statistics: replace PieSeries by QSG nodes

Since there are no disk-segment QSG primitives (one could draw
a triangle fan, but that doesn't seem optimal), this draws
into a pixmap and blits that as a QSG node.

Since this is the only series without axis, it needs a function
that returns the size of the plot area. This didn't exist, so
add it.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

6 files changed, 92 insertions, 50 deletions

diff --git a/stats/chartitem.cpp b/stats/chartitem.cpp
index b8bf0f189..be2b3d635 100644
--- a/stats/chartitem.cpp
+++ b/stats/chartitem.cpp
@@ -224,6 +224,11 @@ ChartTextItem::ChartTextItem(StatsView &v, ChartZValue z, const QFont &f, const
 	resize(QSizeF(totalWidth, totalHeight));
 }
 
+ChartTextItem::ChartTextItem(StatsView &v, ChartZValue z, const QFont &f, const QString &text) :
+	ChartTextItem(v, z, f, std::vector<QString>({ text }), true)
+{
+}
+
 void ChartTextItem::setColor(const QColor &c)
 {
 	img->fill(Qt::transparent);
@@ -240,6 +245,31 @@ void ChartTextItem::setColor(const QColor &c)
 	setTextureDirty();
 }
 
+ChartPieItem::ChartPieItem(StatsView &v, ChartZValue z, double borderWidth) : ChartPixmapItem(v, z),
+	borderWidth(borderWidth)
+{
+}
+
+void ChartPieItem::drawSegment(double from, double to, QColor fill, QColor border)
+{
+	painter->setPen(QPen(border, borderWidth));
+	painter->setBrush(QBrush(fill));
+	// For whatever obscure reason, angles of pie pieces are given as 16th of a degree...?
+	// Angles increase CCW, whereas pie charts usually are read CW. Therfore, startAngle
+	// is dervied from "from" and subtracted from the origin angle at 12:00.
+	int startAngle = 90 * 16 - static_cast<int>(round(to * 360.0 * 16.0));
+	int spanAngle = static_cast<int>(round((to - from) * 360.0 * 16.0));
+	QRectF drawRect(QPointF(0.0, 0.0), rect.size());
+	painter->drawPie(drawRect, startAngle, spanAngle);
+	setTextureDirty();
+}
+
+void ChartPieItem::resize(QSizeF size)
+{
+	ChartPixmapItem::resize(size);
+	img->fill(Qt::transparent);
+}
+
 ChartLineItem::ChartLineItem(StatsView &v, ChartZValue z, QColor color, double width) : HideableChartItem(v, z),
 	color(color), width(width), positionDirty(false), materialDirty(false)
 {
diff --git a/stats/chartitem.h b/stats/chartitem.h
index 338c23b8b..44caae9cc 100644
--- a/stats/chartitem.h
+++ b/stats/chartitem.h
@@ -62,8 +62,8 @@ protected:
 	std::unique_ptr<QImage> img;
 	void setTextureDirty();
 	void setPositionDirty();
-private:
 	QRectF rect;
+private:
 	bool positionDirty;		// true if the position changed since last render
 	bool textureDirty;		// true if the pixmap changed since last render
 	std::unique_ptr<QSGTexture> texture;
@@ -85,6 +85,7 @@ private:
 class ChartTextItem : public ChartPixmapItem {
 public:
 	ChartTextItem(StatsView &v, ChartZValue z, const QFont &f, const std::vector<QString> &text, bool center);
+	ChartTextItem(StatsView &v, ChartZValue z, const QFont &f, const QString &text);
 	void setColor(const QColor &color);
 private:
 	QFont f;
@@ -97,6 +98,16 @@ private:
 	std::vector<Item> items;
 };
 
+// A pie chart item: draws disk segments onto a pixmap.
+class ChartPieItem : public ChartPixmapItem {
+public:
+	ChartPieItem(StatsView &v, ChartZValue z, double borderWidth);
+	void drawSegment(double from, double to, QColor fill, QColor border); // from and to are relative (0-1 is full disk).
+	void resize(QSizeF size);	// As in base class, but clears the canvas
+private:
+	double borderWidth;
+};
+
 class ChartLineItem : public HideableChartItem<HideableQSGNode<QSGGeometryNode>> {
 public:
 	ChartLineItem(StatsView &v, ChartZValue z, QColor color, double width);
diff --git a/stats/pieseries.cpp b/stats/pieseries.cpp
index dc337aa8d..09e74961a 100644
--- a/stats/pieseries.cpp
+++ b/stats/pieseries.cpp
@@ -9,7 +9,6 @@
 
 #include <numeric>
 #include <math.h>
-#include <QGraphicsEllipseItem>
 #include <QLocale>
 
 static const double pieSize = 0.9; // 1.0 = occupy full width of chart
@@ -17,20 +16,15 @@ static const double pieBorderWidth = 1.0;
 static const double innerLabelRadius = 0.75; // 1.0 = at outer border of pie
 static const double outerLabelRadius = 1.01; // 1.0 = at outer border of pie
 
-PieSeries::Item::Item(QGraphicsScene *scene, const QString &name, int from, int count, int totalCount,
+PieSeries::Item::Item(StatsView &view, const QString &name, int from, int count, int totalCount,
 		      int bin_nr, int numBins, bool labels) :
-	item(createItemPtr<QGraphicsEllipseItem>(scene)),
 	name(name),
 	count(count)
 {
+	QFont f; // make configurable
 	QLocale loc;
-	// For whatever obscure reason, angles in QGraphicsEllipseItem are given as 16th of a degree...?
-	// Angles increase CCW, whereas pie charts usually are read CW.
-	item->setStartAngle(90 * 16 - (from + count) * 360 * 16 / totalCount);
-	item->setSpanAngle(count * 360 * 16 / totalCount);
-	item->setPen(QPen(::borderColor));
-	item->setZValue(ZValues::series);
 
+	angleFrom = static_cast<double>(from) / totalCount;
 	angleTo = static_cast<double>(from + count) / totalCount;
 	double meanAngle = M_PI / 2.0 - (from + count / 2.0) / totalCount * M_PI * 2.0; // Note: "-" because we go CW.
 	innerLabelPos = QPointF(cos(meanAngle) * innerLabelRadius, -sin(meanAngle) * innerLabelRadius);
@@ -39,27 +33,24 @@ PieSeries::Item::Item(QGraphicsScene *scene, const QString &name, int from, int
 	if (labels) {
 		double percentage = count * 100.0 / totalCount;
 		QString innerLabelText = QStringLiteral("%1\%").arg(loc.toString(percentage, 'f', 1));
-		innerLabel = createItemPtr<QGraphicsSimpleTextItem>(scene, innerLabelText);
-		innerLabel->setZValue(ZValues::seriesLabels);
+		innerLabel = view.createChartItem<ChartTextItem>(ChartZValue::SeriesLabels, f, innerLabelText);
 
-		outerLabel = createItemPtr<QGraphicsSimpleTextItem>(scene, name);
-		outerLabel->setBrush(QBrush(darkLabelColor));
-		outerLabel->setZValue(ZValues::seriesLabels);
+		outerLabel = view.createChartItem<ChartTextItem>(ChartZValue::SeriesLabels, f, name);
+		outerLabel->setColor(darkLabelColor);
 	}
-
-	highlight(bin_nr, false, numBins);
 }
 
-void PieSeries::Item::updatePositions(const QRectF &rect, const QPointF &center, double radius)
+void PieSeries::Item::updatePositions(const QPointF &center, double radius)
 {
-	item->setRect(rect);
+	// Note: the positions in this functions are rounded to integer values,
+	// because half-integer values gives horrible aliasing artifacts.
 	if (innerLabel) {
-		QRectF labelRect = innerLabel->boundingRect();
-		innerLabel->setPos(center.x() + innerLabelPos.x() * radius - labelRect.width() / 2.0,
-				   center.y() + innerLabelPos.y() * radius - labelRect.height() / 2.0);
+		QRectF labelRect = innerLabel->getRect();
+		innerLabel->setPos(QPointF(round(center.x() + innerLabelPos.x() * radius - labelRect.width() / 2.0),
+					   round(center.y() + innerLabelPos.y() * radius - labelRect.height() / 2.0)));
 	}
 	if (outerLabel) {
-		QRectF labelRect = outerLabel->boundingRect();
+		QRectF labelRect = outerLabel->getRect();
 		QPointF pos(center.x() + outerLabelPos.x() * radius, center.y() + outerLabelPos.y() * radius);
 		if (outerLabelPos.x() < 0.0) {
 			if (outerLabelPos.y() < 0.0)
@@ -70,25 +61,23 @@ void PieSeries::Item::updatePositions(const QRectF &rect, const QPointF &center,
 			pos.ry() -= labelRect.height();
 		}
 
-		outerLabel->setPos(pos);
+		outerLabel->setPos(QPointF(round(pos.x()), round(pos.y())));
 	}
 }
 
-void PieSeries::Item::highlight(int bin_nr, bool highlight, int numBins)
+void PieSeries::Item::highlight(ChartPieItem &item, int bin_nr, bool highlight, int numBins)
 {
-	QBrush brush(highlight ? highlightedColor : binColor(bin_nr, numBins));
-	QPen pen(highlight ? highlightedBorderColor : ::borderColor, pieBorderWidth);
-	item->setBrush(brush);
-	item->setPen(pen);
-	if (innerLabel) {
-		QBrush labelBrush(highlight ? darkLabelColor : labelColor(bin_nr, numBins));
-		innerLabel->setBrush(labelBrush);
-	}
+	if (innerLabel)
+		innerLabel->setColor(highlight ? darkLabelColor : labelColor(bin_nr, numBins));
+	item.drawSegment(angleFrom, angleTo,
+			 highlight ? highlightedColor : binColor(bin_nr, numBins),
+			 highlight ? highlightedBorderColor : ::borderColor);
 }
 
 PieSeries::PieSeries(QGraphicsScene *scene, StatsView &view, StatsAxis *xAxis, StatsAxis *yAxis, const QString &categoryName,
 		     const std::vector<std::pair<QString, int>> &data, bool keepOrder, bool labels) :
 	StatsSeries(scene, view, xAxis, yAxis),
+	item(view.createChartItem<ChartPieItem>(ChartZValue::Series, pieBorderWidth)),
 	categoryName(categoryName),
 	highlighted(-1)
 {
@@ -148,7 +137,7 @@ PieSeries::PieSeries(QGraphicsScene *scene, StatsView &view, StatsAxis *xAxis, S
 	int act = 0;
 	for (auto it2 = sorted.begin(); it2 != it; ++it2) {
 		int count = data[*it2].second;
-		items.emplace_back(scene, data[*it2].first, act, count, totalCount, (int)items.size(), numBins, labels);
+		items.emplace_back(view, data[*it2].first, act, count, totalCount, (int)items.size(), numBins, labels);
 		act += count;
 	}
 
@@ -158,7 +147,7 @@ PieSeries::PieSeries(QGraphicsScene *scene, StatsView &view, StatsAxis *xAxis, S
 		for (auto it2 = it; it2 != sorted.end(); ++it2)
 			other.push_back({ data[*it2].first, data[*it2].second });
 		QString name = StatsTranslations::tr("other (%1 items)").arg(other.size());
-		items.emplace_back(scene, name, act, totalCount - act, totalCount, (int)items.size(), numBins, labels);
+		items.emplace_back(view, name, act, totalCount - act, totalCount, (int)items.size(), numBins, labels);
 	}
 }
 
@@ -168,12 +157,18 @@ PieSeries::~PieSeries()
 
 void PieSeries::updatePositions()
 {
-	QRectF plotRect = scene->sceneRect();
+	QRectF plotRect = view.plotArea();
 	center = plotRect.center();
-	radius = std::min(plotRect.width(), plotRect.height()) * pieSize / 2.0;
-	QRectF rect(center.x() - radius, center.y() - radius, 2.0 * radius, 2.0 * radius);
-	for (Item &item: items)
-		item.updatePositions(rect, center, radius);
+	radius = ceil(std::min(plotRect.width(), plotRect.height()) * pieSize / 2.0);
+	QRectF rect(round(center.x() - radius), round(center.y() - radius), ceil(2.0 * radius), ceil(2.0 * radius));
+	item->resize(rect.size());
+	item->setPos(rect.topLeft());
+	int i = 0;
+	for (Item &segment: items) {
+		segment.updatePositions(center, radius);
+		segment.highlight(*item, i, i == highlighted, (int)items.size()); // Draw segment
+		++i;
+	}
 }
 
 std::vector<QString> PieSeries::binNames()
@@ -245,7 +240,7 @@ bool PieSeries::hover(QPointF pos)
 
 	// Highlight new item (if any)
 	if (highlighted >= 0 && highlighted < (int)items.size()) {
-		items[highlighted].highlight(highlighted, true, (int)items.size());
+		items[highlighted].highlight(*item, highlighted, true, (int)items.size());
 		if (!information)
 			information = view.createChartItem<InformationBox>();
 		information->setText(makeInfo(highlighted), pos);
@@ -258,6 +253,6 @@ bool PieSeries::hover(QPointF pos)
 void PieSeries::unhighlight()
 {
 	if (highlighted >= 0 && highlighted < (int)items.size())
-		items[highlighted].highlight(highlighted, false, (int)items.size());
+		items[highlighted].highlight(*item, highlighted, false, (int)items.size());
 	highlighted = -1;
 }
diff --git a/stats/pieseries.h b/stats/pieseries.h
index 56e56c7d6..d9dd1b5fb 100644
--- a/stats/pieseries.h
+++ b/stats/pieseries.h
@@ -10,9 +10,9 @@
 #include <QString>
 
 struct InformationBox;
-class QGraphicsEllipseItem;
+struct ChartPieItem;
+struct ChartTextItem;
 class QGraphicsScene;
-class QGraphicsSimpleTextItem;
 class QRectF;
 
 class PieSeries : public StatsSeries {
@@ -34,20 +34,20 @@ private:
 	// Get item under mouse pointer, or -1 if none
 	int getItemUnderMouse(const QPointF &f) const;
 
+	std::unique_ptr<ChartPieItem> item;
 	QString categoryName;
 	std::vector<QString> makeInfo(int idx) const;
 
 	struct Item {
-		std::unique_ptr<QGraphicsEllipseItem> item;
-		std::unique_ptr<QGraphicsSimpleTextItem> innerLabel, outerLabel;
+		std::unique_ptr<ChartTextItem> innerLabel, outerLabel;
 		QString name;
-		double angleTo; // In fraction of total
+		double angleFrom, angleTo; // In fraction of total
 		int count;
 		QPointF innerLabelPos, outerLabelPos; // With respect to a (-1, -1)-(1, 1) rectangle.
-		Item(QGraphicsScene *scene, const QString &name, int from, int count, int totalCount,
+		Item(StatsView &view, const QString &name, int from, int count, int totalCount,
 		     int bin_nr, int numBins, bool labels);
-		void updatePositions(const QRectF &rect, const QPointF &center, double radius);
-		void highlight(int bin_nr, bool highlight, int numBins);
+		void updatePositions(const QPointF &center, double radius);
+		void highlight(ChartPieItem &item, int bin_nr, bool highlight, int numBins);
 	};
 	std::vector<Item> items;
 	int totalCount;
diff --git a/stats/statsview.cpp b/stats/statsview.cpp
index 455589976..e616c3e12 100644
--- a/stats/statsview.cpp
+++ b/stats/statsview.cpp
@@ -187,6 +187,11 @@ QSizeF StatsView::size() const
 	return boundingRect().size();
 }
 
+QRectF StatsView::plotArea() const
+{
+	return plotRect;
+}
+
 void StatsView::plotAreaChanged(const QSizeF &s)
 {
 	// Make sure that image is at least one pixel wide / high, otherwise
diff --git a/stats/statsview.h b/stats/statsview.h
index b0a199200..05893ad33 100644
--- a/stats/statsview.h
+++ b/stats/statsview.h
@@ -45,6 +45,7 @@ public:
 	void plot(const StatsState &state);
 	QQuickWindow *w() const;		// Make window available to items
 	QSizeF size() const;
+	QRectF plotArea() const;
 	void addQSGNode(QSGNode *node, ChartZValue z);	// Must only be called in render thread!
 	void registerDirtyChartItem(ChartItem &item);
 	void unregisterDirtyChartItem(ChartItem &item);