3 files changed, 43 insertions, 12 deletions

diff --git a/stats/legend.cpp b/stats/legend.cpp
index 590de21b0..d0a5c19b1 100644
--- a/stats/legend.cpp
+++ b/stats/legend.cpp
@@ -3,6 +3,7 @@
 #include "statscolors.h"
 #include "zvalues.h"
 
+#include <cmath>
 #include <QFontMetrics>
 #include <QPen>
 
@@ -18,7 +19,8 @@ Legend::Legend(StatsView &view, const std::vector<QString> &names) :
 	ChartRectItem(view, ChartZValue::Legend,
 		      QPen(legendBorderColor, legendBorderSize), QBrush(legendColor), legendBoxBorderRadius),
 	displayedItems(0), width(0.0), height(0.0),
-	font(QFont())	// Make configurable
+	font(QFont()),	// Make configurable
+	posInitialized(false)
 {
 	entries.reserve(names.size());
 	QFontMetrics fm(font);
@@ -103,7 +105,38 @@ void Legend::resize()
 		painter->drawText(rect, entries[i].name);
 	}
 
-	// For now, place the legend in the top right corner.
-	QPointF pos(size.width() - width - 10.0, 10.0);
-	setPos(pos);
+	if (!posInitialized) {
+		// At first, place in top right corner
+		setPos(QPointF(size.width() - width - 10.0, 10.0));
+		posInitialized = true;
+	} else {
+		// Try to keep relative position with what it was before
+		setPos(QPointF(size.width() * centerPos.x() - width / 2.0,
+			       size.height() * centerPos.y() - height / 2.0));
+	}
+}
+
+void Legend::setPos(QPointF newPos)
+{
+	// Round the position to integers or horrible artifacts appear (at least on desktop)
+	QPointF posInt(round(newPos.x()), round(newPos.y()));
+
+	// Make sure that the center is inside the drawing area,
+	// so that the user can't lose the legend.
+	QSizeF size = sceneSize();
+	if (size.width() < 1.0 || size.height() < 1.0)
+		return;
+	double widthHalf = floor(width / 2.0);
+	double heightHalf = floor(height / 2.0);
+	QPointF sanitizedPos(std::clamp(posInt.x(), -widthHalf, size.width() - widthHalf - 1.0),
+			     std::clamp(posInt.y(), -heightHalf, size.height() - heightHalf - 1.0));
+
+	// Set position
+	ChartRectItem::setPos(sanitizedPos);
+
+	// Remember relative position of center for next time
+	QPointF centerPosAbsolute(sanitizedPos.x() + width / 2.0,
+				  sanitizedPos.y() + height / 2.0);
+	centerPos = QPointF(centerPosAbsolute.x() / size.width(),
+			    centerPosAbsolute.y() / size.height());
 }
diff --git a/stats/legend.h b/stats/legend.h
index 1e38f705a..fb88920bd 100644
--- a/stats/legend.h
+++ b/stats/legend.h
@@ -15,6 +15,7 @@ class Legend : public ChartRectItem {
 public:
 	Legend(StatsView &view, const std::vector<QString> &names);
 	void resize(); // called when the chart size changes.
+	void setPos(QPointF pos); // Attention: not virtual - always call on this class.
 private:
 	// Each entry is a text besides a rectangle showing the color
 	struct Entry {
@@ -28,6 +29,10 @@ private:
 	double width;
 	double height;
 	QFont font;
+	// The position is specified with respect to the center and in relative terms
+	// with respect to the canvas.
+	QPointF centerPos;
+	bool posInitialized;
 	int fontHeight;
 	std::vector<Entry> entries;
 	void hide();
diff --git a/stats/statsview.cpp b/stats/statsview.cpp
index 983b128fe..f07b00896 100644
--- a/stats/statsview.cpp
+++ b/stats/statsview.cpp
@@ -236,14 +236,7 @@ void StatsView::mouseMoveEvent(QMouseEvent *event)
 	QSizeF sceneSize = size();
 	if (sceneSize.width() <= 1.0 || sceneSize.height() <= 1.0)
 		return;
-	QPointF pos = event->pos() - dragStartMouse + dragStartItem;;
-	QSizeF itemSize = draggedItem->getRect().size();
-	double widthHalf = floor(itemSize.width() / 2);
-	double heightHalf = floor(itemSize.height() / 2);
-	QSizeF itemSizeHalf(floor(itemSize.width() / 2), floor(itemSize.height() / 2));
-	QPointF sanitizedPos(std::clamp(pos.x(), -widthHalf, sceneSize.width() - widthHalf - 1.0),
-			     std::clamp(pos.y(), -heightHalf, sceneSize.height() - heightHalf - 1.0));
-	draggedItem->setPos(sanitizedPos);
+	draggedItem->setPos(event->pos() - dragStartMouse + dragStartItem);
 	update();
 }