Block the emulator thread when idle

Cargo.lock

@@ -1892,6 +1892,12 @@ dependencies = [
  "windows-sys 0.52.0",
 ]
 
+[[package]]
+name = "rustversion"
+version = "1.0.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0e819f2bc632f285be6d7cd36e25940d45b2391dd6d9b939e79de557f7014248"
+
 [[package]]
 name = "same-file"
 version = "1.0.6"
@@ -1972,6 +1978,7 @@ dependencies = [
  "pollster",
  "rtrb",
  "rubato",
+ "thread-priority",
  "wgpu",
  "winit",
 ]
@@ -2118,6 +2125,20 @@ dependencies = [
  "syn 2.0.87",
 ]
 
+[[package]]
+name = "thread-priority"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cfe075d7053dae61ac5413a34ea7d4913b6e6207844fd726bdd858b37ff72bf5"
+dependencies = [
+ "bitflags 2.6.0",
+ "cfg-if",
+ "libc",
+ "log",
+ "rustversion",
+ "winapi",
+]
+
 [[package]]
 name = "tiny-skia"
 version = "0.11.4"

Cargo.toml

@@ -19,6 +19,7 @@ num-traits = "0.2"
 pollster = "0.4"
 rtrb = "0.3"
 rubato = "0.16"
+thread-priority = "1"
 wgpu = "22.1"
 winit = "0.30"
 

src/emulator.rs

@@ -3,7 +3,7 @@ use std::{
     path::{Path, PathBuf},
     sync::{
         atomic::{AtomicBool, Ordering},
-        mpsc::{self, TryRecvError},
+        mpsc::{self, RecvError, TryRecvError},
         Arc,
     },
 };
@@ -94,19 +94,33 @@ impl Emulator {
         let mut eye_contents = vec![0u8; 384 * 224 * 2];
         let mut audio_samples = vec![];
         loop {
+            let mut idle = true;
             if self.running.load(Ordering::Acquire) {
+                idle = false;
                 self.sim.emulate_frame();
             }
             if let Some(renderer) = &mut self.renderer {
                 if self.sim.read_pixels(&mut eye_contents) {
+                    idle = false;
                     renderer.render(&eye_contents);
                 }
             }
             self.sim.read_samples(&mut audio_samples);
             if !audio_samples.is_empty() {
+                idle = false;
                 self.audio.update(&audio_samples);
                 audio_samples.clear();
             }
+            if idle {
+                // The game is paused, and we have output all the video/audio we have.
+                // Block the thread until a new command comes in.
+                match self.commands.recv() {
+                    Ok(command) => self.handle_command(command),
+                    Err(RecvError) => {
+                        return;
+                    }
+                }
+            }
             loop {
                 match self.commands.try_recv() {
                     Ok(command) => self.handle_command(command),

src/main.rs

@@ -1,9 +1,10 @@
-use std::{path::PathBuf, process, thread};
+use std::{path::PathBuf, process};
 
 use anyhow::Result;
 use app::App;
 use clap::Parser;
 use emulator::EmulatorBuilder;
+use thread_priority::{ThreadBuilder, ThreadPriority};
 use winit::event_loop::{ControlFlow, EventLoop};
 
 mod app;
@@ -26,7 +27,11 @@ fn main() -> Result<()> {
     if let Some(path) = args.rom {
         builder = builder.with_rom(&path);
     }
-    thread::spawn(move || {
+
+    ThreadBuilder::default()
+        .name("Emulator".to_owned())
+        .priority(ThreadPriority::Max)
+        .spawn_careless(move || {
             let mut emulator = match builder.build() {
                 Ok(e) => e,
                 Err(err) => {
@@ -35,7 +40,7 @@ fn main() -> Result<()> {
                 }
             };
             emulator.run();
-    });
+        })?;
 
     let event_loop = EventLoop::with_user_event().build().unwrap();
     event_loop.set_control_flow(ControlFlow::Poll);