[discreteevent]

You can write all of your Qt logic in javascript if you want to. It will probalbly still be much faster than a browser. But the thing is that Qt allows you to write your logic (and your ui) in C++ if you need to. It gives you somewhere to go when performance is an issue. And on mobile or embedded there is a high chance that only a compiled, no-vm, no-gc language like C/C++ or Objective C or Rust will give you the performance you need. One thing is for sure: If you have to build a cross platform native application be sure to first prototype the performance and processor/battery use of your technology choice. Even if you don't choose something like Qt at least you can write your backend in C++ and write a different native front end for each OS. But if you use e.g. web technology and don't prototype first there will be absolutely fire escape later. A lot of people have learned this the hard way.

[insulanian]

> You can write all of your Qt logic in javascript if you want to. ... But the thing is that Qt allows you to write your logic (and your ui) in C++ if you need to.

Maybe that sounds appealing to some, but for me is just choosing between two evils. Unsafe dynamic language on one side - kitchen-sink low-level language on the other side.

I personally would like something in between, but still cross platform. F# with Xamarin looks most appealing to me, but Xamarin is unfortunately not free, so...

[zerr]

All these QML/js stuff smells rather artificially put (into Qt) to me... I mean, why not have a functionality to define the scene (and not just a logic) in pure C++? I think one reason for QML/js is to (try) attract contemporary js/web devs.