Concurrency and tasks

GPUI has one foreground thread. All entity access and all rendering happen there. Background threads do work that touches no entity.

// Foreground: may touch entities through the AsyncApp it receives.
cx.spawn(async move |this: WeakEntity<Self>, cx: &mut AsyncApp| {
    let result = cx.background_spawn(async move { expensive() }).await;
    this.update(cx, |this, cx| {
        this.result = Some(result);
        cx.notify();
    })
})
.detach();

Both spawn and background_spawn return a Task<R>. Dropping a task cancels it, so every task must be awaited, detached (.detach() or .detach_and_log_err(cx)), or stored in a field for as long as the work should run.

Two conventions from Zed that this fork keeps:

• Scope clones with shadowing inside the spawn block:

  executor.spawn({
      let task_ran = task_ran.clone();
      async move { *task_ran.borrow_mut() = true; }
  });

• In tests, use the executor’s timers (cx.background_executor().timer(duration).await) rather than smol timers, so run_until_parked() can drive them.