ui: create a RoundRectItem class

Factor out code from ProfileWidget's ToolTipItem, but make
the radius of the corners dynamic. Move into backend-shared,
though a new ui-shared might be preferred.

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

backend-shared/roundrectitem.cpp

@@ -0,0 +1,18 @@
+#include "roundrectitem.h"
+#include <QPainter>
+#include <QStyleOptionGraphicsItem>
+
+RoundRectItem::RoundRectItem(double radius, QGraphicsItem *parent) : QGraphicsRectItem(parent),
+	radius(radius)
+{
+}
+
+void RoundRectItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *)
+{
+	painter->save();
+	painter->setClipRect(option->rect);
+	painter->setPen(pen());
+	painter->setBrush(brush());
+	painter->drawRoundedRect(rect(), radius, radius, Qt::AbsoluteSize);
+	painter->restore();
+}