Just changing the root widget of my application from QWidget to QQuickWidget fixed the problem. Well, that was way easier than I expected! Thanks for the help.

@Turbotroop
OK, so:

Is the code pasted now currently what you have, exactly? What error do you currently have? Have you acted on the previous comments?

For example: although it won't generate a compilation error, it does not make any sense to set up all these boxes or arrays in the main window destructor, does it? Why not in, say, the constructor instead?

@tague Are you currently updating every time a point is added? If so, I wondered if you could buffer the incoming data so that you do not update so frequently? Perhaps use a QTimer to control update frequency.

@dariusz said

me not knowing 60% of STL

I would concentrate on fixing that. You're missing a large chunk of ready to use stuff and you'll be reinventing a lot of wheels without it.

@JKSH Yes I did.

On QT part, we followed a lot of techniques mentioned in that post. Using Loaders for lazy loading, optimizing images, using qtquickcompiler. The major challenge is on the OS boot time that we are working on.