I've had some issues with Browser reporting problems ("A script is slowing down your browser") with a medium-sized Qt for WASM application.
Due to this, I've tried compiling Qt for WebAssembly and my application with current emscripten 2.0.0.
This version emits the following warning:
Blocking on the main thread is very dangerous, see https://emscripten.org/docs/porting/pthreads.html#blocking-on-the-main-browser-thread
I understand that Qt currently has no official support for other emscripten versions than the one mentioned at https://doc.qt.io/qt-5/wasm.html. However, I think this is a serious issue that probably also affects those versions and should be handled.|