No, just using plain QML. Basically, it's a C++ application with application logic written in JS (using a rather bad JIT), and where we went wrong was writing a lot of application logic in JS rather than just writing the UI specific application logic in JS and the remaining part of the application logic in C++. OTOH, we already had huge parts of the system in C++ and the JS access was mainly small data transformations, but even this turned out to be too slow.