engine/src/performance.rs


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use std::time::Instant;

use ecs::component::local::Local;
use ecs::system::{Into, System};
use ecs::Component;

use crate::event::PostPresent as PostPresentEvent;

#[derive(Debug, Default)]
#[non_exhaustive]
pub struct Extension {}

impl ecs::extension::Extension for Extension
{
    fn collect(self, mut collector: ecs::extension::Collector<'_>)
    {
        collector.add_system(
            PostPresentEvent,
            log_perf.into_system().initialize((State::default(),)),
        );
    }
}

#[cfg(feature = "debug")]
macro_rules! log_perf {
    ($($tt: tt)*) => {
        tracing::info!($($tt)*);
    };
}

#[cfg(not(feature = "debug"))]
macro_rules! log_perf {
    ($($tt: tt)*) => {
        println!($($tt)*);
    };
}

fn log_perf(mut state: Local<State>)
{
    let Some(last_time) = state.last_time else {
        state.last_time = Some(Instant::now());
        return;
    };

    let time_now = Instant::now();

    state.last_time = Some(time_now);

    log_perf!(
        "Frame time: {}us",
        time_now.duration_since(last_time).as_micros()
    );
}

#[derive(Debug, Default, Component)]
struct State
{
    last_time: Option<Instant>,
}