[Qt-interest] When is QT_FORWARD_DECLARE_CLASS to be used?

[Tony Rietwyk]

Hi Everybody, 

In 4.5.0, demos\books\bookdelegate.h has: 

#ifndef BOOKDELEGATE_H
#define BOOKDELEGATE_H

#include <QModelIndex>
#include <QPixmap>
#include <QSize>
#include <QSqlRelationalDelegate>

QT_FORWARD_DECLARE_CLASS(QPainter)

class BookDelegate : public QSqlRelationalDelegate
{
public:

... etc. 


Is QT_FORWARD_DECLARE_CLASS also required in our code?  

It's not in the QtAssistant index, and searching only provides links to demos. 

Can someone provide the missing documentation. 

Thanks, 

Tony.