It's a combination of JavaFX, a custom controls library that implements Material Design and GraalVM native image. Whether you want a non-native UI toolkit on iOS is a separate matter, but it can be done technically.
In fact, you can ship JavaFX apps to the web too. It doesn't compile to megabytes of JS either - instead, the JavaFX app runs on the server and the UI is projected to divs and SVG elements on the fly. The browser provides native scrolling and text selection. If you have low latency to the server (e.g. same continent) it can work remarkably well. Check out https://www.jpro.one/ - the entire website is a JavaFX app.
https://gluonhq.com/
It's a combination of JavaFX, a custom controls library that implements Material Design and GraalVM native image. Whether you want a non-native UI toolkit on iOS is a separate matter, but it can be done technically.
In fact, you can ship JavaFX apps to the web too. It doesn't compile to megabytes of JS either - instead, the JavaFX app runs on the server and the UI is projected to divs and SVG elements on the fly. The browser provides native scrolling and text selection. If you have low latency to the server (e.g. same continent) it can work remarkably well. Check out https://www.jpro.one/ - the entire website is a JavaFX app.