1 files changed, 59 insertions, 0 deletions
diff --git a/engine/src/performance.rs b/engine/src/performance.rs
new file mode 100644
index 0000000..ffc5c27
--- /dev/null
+++ b/engine/src/performance.rs
@@ -0,0 +1,59 @@
+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>,
+}