I decided to build it using Qt (Qt Widgets in c++) mainly because my whole data engine is also in c++. Since it just uses standard windows and dialog boxes; I haven't felt the need to keep up with the latest Qt version. I am still using Qt 5 (I think revision 13 or 15).
I have been contemplating moving to Qt 6. Have users noticed a big difference (e.g. performance) between Qt 5 and Qt 6?
QtQuick uses a different runtime which is (afaik) faster and targets modern graphics backends (eg. Vulcan) in a way widgets does not.
It also uses an a javascript scripting engine.
Saying “they’re both c++” is seems kind of misleading and meaningless right?
It’s probably more accurate to say QML is actively being worked on and receiving performance enhancements and updates and widgets is not, and has not for some time.
So yes, it’s actually pretty unlikely that QML would be slower (depending on what you do with your scripts) but it’s probably not as clear cut as you are suggesting.
QML apps that heavily implement core logic in javascript would be slow as balls.
Not really, if you avoid writing Javascript code in your QML components, than most of your executable will end up being compiled C++ code. If you do write Javascript code in your QML components, than it *could also* be compiled to C++ code using the QML script compiler[1[2].
> QML apps that heavily implement core logic in javascript would be slow as balls.
The entire point is to separate logic and view where logic is written in C++ and QML simply represents the view (which almost end up being built upon simple primitives that *are* C++ objects). So if you keep this separation you get amazing performance with great simplicity and velocity.
People who are going to use it should read the documentation.
“It depends” and “it’s still slow” are the fairest comments I can make about this.
You can't claim something is slow without showing empiric data. I showed mine when I claimed programming Qt C++ and QML together is fast. If you claim otherwise, you need to support it with data.
> The most common performance issues in decently written applications are rendering of invisible items aka overdraw
That's indeed what I found as well! Especially, these hidden items consume a lot of unnecessary RAM. What tools do you know for Qt/QML that can help with this issue?
For another perspective and more details, RenderDoc (or another frame debugger if you have one) is a nice tool as well.
Also don't use Rectangle { color: "transparent" }, use Item {}. An Item has geometry, but doesn't render anything. A transparent Rectangle probably also doesn't render, but it's still (at least slightly) more resource-intensive and makes you look like you don't know what you're doing.
Use Loader, StackView and visible liberally to disable stuff that isn't currently relevant. If unloading causes trouble with lost state, you may be carrying too much state on the QML side.