Challenges in migration of Qt 4.8.2 project into Qt 5.7 and above

[Anjali Srivastava]

Hi anda_skoa,

If you are using the declarative framework for the actual item construction, I would recommend not interacting with the QGraphicsScene from C++. This will then nicely map to using Qt5 QtQuick.

Some of the items are created as QGraphicsItem and some are QDeclarativeItem, If we will not use QGraphicsScene, then how will we add QGraphicsItems to the scene?

You would be using the QQuickWidget instead of the QGraphicsView, not as a part of it

QGracphicsView and QGraphicsScene is already there and we used QQuickWidget to show the QML items into the scene.

[anda_skoa]

Some of the items are created as QGraphicsItem and some are QDeclarativeItem, If we will not use QGraphicsScene, then how will we add QGraphicsItems to the scene?

What kind if items do you create as graphics items?

It might be possible to just make custom declarative items and create all items from QML.

QGracphicsView and QGraphicsScene is already there and we used QQuickWidget to show the QML items into the scene.

So currently you have a QDeclarativeView as an item in your QGraphicsScene?

Cheers,
_

[Anjali Srivastava]

What kind if items do you create as graphics items?

Grids and Ellipses are created as graphics item and in future vendor company will also create some items as graphics Item.

It might be possible to just make custom declarative items and create all items from QML.

In Qt 4.8.2 we used QDeclalativeItem to create some objects in QML and added it to QGraphicsScene. But now in Qt 5.7 how will we create it?

So currently you have a QDeclarativeView as an item in your QGraphicsScene?

No, We are not using QDeclarativeView. We used QQuickWidget to access Item form QML file and added it to QGraphicsScene.

[anda_skoa]

Grids and Ellipses are created as graphics item and in future vendor company will also create some items as graphics Item.

Should be trivial to create these as custom QDeclarativeItems

In Qt 4.8.2 we used QDeclalativeItem to create some objects in QML and added it to QGraphicsScene.

Ah, ok, very hacky.

If you use a QDeclarativeView instead then you can use the same approach when moving to a QQuickWidget.

We used QQuickWidget to access Item form QML file and added it to QGraphicsScene.

Well, that's not possible since Qt5 QQuickItems are not QGraphicsItems.
QtQuick is rendered with an OpenGL based scene graph.

As far as I understood your setup you have these options:

1) Remove the usage of QML

2) Keep using QGraphicsView and just use QQmlEngine with custom types to create QGraphicItem based objects in QML

3) Move the Qt4 version to use QDeclarativeView and custom QDeclarativeItem and then port that almost unchanged to QtQuickWidget and custom QQuickPaintedItems.

Cheers,
_

[Anjali Srivastava]

Should be trivial to create these as custom QDeclarativeItems

1) Remove the usage of QML

2) Keep using QGraphicsView and just use QQmlEngine with custom types to create QGraphicItem based objects in QML

3) Move the Qt4 version to use QDeclarativeView and custom QDeclarativeItem and then port that almost unchanged to QtQuickWidget and custom QQuickPaintedItems.


_

Yes I think you are right, If I follow the point two then could you provide any example or link for the same.

[anda_skoa]

The QML engine (in both Qt4 and Qt5) can essentially create instances of any class that is derived from QObject (directly or indirectly).

So for example if you have a class that derives from QGraphicsObject you should be able to register that with the QML engine's type system and then use in QML like any of the "built-in" types.

http://doc.qt.io/archives/qt-4.8/qde...mlRegisterType
http://doc.qt.io/qt-5/qqmlengine.html#qmlRegisterType

Cheers,
_