Add FPS counter

src/bin/wireframe/main.rs

@@ -116,6 +116,7 @@ struct State<'a> {
 	device: wgpu::Device,
 	queue: wgpu::Queue,
 
+	fps: fps::Counter,
 	kbd: keyctl::Keyboard,
 	t1: Instant,
 
@@ -187,12 +188,15 @@ impl<'a> State<'a> {
 
 		let scene = prepare_scene(&device);
 
+		let fps = fps::Counter::new();
+
 		Self {
 			device,
 			queue,
 			viewport,
 			line_rend,
 			kbd,
+			fps,
 			cam_loc,
 			cam_obj,
 			t1,
@@ -229,6 +233,9 @@ impl<'a> State<'a> {
 	}
 
 	fn render(&mut self) -> Result<(), wgpu::SurfaceError> {
+		self.fps.on_frame();
+		self.window
+			.set_title(&format!("Space Refraction ({:.1} FPS)", self.fps.get()));
 		self.viewport
 			.render_single_pass(&self.device, &self.queue, |mut render_pass| {
 				self.line_rend.render(
@@ -310,3 +317,40 @@ pub async fn run() {
 fn main() {
 	pollster::block_on(run());
 }
+
+mod fps {
+	use std::time::{Duration, Instant};
+
+	pub struct Counter {
+		fps: f32,
+		t1: Instant,
+		frames: u32,
+	}
+
+	impl Counter {
+		pub fn new() -> Self {
+			Self {
+				fps: 0.,
+				t1: Instant::now(),
+				frames: 0,
+			}
+		}
+
+		pub fn get(&self) -> f32 {
+			self.fps
+		}
+
+		pub fn on_frame(&mut self) {
+			self.frames += 1;
+			let t2 = Instant::now();
+			let dt = t2 - self.t1;
+			if dt >= Duration::from_secs(1) {
+				*self = Self {
+					fps: self.frames as f32 / dt.as_secs_f32(),
+					t1: t2,
+					frames: 0,
+				}
+			}
+		}
+	}
+}