Wait, so they were using QtWebEngine not as a way to just embed simple web pages, but to make full-fledged interfaces in HTML+JS, essentially using it like Electron (before Electron was born)? While ignoring the rest of the entire Qt landscape? That’s totally bonkers, it’s like taking a screwdriver and using it as a nail! I mean it works, it is one of the possible ways to serve web applications for cross-platform, but oh god that was why the whole UI was god damn slow. (Even if QtWebEngine is wrapper of Chromium it’s incredibly slow for some reason and isn’t really equipped well to run full-fledged JS applications.)