Support showing median values in CandleStick plots.

examples/Stock/Advanced/OHLC.csv

@@ -1,8 +1,8 @@
 ,"Foobar Inc."
-January, 20.3, 42.4, 10.3, 32.0
-February, 32.0, 37.3, 20.0, 25.9
-March, 25.9, 33.7, 20.3, 29.0
-April, 29.9, 53.3, 28.1, 39.0
-May, 39.0, 45.0, 36.4, 41.9
-June, 41.9, 63.3, 41.0, 58.7
-July, 58.7, 68.5, 50.7, 55.3
+January, 20.3, 42.4, 10.3, 32.0, 23
+February, 32.0, 37.3, 20.0, 25.9, 28.4
+March, 25.9, 33.7, 20.3, 29.0, 26.5
+April, 29.9, 53.3, 28.1, 39.0, 35
+May, 39.0, 45.0, 36.4, 41.9, 40
+June, 41.9, 63.3, 41.0, 58.7, 55
+July, 58.7, 68.5, 50.7, 55.3, 56

examples/Stock/Advanced/mainwindow.cpp

@@ -72,6 +72,7 @@ void MainWindow::applyColor(const QColor &color)
         QColor inverse(255 - color.red(), 255 - color.green(), 255 - color.blue());
         m_diagram.setPen(1, QPen(inverse.darker(130)));
         m_diagram.setBrush(1, QBrush(inverse));
+
         QPalette pal = colorChooser->palette();
         pal.setBrush(QPalette::Button, QBrush(color));
         colorChooser->setPalette(pal);
@@ -133,6 +134,7 @@ void MainWindow::on_stockTypeCB_currentIndexChanged(int index)
     } else if (text == "Candlestick") {
         m_diagram.setType(StockDiagram::Candlestick);
         m_diagram.setModel(&m_OHLCModel);
+        m_diagram.setDataContainsMedianValues(true);
     }
 
     m_chart->coordinatePlane()->replaceDiagram(&m_diagram);

src/KDChart/Cartesian/KDChartStockDiagram.cpp

@@ -286,7 +286,18 @@ void StockDiagram::paint(PaintContext *context)
 
     PainterSaver painterSaver(context->painter());
     const int rowCount = attributesModel()->rowCount(attributesModelRootIndex());
-    const int divisor = (d->type == OpenHighLowClose || d->type == Candlestick) ? 4 : 3;
+    const int divisor = [&] {
+        switch (d->type) {
+        case HighLowClose:
+            return 3;
+        case OpenHighLowClose:
+            return 4;
+        case Candlestick:
+            return d->dataContainsMedian ? 5 : 4;
+        }
+        Q_UNREACHABLE();
+    }();
+
     const int colCount = attributesModel()->columnCount(attributesModelRootIndex()) / divisor;
     for (int col = 0; col < colCount; ++col) {
         for (int row = 0; row < rowCount; row++) {
@@ -295,6 +306,8 @@ void StockDiagram::paint(PaintContext *context)
             CartesianDiagramDataCompressor::DataPoint open;
             CartesianDiagramDataCompressor::DataPoint close;
             CartesianDiagramDataCompressor::DataPoint volume;
+            CartesianDiagramDataCompressor::DataPoint median;
+
 
             if (d->type == HighLowClose) {
                 const CartesianDiagramDataCompressor::CachePosition highPos(row, col * divisor);
@@ -312,6 +325,10 @@ void StockDiagram::paint(PaintContext *context)
                 low = d->compressor.data(lowPos);
                 high = d->compressor.data(highPos);
                 close = d->compressor.data(closePos);
+                if (d->type == Candlestick) {
+                    const CartesianDiagramDataCompressor::CachePosition medianPos(row, col * divisor + 4);
+                    median = d->compressor.data(medianPos);
+                }
             }
 
             switch (d->type) {
@@ -323,7 +340,8 @@ void StockDiagram::paint(PaintContext *context)
                     d->drawOHLCBar(col, open, high, low, close, context);
                 break;
             case Candlestick:
-                d->drawCandlestick(col, open, high, low, close, context);
+                median.hidden = !d->dataContainsMedian;
+                d->drawCandlestick(col, open, high, low, close, median, context);
                 break;
             }
         }
@@ -352,6 +370,11 @@ qreal StockDiagram::threeDItemDepth(const QModelIndex &index) const
     return 1.0;
 }
 
+void StockDiagram::setDataContainsMedianValues(bool b)
+{
+    d->dataContainsMedian = b;
+}
+
 const QPair<QPointF, QPointF> StockDiagram::calculateDataBoundaries() const
 {
     const int rowCount = attributesModel()->rowCount(attributesModelRootIndex());

src/KDChart/Cartesian/KDChartStockDiagram.h

@@ -98,6 +98,8 @@ class KDCHART_EXPORT StockDiagram : public AbstractCartesianDiagram
     qreal threeDItemDepth(int column) const override;
     qreal threeDItemDepth(const QModelIndex &index) const override;
 
+    void setDataContainsMedianValues(bool b = true);
+
 protected:
     const QPair<QPointF, QPointF> calculateDataBoundaries() const override;
 };

src/KDChart/Cartesian/KDChartStockDiagram_p.cpp

@@ -328,6 +328,7 @@ void StockDiagram::Private::drawCandlestick(int /*dataset*/, const CartesianDiag
                                             const CartesianDiagramDataCompressor::DataPoint &high,
                                             const CartesianDiagramDataCompressor::DataPoint &low,
                                             const CartesianDiagramDataCompressor::DataPoint &close,
+                                            const CartesianDiagramDataCompressor::DataPoint &median,
                                             PaintContext *context)
 {
     PainterSaver painterSaver(context->painter());
@@ -342,6 +343,7 @@ void StockDiagram::Private::drawCandlestick(int /*dataset*/, const CartesianDiag
     QPen pen;
     bool drawLowerLine;
     bool drawCandlestick = !open.hidden && !close.hidden;
+    bool drawMedian = !median.hidden;
     bool drawUpperLine;
 
     // Find out if we need to paint a down-trend or up-trend candlestick
@@ -363,6 +365,19 @@ void StockDiagram::Private::drawCandlestick(int /*dataset*/, const CartesianDiag
         drawUpperLine = !low.hidden && !open.hidden;
     }
 
+    auto medianColor = [&] {
+        auto brushColor = brush.color();
+        if (brushColor.isValid()) {
+            return (0.21 * brushColor.red() + 0.72 * brushColor.green() + 0.07 * brushColor.blue()) < 127
+                ? QColor(Qt::white)
+                : QColor(Qt::black);
+        } else {
+            // Fallback to pen color, we could do better by letting the caller provide the pen, but I'm out of attention span for that.
+            return pen.color();
+        }
+    };
+
+
     StockBarAttributes attr = stockDiagram()->stockBarAttributes(col);
     ThreeDBarAttributes threeDAttr = stockDiagram()->threeDBarAttributes(col);
 
@@ -375,6 +390,11 @@ void StockDiagram::Private::drawCandlestick(int /*dataset*/, const CartesianDiag
     QRectF candlestick = projectCandlestick(context, bottomCandlestickPoint,
                                             topCandlestickPoint, attr.candlestickWidth());
 
+    const auto medianLine = [&] {
+        const QPointF medianPoint = projectPoint(context, QPointF(median.key, median.value));
+        return QLineF(candlestick.left(), medianPoint.y(), candlestick.right(), medianPoint.y());
+    };
+
     // Remember the drawn polygon to add it to the ReverseMapper later
     QPolygonF drawnPolygon;
 
@@ -396,13 +416,15 @@ void StockDiagram::Private::drawCandlestick(int /*dataset*/, const CartesianDiag
                 drawnPolygon = threeDPainter.drawThreeDRect(candlestick, brush, pen, threeDProps);
             if (drawUpperLine)
                 drawnPolygon = threeDPainter.drawTwoDLine(upperLine, pen, threeDProps);
+            // TODO: Draw median in 3D
         } else {
             if (drawUpperLine)
                 drawnPolygon = threeDPainter.drawTwoDLine(upperLine, pen, threeDProps);
             if (drawCandlestick)
                 drawnPolygon = threeDPainter.drawThreeDRect(candlestick, brush, pen, threeDProps);
             if (drawLowerLine)
                 drawnPolygon = threeDPainter.drawTwoDLine(lowerLine, pen, threeDProps);
+            // TODO: Draw median in 3D
         }
     } else {
         QPainter *const painter = context->painter();
@@ -414,6 +436,11 @@ void StockDiagram::Private::drawCandlestick(int /*dataset*/, const CartesianDiag
             painter->drawLine(upperLine);
         if (drawCandlestick)
             painter->drawRect(candlestick);
+        if (drawMedian) {
+            painter->setPen(medianColor());
+            painter->drawLine(medianLine());
+            painter->setPen(pen);
+        }
 
         // The 2D representation is the projected candlestick itself
         drawnPolygon = candlestick;

src/KDChart/Cartesian/KDChartStockDiagram_p.h

@@ -45,6 +45,7 @@ class StockDiagram::Private : public AbstractCartesianDiagram::Private
 
     QPen lowHighLinePen;
     QMap<int, QPen> lowHighLinePens;
+    bool dataContainsMedian = false;
 
     void drawOHLCBar(int dataset, const CartesianDiagramDataCompressor::DataPoint &open,
                      const CartesianDiagramDataCompressor::DataPoint &high,
@@ -59,6 +60,7 @@ class StockDiagram::Private : public AbstractCartesianDiagram::Private
                          const CartesianDiagramDataCompressor::DataPoint &high,
                          const CartesianDiagramDataCompressor::DataPoint &low,
                          const CartesianDiagramDataCompressor::DataPoint &close,
+                         const CartesianDiagramDataCompressor::DataPoint &median,
                          PaintContext *context);
 
 private: