ASSERT: "!item->d_ptr->itemDiscovered" in file graphicsview\qgraphicsscenebsptreeindex.cpp, line 343

[LCL_data]

I want to get the thumbnail from QGraphicsScene:
@ QImage image;
QPainter painter(&image);
painter.setRenderHint(QPainter::Antialiasing);
scene->render(&painter);
image.save("scene.png");@

scene->render throw the error and error detail is:
@---------------------------
Microsoft Visual C++ Debug Library

Debug Error!

Program: ...\PBMaker\Source\Trunk\PBMaker\PBMaker\Win32\Debug\PBMaker.exe
Module: 5.0.1
File: global\qglobal.cpp
Line: 1951

ASSERT: "!item->d_ptr->itemDiscovered" in file graphicsview\qgraphicsscenebsptreeindex.cpp, line 343

(Press Retry to debug the application)

Abort Retry Ignore

@

and my scene is :
@ QGraphicsScene *scene = new QGraphicsScene();
scene->setBackgroundBrush(Qt::white);
scene->addWidget(page);
scene->setSceneRect(0,0,mSceneSize.width(),mSceneSize.height());

    //add all areas
    QList<PBArea *> areas =  page->getArea();  
    int areaTotalNumber = areas.size();
    for ( int areaIndex = 0 ; areaIndex < areaTotalNumber ; areaIndex++ )
    {       
        scene->addItem(areas[areaIndex]);
    }@

page inherts from QWidget , PBArea inherts from QGraphicsItem.

a little strange to get this debug error. am i missing something ?

[LCL_data]

and I test the scene->render again in a clear Qt project:
@#include "qttest501.h"
#include <QGraphicsScene>
#include <QPainter>
#include <QDesktopWidget>
qtTest501::qtTest501(QWidget *parent)
: QMainWindow(parent)
{
ui.setupUi(this);

QGraphicsScene *scene = new QGraphicsScene();
scene->addRect(QRectF(0, 0, 100, 200), QPen(Qt::black), QBrush(Qt::green));   

QPixmap pixmap;
QPainter painter(&pixmap);
painter.setRenderHint(QPainter::Antialiasing);
scene->render(&painter);
painter.end();

bool sceneRet =  pixmap.save("scene.png","png");

pixmap = QPixmap::grabWindow(QApplication::desktop()->winId(),pos().x(),pos().y(),frameGeometry().width(),frameGeometry().height());
bool pixmapRet =  pixmap.save("blog.png","png");

}

qtTest501::~qtTest501()
{

}
@
and sceneRet is false and pixmapRet is true... also strange..

[LCL_data]

I modify
@QPixmap pixmap;@
to
@QPixmap pixmap(130,130);@
and sceneRet can return true and get the correct thunbnail.

but for the ASSERT error still have even if i change
@QImage image;@
to
@ QImage image(70,70,QImage::Format_ARGB32);@

if i try to get the thumbnail from QGraphicsView, it success .

STRANGE.

[LCL_data]

I know why the Debug error pop-up:
my scene 's size is 100100, but one of my item is position is 200105. change it back into the scene's size. debug error disappear.