How to resize QWidget added in QGraphicScene through QGraphicsProxy? - c++

Question

I have added a widget to a graphic scene (QGraphicScene) through a QGraphicsProxyWidget. To move and select the widget added QGraphicsRectItem handle.
To resize widget added QSizegrip to widget. But when i resize widget more than the QGraphicsRect item rect right and bottom edges goes behind .How to overcome this problem?
When i resize widget graphics rect item should resize or vice-versa should happen. how to do this? Any other ideas are welcome.
Here is the code
auto *dial= new QDial(); // The widget
auto *handle = new QGraphicsRectItem(QRect(0, 0, 120, 120)); // Created to move and select on scene
auto *proxy = new QGraphicsProxyWidget(handle); // Adding the widget through the proxy
dial->setGeometry(0, 0, 100, 100);
dial->move(10, 10);
proxy->setWidget(dial);
QSizeGrip * sizeGrip = new QSizeGrip(dial);
QHBoxLayout *layout = new QHBoxLayout(dial);
layout->setContentsMargins(0, 0, 0, 0);
layout->addWidget(sizeGrip, 0, Qt::AlignRight | Qt::AlignBottom);
handle->setPen(QPen(Qt::transparent));
handle->setBrush(Qt::gray);
handle->setFlags(QGraphicsItem::ItemIsMovable |
QGraphicsItem::ItemIsSelectable);
Scene->addItem(handle); // adding to scene
Here is the Output::
Before Resize
After Resize

Answer 1

Cause
The QGraphicsRectItem, which you use as a handle, is not aware of the size changes of QDial, so it does not respond by resizing itself.
Limitation
QWidget and its subclases do not provide something like a sizeChanged signal out of the box.
Solution
Considering the cause and the given limitation, my solution would be the following:
In a subcalss of QDial, say Dial, add a new signal void sizeChanged();
Reimplement the resizeEvent of Dial like this:
in dial.cpp
void Dial::resizeEvent(QResizeEvent *event)
{
QDial::resizeEvent(event);
sizeChanged();
}
Change auto *dial= new QDial(); to auto *dial= new Dial();
Add the following code after Scene->addItem(handle); // adding to scene:
in the place, where your example code is
connect(dial, &Dial::sizeChanged, [dial, handle](){
handle->setRect(dial->geometry().adjusted(-10, -10, 10, 10));
});
Note: This could be also solved using eventFilter instead of subclassing QDial. However, from your other question I know that you already subclass QDial, that is why I find the proposed solution more suitable for you.
Result
This is the result of the proposed solution: