How to sleep in the main game loop?

[PonasKovas]

I'm used to having game loops somewhat like this:

loop {
    do_logic();

    std::thread::sleep(std::time::Duration::from_nanos(1_000_000_000/60)); // 60 fps
}

But I doing this on quicksilver appears to break the app: the game gets stuck on the first frame and I get a bunch of RuntimeError: unreachable executed errors in the console.

How am I supposed to get 60 fps (and not more)?

[lenscas]

assuming quicksilver 3: the update and draw function get executed as often as specified in the settings https://docs.rs/quicksilver/0.3.20/quicksilver/lifecycle/struct.Settings.html

For quicksilver 4: I believe the same is true, but then for the events. (I may be wrong on that as I haven't used that version yet).

Either way, you shouldn't have a need to sleep yourself

[ryanisaacg]

@PonasKovas I'm assuming from your error that you're running the web backend, where the std::thread module is not available (which is the source of your error).

As @lenscas mentioned, the update and draw functions in the old lifecycle system provide this functionality, but they don't currently have equivalents in the 0.4 alpha versions. If you check #552, there is a bullet point for them: "Helpers for planning when to update / draw"

[PonasKovas]

Are there any plans on how to implement that? I may want to contribute

[ryanisaacg]

I don't have firm plans yet; one draft design would look something like:

pub struct Timer { ... }
impl Timer {
    pub fn new(period_in_ms: f32) -> Timer { ... }
    pub fn tick(&mut self) -> bool { ... }
    pub fn ms_remaining(&self) -> f32 { ... {
}

with a usage pattern that looks roughly like:

loop {
    // handle events
    if update.tick() {
        // handle update
    }
    if draw.tick() {
        // handle draw
    }

A good reference is Fix Your Timestep when implementing timing functionality.

[johnpmayer]

I've implemented sleep (works in all build targets - desktop/stdweb/web-sys) in https://crates.io/crates/quicksilver-utils-async

[ryanisaacg]

@PonasKovas check out the new timer example, this should let you lock your update and draw rates to whatever speeds you like.