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, 16 insertions, 15 deletions

diff --git a/stats/barseries.cpp b/stats/barseries.cpp
index 5727745a0..986aa7e0d 100644
--- a/stats/barseries.cpp
+++ b/stats/barseries.cpp
@@ -2,6 +2,7 @@
 #include "barseries.h"
 #include "informationbox.h"
 #include "statscolors.h"
+#include "statshelper.h"
 #include "statstranslations.h"
 #include "zvalues.h"
 
@@ -27,19 +28,19 @@ bool BarSeries::Index::operator==(const Index &i2) const
 	return std::tie(bar, subitem) == std::tie(i2.bar, i2.subitem);
 }
 
-BarSeries::BarSeries(QtCharts::QChart *chart, StatsAxis *xAxis, StatsAxis *yAxis,
+BarSeries::BarSeries(QGraphicsScene *scene, StatsAxis *xAxis, StatsAxis *yAxis,
 		     bool horizontal, bool stacked, const QString &categoryName,
 		     const StatsVariable *valueVariable, std::vector<QString> valueBinNames) :
-	StatsSeries(chart, xAxis, yAxis),
+	StatsSeries(scene, xAxis, yAxis),
 	horizontal(horizontal), stacked(stacked), categoryName(categoryName),
 	valueVariable(valueVariable), valueBinNames(std::move(valueBinNames))
 {
 }
 
-BarSeries::BarSeries(QtCharts::QChart *chart, StatsAxis *xAxis, StatsAxis *yAxis,
+BarSeries::BarSeries(QGraphicsScene *scene, StatsAxis *xAxis, StatsAxis *yAxis,
 		     bool horizontal, const QString &categoryName,
 		     const std::vector<CountItem> &items) :
-	BarSeries(chart, xAxis, yAxis, horizontal, false, categoryName, nullptr, std::vector<QString>())
+	BarSeries(scene, xAxis, yAxis, horizontal, false, categoryName, nullptr, std::vector<QString>())
 {
 	for (const CountItem &item: items) {
 		StatsOperationResults res;
@@ -50,10 +51,10 @@ BarSeries::BarSeries(QtCharts::QChart *chart, StatsAxis *xAxis, StatsAxis *yAxis
 	}
 }
 
-BarSeries::BarSeries(QtCharts::QChart *chart, StatsAxis *xAxis, StatsAxis *yAxis,
+BarSeries::BarSeries(QGraphicsScene *scene, StatsAxis *xAxis, StatsAxis *yAxis,
 		     bool horizontal, const QString &categoryName, const StatsVariable *valueVariable,
 		     const std::vector<ValueItem> &items) :
-	BarSeries(chart, xAxis, yAxis, horizontal, false, categoryName, valueVariable, std::vector<QString>())
+	BarSeries(scene, xAxis, yAxis, horizontal, false, categoryName, valueVariable, std::vector<QString>())
 {
 	for (const ValueItem &item: items) {
 		add_item(item.lowerBound, item.upperBound, makeSubItems(item.value, item.label),
@@ -61,11 +62,11 @@ BarSeries::BarSeries(QtCharts::QChart *chart, StatsAxis *xAxis, StatsAxis *yAxis
 	}
 }
 
-BarSeries::BarSeries(QtCharts::QChart *chart, StatsAxis *xAxis, StatsAxis *yAxis,
+BarSeries::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) :
-	BarSeries(chart, xAxis, yAxis, horizontal, stacked, categoryName, valueVariable, std::move(valueBinNames))
+	BarSeries(scene, xAxis, yAxis, horizontal, stacked, categoryName, valueVariable, std::move(valueBinNames))
 {
 	for (const MultiItem &item: items) {
 		StatsOperationResults res;
@@ -85,12 +86,12 @@ BarSeries::~BarSeries()
 {
 }
 
-BarSeries::BarLabel::BarLabel(QtCharts::QChart *chart, const std::vector<QString> &labels, int bin_nr, int binCount) :
+BarSeries::BarLabel::BarLabel(QGraphicsScene *scene, const std::vector<QString> &labels, int bin_nr, int binCount) :
 	totalWidth(0.0), totalHeight(0.0), isOutside(false)
 {
 	items.reserve(labels.size());
 	for (const QString &label: labels) {
-		items.emplace_back(new QGraphicsSimpleTextItem(chart));
+		items.emplace_back(createItem<QGraphicsSimpleTextItem>(scene));
 		items.back()->setText(label);
 		items.back()->setZValue(ZValues::seriesLabels);
 		QRectF rect = items.back()->boundingRect();
@@ -175,7 +176,7 @@ void BarSeries::BarLabel::updatePosition(bool horizontal, bool center, const QRe
 	highlight(false, bin_nr, binCount);
 }
 
-BarSeries::Item::Item(QtCharts::QChart *chart, BarSeries *series, double lowerBound, double upperBound,
+BarSeries::Item::Item(QGraphicsScene *scene, BarSeries *series, double lowerBound, double upperBound,
 		      std::vector<SubItem> subitemsIn,
 		      const QString &binName, const StatsOperationResults &res, int total,
 		      bool horizontal, bool stacked, int binCount) :
@@ -264,9 +265,9 @@ std::vector<BarSeries::SubItem> BarSeries::makeSubItems(const std::vector<std::p
 	int bin_nr = 0;
 	for (auto &[v, label]: values) {
 		if (v > 0.0) {
-			res.push_back({ std::make_unique<QGraphicsRectItem>(chart), {}, from, from + v, bin_nr });
+			res.push_back({ createItemPtr<QGraphicsRectItem>(scene), {}, from, from + v, bin_nr });
 			if (!label.empty())
-				res.back().label = std::make_unique<BarLabel>(chart, label, bin_nr, binCount());
+				res.back().label = std::make_unique<BarLabel>(scene, label, bin_nr, binCount());
 		}
 		if (stacked)
 			from += v;
@@ -292,7 +293,7 @@ void BarSeries::add_item(double lowerBound, double upperBound, std::vector<SubIt
 	// Don't add empty items, as that messes with the "find item under mouse" routine.
 	if (subitems.empty())
 		return;
-	items.emplace_back(chart, this, lowerBound, upperBound, std::move(subitems), binName, res,
+	items.emplace_back(scene, this, lowerBound, upperBound, std::move(subitems), binName, res,
 			   total, horizontal, stacked, binCount());
 }
 
@@ -403,7 +404,7 @@ bool BarSeries::hover(QPointF pos)
 		Item &item = items[highlighted.bar];
 		item.highlight(index.subitem, true, binCount());
 		if (!information)
-			information.reset(new InformationBox(chart));
+			information = createItemPtr<InformationBox>(scene);
 		information->setText(makeInfo(item, highlighted.subitem), pos);
 	} else {
 		information.reset();