@JonB Thanks for your feedback :)

Hi,

See if this provides some explanation (read the comments as well):

StackOverflow: Qt6 QLabel / QPixmap excessive memory usage

@JonB I moved my code into QGraphicsView::drawBackground() as you recommended, it works nicely. Thanks a lot!

@wrosecrans
I know that I need them. But don‘t know how to apply them on the scene and keep everything thats on that. I thought that the rect itself has the points in it using the render function of the QGraphicsScene is enough.

What I do: I set the DragMode of the QGraphicsView to rubberband so the user can select some part pf the scene by simply dragging. The returned rect is now sent to the view to get the underlying image of the scene.

Animation, composition, overlaying and whatever comes to your imagination.

That said, if you are really only showing one single image and nothing more then, indeed, a QLabel is enough.

At the end I've researched again the view's transformations and concluded to support both features and warn for the complexity.

I did not re-implement the add/remove items of the scene together with a group. Thanks for the hint @Asperamanca .

Hey, not sure if you found the solution yet. But you can try this:

QGraphicsPixmapItem *pixmapItem = new QGraphicsPixmapItem; pixmapItem->setPixmap(QPixmap(":/images/pixmap.png")); _scene->addItem(pixmapItem); pixmapItem->setRotation(pixmapItem->rotation() + 45.0); QGraphicsRectItem *boundingRect = new QGraphicsRectItem(pixmapItem->sceneBoundingRect()); QPen outlinePen; outlinePen.setWidth(2); outlinePen.setColor(Qt::red); boundingRect->setPen(outlinePen); _scene->addItem(boundingRect);

I believe what you want is the sceneBoundingRect() and not the boundingRect().

@HappyVisualizer

Since your view is in a layout... have you tried to set the layout margin to 0?

I solved my problem via event filter of scene.

ui->graphicsView->scene()->installEventFilter(this); bool MainWindow::eventFilter(QObject* obj, QEvent* event){ if(event->type() == QEvent::GraphicsSceneMousePress){ if(ui->addServerBtn->isChecked()){ QGraphicsSceneMouseEvent* mouseSceneEvent; mouseSceneEvent = static_cast<QGraphicsSceneMouseEvent *>(event); Server *serv = new Server(mouseSceneEvent->scenePos().toPoint()); scene->addItem((QGraphicsPixmapItem*)serv); } } return false; }

For any1 wondering, its more or less >
item->setPos(mNodeViewPtr->mapToScene(mNodeViewPtr->mapFromGlobal(QCursor::pos())));
you can most likely do mNodeViewPtr->viewport()->mapFromGlobal() for more precision I think but I didn't test it.

@sticky-thermos said in Receive Drag/Drop events for items in QGraphicsScene:

void ChessBoard::mouseMoveEvent(QMouseEvent *event) {
std::cout << FUNCTION << std::endl;
QGraphicsView::mousePressEvent(event);
QDrag *drag = new QDrag(this);
QMimeData *mime = new QMimeData; // this is necessary even if nothing is set in the mime data
drag->setMimeData(mime);
drag->exec();
}

Looks good, but I would add a check to differenciate whether your mouseButton is down. Otherwise you are creating a lot of drags from just moving your mouse around on your chessBoard.

Also, you are passing the ChessBoard::mouseMoveEvent(QMouseEvent *event) to QGraphicsView::mousePressEvent(event).
QGraphicsView::mouseMoveEvent would be more fitting :)

Thanks for the reply @SGaist . This helps

@Chris-Kawa Noted thank you. Now it compiles without errors. I think I need to read a bit about newer c++...

@TenG
Be aware that not all of Qt modules are supported in WASM. Before anything, check the list at https://doc.qt.io/qt-5/wasm.html#supported-qt-modules against what is in your app. For example, it doesn't do databases, you can't access the local file system, and so on. Also I noticed this time that it requires a Qt static build, but maybe you have to have that for iOS anyway, I don't know.

If it works for you it's a really simple solution compared to rewriting anything. Just check out the gotchas.

I guess I provided inadequate subtext for that example. It's documentation in a project I work on, explaining that qObject.signal.connect(lambda: anotherQObject.function(arg)) is unsafe in PyQt if anotherQObject might be destroyed before qObject. The same would happen in C++ with QObject::connect(qObject, &MyClass::signal, [&]() { anotherQObject->function(arg); });

In C++, one possible solution is to use QObject::Connect(sender, signal, context object, functor). To the best of my knowledge In PyQt5, and I suspect in PySide2/Qt for Python, there is no equivalent. You can write one by taking the connection object returned by object.signal.connect() and using it in a slot connected to anotherQObject.destroyed.