src/app/game.rs

@@ -211,8 +211,8 @@ impl GameWindow {
                 }
             });
             ui.menu("Emulation", || {
-                let has_game = self.client.has_game();
+                let has_game = self.client.has_game(self.sim_id);
-                if self.client.is_running() {
+                if self.client.is_running(self.sim_id) {
                     if ui.menu_item_config("Pause").enabled(has_game).build() {
                         self.client.send_command(EmulatorCommand::Pause);
                     }
@@ -220,7 +220,8 @@ impl GameWindow {
                     self.client.send_command(EmulatorCommand::Resume);
                 }
                 if ui.menu_item_config("Reset").enabled(has_game).build() {
-                    self.client.send_command(EmulatorCommand::Reset);
+                    self.client
+                        .send_command(EmulatorCommand::Reset(self.sim_id));
                 }
             });
             ui.menu("Video", || {
@@ -243,11 +244,23 @@ impl GameWindow {
                 }
             });
             ui.menu("Multiplayer", || {
-                if self.sim_id == SimId::Player1 && ui.menu_item("Open Player 2") {
+                if self.sim_id == SimId::Player1
+                    && !self.client.has_player_2()
+                    && ui.menu_item("Open Player 2")
+                {
                     self.client
                         .send_command(EmulatorCommand::StartSecondSim(None));
                     self.proxy.send_event(UserEvent::OpenPlayer2Window).unwrap();
                 }
+                if self.client.has_player_2() {
+                    let linked = self.client.are_sims_linked();
+                    if linked && ui.menu_item("Unlink") {
+                        self.client.send_command(EmulatorCommand::Unlink);
+                    }
+                    if !linked && ui.menu_item("Link") {
+                        self.client.send_command(EmulatorCommand::Link);
+                    }
+                }
             });
         });
 
@@ -326,7 +339,7 @@ impl AppWindow for GameWindow {
                 WindowEvent::Resized(size) => {
                     self.window.handle_resize(size);
                     if self.window.minimized {
-                        if self.client.is_running() {
+                        if self.client.is_running(self.sim_id) {
                             self.client.send_command(EmulatorCommand::Pause);
                             self.paused_due_to_minimize = true;
                         }

src/emulator.rs

@@ -3,7 +3,7 @@ use std::{
     fs,
     path::{Path, PathBuf},
     sync::{
-        atomic::{AtomicBool, Ordering},
+        atomic::{AtomicBool, AtomicUsize, Ordering},
         mpsc::{self, RecvError, TryRecvError},
         Arc,
     },
@@ -20,8 +20,10 @@ mod shrooms_vb_core;
 pub struct EmulatorBuilder {
     rom: Option<PathBuf>,
     commands: mpsc::Receiver<EmulatorCommand>,
-    running: Arc<AtomicBool>,
+    sim_count: Arc<AtomicUsize>,
-    has_game: Arc<AtomicBool>,
+    running: Arc<[AtomicBool; 2]>,
+    has_game: Arc<[AtomicBool; 2]>,
+    linked: Arc<AtomicBool>,
 }
 
 #[derive(PartialEq, Eq, Hash, Clone, Copy, Debug)]
@@ -47,13 +49,17 @@ impl EmulatorBuilder {
         let builder = Self {
             rom: None,
             commands,
-            running: Arc::new(AtomicBool::new(false)),
+            sim_count: Arc::new(AtomicUsize::new(0)),
-            has_game: Arc::new(AtomicBool::new(false)),
+            running: Arc::new([AtomicBool::new(false), AtomicBool::new(false)]),
+            has_game: Arc::new([AtomicBool::new(false), AtomicBool::new(false)]),
+            linked: Arc::new(AtomicBool::new(false)),
         };
         let client = EmulatorClient {
             queue,
+            sim_count: builder.sim_count.clone(),
             running: builder.running.clone(),
             has_game: builder.has_game.clone(),
+            linked: builder.linked.clone(),
         };
         (builder, client)
     }
@@ -66,9 +72,15 @@ impl EmulatorBuilder {
     }
 
     pub fn build(self) -> Result<Emulator> {
-        let mut emulator = Emulator::new(self.commands, self.running, self.has_game)?;
+        let mut emulator = Emulator::new(
+            self.commands,
+            self.sim_count,
+            self.running,
+            self.has_game,
+            self.linked,
+        )?;
         if let Some(path) = self.rom {
-            emulator.load_rom_from_file(SimId::Player1, &path)?;
+            emulator.load_rom(SimId::Player1, &path)?;
         }
         Ok(emulator)
     }
@@ -78,73 +90,112 @@ pub struct Emulator {
     sims: Vec<Sim>,
     audio: Audio,
     commands: mpsc::Receiver<EmulatorCommand>,
+    sim_count: Arc<AtomicUsize>,
+    running: Arc<[AtomicBool; 2]>,
+    has_game: Arc<[AtomicBool; 2]>,
+    linked: Arc<AtomicBool>,
     renderers: HashMap<SimId, TextureSink>,
-    running: Arc<AtomicBool>,
-    has_game: Arc<AtomicBool>,
 }
 
 impl Emulator {
     fn new(
         commands: mpsc::Receiver<EmulatorCommand>,
-        running: Arc<AtomicBool>,
+        sim_count: Arc<AtomicUsize>,
-        has_game: Arc<AtomicBool>,
+        running: Arc<[AtomicBool; 2]>,
+        has_game: Arc<[AtomicBool; 2]>,
+        linked: Arc<AtomicBool>,
     ) -> Result<Self> {
         Ok(Self {
             sims: vec![],
             audio: Audio::init()?,
             commands,
-            renderers: HashMap::new(),
+            sim_count,
             running,
             has_game,
+            linked,
+            renderers: HashMap::new(),
         })
     }
 
-    pub fn load_rom_from_file(&mut self, sim_id: SimId, path: &Path) -> Result<()> {
+    pub fn load_rom(&mut self, sim_id: SimId, path: &Path) -> Result<()> {
         let bytes = fs::read(path)?;
-        self.load_rom(sim_id, bytes)?;
+        self.reset_sim(sim_id, Some(bytes))?;
         Ok(())
     }
 
     pub fn start_second_sim(&mut self, rom: Option<PathBuf>) -> Result<()> {
         let bytes = if let Some(path) = rom {
-            fs::read(path)?
+            Some(fs::read(path)?)
-        } else if let Some(rom) = self.sims.first().and_then(|s| s.clone_rom()) {
-            rom
         } else {
-            return Ok(());
+            self.sims.first().and_then(|s| s.clone_rom())
         };
-        self.load_rom(SimId::Player2, bytes)?;
+        self.reset_sim(SimId::Player2, bytes)?;
-        let (first, second) = self.sims.split_at_mut(1);
+        self.link_sims();
-        first[0].link(&mut second[0]);
         Ok(())
     }
 
-    fn load_rom(&mut self, sim_id: SimId, bytes: Vec<u8>) -> Result<()> {
+    fn reset_sim(&mut self, sim_id: SimId, new_rom: Option<Vec<u8>>) -> Result<()> {
-        while self.sims.len() <= sim_id.to_index() {
+        let index = sim_id.to_index();
+        while self.sims.len() <= index {
             self.sims.push(Sim::new());
         }
-        let sim = &mut self.sims[sim_id.to_index()];
+        self.sim_count.store(self.sims.len(), Ordering::Relaxed);
+        let sim = &mut self.sims[index];
         sim.reset();
-        sim.load_rom(bytes)?;
+        if let Some(bytes) = new_rom {
-        self.has_game.store(true, Ordering::Release);
+            sim.load_rom(bytes)?;
-        self.running.store(true, Ordering::Release);
+            self.has_game[index].store(true, Ordering::Release);
+        }
+        if self.has_game[index].load(Ordering::Acquire) {
+            self.running[index].store(true, Ordering::Release);
+        }
         Ok(())
     }
 
+    fn link_sims(&mut self) {
+        let (first, second) = self.sims.split_at_mut(1);
+        let Some(first) = first.first_mut() else {
+            return;
+        };
+        let Some(second) = second.first_mut() else {
+            return;
+        };
+        first.link(second);
+        self.linked.store(true, Ordering::Release);
+    }
+
+    fn unlink_sims(&mut self) {
+        let Some(first) = self.sims.first_mut() else {
+            return;
+        };
+        first.unlink();
+        self.linked.store(false, Ordering::Release);
+    }
+
     pub fn stop_second_sim(&mut self) {
         self.renderers.remove(&SimId::Player2);
         self.sims.truncate(1);
+        self.sim_count.store(self.sims.len(), Ordering::Relaxed);
+        self.running[SimId::Player2.to_index()].store(false, Ordering::Release);
+        self.has_game[SimId::Player2.to_index()].store(false, Ordering::Release);
+        self.linked.store(false, Ordering::Release);
     }
 
     pub fn run(&mut self) {
         let mut eye_contents = vec![0u8; 384 * 224 * 2];
         let mut audio_samples = vec![];
         loop {
-            let mut idle = true;
+            let p1_running = self.running[SimId::Player1.to_index()].load(Ordering::Acquire);
-            if self.running.load(Ordering::Acquire) {
+            let p2_running = self.running[SimId::Player2.to_index()].load(Ordering::Acquire);
-                idle = false;
+            let mut idle = p1_running || p2_running;
+            if p1_running && p2_running {
                 Sim::emulate_many(&mut self.sims);
+            } else if p1_running {
+                self.sims[SimId::Player1.to_index()].emulate();
+            } else if p2_running {
+                self.sims[SimId::Player2.to_index()].emulate();
             }
+
             for sim_id in SimId::values() {
                 let Some(renderer) = self.renderers.get_mut(&sim_id) else {
                     continue;
@@ -198,7 +249,7 @@ impl Emulator {
                 self.renderers.insert(sim_id, renderer);
             }
             EmulatorCommand::LoadGame(sim_id, path) => {
-                if let Err(error) = self.load_rom_from_file(sim_id, &path) {
+                if let Err(error) = self.load_rom(sim_id, &path) {
                     eprintln!("error loading rom: {}", error);
                 }
             }
@@ -211,19 +262,27 @@ impl Emulator {
                 self.stop_second_sim();
             }
             EmulatorCommand::Pause => {
-                self.running.store(false, Ordering::Release);
+                for sim in SimId::values() {
+                    self.running[sim.to_index()].store(false, Ordering::Release);
+                }
             }
             EmulatorCommand::Resume => {
-                if self.has_game.load(Ordering::Acquire) {
+                for sim_id in SimId::values() {
-                    self.running.store(true, Ordering::Relaxed);
+                    let index = sim_id.to_index();
+                    if self.has_game[index].load(Ordering::Acquire) {
+                        self.running[index].store(true, Ordering::Relaxed);
+                    }
                 }
             }
-            EmulatorCommand::Reset => {
+            EmulatorCommand::Link => {
-                for sim in self.sims.iter_mut() {
+                self.link_sims();
-                    sim.reset();
+            }
-                }
+            EmulatorCommand::Unlink => {
-                if !self.sims.is_empty() {
+                self.unlink_sims();
-                    self.running.store(true, Ordering::Release);
+            }
+            EmulatorCommand::Reset(sim_id) => {
+                if let Err(error) = self.reset_sim(sim_id, None) {
+                    eprintln!("error resetting sim: {}", error);
                 }
             }
             EmulatorCommand::SetKeys(sim_id, keys) => {
@@ -243,23 +302,33 @@ pub enum EmulatorCommand {
     StopSecondSim,
     Pause,
     Resume,
-    Reset,
+    Link,
+    Unlink,
+    Reset(SimId),
     SetKeys(SimId, VBKey),
 }
 
 #[derive(Clone)]
 pub struct EmulatorClient {
     queue: mpsc::Sender<EmulatorCommand>,
-    running: Arc<AtomicBool>,
+    sim_count: Arc<AtomicUsize>,
-    has_game: Arc<AtomicBool>,
+    running: Arc<[AtomicBool; 2]>,
+    has_game: Arc<[AtomicBool; 2]>,
+    linked: Arc<AtomicBool>,
 }
 
 impl EmulatorClient {
-    pub fn is_running(&self) -> bool {
+    pub fn has_player_2(&self) -> bool {
-        self.running.load(Ordering::Acquire)
+        self.sim_count.load(Ordering::Acquire) == 2
     }
-    pub fn has_game(&self) -> bool {
+    pub fn is_running(&self, sim_id: SimId) -> bool {
-        self.has_game.load(Ordering::Acquire)
+        self.running[sim_id.to_index()].load(Ordering::Acquire)
+    }
+    pub fn has_game(&self, sim_id: SimId) -> bool {
+        self.has_game[sim_id.to_index()].load(Ordering::Acquire)
+    }
+    pub fn are_sims_linked(&self) -> bool {
+        self.linked.load(Ordering::Acquire)
     }
     pub fn send_command(&self, command: EmulatorCommand) {
         if let Err(err) = self.queue.send(command) {

src/emulator/shrooms_vb_core.rs

@@ -58,6 +58,8 @@ type OnFrame = extern "C" fn(sim: *mut VB) -> c_int;
 
 #[link(name = "vb")]
 extern "C" {
+    #[link_name = "vbEmulate"]
+    fn vb_emulate(sim: *mut VB, cycles: *mut u32) -> c_int;
     #[link_name = "vbEmulateEx"]
     fn vb_emulate_ex(sims: *mut *mut VB, count: c_uint, cycles: *mut u32) -> c_int;
     #[link_name = "vbGetCartROM"]
@@ -202,6 +204,19 @@ impl Sim {
         unsafe { vb_set_peer(self.sim, peer.sim) };
     }
 
+    pub fn unlink(&mut self) {
+        let peer = unsafe { vb_get_peer(self.sim) };
+        if !peer.is_null() {
+            unsafe { vb_set_peer(peer, ptr::null_mut()) };
+            unsafe { vb_set_peer(self.sim, ptr::null_mut()) };
+        }
+    }
+
+    pub fn emulate(&mut self) {
+        let mut cycles = 20_000_000;
+        unsafe { vb_emulate(self.sim, &mut cycles) };
+    }
+
     pub fn emulate_many(sims: &mut [Sim]) {
         let mut cycles = 20_000_000;
         let count = sims.len() as c_uint;