Sublassing QGraphicsLayoutItem

[onurozcelik]

How exactly can I subclass QGraphicsLayoutItem?
I write a class that subclass QGraphicsLayoutItem and reimplement sizeHint and setGeometry but when I add my custom item to linear or grid layout. It does not shown?
What is missing?

[SixDegrees]

QGraphicsItem is not a QWidget; it's meant to be displayed when it is placed into a QGraphicsScene which is then viewed with a QGraphicsView. It won't show up in a QLayout. In fact, I'm surprised you're able to add it in the first place.

A QGraphicsView descends from QWidget, and can be added to a QLayout.

[onurozcelik]

I think you got me wrong. Cause there are existing layouts for QGraphicsView.
Look at these QGraphicsLinearLayout, QGraphicsGridLayout

[SixDegrees]

In your original post, you were talking about a QGraphicsItem, not a QGraphicsView.

Maybe you could post a short example that demonstrates the problem?

[onurozcelik]

Here my trial.

//compositeitem.h
 
class CompositeItem : public QGraphicsLayoutItem,public QGraphicsItemGroup
{
     CompositeItem(QString id, QList<QGraphicsWidget *> children);
     ~CompositeItem();
      QSizeF sizeHint() const;
      void setGeometry(const QRectF &rect);
};
 
//compositeitem.cpp
CompositeItem::CompositeItem(QString id,QList<QGraphicsWidget *> children)
{
   QGraphicsWidget *child;
   foreach(child,children)
   {
      addToGroup(child);
   }
}
 
CompositeItem::~CompositeItem()
{
}
 
QSizeF CompositeItem::sizeHint()
{
   ...
}
 
void CompositeItem:: setGeometry(const QRectF &rect)
{
    QGraphicsLayoutItem::setGeometry(rect);
}
 
//mainwindow.cpp
 
QGraphicsScene *scene = new QGraphicsScene;
ui.graphicsView->setScene(scene);
 
QGraphicsLinearLayout *layout = new QGraphicsLinearLayout;
CompositeItem * ci = new CompositeItem(...);
layout->addItem(ci);
QGraphicsWidget *container = new QGraphicsWidget;
container->setLayout(layout);
scene->addItem(container);

//compositeitem.h

class CompositeItem : public QGraphicsLayoutItem,public QGraphicsItemGroup
{
     CompositeItem(QString id, QList<QGraphicsWidget *> children);
     ~CompositeItem();
      QSizeF sizeHint() const;
      void setGeometry(const QRectF &rect);
};

//compositeitem.cpp
CompositeItem::CompositeItem(QString id,QList<QGraphicsWidget *> children)
{
   QGraphicsWidget *child;
   foreach(child,children)
   {
      addToGroup(child);
   }
}

CompositeItem::~CompositeItem()
{
}

QSizeF CompositeItem::sizeHint()
{
   ...
}

void CompositeItem:: setGeometry(const QRectF &rect)
{
    QGraphicsLayoutItem::setGeometry(rect);
}

//mainwindow.cpp

QGraphicsScene *scene = new QGraphicsScene;
ui.graphicsView->setScene(scene);

QGraphicsLinearLayout *layout = new QGraphicsLinearLayout;
CompositeItem * ci = new CompositeItem(...);
layout->addItem(ci);
QGraphicsWidget *container = new QGraphicsWidget;
container->setLayout(layout);
scene->addItem(container);

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Here i do not see my compositeitem drawing on scene.

[GuL]

Did you solve your problem?

[SixDegrees]

What happens if you add your CompositeItem directly to the scene?

And what is it you expect to see? I don't see any paint() routine or other functions that will cause anything to be displayed.

[onurozcelik]

@GuL I don't solve my problem with this approach. But I write a custom composite item class that acts like a QGraphicsItemGroup, also can be added inside QGraphicsLayout.

@SixDegrees if I add my composite item directly to scene I see empty scene. There is no paint because I expect to see child items paints themselves.