statistics: turn axes into QSGNode

Render the labels and the title into a pixmap and render
the ticks and the base line using individual QSGNodes.
Attempting to render the ticks likewise into the pixmap
gave horrible results, because (quite obviously) rendering
with QPainter and the QSG shader gives non-matching ticks
and grid lines.

The memory management had to be changed a bit: The ChartItems
were collected in the root QSGNode. However, the axes are added
before the first plotting, so this node might not exist.
Therefore, store the axes in the StatsView object.

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

1 files changed, 23 insertions, 16 deletions

diff --git a/stats/statsaxis.h b/stats/statsaxis.h
index 9d46f753a..89c9edbe2 100644
--- a/stats/statsaxis.h
+++ b/stats/statsaxis.h
@@ -2,15 +2,19 @@
 #ifndef STATS_AXIS_H
 #define STATS_AXIS_H
 
+#include "chartitem.h"
+
 #include <memory>
 #include <vector>
 #include <QFont>
-#include <QGraphicsSimpleTextItem>
-#include <QGraphicsLineItem>
 
-class QGraphicsScene;
+class StatsView;
+class ChartLineItem;
+class QFontMetrics;
 
-class StatsAxis : public QGraphicsLineItem {
+// The labels and the title of the axis are rendered into a pixmap.
+// The ticks and the baseline are realized as individual ChartLineItems.
+class StatsAxis : public ChartPixmapItem {
 public:
 	virtual ~StatsAxis();
 	// Returns minimum and maximum of shown range, not of data points.
@@ -30,22 +34,25 @@ public:
 
 	std::vector<double> ticksPositions() const; // Positions in screen coordinates
 protected:
-	StatsAxis(const QString &title, bool horizontal, bool labelsBetweenTicks);
+	StatsAxis(StatsView &view, const QString &title, bool horizontal, bool labelsBetweenTicks);
+
+	std::unique_ptr<ChartLineItem> line;
+	QString title;
+	double titleWidth;
 
 	struct Label {
-		std::unique_ptr<QGraphicsSimpleTextItem> label;
+		QString label;
+		int width;
 		double pos;
-		Label(const QString &name, double pos, QGraphicsScene *scene, const QFont &font);
 	};
 	std::vector<Label> labels;
-	void addLabel(const QString &label, double pos);
+	void addLabel(const QFontMetrics &fm, const QString &label, double pos);
 	virtual void updateLabels() = 0;
 	virtual std::pair<QString, QString> getFirstLastLabel() const = 0;
 
 	struct Tick {
-		std::unique_ptr<QGraphicsLineItem> item;
+		std::unique_ptr<ChartLineItem> item;
 		double pos;
-		Tick(double pos, QGraphicsScene *scene);
 	};
 	std::vector<Tick> ticks;
 	void addTick(double pos);
@@ -55,9 +62,9 @@ protected:
 	bool labelsBetweenTicks;	// When labels are between ticks, they can be moved closer to the axis
 
 	QFont labelFont, titleFont;
-	std::unique_ptr<QGraphicsSimpleTextItem> title;
 	double size;			// width for horizontal, height for vertical
 	double zeroOnScreen;
+	QPointF offset;			// Offset of the label and title pixmap with respect to the (0,0) position.
 	double min, max;
 	double labelWidth;		// Maximum width of labels
 private:
@@ -66,7 +73,7 @@ private:
 
 class ValueAxis : public StatsAxis {
 public:
-	ValueAxis(const QString &title, double min, double max, int decimals, bool horizontal);
+	ValueAxis(StatsView &view, const QString &title, double min, double max, int decimals, bool horizontal);
 private:
 	double min, max;
 	int decimals;
@@ -76,7 +83,7 @@ private:
 
 class CountAxis : public ValueAxis {
 public:
-	CountAxis(const QString &title, int count, bool horizontal);
+	CountAxis(StatsView &view, const QString &title, int count, bool horizontal);
 private:
 	int count;
 	void updateLabels() override;
@@ -85,7 +92,7 @@ private:
 
 class CategoryAxis : public StatsAxis {
 public:
-	CategoryAxis(const QString &title, const std::vector<QString> &labels, bool horizontal);
+	CategoryAxis(StatsView &view, const QString &title, const std::vector<QString> &labels, bool horizontal);
 private:
 	std::vector<QString> labelsText;
 	void updateLabels();
@@ -100,7 +107,7 @@ struct HistogramAxisEntry {
 
 class HistogramAxis : public StatsAxis {
 public:
-	HistogramAxis(const QString &title, std::vector<HistogramAxisEntry> bin_values, bool horizontal);
+	HistogramAxis(StatsView &view, const QString &title, std::vector<HistogramAxisEntry> bin_values, bool horizontal);
 private:
 	void updateLabels() override;
 	std::pair<QString, QString> getFirstLastLabel() const override;
@@ -110,7 +117,7 @@ private:
 
 class DateAxis : public HistogramAxis {
 public:
-	DateAxis(const QString &title, double from, double to, bool horizontal);
+	DateAxis(StatsView &view, const QString &title, double from, double to, bool horizontal);
 };
 
 #endif