File indexing completed on 2024-04-14 14:27:07

 /*
  * This file is part of KQuickCharts
  * SPDX-FileCopyrightText: 2019 Arjen Hiemstra <ahiemstra@heimr.nl>
  *
  * SPDX-License-Identifier: LGPL-2.1-only OR LGPL-3.0-only OR LicenseRef-KDE-Accepted-LGPL
  */
 
 #include "LineChart.h"
 
 #include <cmath>
 
 #include <QPainter>
 #include <QPainterPath>
 #include <QQuickWindow>
 
 #include "RangeGroup.h"
 #include "datasource/ChartDataSource.h"
 #include "scenegraph/LineChartNode.h"
 #include "scenegraph/LineGridNode.h"
 
 static const float PixelsPerStep = 2.0;
 
 QVector<QVector2D> interpolate(const QVector<QVector2D> &points, float height);
 QVector<float> calculateTangents(const QVector<QVector2D> &points, float height);
 QVector2D cubicHermite(const QVector2D &first, const QVector2D &second, float step, float mFirst, float mSecond);
 
 QColor colorWithAlpha(const QColor &color, qreal opacity)
 {
     auto result = color;
     result.setRedF(result.redF() * opacity);
     result.setGreenF(result.greenF() * opacity);
     result.setBlueF(result.blueF() * opacity);
     result.setAlphaF(opacity);
     return result;
 }
 
 LineChartAttached::LineChartAttached(QObject *parent)
     : QObject(parent)
 {
 }
 
 QVariant LineChartAttached::value() const
 {
     return m_value;
 }
 
 void LineChartAttached::setValue(const QVariant &value)
 {
     if (value == m_value) {
         return;
     }
 
     m_value = value;
     Q_EMIT valueChanged();
 }
 
 QColor LineChartAttached::color() const
 {
     return m_color;
 }
 
 void LineChartAttached::setColor(const QColor &color)
 {
     if (color == m_color) {
         return;
     }
 
     m_color = color;
     Q_EMIT colorChanged();
 }
 
 QString LineChartAttached::name() const
 {
     return m_name;
 }
 
 void LineChartAttached::setName(const QString &newName)
 {
     if (newName == m_name) {
         return;
     }
 
     m_name = newName;
     Q_EMIT nameChanged();
 }
 
 QString LineChartAttached::shortName() const
 {
     if (m_shortName.isEmpty()) {
         return m_name;
     } else {
         return m_shortName;
     }
 }
 
 void LineChartAttached::setShortName(const QString &newShortName)
 {
     if (newShortName == m_shortName) {
         return;
     }
 
     m_shortName = newShortName;
     Q_EMIT shortNameChanged();
 }
 
 LineChart::LineChart(QQuickItem *parent)
     : XYChart(parent)
 {
 }
 
 bool LineChart::smooth() const
 {
     return m_smooth;
 }
 
 qreal LineChart::lineWidth() const
 {
     return m_lineWidth;
 }
 
 qreal LineChart::fillOpacity() const
 {
     return m_fillOpacity;
 }
 
 void LineChart::setSmooth(bool smooth)
 {
     if (smooth == m_smooth) {
         return;
     }
 
     m_smooth = smooth;
     polish();
     Q_EMIT smoothChanged();
 }
 
 void LineChart::setLineWidth(qreal width)
 {
     if (qFuzzyCompare(m_lineWidth, width)) {
         return;
     }
 
     m_lineWidth = width;
     update();
     Q_EMIT lineWidthChanged();
 }
 
 void LineChart::setFillOpacity(qreal opacity)
 {
     if (qFuzzyCompare(m_fillOpacity, opacity)) {
         return;
     }
 
     m_fillOpacity = opacity;
     update();
     Q_EMIT fillOpacityChanged();
 }
 
 ChartDataSource *LineChart::fillColorSource() const
 {
     return m_fillColorSource;
 }
 
 void LineChart::setFillColorSource(ChartDataSource *newFillColorSource)
 {
     if (newFillColorSource == m_fillColorSource) {
         return;
     }
 
     m_fillColorSource = newFillColorSource;
     update();
     Q_EMIT fillColorSourceChanged();
 }
 
 QQmlComponent *LineChart::pointDelegate() const
 {
     return m_pointDelegate;
 }
 
 void LineChart::setPointDelegate(QQmlComponent *newPointDelegate)
 {
     if (newPointDelegate == m_pointDelegate) {
         return;
     }
 
     m_pointDelegate = newPointDelegate;
     for (auto entry : std::as_const(m_pointDelegates)) {
         qDeleteAll(entry);
     }
     m_pointDelegates.clear();
     polish();
     Q_EMIT pointDelegateChanged();
 }
 
 void LineChart::updatePolish()
 {
     if (m_rangeInvalid) {
         updateComputedRange();
         m_rangeInvalid = false;
     }
 
     QVector<QVector2D> previousValues;
 
     const auto range = computedRange();
     const auto sources = valueSources();
     for (int i = 0; i < sources.size(); ++i) {
         auto valueSource = sources.at(i);
 
         float stepSize = width() / (range.distanceX - 1);
         QVector<QVector2D> values(range.distanceX);
         auto generator = [&, i = range.startX]() mutable -> QVector2D {
             float value = 0;
             if (range.distanceY != 0) {
                 value = (valueSource->item(i).toFloat() - range.startY) / range.distanceY;
             }
 
             auto result = QVector2D{direction() == Direction::ZeroAtStart ? i * stepSize : float(boundingRect().right()) - i * stepSize, value};
             i++;
             return result;
         };
 
         if (direction() == Direction::ZeroAtStart) {
             std::generate_n(values.begin(), range.distanceX, generator);
         } else {
             std::generate_n(values.rbegin(), range.distanceX, generator);
         }
 
         if (stacked() && !previousValues.isEmpty()) {
             if (values.size() != previousValues.size()) {
                 qWarning() << "Value source" << valueSource->objectName()
                            << "has a different number of elements from the previous source. Ignoring stacking for this source.";
             } else {
                 std::for_each(values.begin(), values.end(), [previousValues, i = 0](QVector2D &point) mutable {
                     point.setY(point.y() + previousValues.at(i++).y());
                 });
             }
         }
         previousValues = values;
 
         if (m_pointDelegate) {
             auto &delegates = m_pointDelegates[valueSource];
             if (delegates.size() != values.size()) {
                 qDeleteAll(delegates);
                 createPointDelegates(values, i);
             } else {
                 for (int item = 0; item < values.size(); ++item) {
                     auto delegate = delegates.at(item);
                     updatePointDelegate(delegate, values.at(item), valueSource->item(item), i);
                 }
             }
         }
 
         if (m_smooth) {
             m_values[valueSource] = interpolate(values, height());
         } else {
             m_values[valueSource] = values;
         }
     }
 
     const auto pointKeys = m_pointDelegates.keys();
     for (auto key : pointKeys) {
         if (!sources.contains(key)) {
             qDeleteAll(m_pointDelegates[key]);
             m_pointDelegates.remove(key);
         }
     }
 
     update();
 }
 
 QSGNode *LineChart::updatePaintNode(QSGNode *node, QQuickItem::UpdatePaintNodeData *data)
 {
     Q_UNUSED(data);
 
     if (!node) {
         node = new QSGNode();
     }
 
     const auto sources = valueSources();
     for (int i = 0; i < sources.size(); ++i) {
         int childIndex = sources.size() - 1 - i;
         while (childIndex >= node->childCount()) {
             node->appendChildNode(new LineChartNode{});
         }
         auto lineNode = static_cast<LineChartNode *>(node->childAtIndex(childIndex));
         auto color = colorSource() ? colorSource()->item(i).value<QColor>() : Qt::black;
         auto fillColor = m_fillColorSource ? m_fillColorSource->item(i).value<QColor>() : colorWithAlpha(color, m_fillOpacity);
         updateLineNode(lineNode, color, fillColor, sources.at(i));
     }
 
     while (node->childCount() > sources.size()) {
         // removeChildNode unfortunately does not take care of deletion so we
         // need to handle this manually.
         auto lastNode = node->childAtIndex(node->childCount() - 1);
         node->removeChildNode(lastNode);
         delete lastNode;
     }
 
     return node;
 }
 
 void LineChart::onDataChanged()
 {
     m_rangeInvalid = true;
     polish();
 }
 
 #if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
 void LineChart::geometryChanged(const QRectF &newGeometry, const QRectF &oldGeometry)
 #else
 void LineChart::geometryChange(const QRectF &newGeometry, const QRectF &oldGeometry)
 #endif
 {
 #if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
     XYChart::geometryChanged(newGeometry, oldGeometry);
 #else
     XYChart::geometryChange(newGeometry, oldGeometry);
 #endif
     if (newGeometry != oldGeometry) {
         polish();
     }
 }
 
 void LineChart::updateLineNode(LineChartNode *node, const QColor &lineColor, const QColor &fillColor, ChartDataSource *valueSource)
 {
     if (window()) {
         node->setRect(boundingRect(), window()->devicePixelRatio());
     } else {
         node->setRect(boundingRect(), 1.0);
     }
     node->setLineColor(lineColor);
     node->setFillColor(fillColor);
     node->setLineWidth(m_lineWidth);
 
     auto values = m_values.value(valueSource);
     node->setValues(values);
 
     node->updatePoints();
 }
 
 void LineChart::createPointDelegates(const QVector<QVector2D> &values, int sourceIndex)
 {
     auto valueSource = valueSources().at(sourceIndex);
 
     QVector<QQuickItem *> delegates;
     for (int i = 0; i < values.size(); ++i) {
         auto delegate = qobject_cast<QQuickItem *>(m_pointDelegate->beginCreate(qmlContext(m_pointDelegate)));
         if (!delegate) {
             qWarning() << "Delegate creation for point" << i << "of value source" << valueSource->objectName()
                        << "failed, make sure pointDelegate is a QQuickItem";
             delegate = new QQuickItem(this);
         }
 
         delegate->setParent(this);
         delegate->setParentItem(this);
         updatePointDelegate(delegate, values.at(i), valueSource->item(i), sourceIndex);
 
         m_pointDelegate->completeCreate();
 
         delegates.append(delegate);
     }
 
     m_pointDelegates.insert(valueSource, delegates);
 }
 
 void LineChart::updatePointDelegate(QQuickItem *delegate, const QVector2D &position, const QVariant &value, int sourceIndex)
 {
     auto pos = QPointF{position.x() - delegate->width() / 2, (1.0 - position.y()) * height() - delegate->height() / 2};
     delegate->setPosition(pos);
 
     auto attached = static_cast<LineChartAttached *>(qmlAttachedPropertiesObject<LineChart>(delegate, true));
     attached->setValue(value);
     attached->setColor(colorSource() ? colorSource()->item(sourceIndex).value<QColor>() : Qt::black);
     attached->setName(nameSource() ? nameSource()->item(sourceIndex).toString() : QString{});
     attached->setShortName(shortNameSource() ? shortNameSource()->item(sourceIndex).toString() : QString{});
 }
 
 // Smoothly interpolate between points, using monotonic cubic interpolation.
 QVector<QVector2D> interpolate(const QVector<QVector2D> &points, float height)
 {
     if (points.size() < 2) {
         return points;
     }
 
     auto tangents = calculateTangents(points, height);
 
     QVector<QVector2D> result;
 
     auto current = QVector2D{0.0, points.first().y() * height};
     result.append(QVector2D{0.0, points.first().y()});
 
     for (int i = 0; i < points.size() - 1; ++i) {
         auto next = QVector2D{points.at(i + 1).x(), points.at(i + 1).y() * height};
 
         auto currentTangent = tangents.at(i);
         auto nextTangent = tangents.at(i + 1);
 
         auto stepCount = int(std::max(1.0f, (next.x() - current.x()) / PixelsPerStep));
         auto stepSize = (next.x() - current.x()) / stepCount;
 
         if (stepCount == 1 || qFuzzyIsNull(next.y() - current.y())) {
             result.append(QVector2D{next.x(), next.y() / height});
             current = next;
             continue;
         }
 
         for (auto delta = current.x(); delta < next.x(); delta += stepSize) {
             auto interpolated = cubicHermite(current, next, delta, currentTangent, nextTangent);
             interpolated.setY(interpolated.y() / height);
             result.append(interpolated);
         }
 
         current = next;
     }
 
     current.setY(current.y() / height);
     result.append(current);
 
     return result;
 }
 
 // This calculates the tangents for monotonic cubic spline interpolation.
 // See https://en.wikipedia.org/wiki/Monotone_cubic_interpolation for details.
 QVector<float> calculateTangents(const QVector<QVector2D> &points, float height)
 {
     QVector<float> secantSlopes;
     secantSlopes.reserve(points.size());
 
     QVector<float> tangents;
     tangents.reserve(points.size());
 
     float previousSlope = 0.0;
     float slope = 0.0;
 
     for (int i = 0; i < points.size() - 1; ++i) {
         auto current = points.at(i);
         auto next = points.at(i + 1);
 
         previousSlope = slope;
         slope = (next.y() * height - current.y() * height) / (next.x() - current.x());
 
         secantSlopes.append(slope);
 
         if (i == 0) {
             tangents.append(slope);
         } else if (previousSlope * slope < 0.0) {
             tangents.append(0.0);
         } else {
             tangents.append((previousSlope + slope) / 2.0);
         }
     }
     tangents.append(secantSlopes.last());
 
     for (int i = 0; i < points.size() - 1; ++i) {
         auto slope = secantSlopes.at(i);
 
         if (qFuzzyIsNull(slope)) {
             tangents[i] = 0.0;
             tangents[i + 1] = 0.0;
             continue;
         }
 
         auto alpha = tangents.at(i) / slope;
         auto beta = tangents.at(i + 1) / slope;
 
         if (alpha < 0.0) {
             tangents[i] = 0.0;
         }
 
         if (beta < 0.0) {
             tangents[i + 1] = 0.0;
         }
 
         auto length = alpha * alpha + beta * beta;
         if (length > 9) {
             auto tau = 3.0 / sqrt(length);
             tangents[i] = tau * alpha * slope;
             tangents[i + 1] = tau * beta * slope;
         }
     }
 
     return tangents;
 }
 
 // Cubic Hermite Interpolation between two points
 // Given two points, an X value between those two points and two tangents, this
 // will perform cubic hermite interpolation between the two points.
 // See https://en.wikipedia.org/wiki/Cubic_Hermite_spline for details as well as
 // the above mentioned article on monotonic interpolation.
 QVector2D cubicHermite(const QVector2D &first, const QVector2D &second, float step, float mFirst, float mSecond)
 {
     const auto delta = second.x() - first.x();
     const auto t = (step - first.x()) / delta;
 
     // Hermite basis values
     // h₀₀(t) = 2t³ - 3t² + 1
     const auto h00 = 2.0f * std::pow(t, 3.0f) - 3.0f * std::pow(t, 2.0f) + 1.0f;
     // h₁₀(t) = t³ - 2t² + t
     const auto h10 = std::pow(t, 3.0f) - 2.0f * std::pow(t, 2.0f) + t;
     // h₀₁(t) = -2t³ + 3t²
     const auto h01 = -2.0f * std::pow(t, 3.0f) + 3.0f * std::pow(t, 2.0f);
     // h₁₁(t) = t³ - t²
     const auto h11 = std::pow(t, 3.0f) - std::pow(t, 2.0f);
 
     auto result = QVector2D{step, first.y() * h00 + delta * mFirst * h10 + second.y() * h01 + delta * mSecond * h11};
     return result;
 }
 
 #include "moc_LineChart.cpp"