1 files changed, 121 insertions, 0 deletions
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..6303919
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,121 @@
+use std::{
+    hint,
+    sync::Arc,
+    thread,
+    time::{Duration, Instant},
+};
+use winit::{
+    application::ApplicationHandler,
+    dpi::LogicalSize,
+    event::{ElementState, WindowEvent},
+    event_loop::{ActiveEventLoop, ControlFlow, EventLoop},
+    window::{Window, WindowId},
+};
+
+struct App {
+    window: Option<Arc<Window>>,
+}
+
+impl App {
+    fn new() -> Self {
+        Self { window: None }
+    }
+}
+
+impl ApplicationHandler for App {
+    fn resumed(&mut self, event_loop: &ActiveEventLoop) {
+        // ウィンドウメッセージをpollで捌く
+        // キューが空になる度に`about_to_wait`メソッドが呼ばれる
+        event_loop.set_control_flow(ControlFlow::Poll);
+
+        let attributes = Window::default_attributes()
+            .with_inner_size(LogicalSize::new(1280, 720))
+            .with_fullscreen(None);
+
+        let window = match event_loop.create_window(attributes) {
+            Ok(v) => Arc::new(v),
+            Err(e) => panic!("error: {e}"),
+        };
+
+        self.window = Some(window);
+    }
+
+    fn window_event(&mut self, event_loop: &ActiveEventLoop, _id: WindowId, event: WindowEvent) {
+        match event {
+            WindowEvent::CloseRequested => event_loop.exit(),
+            WindowEvent::MouseInput { state, button, .. } => match state {
+                ElementState::Pressed => {
+                    println!("pressed {:?}", button);
+                }
+                ElementState::Released => {
+                    println!("released {:?}", button);
+                }
+            },
+            WindowEvent::CursorMoved { position, .. } => {
+                let Some(window) = self.window.as_ref() else {
+                    return;
+                };
+                println!(
+                    "moved {:?}",
+                    position.to_logical::<f32>(window.scale_factor())
+                );
+            }
+            WindowEvent::CursorLeft { .. } => {
+                println!("left");
+            }
+            WindowEvent::Focused(false) | WindowEvent::Occluded(true) => {
+                println!("focused or occluded");
+            }
+            _ => {}
+        }
+    }
+
+    fn about_to_wait(&mut self, event_loop: &ActiveEventLoop) {
+        let start = Instant::now();
+
+        let Some(_) = &self.window else {
+            // NOTE: `window`が`Some`になる`resumed`メソッドで`ControlFlow::Poll`を指定しているため、
+            //       ここで`ControlFlow::WaitUntil`を指定しても問題ない。
+            event_loop.set_control_flow(ControlFlow::WaitUntil(start + Duration::from_millis(16)));
+            return;
+        };
+
+        sync_60fps(start);
+    }
+}
+
+/// 60fpsになるようにスレッドを停止する関数
+///
+/// * start - フレーム開始時刻
+///
+/// 15.66...msをsleepし、不足時間をスピンウェイトする。
+/// 正直アニメーションの強いゲームではないので厳密さは要らないのだけれど、
+/// 一応アニメーションのあるゲームだからね多少はね。
+fn sync_60fps(start: Instant) {
+    const TARGET_FRAME_TIME: Duration = Duration::from_nanos(1_000_000_000 / 60); // 60FPS
+    const SPIN_THRESHOLD: Duration = Duration::from_millis(1);
+
+    let elapsed = start.elapsed();
+
+    if elapsed < TARGET_FRAME_TIME {
+        let remaining = TARGET_FRAME_TIME - elapsed;
+        if remaining > SPIN_THRESHOLD {
+            thread::sleep(remaining - SPIN_THRESHOLD);
+        }
+        while start.elapsed() < TARGET_FRAME_TIME {
+            hint::spin_loop();
+        }
+    }
+}
+
+fn main() {
+    let event_loop = match EventLoop::new() {
+        Ok(v) => v,
+        Err(e) => panic!("error: {e}"),
+    };
+
+    match event_loop.run_app(&mut App::new()) {
+        Ok(()) => {}
+        Err(e) => panic!("error: {e}"),
+    }
+}