Added graph grid option

Code cleanup

src/griditem.cpp

@@ -0,0 +1,48 @@
+#include <QPainter>
+#include "griditem.h"
+
+
+#define GRID_WIDTH 1
+
+GridItem::GridItem(QGraphicsItem *parent) : QGraphicsItem(parent)
+{
+
+}
+
+void GridItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option,
+  QWidget *widget)
+{
+	Q_UNUSED(option);
+	Q_UNUSED(widget);
+	QBrush brush(Qt::gray);
+	QPen pen = QPen(brush, GRID_WIDTH, Qt::DotLine);
+
+
+	painter->setRenderHint(QPainter::Antialiasing, false);
+	painter->setPen(pen);
+
+	for (int i = 0; i < _xTicks.size(); i++)
+		painter->drawLine(_xTicks.at(i), 0, _xTicks.at(i),
+		  -_boundingRect.height());
+	for (int i = 0; i < _yTicks.size(); i++)
+		painter->drawLine(0, -_yTicks.at(i), boundingRect().width(),
+		  -_yTicks.at(i));
+
+/*
+	painter->setPen(Qt::red);
+	painter->drawRect(boundingRect());
+*/
+}
+
+void GridItem::setTicks(const QList<qreal> &x, const QList<qreal> &y)
+{
+	_xTicks = x; _yTicks = y;
+	update();
+}
+
+void GridItem::setSize(const QSizeF &size)
+{
+	prepareGeometryChange();
+
+	_boundingRect = QRectF(QPointF(0, -size.height()), size);
+}