stop.first, stop.second);
+
+    g.setSpread(m_spread);
+
+    p->setBrush(g);
+    p->setPen(Qt::NoPen);
+
+    p->drawRect(rect());
+
+}

examples/widgets/painting/gradients/gradients.h

@@ -0,0 +1,143 @@
+// Copyright (C) 2016 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef GRADIENTS_H
+#define GRADIENTS_H
+
+#include "arthurwidgets.h"
+
+QT_BEGIN_NAMESPACE
+class QRadioButton;
+QT_END_NAMESPACE
+
+class HoverPoints;
+
+
+class ShadeWidget : public QWidget
+{
+    Q_OBJECT
+
+public:
+    enum ShadeType {
+        RedShade,
+        GreenShade,
+        BlueShade,
+        ARGBShade
+    };
+
+    ShadeWidget(ShadeType type, QWidget *parent);
+
+    void setGradientStops(const QGradientStops &stops);
+
+    void paintEvent(QPaintEvent *e) override;
+
+    QSize sizeHint() const override { return QSize(150, 40); }
+    QPolygonF points() const;
+
+    HoverPoints *hoverPoints() const { return m_hoverPoints; }
+
+    uint colorAt(int x);
+
+signals:
+    void colorsChanged();
+
+private:
+    void generateShade();
+
+    ShadeType m_shade_type;
+    QImage m_shade;
+    HoverPoints *m_hoverPoints;
+    QLinearGradient m_alpha_gradient;
+};
+
+class GradientEditor : public QWidget
+{
+    Q_OBJECT
+
+public:
+    GradientEditor(QWidget *parent);
+
+    void setGradientStops(const QGradientStops &stops);
+
+public slots:
+    void pointsUpdated();
+
+signals:
+    void gradientStopsChanged(const QGradientStops &stops);
+
+private:
+    ShadeWidget *m_red_shade;
+    ShadeWidget *m_green_shade;
+    ShadeWidget *m_blue_shade;
+    ShadeWidget *m_alpha_shade;
+};
+
+class GradientRenderer : public ArthurFrame
+{
+    Q_OBJECT
+
+public:
+    GradientRenderer(QWidget *parent);
+    void paint(QPainter *p) override;
+
+    QSize sizeHint() const override { return QSize(400, 400); }
+
+    HoverPoints *hoverPoints() const { return m_hoverPoints; }
+    void mousePressEvent(QMouseEvent *e) override;
+
+public slots:
+    void setGradientStops(const QGradientStops &stops);
+
+    void setPadSpread() { m_spread = QGradient::PadSpread; update(); }
+    void setRepeatSpread() { m_spread = QGradient::RepeatSpread; update(); }
+    void setReflectSpread() { m_spread = QGradient::ReflectSpread; update(); }
+
+    void setLinearGradient() { m_gradientType = Qt::LinearGradientPattern; update(); }
+    void setRadialGradient() { m_gradientType = Qt::RadialGradientPattern; update(); }
+    void setConicalGradient() { m_gradientType = Qt::ConicalGradientPattern; update(); }
+
+
+private:
+    QGradientStops m_stops;
+    HoverPoints *m_hoverPoints;
+
+    QGradient::Spread m_spread;
+    Qt::BrushStyle m_gradientType;
+};
+
+class GradientWidget : public QWidget
+{
+    Q_OBJECT
+
+public:
+    GradientWidget(QWidget *parent = nullptr);
+
+public slots:
+    void setDefault1() { setDefault(1); }
+    void setDefault2() { setDefault(2); }
+    void setDefault3() { setDefault(3); }
+    void setDefault4() { setDefault(4); }
+    void setPreset()     { changePresetBy(0); }
+    void setPrevPreset() { changePresetBy(-1); }
+    void setNextPreset() { changePresetBy(1); }
+
+private:
+    void setDefault(int i);
+    void updatePresetName();
+    void changePresetBy(int indexOffset);
+
+    GradientRenderer *m_renderer;
+    GradientEditor *m_editor;
+
+    QRadioButton *m_linearButton;
+    QRadioButton *m_radialButton;
+    QRadioButton *m_conicalButton;
+    QRadioButton *m_padSpreadButton;
+    QRadioButton *m_reflectSpreadButton;
+    QRadioButton *m_repeatSpreadButton;
+    QPushButton *m_presetButton;
+
+    int m_presetIndex = 0;
+};
+
+#endif // GRADIENTS_H

examples/widgets/painting/gradients/gradients.html

@@ -0,0 +1,35 @@
+<html>
+<center>
+<h2>Gradients</h2>
+</center>
+
+<p>In this demo we show the various types of gradients that can
+be used in Qt.</p>
+
+<p>There are three types of gradients:
+
+<ul>
+  <li><b>Linear</b> gradients interpolate colors between start and end
+  points.</li>
+  <li><b>Radial</b> gradients interpolate colors between a focal point and the
+  points on a circle surrounding it.</li>
+  <li><b>Conical</b> gradients interpolate colors around a center point.</li>
+</ul>
+
+</p>
+
+<p>The panel on the right contains a color table editor that defines
+the colors in the gradient. The three topmost controls determine the red,
+green and blue components while the last defines the alpha of the
+gradient. You can move points, and add new ones, by clicking with the left
+mouse button, and remove points by clicking with the right button.</p>
+
+<p>There are three example configurations available at the bottom of
+the page that are provided as suggestions on how a color table could be
+configured.</p>
+
+<p>Qt also provides a suite of named gradient presets. They are based on the
+free WebGradients collection. Click on the name in the Presets box to show the
+gradient. Use the arrow buttons to browse through the available presets.</p>
+
+</html>

examples/widgets/painting/gradients/gradients.pro

@@ -0,0 +1,14 @@
+SOURCES += main.cpp gradients.cpp
+HEADERS += gradients.h
+
+SHARED_FOLDER = ../shared
+
+include($$SHARED_FOLDER/shared.pri)
+
+RESOURCES += gradients.qrc
+QT += widgets
+
+# install
+target.path = $$[QT_INSTALL_EXAMPLES]/widgets/painting/gradients
+INSTALLS += target
+

examples/widgets/painting/gradients/gradients.qrc

@@ -0,0 +1,6 @@
+<!DOCTYPE RCC><RCC version="1.0">
+<qresource prefix="/res/gradients">
+   <file>gradients.cpp</file>
+   <file>gradients.html</file>
+</qresource>
+</RCC>

examples/widgets/painting/gradients/main.cpp

@@ -0,0 +1,25 @@
+// Copyright (C) 2016 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "gradients.h"
+
+#include <QApplication>
+
+int main(int argc, char *argv[])
+{
+    Q_INIT_RESOURCE(gradients);
+
+    QApplication app(argc, argv);
+
+    GradientWidget gradientWidget;
+    QStyle *arthurStyle = new ArthurStyle;
+    gradientWidget.setStyle(arthurStyle);
+    const QList<QWidget *> widgets = gradientWidget.findChildren<QWidget *>();
+    for (QWidget *w : widgets) {
+        w->setStyle(arthurStyle);
+        w->setAttribute(Qt::WA_AcceptTouchEvents);
+    }
+    gradientWidget.show();
+
+    return app.exec();
+}