Camera Raw panel docked beside the canvas: scope, Light, Color, Effects, canvas tools (12.8b1)

src/UI/CameraRawSlider.cpp

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+#include "UI/CameraRawSlider.h"
+#include <QMouseEvent>
+#include <QPainter>
+#include <QPainterPath>
+#include <QStyleOptionSlider>
+#include <cmath>
+
+namespace {
+// Thousandths of the range, as the filter sheet's sliders.
+constexpr int travel = 1000;
+
+QColor hsb(double degrees, double saturation, double brightness)
+{
+    double turns = degrees / 360;
+    turns -= std::floor(turns);
+    return QColor::fromHsvF(float(turns), float(saturation), float(brightness));
+}
+}
+
+std::optional<std::pair<QColor, QColor>> CameraRawSliderTrack::colors() const
+{
+    switch (kind) {
+    case Kind::plain: return std::nullopt;
+    case Kind::temperature: return std::pair(QColor::fromRgbF(0.22f, 0.46f, 0.95f), QColor::fromRgbF(0.98f, 0.82f, 0.18f));
+    case Kind::tint: return std::pair(QColor::fromRgbF(0.28f, 0.70f, 0.34f), QColor::fromRgbF(0.70f, 0.40f, 0.64f));
+    case Kind::chroma: return std::pair(QColor::fromRgbF(0.62f, 0.62f, 0.64f), QColor::fromRgbF(0.86f, 0.18f, 0.20f));
+    case Kind::hue: return std::pair(hsb(degrees - 50, 0.85, 0.9), hsb(degrees + 50, 0.85, 0.9));
+    case Kind::saturation: return std::pair(QColor::fromRgbF(0.55f, 0.55f, 0.56f), hsb(degrees, 0.9, 0.9));
+    case Kind::luminance: return std::pair(hsb(degrees, 0.55, 0.18), hsb(degrees, 0.35, 0.95));
+    }
+    throw std::logic_error("unknown slider track");
+}
+
+CameraRawSlider::CameraRawSlider(double low, double high, CameraRawSliderTrack track, const QString &help, std::function<void(double)> change,
+                                 std::function<void()> reset, QWidget *parent)
+    : QSlider(Qt::Horizontal, parent), m_low(low), m_high(high), m_track(track), m_change(std::move(change)), m_reset(std::move(reset))
+{
+    setRange(0, travel);
+    setMinimumWidth(60);
+    setFixedHeight(22);
+    setToolTip(help);
+    setAccessibleName(help);
+    connect(this, &QSlider::valueChanged, this, [this] { m_change(shown()); });
+}
+
+void CameraRawSlider::display(double value)
+{
+    // Swift's isTrackingValue: a drag keeps its own knob.
+    if (isSliderDown())
+        return;
+    const QSignalBlocker quiet(this);
+    setValue(int(std::lround((value - m_low) / (m_high - m_low) * travel)));
+}
+
+double CameraRawSlider::shown() const
+{
+    return m_low + (m_high - m_low) * value() / travel;
+}
+
+bool CameraRawSlider::isOnKnob(QPoint point) const
+{
+    QStyleOptionSlider option;
+    initStyleOption(&option);
+    return style()->subControlRect(QStyle::CC_Slider, &option, QStyle::SC_SliderHandle, this).adjusted(-2, -2, 2, 2).contains(point);
+}
+
+// Swift's GradientSliderCell: the whole track shows the colours.
+void CameraRawSlider::paintEvent(QPaintEvent *event)
+{
+    const std::optional<std::pair<QColor, QColor>> colors = m_track.colors();
+    if (!colors) {
+        QSlider::paintEvent(event);
+        return;
+    }
+    QStyleOptionSlider option;
+    initStyleOption(&option);
+    const QRect groove = style()->subControlRect(QStyle::CC_Slider, &option, QStyle::SC_SliderGroove, this);
+    QPainter painter(this);
+    painter.setRenderHint(QPainter::Antialiasing);
+    const double height = 4;
+    const QRectF bar(groove.left(), groove.center().y() + 0.5 - height / 2, groove.width(), height);
+    QLinearGradient gradient(bar.topLeft(), bar.topRight());
+    gradient.setColorAt(0, colors->first);
+    gradient.setColorAt(1, colors->second);
+    QPainterPath shape;
+    shape.addRoundedRect(bar, height / 2, height / 2);
+    painter.fillPath(shape, gradient);
+    option.subControls = QStyle::SC_SliderHandle;
+    style()->drawComplexControl(QStyle::CC_Slider, &option, &painter, this);
+}
+
+void CameraRawSlider::mouseDoubleClickEvent(QMouseEvent *event)
+{
+    if (event->button() == Qt::LeftButton && isOnKnob(event->position().toPoint())) {
+        m_reset();
+        return;
+    }
+    QSlider::mouseDoubleClickEvent(event);
+}