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>

CMakeLists.txt

@@ -301,7 +301,7 @@ endif()
 #set up the subsurface_link_libraries variable
 set(SUBSURFACE_LINK_LIBRARIES ${SUBSURFACE_LINK_LIBRARIES} ${LIBDIVECOMPUTER_LIBRARIES} ${LIBGIT2_LIBRARIES} ${LIBUSB_LIBRARIES} ${LIBMTP_LIBRARIES})
 if (NOT SUBSURFACE_TARGET_EXECUTABLE MATCHES "DownloaderExecutable")
-	qt5_add_resources(SUBSURFACE_RESOURCES subsurface.qrc map-widget/qml/map-widget.qrc stats/qml/statsview.qrc)
+	qt5_add_resources(SUBSURFACE_RESOURCES subsurface.qrc map-widget/qml/map-widget.qrc desktop-widgets/qml/statsview2.qrc)
 endif()
 
 # hack to build successfully on LGTM

backend-shared/roundrectitem.cpp

@@ -7,6 +7,10 @@ RoundRectItem::RoundRectItem(double radius, QGraphicsItem *parent) : QGraphicsRe
 {
 }
 
+RoundRectItem::RoundRectItem(double radius) : RoundRectItem(radius, nullptr)
+{
+}
+
 void RoundRectItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *)
 {
 	painter->save();

backend-shared/roundrectitem.h

@@ -7,6 +7,7 @@
 class RoundRectItem : public QGraphicsRectItem {
 public:
 	RoundRectItem(double radius, QGraphicsItem *parent);
+	RoundRectItem(double radius);
 private:
 	void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override;
 	double radius;

desktop-widgets/qml/statsview2.qml

@@ -0,0 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0
+import QtQuick 2.0
+import org.subsurfacedivelog.mobile 1.0
+
+StatsView {
+}

stats/qml/statsview.qrc → desktop-widgets/qml/statsview2.qrc

@@ -1,5 +1,5 @@
 <RCC>
 	<qresource prefix="/qml">
-		<file>statsview.qml</file>
+		<file>statsview2.qml</file>
 	</qresource>
 </RCC>

desktop-widgets/statswidget.cpp

@@ -70,6 +70,7 @@ QSize ChartItemDelegate::sizeHint(const QStyleOptionViewItem &option, const QMod
 	return size;
 }
 
+static const QUrl urlStatsView = QUrl(QStringLiteral("qrc:/qml/statsview2.qml"));
 StatsWidget::StatsWidget(QWidget *parent) : QWidget(parent)
 {
 	ui.setupUi(this);
@@ -83,6 +84,13 @@ StatsWidget::StatsWidget(QWidget *parent) : QWidget(parent)
 	connect(ui.var1Binner, QOverload<int>::of(&QComboBox::activated), this, &StatsWidget::var1BinnerChanged);
 	connect(ui.var2Binner, QOverload<int>::of(&QComboBox::activated), this, &StatsWidget::var2BinnerChanged);
 	connect(ui.var2Operation, QOverload<int>::of(&QComboBox::activated), this, &StatsWidget::var2OperationChanged);
+
+	ui.stats->setSource(urlStatsView);
+	ui.stats->setResizeMode(QQuickWidget::SizeRootObjectToView);
+	QQuickItem *root = ui.stats->rootObject();
+	view = qobject_cast<StatsView *>(root);
+	if (!view)
+		qWarning("Oops. The root of the StatsView is not a StatsView.");
 }
 
 // Initialize QComboBox with list of variables
@@ -96,7 +104,7 @@ static void setVariableList(QComboBox *combo, const StatsState::VariableList &li
 }
 
 // Initialize QComboBox and QLabel of binners. Hide if there are no binners.
-static void setBinList(QLabel *label, QComboBox *combo, const StatsState::BinnerList &list)
+static void setBinList(QComboBox *combo, const StatsState::BinnerList &list)
 {
 	combo->clear();
 	combo->setEnabled(!list.binners.empty());
@@ -114,8 +122,8 @@ void StatsWidget::updateUi()
 	int pos = charts.update(uiState.charts);
 	ui.chartType->setCurrentIndex(pos);
 	ui.chartType->setItemDelegate(new ChartItemDelegate);
-	setBinList(ui.var1BinnerLabel, ui.var1Binner, uiState.binners1);
-	setBinList(ui.var2BinnerLabel, ui.var2Binner, uiState.binners2);
+	setBinList(ui.var1Binner, uiState.binners1);
+	setBinList(ui.var2Binner, uiState.binners2);
 	setVariableList(ui.var2Operation, uiState.operations2);
 
 	// Add checkboxes for additional features
@@ -129,7 +137,8 @@ void StatsWidget::updateUi()
 		ui.features->addWidget(check);
 	}
 
-	ui.stats->plot(state);
+	if (view)
+		view->plot(state);
 }
 
 void StatsWidget::closeStats()

desktop-widgets/statswidget.h

@@ -9,6 +9,7 @@
 #include <memory>
 
 class QCheckBox;
+class StatsView;
 
 class StatsWidget : public QWidget {
 	Q_OBJECT
@@ -27,6 +28,7 @@ private
 private:
 	Ui::StatsWidget ui;
 	StatsState state;
+	StatsView *view;
 	void updateUi();
 	std::vector<std::unique_ptr<QCheckBox>> features;
 

desktop-widgets/statswidget.ui

@@ -105,7 +105,7 @@
     </layout>
    </item>
    <item>
-    <widget class="StatsView" name="stats">
+    <widget class="QQuickWidget" name="stats">
      <property name="sizePolicy">
       <sizepolicy hsizetype="Expanding" vsizetype="Expanding">
        <horstretch>0</horstretch>
@@ -116,14 +116,6 @@
    </item>
   </layout>
  </widget>
- <customwidgets>
-  <customwidget>
-   <class>StatsView</class>
-   <extends>QQuickWidget</extends>
-   <header>stats/statsview.h</header>
-   <container>1</container>
-  </customwidget>
- </customwidgets>
  <resources>
   <include location="../subsurface.qrc"/>
  </resources>

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;
@@ -50,22 +51,22 @@ 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),
 			 item.binName, item.res, -1, horizontal, stacked);
 	}
 }
 
-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();

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 @@ class BarSeries : public StatsSeries {
 	// 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 @@ class BarSeries : public StatsSeries {
 	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 @@ class BarSeries : public StatsSeries {
 		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 @@ class BarSeries : public StatsSeries {
 		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);

stats/boxseries.cpp

@@ -2,6 +2,7 @@
 #include "boxseries.h"
 #include "informationbox.h"
 #include "statscolors.h"
+#include "statshelper.h"
 #include "statstranslations.h"
 #include "zvalues.h"
 
@@ -12,9 +13,9 @@
 static const double boxWidth = 0.8; // 1.0 = full width of category
 static const int boxBorderWidth = 2;
 
-BoxSeries::BoxSeries(QtCharts::QChart *chart, StatsAxis *xAxis, StatsAxis *yAxis,
+BoxSeries::BoxSeries(QGraphicsScene *scene, StatsAxis *xAxis, StatsAxis *yAxis,
 		     const QString &variable, const QString &unit, int decimals) :
-	StatsSeries(chart, xAxis, yAxis),
+	StatsSeries(scene, xAxis, yAxis),
 	variable(variable), unit(unit), decimals(decimals), highlighted(-1)
 {
 }
@@ -23,12 +24,8 @@ BoxSeries::~BoxSeries()
 {
 }
 
-BoxSeries::Item::Item(QtCharts::QChart *chart, BoxSeries *series, double lowerBound, double upperBound,
+BoxSeries::Item::Item(QGraphicsScene *scene, BoxSeries *series, double lowerBound, double upperBound,
 		      const StatsQuartiles &q, const QString &binName) :
-	box(chart),
-	topWhisker(chart), bottomWhisker(chart),
-	topBar(chart), bottomBar(chart),
-	center(chart),
 	lowerBound(lowerBound), upperBound(upperBound), q(q),
 	binName(binName)
 {
@@ -38,6 +35,12 @@ BoxSeries::Item::Item(QtCharts::QChart *chart, BoxSeries *series, double lowerBo
 	topBar.setZValue(ZValues::series);
 	bottomBar.setZValue(ZValues::series);
 	center.setZValue(ZValues::series);
+	scene->addItem(&box);
+	scene->addItem(&topWhisker);
+	scene->addItem(&bottomWhisker);
+	scene->addItem(&topBar);
+	scene->addItem(&bottomBar);
+	scene->addItem(&center);
 	highlight(false);
 	updatePosition(series);
 }
@@ -89,7 +92,7 @@ void BoxSeries::Item::updatePosition(BoxSeries *series)
 
 void BoxSeries::append(double lowerBound, double upperBound, const StatsQuartiles &q, const QString &binName)
 {
-	items.emplace_back(new Item(chart, this, lowerBound, upperBound, q, binName));
+	items.emplace_back(new Item(scene, this, lowerBound, upperBound, q, binName));
 }
 
 void BoxSeries::updatePositions()
@@ -147,7 +150,7 @@ bool BoxSeries::hover(QPointF pos)
 		Item &item = *items[highlighted];
 		item.highlight(true);
 		if (!information)
-			information.reset(new InformationBox(chart));
+			information = createItemPtr<InformationBox>(scene);
 		information->setText(formatInformation(item), pos);
 	} else {
 		information.reset();

stats/boxseries.h

@@ -14,10 +14,11 @@
 #include <QGraphicsRectItem>
 
 class InformationBox;
+class QGraphicsScene;
 
 class BoxSeries : public StatsSeries {
 public:
-	BoxSeries(QtCharts::QChart *chart, StatsAxis *xAxis, StatsAxis *yAxis,
+	BoxSeries(QGraphicsScene *scene, StatsAxis *xAxis, StatsAxis *yAxis,
 		  const QString &variable, const QString &unit, int decimals);
 	~BoxSeries();
 
@@ -44,7 +45,7 @@ class BoxSeries : public StatsSeries {
 		double lowerBound, upperBound;
 		StatsQuartiles q;
 		QString binName;
-		Item(QtCharts::QChart *chart, BoxSeries *series, double lowerBound, double upperBound, const StatsQuartiles &q, const QString &binName);
+		Item(QGraphicsScene *scene, BoxSeries *series, double lowerBound, double upperBound, const StatsQuartiles &q, const QString &binName);
 		void updatePosition(BoxSeries *series);
 		void highlight(bool highlight);
 	};