here is the code:
@#include "Definitions.h"
#include <QGraphicsScene>

class QGraphicsSceneGrid : public QGraphicsScene
{
public:
QGraphicsSceneGrid(QObject parent);
EN_EDIT_MODES pen_current_mode;

protected:
void drawBackground(QPainter * painter, const QRectF & rect );
virtual void mouseMoveEvent(QGraphicsSceneMouseEvent *event);

};@

@#include "ModClasses.h"
#include <QPainter>
#include "Definitions.h"

QGraphicsSceneGrid::QGraphicsSceneGrid(QObject *parent ) : QGraphicsScene(parent)
{}

void QGraphicsSceneGrid::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
if( *pen_current_mode == mode_add_line )
{
QPointF pos1;
pos1 = event->scenePos();
}
}
@

the line "pos1 = event->scenePos();" gives me this errors:

In member function 'virtual void QGraphicsSceneGrid::mouseMoveEvent(QGraphicsSceneMouseEvent*)':
error: invalid use of incomplete type 'struct QGraphicsSceneMouseEvent'
error: forward declaration of 'struct QGraphicsSceneMouseEvent'