statistics: implement pie series

Implement a simple count-based pie chart. Percentage labels
are shown in the pie slices, the names outside the pie slices.
On hovering over a slice, the actual counts are shown.

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

1 files changed, 66 insertions, 0 deletions

diff --git a/stats/pieseries.h b/stats/pieseries.h
new file mode 100644
index 000000000..242cfa781
--- /dev/null
+++ b/stats/pieseries.h
@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: GPL-2.0
+// A pie chart series, which displays percentual information.
+#ifndef PIE_SERIES_H
+#define PIE_SERIES_H
+
+#include "statsseries.h"
+
+#include <memory>
+#include <vector>
+#include <QString>
+
+class InformationBox;
+class QGraphicsEllipseItem;
+class QGraphicsSimpleTextItem;
+
+class PieSeries : public StatsSeries {
+public:
+	// The pie series is initialized with (name, count) pairs.
+	// If keepOrder is false, bins will be sorted by size, otherwise the sorting
+	// of the shown bins will be retained. Small bins are omitted for clarity.
+	PieSeries(QtCharts::QChart *chart, StatsAxis *xAxis, StatsAxis *yAxis, const QString &categoryName,
+		  const std::vector<std::pair<QString, int>> &data, bool keepOrder, bool labels);
+	~PieSeries();
+
+	void updatePositions() override;
+	bool hover(QPointF pos) override;
+	void unhighlight() override;
+
+	std::vector<QString> binNames();
+
+private:
+	// Get item under mouse pointer, or -1 if none
+	int getItemUnderMouse(const QPointF &f) const;
+
+	QString categoryName;
+	std::vector<QString> makeInfo(int idx) const;
+
+	struct Item {
+		std::unique_ptr<QGraphicsEllipseItem> item;
+		std::unique_ptr<QGraphicsSimpleTextItem> innerLabel, outerLabel;
+		QString name;
+		double angleTo; // In fraction of total
+		int count;
+		QPointF innerLabelPos, outerLabelPos; // With respect to a (-1, -1)-(1, 1) rectangle.
+		Item(QtCharts::QChart *chart, 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);
+	};
+	std::vector<Item> items;
+	int totalCount;
+
+	// Entries in the "other" group. If empty, there is no "other" group.
+	struct OtherItem {
+		QString name;
+		int count;
+	};
+	std::vector<OtherItem> other;
+
+	std::unique_ptr<InformationBox> information;
+	QPointF center; // center of drawing area
+	double radius; // radius of pie
+	int highlighted;
+};
+
+#endif