@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.

@Asperamanca said in Future of QGraphicsView and QGraphicsScene: @jeremy_k said in Future of QGraphicsView and QGraphicsScene: @Asperamanca I think my point was missed. There's no need to choose Quick|Graphics View|Widgets for the entire application. Use each where they make sense and use the underlying Qt core functionality to communicate. Yes, I missed your point. But maybe you missed mine: There is currently no better technology (in Qt) for some use cases than GraphicsView. Of course I can mix and match, depending on what I need. No, I didn't. We're in agreement there. It's easy to look at the graphics silos and forget that they can cooperate.

@newToQt26 Hi Good to hear. :) If the user can add or delete layers, it's pretty important you make sure curScene/curView always points to something valid as else you get a nasty crash.

I currently don't know but since the behaviour is different, I would fill a bug. If it's intended, the documentation should reflect that.

@amansahil Check after setting the position if polygon->scenePos() - clickPoint == (0, 0). If it is, there's a problem with the event->scenePos(), and if not, there's a problem with how the polygon position is being set. The right conversion would be polygon->setPos( clickPoint - polygonParent->scenePos() ) mapFromScene() is better than mapToScene() since you have the coordinates in the scene frame and you want them in local coordinates. But it still isn't quite right! You specify position in the local parent coordinates, not the local item frame. So that approach to use is polygon->setPos( polygonParent->mapFromScene(clickPoint) )

@galou_breizh I think point_size is too small and the ellipse generated is "pixelated" because of that. This gives a nice circle filled with blue # -*- coding: utf-8 -*- """Show an incomprehension in setScale for QGraphicsItemGroup.""" from PySide2 import QtCore from PySide2 import QtGui from PySide2 import QtWidgets point_size = 10.0 # In real-world units. # Get entrypoint through which we control underlying Qt framework app = QtWidgets.QApplication([]) scene = QtWidgets.QGraphicsScene() group = QtWidgets.QGraphicsItemGroup() scale = 50.0 # 1 real-world units = 500 px. !! Has no apparent effect. pen = QtGui.QPen(QtCore.Qt.red) brush = QtGui.QBrush(QtCore.Qt.blue) x = 1.0 # Real-world units. y = 2.0 # Real-world units. top_left = (x - point_size / 2.0, y - point_size / 2.0) ellipse = QtWidgets.QGraphicsEllipseItem( QtCore.QRectF(*top_left, point_size, point_size)) ellipse.setPen(pen) ellipse.setBrush(brush) ellipse.setScale(scale) group.addToGroup(ellipse) # group.setScale(scale) scene.addItem(group) view = QtWidgets.QGraphicsView(scene) view.show() # Start Qt/PySide2 application. If we don't show any windows, the # app would just loop at this point without the means to exit app.exec_()

@galou_breizh I answered in the other post. But it's not a good way to duplicate post for the same issue. Please try to avoid it in the future, thanks

@mrjj Yes, it worked. Thank you!

It appears that QGraphicsScene checks if position of item is visible in view and then draws/dont draws it... returning qgraphicsScene->sceneRect() as boundingRect on my curve "solved" the issues but its a problem for selectable items... hmmm

Hi, Can you provide a minimal compilable code that shows that behaviour ?

@sgaist Hmmmmmmmmm I wrote a little routine to use mouse press/release to see what has changed to determine my selection but it does not work as well as I wish. But I missed that focusItemChanged mhmhmhmh thanks! Will go over it again :- )

I have just figured it out. My first misunderstanding was that the boundingRect()'s coordinates must be (-0.5,-0.5) which means they are relative to the current item's position and not absolute on the Scene. and so this is the correct one: QRectF GIPoint::boundingRect() const { // return QRectF(pos().x(), pos().y(), 5, 5); return QRectF(-0.5, -0.5, 5, 5); } My second misunderstanding was in paint(). Do not use the pos() or scenePos() coordinates in order to draw the item. Instead draw it at (0,0). So the corrected paint() is this: void GIPoint::paint( QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget ){ (void )option; (void )widget; QRectF rect = boundingRect(); qWarning() << "painting: scenePos " << scenePos() << ", rect " << rect; QBrush brush = QBrush(Qt::black, Qt::SolidPattern); painter->fillRect(rect, brush); //painter->drawRect(rect); } The original program in my question still needs to be modified. Or shall I edit the changes in?

I've updated the question with gif/some updates... Still fighting with it o.o I think by using int vertOffset = horizontalScrollBar()->sliderPosition(); I can somehow calculate the "jump" value offset and offset position of line by that. Not sure how yet tho...

Call fitInView on the GraphicsView with the Image whenever the size of the GraphicsView changes. The rest should work automatically.

Hi, I got the expected output from grab(QRect) https://stackoverflow.com/questions/16362191/qt-grab-widget-and-save-image m_graphicsView->grab(rect).save("OUT.jpg"); Thanks all.

Thanks @SGaist and @raven-worx , I try both methods to see which one to use better in my program.

I found the problem. I was drawing the beats before the lines, so the lines took precedent over the beats since they are siblings. The solution was to either draw the beats last or set the Z value on the beat, not the note.

The idea is that you have your container widget getting resized and in its resize event, you change the size of the inner widgets with the ratio you want.

@Niagarer Good found. :)

@mrjj There are other obstacles that I need to overcome. But this way seems to be the solution that i am implementing. Thanks

@SGaist Hi Sam, Thank you for your hint, but my first problem was preventing the edit trigger on single click. For the posterity I have ended up with the following solution: Disable the textInteraction flags by default Override the QGraphicsTextItem::sceneEvent with the following: bool ValueAxisLabel::sceneEvent(QEvent *event) { if (event->type() == QEvent::GraphicsSceneMouseDoubleClick) { setTextInteractionFlags(Qt::TextEditorInteraction); bool ret = QGraphicsTextItem::sceneEvent(event); // QGraphicsTextItem::sceneevent needs to be processed before // the focus setFocus(Qt::MouseFocusReason); return ret; } return QGraphicsTextItem::sceneEvent(event); } The textInteractionFlags should be disabled in the overridden focusOutEvent.

In your MyView::paintEvent write QPainter painter(viewport()); instead of QPainter painter(this);.

@AdrianCruz hi Super :) just as a note To avoid getting possible NULLs in the list, i would suggest doing QGraphicsItem *item = qgraphicsitem_cast<QGraphicsItem*>(text); if (item) list.push_back(item);

Hi, You shouldn't use the size of a widget in its own constructor. The widget being not yet visible, the value won't make sense.

@raven-worx I tried the following but didn't work out.. QGraphicsPixmapItem* item = new QGraphicsPixmapItem(QPixmap::fromImage(qImage, Qt::AutoColor)); m_ViewerScene->addItem(item); QGraphicsRectItem* rect = new QGraphicsRectItem(m_BoundingBox); m_ViewerScene->addItem(rect); rect->setParentItem(item); m_ViewerScene->update(); //add the resized QGraphicsPixmapItem to the pixmap item->setPixmap( item->pixmap().scaled(QSize(128, 32),Qt::IgnoreAspectRatio, Qt::SmoothTransformation)); qInfo()<<"Rect resize props:::"<<item->childItems()[0]->boundingRect(); m_BoundingBox = item->childItems()[0]->boundingRect(); later I'm drawing box, on the image in an other viewer, with m_BoundingBox. The grey area within the blue rectangle will be resized to 128 * 32, and then the red rectangle would be added on the resized image. How to get the co-ordinates of red rect on the resized image?

Hi @wthung, I don't think this forum supports file uploads. Can you create a simple example that demonstrates the memory leak? Just post the code here, no need to upload an attachment.

@JEllery Thanks so much for solving this. It seems to solve my deletion-crash issue as well. :)

Hi I just keep a pointer to the "white lines" and adjust if i move yellow. class ColorItem : public QGraphicsItem { .. ConnectorLine* line = nullptr; .. protected: QVariant itemChange(GraphicsItemChange change, const QVariant& value) override { if (change == ItemPositionChange && scene()) { if (line) { line->adjust(); } } return QGraphicsItem::itemChange(change, value); } private: QColor color; }; line->Adjust() alters its endpoints. You could just adjust it directly here.

You're welcome ! Since you have it working now, please mark the thread as solved using the "Topic Tools" button so that other forum users may know a solution has been found :)