QGraphicsScene::drawItems is not called if it's subclassed

[jano_alex_es]

Hi,

I have my subclassed graphicsview and graphicsScene, all works perfectly with more or less 100 graphicsitems and some logic implemented in my custom scene.

I want to control when the items appear, so I tried to subclass QGraphicsScene::drawItems. But when QGraphicsView::drawItems is called it does not go to my subclassed scene, it calls QGraphicsScene::drawItems.

I can solve it writting my code directly in the view... but I would like to ask if it's the normal behavour or I'm missing something.

Thanks!

[tbscope]

But when QGraphicsView::drawItems is called it does not go to my subclassed scene, it calls QGraphicsScene::drawItems.

QGraphicsView calls drawItems of the scene that is added to the view, thus your custom scene.
This in turn means that you did something wrong in your scene subclass.

Post your code.

[jano_alex_es]

QGraphicsView calls drawItems of the scene that is added to the view, thus your custom scene.

that's the problem... but it doesn't :S

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    setWindowTitle("PruebaMagnetica1");
 
    m_pScene = new CScene();
    m_pView = new CView(m_pScene, this);
...
}

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    setWindowTitle("PruebaMagnetica1");

    m_pScene = new CScene();
    m_pView = new CView(m_pScene, this);
...
}

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View.h

class CView : public QGraphicsView
{
public:
    CView(CScene* pScene, QWidget * parent = 0);
    virtual ~CView();
 
	void	enableRendering(){m_bRender = true;}
 
protected:
	void	drawItems ( QPainter * painter, int numItems, QGraphicsItem * items[], 
		const QStyleOptionGraphicsItem options[] );
 
	bool	m_bRender;
};

class CView : public QGraphicsView
{
public:
    CView(CScene* pScene, QWidget * parent = 0);
    virtual ~CView();

	void	enableRendering(){m_bRender = true;}

protected:
	void	drawItems ( QPainter * painter, int numItems, QGraphicsItem * items[], 
		const QStyleOptionGraphicsItem options[] );

	bool	m_bRender;
};

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View.cpp

CView::CView(CScene* pScene, QWidget * parent)
{
    setParent(parent);
    setScene(pScene);
 
	m_bRender = false;
}
 
CView::~CView()
    {
    // TODO Auto-generated destructor stub
}
 
void CView::drawItems( QPainter * painter, int numItems, QGraphicsItem * items[], const QStyleOptionGraphicsItem options[] )
{
	if(m_bRender)
	{
		QGraphicsView::drawItems(painter, numItems, items, options); //It calls QGraphicsScene::drawItems instead of CScene::drawItems
		m_bRender = false;
	}
}

CView::CView(CScene* pScene, QWidget * parent)
{
    setParent(parent);
    setScene(pScene);

	m_bRender = false;
}

CView::~CView()
    {
    // TODO Auto-generated destructor stub
}

void CView::drawItems( QPainter * painter, int numItems, QGraphicsItem * items[], const QStyleOptionGraphicsItem options[] )
{
	if(m_bRender)
	{
		QGraphicsView::drawItems(painter, numItems, items, options); //It calls QGraphicsScene::drawItems instead of CScene::drawItems
		m_bRender = false;
	}
}

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[wysota]

How do you know it calls QGraphicsScene::drawItems()?

[jano_alex_es]

because I have it subclassed as well in "CScene". But debugging it goes into QGraphicsScene class and not into the subclassed one.

Scene.h

class CScene : public QGraphicsScene
{
Q_OBJECT
 
public:
    CScene(QObject *parent = 0);
    virtual ~CScene();
 
protected:
	void	drawItems ( QPainter * painter, int numItems, QGraphicsItem * items[], 
		const QStyleOptionGraphicsItem options[] );

class CScene : public QGraphicsScene
{
Q_OBJECT

public:
    CScene(QObject *parent = 0);
    virtual ~CScene();

protected:
	void	drawItems ( QPainter * painter, int numItems, QGraphicsItem * items[], 
		const QStyleOptionGraphicsItem options[] );

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Scene.cpp

void CScene::drawItems( QPainter * painter, int numItems, QGraphicsItem * items[], const QStyleOptionGraphicsItem options[] )
{
//
//my code here, with a not called breakpoint
//
 
		QGraphicsScene::drawItems(painter, numItems, items, options);
}

void CScene::drawItems( QPainter * painter, int numItems, QGraphicsItem * items[], const QStyleOptionGraphicsItem options[] )
{
//
//my code here, with a not called breakpoint
//

		QGraphicsScene::drawItems(painter, numItems, items, options);
}

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[tbscope]

Can you post the line of code where you set the breakpoint?
Some debuggers don't break on certain lines of code.

[jano_alex_es]

I tried using traces as well

For instance, if I try this in order to test:

void CScene::drawItems( QPainter * painter, int numItems, QGraphicsItem * items[], const QStyleOptionGraphicsItem options[] )
{
	QGraphicsScene::drawItems(painter, numItems, items, options);//breakpoint
}

void CScene::drawItems( QPainter * painter, int numItems, QGraphicsItem * items[], const QStyleOptionGraphicsItem options[] )
{
	QGraphicsScene::drawItems(painter, numItems, items, options);//breakpoint
}

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doesn't work either

[jano_alex_es]

just in case, some extra info: I'm using Visual Studio 2008 with Qt 4.5.0 (unfortunatly I can't update)

[wysota]

Your method has an incorrect signature, you are missing the last argument (QWidget pointer).

[jano_alex_es]

buf, I'm so stupid... thanks