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

@SGaist Its about precision moves, if user wants to move by tiny bit, scaling mouse movement by x value would allow that to happen. Else he would have to type 0.0001 0.0002 0.0003 etc etc.

I think I could handle it using itemChange() and record initial mouse click press/release and calculate delta using that..

Yep that seem to do the trick... I can now move my items by tiny amount and doing "Long precise drags"

deltaX = (newPos.x() - self.mMousePressPosition.x()) / 2 newPos.setX(newPos.x() - deltaX) deltaY = (newPos.y() - self.mMousePressPosition.y()) / 2 newPos.setY(newPos.y() - deltaY)

Small edit, function above works for "simple" items, but as soon as I get to child items with parent it appear to break... sigh. Needs some more math there

Hi
I think you just broke GraphicsView normal handling.
Try also calling base class mousePressEvent as it might use for the actual item selection

void GraphicsView::mousePressEvent(QMouseEvent *event) { if(event->buttons().testFlag(Qt::LeftButton)) { int x,y; x = event->pos().x(); y = event->pos().y(); qDebug() << x << ", " << y; QPointF point = mapToScene(x, y); QGraphicsEllipseItem *ellipse; ellipse = scene->addEllipse(point.x(),point.y(),5,5,QPen(Qt::red), QBrush(Qt::red)); ellipse->setFlag(QGraphicsEllipseItem::ItemIsMovable); } // call base class QGraphicsView::mousePressEvent(event); }

@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 :- )

Scale_5.gif
可以参考这个网站进行进行背景图的绘制，缩放的原理 等https://www.desmos.com/calculator?lang=zh-CN
同时参考这这个链接，进行背景绘制https://stackoverflow.com/questions/24728477/infinite-grid-in-qt

Hi,

Without more details form you side, it looks like that's the function you are looking for.

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

@Skamath The Halcon example using Qt is very simple but it uses the Halcon Graphics Window to show images, regions and XLDs. If you think that it is complicated I recommend you to use the Halcon Graphics Window instead of trying to build your own Graphics Window based on QGraphicsView.

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

@Staslend if your issue is solved, please don't forget to mark your post as such! Thanks.

Hi,

You should add:

Which version of Qt you were using before Which version of Qt you are using now Graphics card + driver Platform you are running on

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. :)

Thanks for the input! I think I'm going to go with QGraphicsView for the notation and use QQuickWidgets throughout the other pieces of the UI that don't need access to the entire model. I'm hoping that won't be too complicated and will give me the best of both worlds. But I do wonder: is there a specific piece of Qt Quick that's supposed to a "replacement" for QGraphicsView? It seems like the scene graph is a bit too low level, but it's also the only way to gain a lot of control and keep things mostly on the C++ side. It would be nice if the built-in QML elements are exposed via a C++ API at some point.

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

Do you mean custom graphicsView or tableView? If custom graphics view wouldn't it be too hard to reimplement everything? Any links or example would help.