Why do not actor-isolated properties support 'await' setter?

[Andropov (Raúl Montón)]

@j-f1

Could you represent all of the view-controllable state (except the model choice) as a struct stored on an @MainActor view model, then synchronously grab a copy of that state before each render pass? That way, the UI will immediately see any changes the user makes reflected back in the controls, and value semantics mean it is impossible for that configuration to change out from under the renderer. For things like the 3D model, you’d still need an actor to manage fetching the updated model choice from disk, but that could be a separate actor from the renderer which could just grab a struct containing the current Metal buffers at the start of each render pass.

Oh, the UI already has its own copy of the values, stored on a few @MainActor view models, so all UI controls see changes reflected immediately, even if the visualization takes a few ms longer to update. So when the UI is updated -> @MainActor View Model is updated -> a task to mutate the renderer is spawned. It's even possible to keep track of those tasks to disable the specific control while the action takes place.

There are a few reasons I went with shared state with reference semantics instead of copying all state from the @MainActor View Models at the start of every frame:

• The combined state is not lightweight enough to copy all of it up to 120 times per second.
• It allows rendering to happen only when a value has changed, using minimal energy if there are no changes.
• It completely avoids requiring a switch to the main thread to render new frames. So even if the main thread is blocked for a few milliseconds, no frames are dropped.