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, 7 insertions, 9 deletions

diff --git a/stats/barseries.h b/stats/barseries.h
index 114df540a..299998bfb 100644
--- a/stats/barseries.h
+++ b/stats/barseries.h
@@ -12,9 +12,7 @@
 #include <vector>
 #include <QGraphicsRectItem>
 
-namespace QtCharts {
-	class QAbstractAxis;
-}
+class QGraphicsScene;
 class InformationBox;
 class StatsVariable;
 
@@ -49,13 +47,13 @@ public:
 	// Note: this expects that all items are added with increasing pos
 	// and that no bar is inside another bar, i.e. lowerBound and upperBound
 	// are ordered identically.
-	BarSeries(QtCharts::QChart *chart, StatsAxis *xAxis, StatsAxis *yAxis,
+	BarSeries(QGraphicsScene *scene, StatsAxis *xAxis, StatsAxis *yAxis,
 		  bool horizontal, const QString &categoryName,
 		  const std::vector<CountItem> &items);
-	BarSeries(QtCharts::QChart *chart, StatsAxis *xAxis, StatsAxis *yAxis,
+	BarSeries(QGraphicsScene *scene, StatsAxis *xAxis, StatsAxis *yAxis,
 		  bool horizontal, const QString &categoryName, const StatsVariable *valueVariable,
 		  const std::vector<ValueItem> &items);
-	BarSeries(QtCharts::QChart *chart, StatsAxis *xAxis, StatsAxis *yAxis,
+	BarSeries(QGraphicsScene *scene, StatsAxis *xAxis, StatsAxis *yAxis,
 		  bool horizontal, bool stacked, const QString &categoryName, const StatsVariable *valueVariable,
 		  std::vector<QString> valueBinNames,
 		  const std::vector<MultiItem> &items);
@@ -65,7 +63,7 @@ public:
 	bool hover(QPointF pos) override;
 	void unhighlight() override;
 private:
-	BarSeries(QtCharts::QChart *chart, StatsAxis *xAxis, StatsAxis *yAxis,
+	BarSeries(QGraphicsScene *scene, StatsAxis *xAxis, StatsAxis *yAxis,
 		  bool horizontal, bool stacked, const QString &categoryName, const StatsVariable *valueVariable,
 		  std::vector<QString> valueBinNames);
 
@@ -85,7 +83,7 @@ private:
 		std::vector<std::unique_ptr<QGraphicsSimpleTextItem>> items;
 		double totalWidth, totalHeight; // Size of the item
 		bool isOutside; // Is shown outside of bar
-		BarLabel(QtCharts::QChart *chart, const std::vector<QString> &labels, int bin_nr, int binCount);
+		BarLabel(QGraphicsScene *scene, const std::vector<QString> &labels, int bin_nr, int binCount);
 		void setVisible(bool visible);
 		void updatePosition(bool horizontal, bool center, const QRectF &rect, int bin_nr, int binCount);
 		void highlight(bool highlight, int bin_nr, int binCount);
@@ -109,7 +107,7 @@ private:
 		const QString binName;
 		StatsOperationResults res;
 		int total;
-		Item(QtCharts::QChart *chart, BarSeries *series, double lowerBound, double upperBound,
+		Item(QGraphicsScene *scene, BarSeries *series, double lowerBound, double upperBound,
 		     std::vector<SubItem> subitems,
 		     const QString &binName, const StatsOperationResults &res, int total, bool horizontal,
 		     bool stacked, int binCount);