statistics: convert chart to QQuickItem

It turns out that the wrong base class was used for the chart.
QQuickWidget can only be used on desktop, not in a mobile UI.

Therefore, turn this into a QQuickItem and move the container
QQuickWidget into desktop-only code.

Currently, this code is insane: The chart is rendered onto a
QGraphicsScene (as it was before), which is then rendered into
a QImage, which is transformed into a QSGTexture, which is then
projected onto the device. This is performed on every mouse
move event, since these events in general change the position
of the info-box.

The plan is to slowly convert elements such as the info-box into
QQuickItems. Browsing the QtQuick documentation, this will
not be much fun.

Also note that the rendering currently tears, flickers and has
antialiasing artifacts, most likely owing to integer (QImage)
to floating point (QGraphicsScene, QQuickItem) conversion
problems. The data flow is
QGraphicsScene (float) -> QImage (int) -> QQuickItem (float).

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

1 files changed, 4 insertions, 2 deletions

diff --git a/stats/pieseries.h b/stats/pieseries.h
index 242cfa781..c7e2af319 100644
--- a/stats/pieseries.h
+++ b/stats/pieseries.h
@@ -11,14 +11,16 @@
 
 class InformationBox;
 class QGraphicsEllipseItem;
+class QGraphicsScene;
 class QGraphicsSimpleTextItem;
+class QRectF;
 
 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,
+	PieSeries(QGraphicsScene *scene, StatsAxis *xAxis, StatsAxis *yAxis, const QString &categoryName,
 		  const std::vector<std::pair<QString, int>> &data, bool keepOrder, bool labels);
 	~PieSeries();
 
@@ -42,7 +44,7 @@ private:
 		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,
+		Item(QGraphicsScene *scene, 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);