[RFC] Command buffers

[alteous]

When updating scene objects, a small message is passed via a std::sync::mpsc channel which is later processed by the hub. This approach works well because it makes for an ergonomic API and is also thread safe; however, it may incur performance penalties for larger applications due to the pointer jumping and atomic operations.

I propose an alternative way of updating scene objects in addition to our current strategy. Essentially, it will let the user build up a Vec<Message> to be passed to the hub in a single large message instead of many small ones. Below is a demonstration of the idea:

Current approach

for object in &objects {
    object.set_visible(false);
}

Proposed alternative approach

let mut cmd_buf = factory.command_buffer();
for object in &objects {
    cmd_buf.set_visible(object, false);
}
cmd_buf.flush();

[kvark]

This approach works well because it makes for an ergonomic API and is also thread safe; however, it may incur performance penalties for larger applications due to the pointer jumping and atomic operations.

Somehow, I don't expect much of a perf penalty for updates. It would be best to gather some numbers before changing the messaging API in this direction.

[vitvakatu]

Agreed with @kvark. We can't decide without exact numbers.