QGraphicsView::setCacheMode(CacheBackground) refresh problem

The problem can be summarised as a lack of repaint on a window that is first partly hidden, minimised and then restored.

The code below reproduces is on Qt 4.5.2:-

#include <QtGui>

int main(int argc, char *argv[])
{
QApplication app(argc, argv);

QMainWindow mainWin;
QMdiArea *mdiArea = new QMdiArea;
mainWin.setCentralWidget(mdiArea);
mainWin.show();

QGraphicsView *view = new QGraphicsView;
view->setCacheMode(QGraphicsView::CacheBackground);
QBrush brush(QLinearGradient(0,0,256,256));
brush.setColor(Qt::blue);
view->setBackgroundBrush(brush);

QGraphicsScene *scene = new QGraphicsScene;
scene->addRect(QRectF(10,10,30,40),QPen(QColor(Qt::yellow)),QBrush(QColor(Qt::red)));
scene->setSceneRect(QRectF(0.0, 0.0, 256, 256));

view->setScene(scene);

mdiArea->addSubWindow(view);

view->show();

return app.exec();
}

To reproduce the problem do the following:

• move the small SubWindow to the left, so that half of the window is hidden
• iconify the window
• restore the window
• move the window to the right, so that the previous hidden part is visible again
  only half of the window background is restored correctly.