Pre-built Qt for WASM with threaing enabled

[terma.aba]

This post is deleted!

[lorn.potter]

Threads are still considered experimental in webassembly, in the browsers as well as Qt WebAssembly. Which is why we do not enable them by default. They require the user to tweak the browsers config settings.

They also need to be served from https due to the shared memory.

AND they are not real threads, and so work a bit different than unix threads, so it can be a bit tricky.