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, 11 insertions, 10 deletions

diff --git a/stats/pieseries.cpp b/stats/pieseries.cpp
index 108046b23..ac43b6d3a 100644
--- a/stats/pieseries.cpp
+++ b/stats/pieseries.cpp
@@ -2,6 +2,7 @@
 #include "pieseries.h"
 #include "informationbox.h"
 #include "statscolors.h"
+#include "statshelper.h"
 #include "statstranslations.h"
 #include "zvalues.h"
 
@@ -16,9 +17,9 @@ 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(QtCharts::QChart *chart, const QString &name, int from, int count, int totalCount,
+PieSeries::Item::Item(QGraphicsScene *scene, const QString &name, int from, int count, int totalCount,
 		      int bin_nr, int numBins, bool labels) :
-	item(new QGraphicsEllipseItem(chart)),
+	item(createItemPtr<QGraphicsEllipseItem>(scene)),
 	name(name),
 	count(count)
 {
@@ -38,10 +39,10 @@ PieSeries::Item::Item(QtCharts::QChart *chart, const QString &name, int from, in
 	if (labels) {
 		double percentage = count * 100.0 / totalCount;
 		QString innerLabelText = QStringLiteral("%1\%").arg(loc.toString(percentage, 'f', 1));
-		innerLabel.reset(new QGraphicsSimpleTextItem(innerLabelText, chart));
+		innerLabel = createItemPtr<QGraphicsSimpleTextItem>(scene, innerLabelText);
 		innerLabel->setZValue(ZValues::seriesLabels);
 
-		outerLabel.reset(new QGraphicsSimpleTextItem(name, chart));
+		outerLabel = createItemPtr<QGraphicsSimpleTextItem>(scene, name);
 		outerLabel->setBrush(QBrush(darkLabelColor));
 		outerLabel->setZValue(ZValues::seriesLabels);
 	}
@@ -85,9 +86,9 @@ void PieSeries::Item::highlight(int bin_nr, bool highlight, int numBins)
 	}
 }
 
-PieSeries::PieSeries(QtCharts::QChart *chart, StatsAxis *xAxis, StatsAxis *yAxis, const QString &categoryName,
+PieSeries::PieSeries(QGraphicsScene *scene, StatsAxis *xAxis, StatsAxis *yAxis, const QString &categoryName,
 		     const std::vector<std::pair<QString, int>> &data, bool keepOrder, bool labels) :
-	StatsSeries(chart, xAxis, yAxis),
+	StatsSeries(scene, xAxis, yAxis),
 	categoryName(categoryName),
 	highlighted(-1)
 {
@@ -147,7 +148,7 @@ PieSeries::PieSeries(QtCharts::QChart *chart, StatsAxis *xAxis, StatsAxis *yAxis
 	int act = 0;
 	for (auto it2 = sorted.begin(); it2 != it; ++it2) {
 		int count = data[*it2].second;
-		items.emplace_back(chart, data[*it2].first, act, count, totalCount, (int)items.size(), numBins, labels);
+		items.emplace_back(scene, data[*it2].first, act, count, totalCount, (int)items.size(), numBins, labels);
 		act += count;
 	}
 
@@ -157,7 +158,7 @@ PieSeries::PieSeries(QtCharts::QChart *chart, StatsAxis *xAxis, StatsAxis *yAxis
 		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(chart, name, act, totalCount - act, totalCount, (int)items.size(), numBins, labels);
+		items.emplace_back(scene, name, act, totalCount - act, totalCount, (int)items.size(), numBins, labels);
 	}
 }
 
@@ -167,7 +168,7 @@ PieSeries::~PieSeries()
 
 void PieSeries::updatePositions()
 {
-	QRectF plotRect = chart->plotArea();
+	QRectF plotRect = scene->sceneRect();
 	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);
@@ -246,7 +247,7 @@ bool PieSeries::hover(QPointF pos)
 	if (highlighted >= 0 && highlighted < (int)items.size()) {
 		items[highlighted].highlight(highlighted, true, (int)items.size());
 		if (!information)
-			information.reset(new InformationBox(chart));
+			information = createItemPtr<InformationBox>(scene);
 		information->setText(makeInfo(highlighted), pos);
 	} else {
 		information.reset();