rework animation loop and add back animation buffer

src/redraw_scheduler.rs

@@ -1,5 +1,5 @@
 use std::sync::{Arc, Mutex};
-use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::atomic::{AtomicU16, Ordering};
 use std::time::{Duration, Instant};
 use std::thread;
 
@@ -9,56 +9,17 @@ lazy_static! {
     pub static ref REDRAW_SCHEDULER: RedrawScheduler = RedrawScheduler::new();
 }
 
+const BUFFER_FRAMES: u16 = 60;
+
 pub struct RedrawScheduler {
-    window: Mutex<Option<Arc<Window>>>, // Would prefer not to have to lock this every time.
-    frame_queued: AtomicBool,
+    frames_queued: AtomicU16,
     scheduled_frame: Mutex<Option<Instant>>
 }
 
-pub fn redraw_loop() {
-    thread::spawn(|| {
-        loop {
-            let frame_start = Instant::now();
-
-            let request_redraw = {
-                if REDRAW_SCHEDULER.frame_queued.load(Ordering::Relaxed) {
-                    REDRAW_SCHEDULER.frame_queued.store(false, Ordering::Relaxed);
-                    true
-                } else {
-                    let mut next_scheduled_frame = REDRAW_SCHEDULER.scheduled_frame.lock().unwrap();
-                    if let Some(scheduled_frame) = next_scheduled_frame.clone() {
-                        if scheduled_frame < frame_start {
-                            *next_scheduled_frame = None;
-                            true
-                        } else {
-                            false
-                        }
-                    } else {
-                        false
-                    }
-                }
-            };
-
-            if request_redraw {
-                let window = REDRAW_SCHEDULER.window.lock().unwrap();
-                if let Some(window) = &*window {
-                    window.request_redraw();
-                }
-            }
-
-            if let Some(time_to_sleep) = Duration::from_secs_f32(1.0 / 60.0).checked_sub(frame_start.elapsed()) {
-                thread::sleep(time_to_sleep)
-            }
-        }
-    });
-}
-
 impl RedrawScheduler {
     pub fn new() -> RedrawScheduler {
-        redraw_loop();
         RedrawScheduler { 
-            window: Mutex::new(None),
-            frame_queued: AtomicBool::new(false),
+            frames_queued: AtomicU16::new(1),
             scheduled_frame: Mutex::new(None)
         }
     }
@@ -75,11 +36,26 @@ impl RedrawScheduler {
     }
 
     pub fn queue_next_frame(&self) {
-        self.frame_queued.store(true, Ordering::Relaxed);
+        self.frames_queued.store(BUFFER_FRAMES, Ordering::Relaxed);
     }
 
-    pub fn set_window(&self, window: &Arc<Window>){
-        let mut window_ref = self.window.lock().unwrap();
-        window_ref.replace(window.clone());
+    pub fn should_draw(&self) -> bool {
+        let frames_queued = self.frames_queued.load(Ordering::Relaxed);
+        if frames_queued > 0 {
+            self.frames_queued.store(frames_queued - 1, Ordering::Relaxed);
+            true
+        } else {
+            let mut next_scheduled_frame = self.scheduled_frame.lock().unwrap();
+            if let Some(scheduled_frame) = next_scheduled_frame.clone() {
+                if scheduled_frame < Instant::now() {
+                    *next_scheduled_frame = None;
+                    true
+                } else {
+                    false
+                }
+            } else {
+                false
+            }
+        }
     }
 }

src/window.rs

@@ -1,4 +1,5 @@
 use std::sync::Arc;
+use std::time::{Duration, Instant};
 
 use image::{load_from_memory, GenericImageView, Pixel};
 use skulpin::{CoordinateSystem, RendererBuilder, PresentMode};
@@ -54,8 +55,6 @@ pub fn ui_loop() {
         .build(&event_loop)
         .expect("Failed to create window"));
 
-    REDRAW_SCHEDULER.set_window(&window);
-
     let mut skulpin_renderer = RendererBuilder::new()
         .prefer_integrated_gpu()
         .use_vulkan_debug_layer(true)
@@ -71,7 +70,10 @@ pub fn ui_loop() {
 
     event_loop.run(move |event, _window_target, control_flow| {
         match event {
-            Event::NewEvents(StartCause::Init) => window.request_redraw(),
+            Event::NewEvents(StartCause::Init) |
+            Event::NewEvents(StartCause::ResumeTimeReached { .. }) => {
+                window.request_redraw()
+            },
 
             Event::WindowEvent {
                 event: WindowEvent::CloseRequested,
@@ -166,16 +168,20 @@ pub fn ui_loop() {
             }
 
             Event::RedrawRequested { .. }  => {
-                if let Err(e) = skulpin_renderer.draw(&window, |canvas, coordinate_system_helper| {
-                    if renderer.draw(canvas, coordinate_system_helper) {
-                        handle_new_grid_size(window.inner_size(), &renderer)
-                    }
+                let frame_start = Instant::now();
 
-                    *control_flow = ControlFlow::Wait;
-                }) {
-                    println!("Error during draw: {:?}", e);
-                    *control_flow = ControlFlow::Exit
+                if REDRAW_SCHEDULER.should_draw() {
+                    if let Err(e) = skulpin_renderer.draw(&window, |canvas, coordinate_system_helper| {
+                        if renderer.draw(canvas, coordinate_system_helper) {
+                            handle_new_grid_size(window.inner_size(), &renderer)
+                        }
+
+                    }) {
+                        println!("Error during draw: {:?}", e);
+                    }
                 }
+
+                *control_flow = ControlFlow::WaitUntil(frame_start + Duration::from_secs_f32(1.0 / 60.0));
             },
 
             _ => {}