chore: Release lemur version 0.14.0

- Support WGPU_FORCE_FALLBACK to run on CPU
 - Pass display when creating wgpu instance
 - Pass compatible surface when constructing adapter
 - Log some settings (at debug level)

Cargo.toml

@@ -4,20 +4,20 @@ description = "An emulator for the Virtual Boy."
 repository = "https://git.virtual-boy.com/PVB/lemur"
 publish = false
 license = "MIT"
-version = "0.11.0"
+version = "0.14.0"
 edition = "2024"
 
 [dependencies]
 anyhow = "1"
-atoi = "2"
-audioadapter-buffers = "2"
+atoi = "3"
+audioadapter-buffers = "4"
 atomic = "0.6"
 bitflags = { version = "2", features = ["serde"] }
 bytemuck = { version = "1", features = ["derive"] }
 clap = { version = "4", features = ["derive"] }
-cpal = { git = "https://github.com/sidit77/cpal.git", rev = "66ed6be" }
+cpal = "0.18"
 directories = "6"
-egui = { version = "0.34", features = ["serde"] }
+egui = { version = "0.34", features = ["persistence", "serde"] }
 egui_extras = { version = "0.34", features = ["image"] }
 egui-notify = "0.22"
 egui-winit = "0.34"
@@ -25,28 +25,28 @@ egui-wgpu = { version = "0.34", features = ["winit"] }
 fxprof-processed-profile = "0.8"
 fixed = { version = "1.28", features = ["num-traits"] }
 gilrs = { version = "0.11", features = ["serde-serialize"] }
-gimli = "0.33"
+gimli = "0.34"
 hex = "0.4"
 image = { version = "0.25", default-features = false, features = ["png"] }
-itertools = "0.14"
+itertools = "0.15"
 normpath = "1"
 notify = "8"
 num-derive = "0.4"
 num-traits = "0.2"
 object = "0.39"
 oneshot = { version = "0.2", features = ["async", "std"] }
-pollster = "0.4"
+pollster = "1"
 rand = "0.10"
 rfd = "0.17"
 rtrb = "0.3"
-rubato = "1"
+rubato = "4"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 thread-priority = "3"
 tokio = { version = "1", features = ["io-util", "macros", "net", "rt", "sync", "time"] }
-tracing = { version = "0.1", features = ["release_max_level_info"] }
+tracing = { version = "0.1", features = ["release_max_level_debug"] }
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
-wgpu = "29"
+wgpu = { version = "29", features = ["serde"] }
 wholesym = "0.8"
 winit = { version = "0.30", features = ["serde"] }
 

build.Dockerfile

@@ -1,7 +1,7 @@
 # This Dockerfile produces a base image for builds.
 # It includes all dependencies necessary to cross-compile for Windows/MacOS/Linux.
 
-FROM debian:bookworm AS osxcross
+FROM debian:trixie AS osxcross
 ADD --chmod=644 "https://apt.llvm.org/llvm-snapshot.gpg.key" /etc/apt/trusted.gpg.d/apt.llvm.org.asc
 WORKDIR /build/osxcross
 ADD "https://github.com/tpoechtrager/osxcross.git#47936a512273bb3b414b5a2e83043c92eabc7ae7" .
@@ -9,35 +9,31 @@ ADD "https://github.com/joseluisq/macosx-sdks/releases/download/14.5/MacOSX14.5.
 RUN apt-get update && \
     apt-get install -y ca-certificates
 COPY llvm.sources /etc/apt/sources.list.d/llvm.sources
-COPY install-llvm.sh .
 RUN apt-get update && \
-    ./install-llvm.sh && \
-    apt-get install -y bash bzip2 git make patch xz-utils && \
-    ln -s $(which clang-21) /usr/bin/clang && \
-    ln -s $(which clang++-21) /usr/bin/clang++ && \
-    ln -s $(which ld64.lld-21) /usr/bin/ld64.lld && \
+    apt-get install -y bash bzip2 clang-22 git lld-22 llvm-22 make patch xz-utils && \
+    ln -s $(which clang-22) /usr/bin/clang && \
+    ln -s $(which clang++-22) /usr/bin/clang++ && \
+    ln -s $(which ld64.lld-22) /usr/bin/ld64.lld && \
     SDK_VERSION=14.5 UNATTENDED=1 ENABLE_COMPILER_RT_INSTALL=1 TARGET_DIR=/osxcross ./build.sh
 
-FROM rust:1.94-bookworm
+FROM rust:1.97-trixie
 ADD --chmod=644 "https://apt.llvm.org/llvm-snapshot.gpg.key" /etc/apt/trusted.gpg.d/apt.llvm.org.asc
 COPY llvm.sources /etc/apt/sources.list.d/llvm.sources
-COPY install-llvm.sh .
 RUN rustup target add x86_64-pc-windows-msvc && \
     rustup target add x86_64-apple-darwin && \
     rustup target add aarch64-apple-darwin && \
     apt-get update && \
-    ./install-llvm.sh && \
-    apt-get install -y libc6-dev libasound2-dev libudev-dev genisoimage mingw-w64 && \
+    apt-get install -y clang-22 lld-22 libc6-dev libasound2-dev libudev-dev genisoimage mingw-w64 && \
     cargo install cargo-bundle xwin && \
     xwin --accept-license splat --output xwin && \
     rm -rf .xwin-cache && \
-    ln -s $(which clang-21) /usr/bin/clang && \
-    ln -s $(which clang++-21) /usr/bin/clang++
+    ln -s $(which clang-22) /usr/bin/clang && \
+    ln -s $(which clang++-22) /usr/bin/clang++
 COPY --from=osxcross /osxcross /osxcross
 
 ENV PATH="/osxcross/bin:$PATH" \
     LD_LIBRARY_PATH="/osxcross/lib" \
-    CC="clang-21" CXX="clang++-21" AR="llvm-ar-21" \
+    CC="clang-22" CXX="clang++-22" AR="llvm-ar-22" \
     CC_x86_64-apple-darwin="o64-clang" \
     CXX_x86_64-apple-darwin="o64-clang++" \
     CC_aarch64-apple-darwin="oa64-clang" \
@@ -47,11 +43,11 @@ ENV PATH="/osxcross/bin:$PATH" \
     SHROOMS_CFLAGS_x86_64-pc-windows-msvc="-flto" \
     CFLAGS_x86_64-pc-windows-msvc="-I/xwin/crt/include -I/xwin/sdk/include/ucrt -I/xwin/sdk/include/um -I/xwin/sdk/include/shared" \
     CARGO_TARGET_X86_64_PC_WINDOWS_MSVC_RUSTFLAGS="-Lnative=/xwin/crt/lib/x86_64 -Lnative=/xwin/sdk/lib/um/x86_64 -Lnative=/xwin/sdk/lib/ucrt/x86_64 -Clinker-plugin-lto -Clink-arg=-fuse-ld=lld" \
-    CARGO_TARGET_X86_64_PC_WINDOWS_MSVC_LINKER="lld-link-21" \
+    CARGO_TARGET_X86_64_PC_WINDOWS_MSVC_LINKER="lld-link-22" \
     CARGO_TARGET_X86_64_APPLE_DARWIN_LINKER="o64-clang" \
-    CARGO_TARGET_X86_64_APPLE_DARWIN_AR="llvm-ar-21" \
+    CARGO_TARGET_X86_64_APPLE_DARWIN_AR="llvm-ar-22" \
     CARGO_TARGET_AARCH64_APPLE_DARWIN_LINKER="oa64-clang" \
-    CARGO_TARGET_AARCH64_APPLE_DARWIN_AR="llvm-ar-21" \
-    RC_PATH="llvm-rc-21" \
+    CARGO_TARGET_AARCH64_APPLE_DARWIN_AR="llvm-ar-22" \
+    RC_PATH="llvm-rc-22" \
     MACOSX_DEPLOYMENT_TARGET="14.5"
 ENTRYPOINT ["bash"]

install-llvm.sh

@@ -1,19 +0,0 @@
-#!/usr/bin/env bash
-
-# Hopefully temporary script to manually install working llvm packages.
-# The apt index for these is broken in bookworm, and upgrading to trixie
-# would make them depend on too new of a libc version.
-
-# https://apt.llvm.org/bookworm/pool/main/l/llvm-toolchain-21/clang-21_21.1.5~%2B%2B20251023083151%2B45afac62e373-1~exp1~20251023083333.51_amd64.deb
-PACKAGES=('clang-21' 'clang-tools-21' 'libclang-common-21-dev' 'libclang-cpp21' 'libclang-rt-21-dev' 'libclang1-21' 'libllvm21' 'lld-21' 'llvm-21' 'llvm-21-dev' 'llvm-21-linker-tools' 'llvm-21-runtime' 'llvm-21-tools')
-FILES=()
-URL='https://apt.llvm.org/bookworm/pool/main/l/llvm-toolchain-21'
-VERSION='21.1.5~%2B%2B20251023083151%2B45afac62e373-1~exp1~20251023083333.51_amd64.deb'
-
-apt-get install -y curl python3
-for package in "${PACKAGES[@]}"; do
-    curl -O -L "$URL/${package}_$VERSION"
-    FILES+=("./${package}_$VERSION")
-done
-
-apt-get install -y "${FILES[@]}"

llvm.sources

@@ -1,4 +1,4 @@
 Types: deb deb-src
-URIs: http://apt.llvm.org/bookworm/
-Suites: llvm-toolchain-bookworm-21
+URIs: http://apt.llvm.org/trixie/
+Suites: llvm-toolchain-trixie-22
 Components: main

src/audio.rs

@@ -3,8 +3,8 @@ use std::time::Duration;
 use anyhow::{Result, bail};
 use audioadapter_buffers::direct::InterleavedSlice;
 use cpal::traits::{DeviceTrait, HostTrait, StreamTrait};
-use rubato::Resampler;
-use tracing::error;
+use rubato::{Adjustable as _, Resampler};
+use tracing::warn;
 
 pub struct Audio {
     #[allow(unused)]
@@ -23,14 +23,14 @@ impl Audio {
         let Some(device) = host.default_output_device() else {
             bail!("No output device available");
         };
-        let Some(config) = device
-            .supported_output_configs()?
-            .find(|c| c.channels() == 2 && c.sample_format().is_float())
-        else {
+        let default_rate = device.default_output_config()?.sample_rate();
+        let Some(config) = device.supported_output_configs()?.find(|c| {
+            c.channels() == 2 && c.sample_format().is_float() && c.contains_rate(default_rate)
+        }) else {
             bail!("No suitable output config available");
         };
-        let mut config = config.with_max_sample_rate().config();
-        let resample_ratio = config.sample_rate.0 as f64 / VB_FREQUENCY as f64;
+        let mut config = config.with_sample_rate(default_rate).config();
+        let resample_ratio = config.sample_rate as f64 / VB_FREQUENCY as f64;
         let chunk_size = (834.0 * resample_ratio) as usize;
         let sampler = rubato::Async::new_poly(
             resample_ratio,
@@ -48,7 +48,7 @@ impl Audio {
             rtrb::RingBuffer::new(sampler.output_frames_max() * 4);
 
         let stream = device.build_output_stream(
-            &config,
+            config,
             move |data: &mut [f32], _| {
                 let requested = data.len();
                 let chunk = match sample_source.read_chunk(data.len()) {
@@ -66,7 +66,7 @@ impl Audio {
                 }
                 chunk.commit_all();
             },
-            move |error| error!(%error, "stream error"),
+            move |error| warn!(%error, "stream error"),
             None,
         )?;
         stream.play()?;

src/config.rs

@@ -1,6 +1,6 @@
 use anyhow::Result;
-use clap::Parser;
-use egui::{Color32, Vec2};
+use clap::{Parser, ValueEnum};
+use egui::{Color32, Pos2, Vec2};
 use serde::{Deserialize, Serialize};
 
 use crate::{emulator::SimId, persistence::Persistence, window::DisplayMode};
@@ -47,6 +47,28 @@ pub struct CliArgs {
     /// Map the first connected controller to Player 2
     #[arg(long)]
     pub player2_controller: bool,
+    /// Force the application to render with CPU, rather than GPU.
+    #[arg(long)]
+    pub wgpu_force_fallback: Option<bool>,
+    /// Set a preference for whether to use a low-power or high-performance GPU adapter
+    #[arg(long)]
+    pub wgpu_power_preference: Option<PowerPreferenceWrapper>,
+}
+
+#[derive(ValueEnum, Clone, Copy)]
+pub enum PowerPreferenceWrapper {
+    Low,
+    High,
+    None,
+}
+impl From<PowerPreferenceWrapper> for wgpu::PowerPreference {
+    fn from(value: PowerPreferenceWrapper) -> Self {
+        match value {
+            PowerPreferenceWrapper::Low => wgpu::PowerPreference::LowPower,
+            PowerPreferenceWrapper::High => wgpu::PowerPreference::HighPerformance,
+            PowerPreferenceWrapper::None => wgpu::PowerPreference::None,
+        }
+    }
 }
 
 pub const COLOR_PRESETS: [[Color32; 2]; 3] = [
@@ -64,6 +86,49 @@ pub const COLOR_PRESETS: [[Color32; 2]; 3] = [
     ],
 ];
 
+const fn default_power_preference() -> wgpu::PowerPreference {
+    wgpu::PowerPreference::LowPower
+}
+
+#[derive(Serialize, Deserialize, Clone, PartialEq, Eq)]
+pub struct AppConfig {
+    #[serde(default = "default_power_preference")]
+    pub power_preference: wgpu::PowerPreference,
+    #[serde(default)]
+    pub force_fallback: bool,
+}
+
+impl AppConfig {
+    pub fn load(persistence: &Persistence) -> Self {
+        if let Ok(config) = persistence.load_config(APP_CONFIG_FILENAME) {
+            return config;
+        }
+        Self {
+            power_preference: default_power_preference(),
+            force_fallback: false,
+        }
+    }
+
+    pub fn save(&self, persistence: &Persistence) -> Result<()> {
+        persistence.save_config(APP_CONFIG_FILENAME, &self)
+    }
+
+    pub fn update(&mut self, args: &CliArgs) -> bool {
+        let mut updated = false;
+        if let Some(pref) = args.wgpu_power_preference {
+            self.power_preference = pref.into();
+            updated = true;
+        }
+        if let Some(force_fallback) = args.wgpu_force_fallback {
+            self.force_fallback = force_fallback;
+            updated = true;
+        }
+        updated
+    }
+}
+
+const APP_CONFIG_FILENAME: &str = "config";
+
 const fn default_audio_enabled() -> bool {
     true
 }
@@ -75,11 +140,13 @@ pub struct SimConfig {
     pub dimensions: Vec2,
     #[serde(default = "default_audio_enabled")]
     pub audio_enabled: bool,
+    #[serde(default)]
+    pub position: Option<Pos2>,
 }
 
 impl SimConfig {
     pub fn load(persistence: &Persistence, sim_id: SimId) -> Self {
-        if let Ok(config) = persistence.load_config(config_filename(sim_id)) {
+        if let Ok(config) = persistence.load_config(sim_config_filename(sim_id)) {
             return config;
         }
         Self {
@@ -87,15 +154,16 @@ impl SimConfig {
             colors: COLOR_PRESETS[0],
             dimensions: DisplayMode::Anaglyph.proportions() + Vec2::new(0.0, 22.0),
             audio_enabled: true,
+            position: None,
         }
     }
 
     pub fn save(&self, persistence: &Persistence, sim_id: SimId) -> Result<()> {
-        persistence.save_config(config_filename(sim_id), self)
+        persistence.save_config(sim_config_filename(sim_id), self)
     }
 }
 
-fn config_filename(sim_id: SimId) -> &'static str {
+fn sim_config_filename(sim_id: SimId) -> &'static str {
     match sim_id {
         SimId::Player1 => "config_p1",
         SimId::Player2 => "config_p2",

src/controller.rs

@@ -1,4 +1,7 @@
-use std::sync::{Arc, RwLock};
+use std::{
+    collections::HashMap,
+    sync::{Arc, RwLock},
+};
 
 use gilrs::{Event as GamepadEvent, EventType, GamepadId, ev::Code};
 use winit::{
@@ -8,12 +11,13 @@ use winit::{
 
 use crate::{
     emulator::{EmulatorClient, EmulatorCommand, SimId, VBKey},
-    input::{InputMapping, MappingProvider},
+    input::{AxisMapping, InputMapping, MappingProvider},
 };
 
 pub struct Controller {
     pub sim_id: SimId,
     state: VBKey,
+    axis_values: HashMap<(GamepadId, Code), f32>,
     mapping: Arc<RwLock<InputMapping>>,
 }
 
@@ -22,6 +26,7 @@ impl Controller {
         Self {
             sim_id,
             state: VBKey::SGN,
+            axis_values: HashMap::new(),
             mapping: mappings.for_sim(sim_id).clone(),
         }
     }
@@ -45,20 +50,23 @@ impl Controller {
                 (VBKey::empty(), mappings)
             }
             EventType::AxisChanged(_, value, code) => {
-                let (neg, pos) = self.map_axis(&event.id, &code)?;
-                let mut pressed = VBKey::empty();
-                let mut released = VBKey::empty();
-                if value < -0.75 {
-                    pressed = pressed.union(neg);
-                }
-                if value > 0.75 {
-                    pressed = pressed.union(pos);
-                }
-                if value > -0.65 {
-                    released = released.union(neg);
-                }
-                if value < 0.65 {
-                    released = released.union(pos);
+                let mapping = self.map_axis(&event.id, &code)?;
+                self.axis_values.insert((event.id, code), value);
+
+                let pair_value = mapping
+                    .pair
+                    .and_then(|p| self.axis_values.get(&(event.id, p)))
+                    .copied()
+                    .unwrap_or_default();
+                let neg = mapping.neg;
+                let pos = mapping.pos;
+
+                let (mut pressed, mut released) = axis_presses(value, pair_value, neg, pos);
+                if let Some(other) = mapping.pair.and_then(|p| self.map_axis(&event.id, &p)) {
+                    let (other_pressed, other_released) =
+                        axis_presses(pair_value, value, other.neg, other.pos);
+                    pressed = pressed.union(other_pressed);
+                    released = released.union(other_released);
                 }
                 (pressed, released)
             }
@@ -87,7 +95,7 @@ impl Controller {
         self.mapping.read().unwrap().map_button(id, code)
     }
 
-    fn map_axis(&self, id: &GamepadId, code: &Code) -> Option<(VBKey, VBKey)> {
+    fn map_axis(&self, id: &GamepadId, code: &Code) -> Option<AxisMapping> {
         self.mapping.read().unwrap().map_axis(id, code)
     }
 }
@@ -126,3 +134,95 @@ impl ControllerManager {
         }
     }
 }
+
+fn axis_presses(value: f32, pair_value: f32, neg: VBKey, pos: VBKey) -> (VBKey, VBKey) {
+    use std::f32::consts::FRAC_PI_3;
+
+    let mut pressed = VBKey::empty();
+    let mut released = VBKey::empty();
+
+    let magnitude = value.hypot(pair_value);
+    let abs_angle = pair_value.atan2(value).abs();
+
+    if magnitude < 0.65 {
+        released = released.union(neg).union(pos);
+    } else if abs_angle <= FRAC_PI_3 {
+        // stick tilted towards positive
+        released = released.union(neg);
+
+        if magnitude >= 0.75 {
+            pressed = pressed.union(pos);
+        }
+    } else if abs_angle >= 2.0 * FRAC_PI_3 {
+        // stick tilted towards negative
+        released = released.union(pos);
+
+        if magnitude >= 0.75 {
+            pressed = pressed.union(neg);
+        }
+    } else {
+        released = released.union(neg).union(pos);
+    }
+
+    (pressed, released)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{VBKey, axis_presses};
+
+    const NEG: VBKey = VBKey::LL;
+    const POS: VBKey = VBKey::LR;
+
+    const NONE: VBKey = VBKey::empty();
+    const BOTH: VBKey = NEG.union(POS);
+
+    #[test]
+    fn detects_no_input() {
+        let (pressed, released) = axis_presses(0.0, 0.0, NEG, POS);
+        assert_eq!(pressed, NONE);
+        assert_eq!(released, BOTH);
+    }
+
+    #[test]
+    fn detects_pos_input() {
+        let (pressed, released) = axis_presses(1.0, 0.0, NEG, POS);
+        assert_eq!(pressed, POS);
+        assert_eq!(released, NEG);
+    }
+
+    #[test]
+    fn detects_neg_input() {
+        let (pressed, released) = axis_presses(-1.0, 0.0, NEG, POS);
+        assert_eq!(pressed, NEG);
+        assert_eq!(released, POS);
+    }
+
+    #[test]
+    fn respects_dead_zone() {
+        let (pressed, released) = axis_presses(0.70, 0.0, NEG, POS);
+        assert_eq!(pressed, NONE);
+        assert_eq!(released, NEG);
+    }
+
+    #[test]
+    fn handles_diagonals_ok() {
+        let (pressed, released) = axis_presses(0.6, 0.6, NEG, POS);
+        assert_eq!(pressed, POS);
+        assert_eq!(released, NEG);
+    }
+
+    #[test]
+    fn ignores_diagonal_noise() {
+        let (pressed, released) = axis_presses(-1.0, -0.1484245, NEG, POS);
+        assert_eq!(pressed, NEG);
+        assert_eq!(released, POS);
+    }
+
+    #[test]
+    fn ignores_small_values() {
+        let (pressed, released) = axis_presses(-0.1484245, -1.0, NEG, POS);
+        assert_eq!(pressed, NONE);
+        assert_eq!(released, BOTH);
+    }
+}

src/emulator.rs

@@ -265,7 +265,8 @@ impl Emulator {
         } else if let Some(cart) = self.carts[index].as_mut()
             && cart.is_watching()
         {
-            cart.restart_watching();
+            cart.reload()?;
+            sim.load_cart(cart.rom.clone(), cart.sram.clone())?;
         }
         let mut profiling = false;
         if let Some(profiler) = self.profilers[sim_id.to_index()].as_ref()
@@ -946,6 +947,9 @@ pub struct EmulatorClient {
 }
 
 impl EmulatorClient {
+    pub fn has_player_2(&self) -> bool {
+        self.sim_state(SimId::Player2) != SimState::Uninitialized
+    }
     pub fn sim_state(&self, sim_id: SimId) -> SimState {
         self.sim_state[sim_id.to_index()].load(Ordering::Acquire)
     }

src/emulator/cart.rs

@@ -22,10 +22,7 @@ pub struct Cart {
 
 impl Cart {
     pub fn load(file_path: &Path, sim_id: SimId, watch: bool) -> Result<Self> {
-        let rom = fs::read(file_path)?;
-        let (rom, info) = try_parse_isx(file_path, &rom)
-            .or_else(|| try_parse_elf(file_path, &rom))
-            .unwrap_or_else(|| (rom, GameInfo::empty(file_path)));
+        let (rom, info) = Self::read_rom(file_path)?;
 
         let mut sram_file = File::options()
             .read(true)
@@ -66,6 +63,16 @@ impl Cart {
         })
     }
 
+    pub fn reload(&mut self) -> Result<()> {
+        let (rom, info) = Self::read_rom(&self.file_path)?;
+        self.rom = rom;
+        self.info = Arc::new(info);
+        if self.is_watching() {
+            self.restart_watching();
+        }
+        Ok(())
+    }
+
     pub fn save_sram(&mut self) -> Result<()> {
         self.sram_file.seek(SeekFrom::Start(0))?;
         self.sram_file.write_all(&self.sram)?;
@@ -92,6 +99,14 @@ impl Cart {
         self.changed = Arc::new(AtomicBool::new(false));
         self.watcher = None;
     }
+
+    fn read_rom(file_path: &Path) -> Result<(Vec<u8>, GameInfo)> {
+        let rom = fs::read(file_path)?;
+        let (rom, info) = try_parse_isx(file_path, &rom)
+            .or_else(|| try_parse_elf(file_path, &rom))
+            .unwrap_or_else(|| (rom, GameInfo::empty(file_path)));
+        Ok((rom, info))
+    }
 }
 
 fn build_watcher(file_path: &Path, changed: Arc<AtomicBool>) -> Option<notify::RecommendedWatcher> {

src/filepicker.rs

@@ -0,0 +1,84 @@
+use std::{
+    path::PathBuf,
+    sync::{Arc, Weak},
+};
+
+use winit::window::Window;
+
+pub struct FilePicker {
+    window: Option<Weak<Window>>,
+}
+
+impl FilePicker {
+    pub fn new() -> Self {
+        Self { window: None }
+    }
+
+    pub fn set_window(&mut self, window: &Arc<Window>) {
+        self.window = Some(Arc::downgrade(window));
+    }
+
+    pub fn pick_file_dialog(&self) -> FileDialogBuilder {
+        self.new_dialog(FileDialogAction::PickFile, false)
+    }
+
+    pub fn save_file_dialog(&self) -> FileDialogBuilder {
+        self.new_dialog(FileDialogAction::SaveFile, cfg!(not(target_os = "windows")))
+    }
+
+    fn new_dialog(&self, action: FileDialogAction, attach_window: bool) -> FileDialogBuilder {
+        #[cfg(not(target_os = "macos"))]
+        let mut dialog = rfd::AsyncFileDialog::new();
+        #[cfg(target_os = "macos")]
+        let mut dialog = rfd::FileDialog::new();
+
+        if attach_window && let Some(window) = self.window.as_ref().and_then(|w| w.upgrade()) {
+            dialog = dialog.set_parent(&window);
+        }
+        FileDialogBuilder { dialog, action }
+    }
+}
+
+pub struct FileDialogBuilder {
+    #[cfg(not(target_os = "macos"))]
+    dialog: rfd::AsyncFileDialog,
+    #[cfg(target_os = "macos")]
+    dialog: rfd::FileDialog,
+    action: FileDialogAction,
+}
+
+impl FileDialogBuilder {
+    pub fn add_filter(self, name: impl Into<String>, extensions: &[impl ToString]) -> Self {
+        Self {
+            dialog: self.dialog.add_filter(name, extensions),
+            ..self
+        }
+    }
+
+    pub fn set_file_name(self, file_name: impl Into<String>) -> Self {
+        Self {
+            dialog: self.dialog.set_file_name(file_name),
+            ..self
+        }
+    }
+
+    pub fn open(self) -> Option<PathBuf> {
+        #[cfg(not(target_os = "macos"))]
+        fn resolve(action: impl Future<Output = Option<rfd::FileHandle>>) -> Option<PathBuf> {
+            pollster::block_on(action).map(Into::into)
+        }
+        #[cfg(target_os = "macos")]
+        fn resolve(action: Option<PathBuf>) -> Option<PathBuf> {
+            action
+        }
+        match self.action {
+            FileDialogAction::PickFile => resolve(self.dialog.pick_file()),
+            FileDialogAction::SaveFile => resolve(self.dialog.save_file()),
+        }
+    }
+}
+
+enum FileDialogAction {
+    PickFile,
+    SaveFile,
+}

src/input.rs

@@ -52,12 +52,28 @@ pub trait Mappings {
     fn use_default_mappings(&mut self);
 }
 
+#[derive(Clone, Copy, Serialize, Deserialize)]
+pub struct AxisMapping {
+    pub neg: VBKey,
+    pub pos: VBKey,
+    pub pair: Option<Code>,
+}
+impl Default for AxisMapping {
+    fn default() -> Self {
+        Self {
+            neg: VBKey::empty(),
+            pos: VBKey::empty(),
+            pair: None,
+        }
+    }
+}
+
 #[derive(Serialize, Deserialize)]
 pub struct GamepadMapping {
     buttons: HashMap<Code, VBKey>,
-    axes: HashMap<Code, (VBKey, VBKey)>,
+    axes: HashMap<Code, AxisMapping>,
     default_buttons: HashMap<Code, VBKey>,
-    default_axes: HashMap<Code, (VBKey, VBKey)>,
+    default_axes: HashMap<Code, AxisMapping>,
 }
 
 impl GamepadMapping {
@@ -78,7 +94,8 @@ impl GamepadMapping {
         let mut default_axes = HashMap::new();
         let mut default_axis = |axis: Axis, neg: VBKey, pos: VBKey| {
             if let Some(code) = gamepad.axis_code(axis) {
-                default_axes.insert(code, (neg, pos));
+                let pair = axis.second_axis().and_then(|a| gamepad.axis_code(a));
+                default_axes.insert(code, AxisMapping { neg, pos, pair });
             }
         };
         default_axis(Axis::LeftStickX, VBKey::LL, VBKey::LR);
@@ -102,19 +119,13 @@ impl GamepadMapping {
     }
 
     pub fn add_axis_neg_mapping(&mut self, key: VBKey, code: Code) {
-        let entry = self
-            .axes
-            .entry(code)
-            .or_insert((VBKey::empty(), VBKey::empty()));
-        entry.0 = entry.0.union(key);
+        let entry = self.axes.entry(code).or_default();
+        entry.neg = entry.neg.union(key);
     }
 
     pub fn add_axis_pos_mapping(&mut self, key: VBKey, code: Code) {
-        let entry = self
-            .axes
-            .entry(code)
-            .or_insert((VBKey::empty(), VBKey::empty()));
-        entry.1 = entry.1.union(key);
+        let entry = self.axes.entry(code).or_default();
+        entry.pos = entry.pos.union(key);
     }
 
     fn save_mappings(&self) -> PersistedGamepadMapping {
@@ -145,11 +156,11 @@ impl GamepadMapping {
 impl Mappings for GamepadMapping {
     fn mapping_names(&self) -> HashMap<VBKey, Vec<String>> {
         let mut results: HashMap<VBKey, Vec<String>> = HashMap::new();
-        for (axis, (left_keys, right_keys)) in &self.axes {
-            for key in left_keys.iter() {
+        for (axis, mapping) in &self.axes {
+            for key in mapping.neg.iter() {
                 results.entry(key).or_default().push(format!("-{axis}"));
             }
-            for key in right_keys.iter() {
+            for key in mapping.pos.iter() {
                 results.entry(key).or_default().push(format!("+{axis}"));
             }
         }
@@ -162,10 +173,10 @@ impl Mappings for GamepadMapping {
     }
 
     fn clear_mappings(&mut self, key: VBKey) {
-        self.axes.retain(|_, (left, right)| {
-            *left = left.difference(key);
-            *right = right.difference(key);
-            !(left.is_empty() && right.is_empty())
+        self.axes.retain(|_, mapping| {
+            mapping.neg = mapping.neg.difference(key);
+            mapping.pos = mapping.pos.difference(key);
+            !(mapping.neg.is_empty() && mapping.pos.is_empty())
         });
         self.buttons.retain(|_, keys| {
             *keys = keys.difference(key);
@@ -200,7 +211,7 @@ impl InputMapping {
         mappings.buttons.get(code).copied()
     }
 
-    pub fn map_axis(&self, id: &GamepadId, code: &Code) -> Option<(VBKey, VBKey)> {
+    pub fn map_axis(&self, id: &GamepadId, code: &Code) -> Option<AxisMapping> {
         let mappings = self.gamepads.get(id)?.read().unwrap();
         mappings.axes.get(code).copied()
     }
@@ -459,9 +470,9 @@ struct PersistedKeyboardMapping {
 #[derive(Serialize, Deserialize)]
 struct PersistedGamepadMapping {
     buttons: Vec<(Code, VBKey)>,
-    axes: Vec<(Code, (VBKey, VBKey))>,
+    axes: Vec<(Code, AxisMapping)>,
     default_buttons: Vec<(Code, VBKey)>,
-    default_axes: Vec<(Code, (VBKey, VBKey))>,
+    default_axes: Vec<(Code, AxisMapping)>,
 }
 
 #[derive(Clone, Copy, Serialize, Deserialize, PartialEq, Eq, Hash)]

src/main.rs

@@ -13,7 +13,7 @@ use tracing_subscriber::{EnvFilter, Layer, layer::SubscriberExt, util::Subscribe
 use winit::event_loop::{ControlFlow, EventLoop};
 
 use crate::{
-    config::{CliArgs, SimConfig},
+    config::{AppConfig, CliArgs, SimConfig},
     emulator::SimId,
     persistence::Persistence,
 };
@@ -23,6 +23,7 @@ mod audio;
 mod config;
 mod controller;
 mod emulator;
+mod filepicker;
 mod gdbserver;
 mod graphics;
 mod images;
@@ -110,6 +111,10 @@ fn main() -> Result<()> {
     if args.profile {
         builder = builder.start_paused(true)
     }
+    let mut config = AppConfig::load(&persistence);
+    if config.update(&args) {
+        let _ = config.save(&persistence);
+    }
     let p1 = SimConfig::load(&persistence, SimId::Player1);
     let p2 = SimConfig::load(&persistence, SimId::Player2);
 
@@ -136,6 +141,14 @@ fn main() -> Result<()> {
     let event_loop = EventLoop::with_user_event().build().unwrap();
     event_loop.set_control_flow(ControlFlow::Poll);
     let proxy = event_loop.create_proxy();
-    event_loop.run_app(&mut Application::new(client, proxy, persistence, args))?;
+    let handle = event_loop.owned_display_handle();
+    event_loop.run_app(&mut Application::new(
+        client,
+        proxy,
+        handle,
+        persistence,
+        args,
+        config,
+    ))?;
     Ok(())
 }

src/window.rs

@@ -1,9 +1,9 @@
 use std::sync::Arc;
 
 pub use about::AboutWindow;
-use egui::{Ui, ViewportBuilder, ViewportId};
-pub use game::GameWindow;
-pub use game_screen::DisplayMode;
+use egui::{Ui, ViewportBuilder};
+pub use game::{ChildWindow, GameWindow};
+pub use game_screen::{DisplayMode, GameScreen};
 pub use gdb::GdbServerWindow;
 pub use hotkeys::HotkeysWindow;
 pub use input::InputWindow;
@@ -28,19 +28,17 @@ mod utils;
 mod vip;
 
 pub trait AppWindow {
-    fn viewport_id(&self) -> ViewportId;
-    fn sim_id(&self) -> SimId {
-        SimId::Player1
+    fn sim_id(&self) -> Option<SimId> {
+        None
     }
     fn image_url(&self, name: &str) -> String {
-        format!("vip://{}/{name}", self.sim_id())
+        format!("vip://{}/{name}", self.sim_id().unwrap_or(SimId::Player1))
     }
     fn initial_viewport(&self) -> ViewportBuilder;
     fn show(&mut self, ui: &mut Ui);
     fn on_init(&mut self, args: InitArgs) {
         let _ = args;
     }
-    fn on_destroy(&mut self) {}
     fn handle_key_event(&mut self, event: &KeyEvent) -> bool {
         let _ = event;
         false

src/window/about.rs

@@ -1,14 +1,10 @@
-use egui::{CentralPanel, Image, Ui, ViewportBuilder, ViewportId};
+use egui::{CentralPanel, Image, Ui, ViewportBuilder};
 
 use super::AppWindow;
 
 pub struct AboutWindow;
 
 impl AppWindow for AboutWindow {
-    fn viewport_id(&self) -> ViewportId {
-        ViewportId::from_hash_of("About")
-    }
-
     fn initial_viewport(&self) -> ViewportBuilder {
         ViewportBuilder::default()
             .with_title("About Lemur")

src/window/game.rs

@@ -1,5 +1,6 @@
 use std::{
-    sync::{Arc, mpsc},
+    ops::{Deref, DerefMut},
+    sync::{Arc, Mutex, atomic::AtomicBool, mpsc},
     time::Duration,
 };
 
@@ -7,17 +8,25 @@ use crate::{
     app::UserEvent,
     config::{COLOR_PRESETS, SimConfig},
     emulator::{EmulatorClient, EmulatorCommand, EmulatorState, SimId, SimState},
-    input::{Command, ShortcutProvider},
+    filepicker::FilePicker,
+    images::ImageTextureLoader,
+    input::{Command, MappingProvider, ShortcutProvider},
+    memory::MemoryClient,
     persistence::Persistence,
-    window::InitArgs,
+    window::{
+        AboutWindow, BgMapWindow, CharacterDataWindow, FrameBufferWindow, GdbServerWindow,
+        HotkeysWindow, InitArgs, InputWindow, ObjectWindow, ProfileWindow, RegisterWindow,
+        TerminalWindow, WorldWindow, utils::UiData,
+    },
 };
 use anyhow::Context as _;
 use egui::{
-    Align2, Button, CentralPanel, Color32, Context, Frame, MenuBar, Panel, Ui, Vec2,
-    ViewportBuilder, ViewportCommand, ViewportId, Window,
+    Align2, Button, CentralPanel, Color32, Context, Frame, MenuBar, Panel, Pos2, Ui, Vec2,
+    ViewportBuilder, ViewportCommand, ViewportId, ViewportIdMap, Window,
 };
 use egui_notify::{Anchor, Toast, Toasts};
-use winit::event_loop::EventLoopProxy;
+use serde::{Deserialize, Serialize};
+use winit::{event::KeyEvent, event_loop::EventLoopProxy};
 
 use super::{
     AppWindow,
@@ -26,6 +35,7 @@ use super::{
 };
 
 pub struct GameWindow {
+    viewport_id: ViewportId,
     client: EmulatorClient,
     proxy: EventLoopProxy<UserEvent>,
     persistence: Persistence,
@@ -34,17 +44,30 @@ pub struct GameWindow {
     config: SimConfig,
     toasts: Toasts,
     screen: Option<GameScreen>,
-    messages: Option<mpsc::Receiver<Toast>>,
+    messages: mpsc::Receiver<Toast>,
+    message_sink: mpsc::Sender<Toast>,
     color_picker: Option<ColorPickerState>,
-    window: Option<Arc<winit::window::Window>>,
+    file_picker: FilePicker,
+    memory: Arc<MemoryClient>,
+    images: Arc<ImageTextureLoader>,
+    mappings: MappingProvider,
+    children: ViewportIdMap<ChildWindowWrapper>,
+    child_states: UiData<ViewportIdMap<ChildState>>,
+    queued_children: Vec<ChildWindow>,
+    show_player_name: bool,
 }
 
 impl GameWindow {
+    #[expect(clippy::too_many_arguments)]
     pub fn new(
+        viewport_id: ViewportId,
         client: EmulatorClient,
         proxy: EventLoopProxy<UserEvent>,
         persistence: Persistence,
         shortcuts: ShortcutProvider,
+        memory: &Arc<MemoryClient>,
+        images: &Arc<ImageTextureLoader>,
+        mappings: MappingProvider,
         sim_id: SimId,
     ) -> Self {
         let config = SimConfig::load(&persistence, sim_id);
@@ -52,7 +75,9 @@ impl GameWindow {
             .with_anchor(Anchor::BottomLeft)
             .with_margin((10.0, 10.0).into())
             .reverse(true);
+        let (message_sink, messages) = mpsc::channel();
         Self {
+            viewport_id,
             client,
             proxy,
             persistence,
@@ -61,9 +86,157 @@ impl GameWindow {
             config,
             toasts,
             screen: None,
-            messages: None,
+            messages,
+            message_sink,
             color_picker: None,
-            window: None,
+            file_picker: FilePicker::new(),
+            memory: memory.clone(),
+            images: images.clone(),
+            mappings: mappings.clone(),
+            children: ViewportIdMap::default(),
+            child_states: UiData::new(),
+            queued_children: vec![],
+            show_player_name: false,
+        }
+    }
+
+    pub fn open(&mut self, window: ChildWindow) {
+        // queue opening this child until our next render call,
+        // so that we get a chance to look up its size
+        self.queued_children.push(window);
+    }
+
+    pub fn close(&mut self, window: ChildWindow) {
+        let id = window.viewport_id(self.sim_id);
+        self.children.remove(&id);
+    }
+
+    fn do_open(&mut self, window: ChildWindow) {
+        let viewport_id = window.viewport_id(self.sim_id);
+        if self.children.contains_key(&viewport_id) {
+            return;
+        }
+        let child = match window {
+            ChildWindow::About => AppWrapper::of_dyn(AboutWindow),
+            ChildWindow::CharacterData => AppWrapper::of_dyn(CharacterDataWindow::new(
+                self.sim_id,
+                &self.memory,
+                &self.images,
+            )),
+            ChildWindow::BgMap => {
+                AppWrapper::of_dyn(BgMapWindow::new(self.sim_id, &self.memory, &self.images))
+            }
+            ChildWindow::Objects => {
+                AppWrapper::of_dyn(ObjectWindow::new(self.sim_id, &self.memory, &self.images))
+            }
+            ChildWindow::Worlds => {
+                AppWrapper::of_dyn(WorldWindow::new(self.sim_id, &self.memory, &self.images))
+            }
+            ChildWindow::FrameBuffers => AppWrapper::of_dyn(FrameBufferWindow::new(
+                self.sim_id,
+                &self.memory,
+                &self.images,
+            )),
+            ChildWindow::Registers => {
+                AppWrapper::of_dyn(RegisterWindow::new(self.sim_id, &self.memory))
+            }
+            ChildWindow::Terminal => {
+                AppWrapper::of_dyn(TerminalWindow::new(self.sim_id, &self.client))
+            }
+            ChildWindow::Profiler { launch } => {
+                let mut profile = ProfileWindow::new(self.sim_id, self.client.clone());
+                if launch {
+                    profile.launch();
+                }
+                AppWrapper::of_dyn(profile)
+            }
+            ChildWindow::Debugger { port } => {
+                let mut debugger =
+                    GdbServerWindow::new(self.sim_id, self.client.clone(), self.proxy.clone());
+                if let Some(port) = port {
+                    debugger.launch(port);
+                }
+                AppWrapper::of_dyn(debugger)
+            }
+            ChildWindow::Input => AppWrapper::of_dyn(InputWindow::new(self.mappings.clone())),
+            ChildWindow::Hotkeys => AppWrapper::of_dyn(HotkeysWindow::new(self.shortcuts.clone())),
+            ChildWindow::Player2 => {
+                if self.sim_id == SimId::Player2 {
+                    return;
+                }
+                AppWrapper::of_game(GameWindow::new(
+                    viewport_id,
+                    self.client.clone(),
+                    self.proxy.clone(),
+                    self.persistence.clone(),
+                    self.shortcuts.clone(),
+                    &self.memory,
+                    &self.images,
+                    self.mappings.clone(),
+                    SimId::Player2,
+                ))
+            }
+        };
+
+        let mut viewport = child.initial_viewport();
+        let title = viewport.title.clone().unwrap();
+        let sim_id = child.sim_id();
+        if let Some(sim_id) = sim_id
+            && self.show_player_name
+        {
+            viewport.title = Some(format!("{title} ({sim_id})"));
+        }
+        if let Some(state) = self.child_states.get(&viewport_id) {
+            viewport.position = Some(state.position);
+            viewport.inner_size = Some(state.size);
+        }
+        self.children.insert(
+            viewport_id,
+            ChildWindowWrapper {
+                app: Arc::new(Mutex::new(child)),
+                title,
+                sim_id,
+                updates: Some(viewport),
+                close_requested: Arc::new(AtomicBool::new(false)),
+            },
+        );
+    }
+
+    pub fn handle_init(&mut self, viewport_id: ViewportId, args: InitArgs) {
+        self.handle_event(viewport_id, |window| window.on_init(args))
+    }
+
+    pub fn handle_key_event(&mut self, viewport_id: ViewportId, event: &KeyEvent) -> bool {
+        self.handle_event(viewport_id, |window| window.handle_key_event(event))
+    }
+
+    pub fn handle_gamepad_event(&mut self, viewport_id: ViewportId, event: &gilrs::Event) -> bool {
+        self.handle_event(viewport_id, |window| window.handle_gamepad_event(event))
+    }
+
+    fn handle_event<F, R>(&mut self, viewport_id: ViewportId, cb: F) -> R
+    where
+        F: FnOnce(&mut dyn AppWindow) -> R,
+        R: Default,
+    {
+        let p2_viewport_id = ChildWindow::Player2.viewport_id(SimId::Player1);
+
+        if self.viewport_id == viewport_id {
+            cb(self)
+        } else if let Some(child) = self.children.get_mut(&viewport_id) {
+            cb(child.app.lock().unwrap().deref_mut().deref_mut())
+        } else if let Some(mut p2) = self
+            .children
+            .get_mut(&p2_viewport_id)
+            .map(|w| w.app.lock().unwrap())
+        {
+            if let AppWrapper::Game(g) = p2.deref_mut() {
+                g.handle_event(viewport_id, cb)
+            } else {
+                R::default()
+            }
+        } else {
+            R::default()
         }
     }
 
@@ -77,9 +250,11 @@ impl GameWindow {
         for command in ui.input_mut(|input| self.shortcuts.consume_all(input)) {
             match command {
                 Command::OpenRom => {
-                    let rom = rfd::FileDialog::new()
+                    let rom = self
+                        .file_picker
+                        .pick_file_dialog()
                         .add_filter("Virtual Boy ROMs", &["vb", "vbrom", "elf", "isx"])
-                        .pick_file();
+                        .open();
                     if let Some(path) = rom {
                         self.client
                             .send_command(EmulatorCommand::LoadGame(self.sim_id, path));
@@ -133,9 +308,11 @@ impl GameWindow {
                 .add(self.button_for(ui.ctx(), "Open ROM", Command::OpenRom))
                 .clicked()
             {
-                let rom = rfd::FileDialog::new()
+                let rom = self
+                    .file_picker
+                    .pick_file_dialog()
                     .add_filter("Virtual Boy ROMs", &["vb", "vbrom", "elf", "isx"])
-                    .pick_file();
+                    .open();
                 if let Some(path) = rom {
                     self.client
                         .send_command(EmulatorCommand::LoadGame(self.sim_id, path));
@@ -210,14 +387,14 @@ impl GameWindow {
         });
         ui.menu_button("Options", |ui| self.show_options_menu(ui));
         ui.menu_button("Multiplayer", |ui| {
-            let has_player_2 = self.client.sim_state(SimId::Player2) != SimState::Uninitialized;
+            let has_player_2 = self.client.has_player_2();
             if self.sim_id == SimId::Player1
                 && !has_player_2
                 && ui.button("Open Player 2").clicked()
             {
                 self.client
                     .send_command(EmulatorCommand::StartSecondSim(None));
-                self.proxy.send_event(UserEvent::OpenPlayer2).unwrap();
+                self.open(ChildWindow::Player2);
             }
             if has_player_2 {
                 let linked = self.client.are_sims_linked();
@@ -231,55 +408,37 @@ impl GameWindow {
         });
         ui.menu_button("Tools", |ui| {
             if ui.button("Terminal").clicked() {
-                self.proxy
-                    .send_event(UserEvent::OpenTerminal(self.sim_id))
-                    .unwrap();
+                self.open(ChildWindow::Terminal);
             }
             if ui.button("Profiler").clicked() {
-                self.proxy
-                    .send_event(UserEvent::OpenProfiler(self.sim_id))
-                    .unwrap();
+                self.open(ChildWindow::Profiler { launch: false });
             }
             if ui.button("GDB Server").clicked() {
-                self.proxy
-                    .send_event(UserEvent::OpenDebugger(self.sim_id))
-                    .unwrap();
+                self.open(ChildWindow::Debugger { port: None });
             }
             ui.separator();
             if ui.button("Character Data").clicked() {
-                self.proxy
-                    .send_event(UserEvent::OpenCharacterData(self.sim_id))
-                    .unwrap();
+                self.open(ChildWindow::CharacterData);
             }
             if ui.button("Background Maps").clicked() {
-                self.proxy
-                    .send_event(UserEvent::OpenBgMap(self.sim_id))
-                    .unwrap();
+                self.open(ChildWindow::BgMap);
             }
             if ui.button("Objects").clicked() {
-                self.proxy
-                    .send_event(UserEvent::OpenObjects(self.sim_id))
-                    .unwrap();
+                self.open(ChildWindow::Objects);
             }
             if ui.button("Worlds").clicked() {
-                self.proxy
-                    .send_event(UserEvent::OpenWorlds(self.sim_id))
-                    .unwrap();
+                self.open(ChildWindow::Worlds);
             }
             if ui.button("Frame Buffers").clicked() {
-                self.proxy
-                    .send_event(UserEvent::OpenFrameBuffers(self.sim_id))
-                    .unwrap();
+                self.open(ChildWindow::FrameBuffers);
             }
             if ui.button("Registers").clicked() {
-                self.proxy
-                    .send_event(UserEvent::OpenRegisters(self.sim_id))
-                    .unwrap();
+                self.open(ChildWindow::Registers);
             }
         });
         ui.menu_button("Help", |ui| {
             if ui.button("About").clicked() {
-                self.proxy.send_event(UserEvent::OpenAbout).unwrap();
+                self.open(ChildWindow::About);
             }
         });
     }
@@ -305,13 +464,12 @@ impl GameWindow {
         self.client
             .send_command(EmulatorCommand::Screenshot(self.sim_id, tx));
         let bytes = rx.await.context("Could not take screenshot")?;
-        let mut file_dialog = rfd::FileDialog::new()
+        let file = self
+            .file_picker
+            .save_file_dialog()
             .add_filter("PNG images", &["png"])
-            .set_file_name("screenshot.png");
-        if let Some(window) = self.window.as_ref() {
-            file_dialog = file_dialog.set_parent(window);
-        }
-        let file = file_dialog.save_file();
+            .set_file_name("screenshot.png")
+            .open();
         let Some(path) = file else {
             return Ok(None);
         };
@@ -424,11 +582,11 @@ impl GameWindow {
         });
         ui.menu_button("Input", |ui| {
             if ui.button("Bind Inputs").clicked() {
-                self.proxy.send_event(UserEvent::OpenInput).unwrap();
+                self.open(ChildWindow::Input);
             }
         });
         if ui.button("Hotkeys").clicked() {
-            self.proxy.send_event(UserEvent::OpenHotkeys).unwrap();
+            self.open(ChildWindow::Hotkeys);
         }
     }
 
@@ -480,35 +638,60 @@ impl GameWindow {
 }
 
 impl AppWindow for GameWindow {
-    fn viewport_id(&self) -> ViewportId {
-        match self.sim_id {
-            SimId::Player1 => ViewportId::ROOT,
-            SimId::Player2 => ViewportId::from_hash_of("Player2"),
-        }
-    }
-
-    fn sim_id(&self) -> SimId {
-        self.sim_id
+    fn sim_id(&self) -> Option<SimId> {
+        Some(self.sim_id)
     }
 
     fn initial_viewport(&self) -> ViewportBuilder {
-        ViewportBuilder::default()
+        let builder = ViewportBuilder::default()
             .with_title("Lemur")
-            .with_inner_size(self.config.dimensions)
+            .with_inner_size(self.config.dimensions);
+        if let Some(position) = self.config.position {
+            builder.with_position(position)
+        } else {
+            builder
+        }
     }
 
     fn show(&mut self, ui: &mut Ui) {
+        let has_player_2 = self.client.has_player_2();
+        if !self.show_player_name && has_player_2 {
+            ui.send_viewport_cmd(ViewportCommand::Title(format!("Lemur ({})", self.sim_id)));
+            for (viewport_id, child) in &self.children {
+                if let Some(sim_id) = child.sim_id {
+                    ui.send_viewport_cmd_to(
+                        *viewport_id,
+                        ViewportCommand::Title(format!("{} ({sim_id})", child.title)),
+                    );
+                }
+            }
+            self.show_player_name = true;
+        } else if self.show_player_name && !has_player_2 {
+            ui.send_viewport_cmd(ViewportCommand::Title("Lemur".to_string()));
+            for (viewport_id, child) in &self.children {
+                if child.sim_id.is_some() {
+                    ui.send_viewport_cmd_to(
+                        *viewport_id,
+                        ViewportCommand::Title(child.title.clone()),
+                    );
+                }
+            }
+            self.show_player_name = false;
+        }
+        self.child_states.load(ui);
         let dimensions = {
             let bounds = ui.content_rect();
             bounds.max - bounds.min
         };
-        self.update_config(|c| c.dimensions = dimensions);
+        let position = ui.input(|i| i.viewport().outer_rect.map(|r| r.min));
+        self.update_config(|c| {
+            c.dimensions = dimensions;
+            c.position = position;
+        });
 
-        if let Some(messages) = self.messages.as_mut() {
-            while let Ok(toast) = messages.try_recv() {
+        while let Ok(toast) = self.messages.try_recv() {
             self.toasts.add(toast);
         }
-        }
         Panel::top("menubar")
             .exact_size(22.0)
             .show_inside(ui, |ui| {
@@ -533,22 +716,59 @@ impl AppWindow for GameWindow {
             }
         });
         self.toasts.show(ui);
+        for window in std::mem::take(&mut self.queued_children) {
+            self.do_open(window);
+        }
+        self.children.retain(|id, child| {
+            if child
+                .close_requested
+                .load(std::sync::atomic::Ordering::Relaxed)
+            {
+                return false;
+            }
+            let app = child.app.clone();
+            let viewport_builder = child.updates.take().unwrap_or_default();
+            let close_requested = child.close_requested.clone();
+            if let (Some(outer), Some(inner)) = ui.input_for(*id, |inp| {
+                let viewport = inp.viewport();
+                (viewport.outer_rect, viewport.inner_rect)
+            }) {
+                self.child_states.insert(
+                    *id,
+                    ChildState {
+                        position: outer.min,
+                        size: inner.size(),
+                    },
+                );
+            }
+            ui.show_viewport_deferred(*id, viewport_builder, move |ui, _| {
+                app.lock().unwrap().show(ui);
+                if ui.input(|s| s.viewport().close_requested()) {
+                    close_requested.store(true, std::sync::atomic::Ordering::Relaxed);
+                }
+            });
+            true
+        });
+        self.child_states.save(ui);
+        ui.request_repaint_after(Duration::from_millis(10));
     }
 
     fn on_init(&mut self, args: InitArgs) {
+        if self.screen.is_none() {
             let (screen, sink) = GameScreen::init(args.render_state);
-        let (message_sink, message_source) = mpsc::channel();
             self.client.send_command(EmulatorCommand::ConnectToSim(
                 self.sim_id,
                 sink,
-            message_sink,
+                self.message_sink.clone(),
             ));
             self.screen = Some(screen);
-        self.messages = Some(message_source);
-        self.window = Some(args.window.clone());
         }
+        self.file_picker.set_window(args.window);
+    }
+}
 
-    fn on_destroy(&mut self) {
+impl Drop for GameWindow {
+    fn drop(&mut self) {
         if self.sim_id == SimId::Player2 {
             self.client.send_command(EmulatorCommand::StopSecondSim);
         }
@@ -561,3 +781,85 @@ struct ColorPickerState {
     just_opened: bool,
     unpause_on_close: bool,
 }
+
+struct ChildWindowWrapper {
+    app: Arc<Mutex<AppWrapper>>,
+    title: String,
+    sim_id: Option<SimId>,
+    updates: Option<ViewportBuilder>,
+    close_requested: Arc<AtomicBool>,
+}
+enum AppWrapper {
+    Game(Box<GameWindow>),
+    Dyn(Box<dyn AppWindow + Send + 'static>),
+}
+impl AppWrapper {
+    fn of_game(game: GameWindow) -> Self {
+        Self::Game(Box::new(game))
+    }
+    fn of_dyn<T: AppWindow + Send + 'static>(inner: T) -> Self {
+        Self::Dyn(Box::new(inner))
+    }
+}
+impl Deref for AppWrapper {
+    type Target = dyn AppWindow + Send + 'static;
+    fn deref(&self) -> &Self::Target {
+        match self {
+            Self::Dyn(inner) => inner.as_ref(),
+            Self::Game(inner) => inner.as_ref(),
+        }
+    }
+}
+impl DerefMut for AppWrapper {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        match self {
+            Self::Dyn(inner) => inner.as_mut(),
+            Self::Game(inner) => inner.as_mut(),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub enum ChildWindow {
+    About,
+    CharacterData,
+    BgMap,
+    Objects,
+    Worlds,
+    FrameBuffers,
+    Registers,
+    Terminal,
+    Profiler { launch: bool },
+    Debugger { port: Option<u16> },
+    Input,
+    Hotkeys,
+    Player2,
+}
+impl ChildWindow {
+    fn viewport_id(&self, sim_id: SimId) -> ViewportId {
+        ViewportId::from_hash_of(format!("{sim_id:?}{}", self.name()))
+    }
+    fn name(&self) -> &'static str {
+        match self {
+            Self::About => "About",
+            Self::CharacterData => "CharacterData",
+            Self::BgMap => "BgMap",
+            Self::Objects => "Objects",
+            Self::Worlds => "Worlds",
+            Self::FrameBuffers => "FrameBuffers",
+            Self::Registers => "Registers",
+            Self::Terminal => "Terminal",
+            Self::Profiler { .. } => "Profiler",
+            Self::Debugger { .. } => "Debugger",
+            Self::Input => "Input",
+            Self::Hotkeys => "Hotkeys",
+            Self::Player2 => "Player2",
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+struct ChildState {
+    position: Pos2,
+    size: Vec2,
+}

src/window/game_screen.rs

@@ -14,7 +14,7 @@ pub struct GameScreen {
 }
 
 impl GameScreen {
-    fn init_pipeline(render_state: &egui_wgpu::RenderState) {
+    pub fn init_pipeline(render_state: &egui_wgpu::RenderState) {
         let device = &render_state.device;
 
         let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
@@ -117,8 +117,6 @@ impl GameScreen {
     }
 
     pub fn init(render_state: &egui_wgpu::RenderState) -> (Self, TextureSink) {
-        Self::init_pipeline(render_state);
-
         let device = &render_state.device;
         let queue = &render_state.queue;
 

src/window/gdb.rs

@@ -1,4 +1,4 @@
-use egui::{Button, CentralPanel, TextEdit, ViewportBuilder, ViewportId};
+use egui::{Button, CentralPanel, TextEdit, ViewportBuilder};
 use winit::event_loop::EventLoopProxy;
 
 use crate::{
@@ -42,17 +42,13 @@ impl GdbServerWindow {
 }
 
 impl AppWindow for GdbServerWindow {
-    fn viewport_id(&self) -> ViewportId {
-        ViewportId::from_hash_of(format!("Debugger-{}", self.sim_id))
-    }
-
-    fn sim_id(&self) -> SimId {
-        self.sim_id
+    fn sim_id(&self) -> Option<SimId> {
+        Some(self.sim_id)
     }
 
     fn initial_viewport(&self) -> ViewportBuilder {
         ViewportBuilder::default()
-            .with_title(format!("GDB Server ({})", self.sim_id))
+            .with_title("GDB Server")
             .with_inner_size((300.0, 200.0))
     }
 

src/window/hotkeys.rs

@@ -1,6 +1,5 @@
 use egui::{
     Button, CentralPanel, Event, KeyboardShortcut, Label, Layout, Slider, Ui, ViewportBuilder,
-    ViewportId,
 };
 use egui_extras::{Column, TableBuilder};
 
@@ -125,10 +124,6 @@ impl HotkeysWindow {
 }
 
 impl AppWindow for HotkeysWindow {
-    fn viewport_id(&self) -> ViewportId {
-        ViewportId::from_hash_of("shortcuts")
-    }
-
     fn initial_viewport(&self) -> ViewportBuilder {
         ViewportBuilder::default()
             .with_title("Keyboard Shortcuts")

src/window/input.rs

@@ -1,4 +1,4 @@
-use egui::{Button, CentralPanel, Label, Layout, Panel, Ui, ViewportBuilder, ViewportId};
+use egui::{Button, CentralPanel, Label, Layout, Panel, Ui, ViewportBuilder};
 use egui_extras::{Column, TableBuilder};
 use gilrs::{EventType, GamepadId};
 use std::sync::RwLock;
@@ -160,10 +160,6 @@ impl InputWindow {
 }
 
 impl AppWindow for InputWindow {
-    fn viewport_id(&self) -> ViewportId {
-        ViewportId::from_hash_of("input")
-    }
-
     fn initial_viewport(&self) -> ViewportBuilder {
         ViewportBuilder::default()
             .with_title("Bind Inputs")

src/window/profile.rs

@@ -1,12 +1,12 @@
-use std::{fs, sync::Arc, time::Duration};
+use std::{fs, time::Duration};
 
 use anyhow::Result;
-use egui::{Button, CentralPanel, Checkbox, Label, ViewportBuilder, ViewportId};
+use egui::{Button, CentralPanel, Checkbox, Label, ViewportBuilder};
 use egui_notify::{Anchor, Toast, Toasts};
-use winit::window::Window;
 
 use crate::{
     emulator::{EmulatorClient, EmulatorCommand, EmulatorState, SimId},
+    filepicker::FilePicker,
     profiler::{Profiler, ProfilerStatus},
     window::{AppWindow, InitArgs},
 };
@@ -16,7 +16,7 @@ pub struct ProfileWindow {
     client: EmulatorClient,
     profiler: Profiler,
     toasts: Toasts,
-    window: Option<Arc<Window>>,
+    file_picker: FilePicker,
 }
 
 impl ProfileWindow {
@@ -29,7 +29,7 @@ impl ProfileWindow {
                 .with_anchor(Anchor::BottomLeft)
                 .with_margin((10.0, 10.0).into())
                 .reverse(true),
-            window: None,
+            file_picker: FilePicker::new(),
         }
     }
 
@@ -62,13 +62,12 @@ impl ProfileWindow {
 
     fn try_finish_recording(&mut self) -> Result<Option<String>> {
         let bytes_receiver = self.profiler.finish_recording();
-        let mut file_dialog = rfd::FileDialog::new()
+        let file = self
+            .file_picker
+            .save_file_dialog()
             .add_filter("Profiler files", &["json"])
-            .set_file_name("profile.json");
-        if let Some(window) = self.window.as_ref() {
-            file_dialog = file_dialog.set_parent(window);
-        }
-        let file = file_dialog.save_file();
+            .set_file_name("profile.json")
+            .open();
         if let Some(path) = file {
             let bytes = pollster::block_on(bytes_receiver)?;
             let _ = fs::remove_file(&path);
@@ -82,17 +81,13 @@ impl ProfileWindow {
 }
 
 impl AppWindow for ProfileWindow {
-    fn viewport_id(&self) -> ViewportId {
-        ViewportId::from_hash_of(format!("Profile-{}", self.sim_id))
-    }
-
-    fn sim_id(&self) -> SimId {
-        self.sim_id
+    fn sim_id(&self) -> Option<SimId> {
+        Some(self.sim_id)
     }
 
     fn initial_viewport(&self) -> ViewportBuilder {
         ViewportBuilder::default()
-            .with_title(format!("Profiler ({})", self.sim_id))
+            .with_title("Profiler")
             .with_inner_size((300.0, 200.0))
     }
 
@@ -168,6 +163,6 @@ impl AppWindow for ProfileWindow {
     }
 
     fn on_init(&mut self, args: InitArgs) {
-        self.window = Some(args.window.clone());
+        self.file_picker.set_window(args.window);
     }
 }

src/window/terminal.rs

@@ -1,8 +1,6 @@
 use std::{collections::VecDeque, sync::mpsc};
 
-use egui::{
-    Align, CentralPanel, FontFamily, Label, RichText, ScrollArea, Ui, ViewportBuilder, ViewportId,
-};
+use egui::{Align, CentralPanel, FontFamily, Label, RichText, ScrollArea, Ui, ViewportBuilder};
 
 use crate::emulator::{EmulatorClient, EmulatorCommand, SimId};
 
@@ -31,17 +29,13 @@ impl TerminalWindow {
 }
 
 impl AppWindow for TerminalWindow {
-    fn viewport_id(&self) -> ViewportId {
-        ViewportId::from_hash_of(format!("terminal-{}", self.sim_id))
-    }
-
-    fn sim_id(&self) -> SimId {
-        self.sim_id
+    fn sim_id(&self) -> Option<SimId> {
+        Some(self.sim_id)
     }
 
     fn initial_viewport(&self) -> ViewportBuilder {
         ViewportBuilder::default()
-            .with_title(format!("Terminal ({})", self.sim_id))
+            .with_title("Terminal")
             .with_inner_size((640.0, 480.0))
     }
 

src/window/utils.rs

@@ -1,6 +1,6 @@
 use std::{
     fmt::{Display, UpperHex},
-    ops::{Bound, RangeBounds},
+    ops::{AddAssign, Bound, Deref, DerefMut, MulAssign, RangeBounds},
     str::FromStr,
 };
 
@@ -8,9 +8,9 @@ use atoi::FromRadix16;
 use egui::{
     Align, Color32, CornerRadius, CursorIcon, Event, Frame, Key, Layout, Margin, Rect, Response,
     RichText, Sense, Shape, Stroke, StrokeKind, TextEdit, Ui, UiBuilder, Vec2, Widget, WidgetText,
-    ecolor::HexColor,
+    ecolor::HexColor, util::id_type_map::SerializableAny,
 };
-use num_traits::{CheckedAdd, CheckedSub, One};
+use num_traits::{CheckedAdd, CheckedSub, One, Zero};
 
 pub trait UiExt {
     fn section(&mut self, title: impl Into<String>, add_contents: impl FnOnce(&mut Ui));
@@ -105,14 +105,16 @@ enum Direction {
 
 pub trait Number:
     Copy
+    + Zero
     + One
+    + AddAssign
+    + MulAssign
     + CheckedAdd
     + CheckedSub
     + Eq
     + Ord
     + Display
     + FromStr
-    + FromRadix16
     + UpperHex
     + Send
     + Sync
@@ -121,14 +123,16 @@ pub trait Number:
 }
 impl<
     T: Copy
+        + Zero
         + One
+        + AddAssign
+        + MulAssign
         + CheckedAdd
         + CheckedSub
         + Eq
         + Ord
         + Display
         + FromStr
-        + FromRadix16
         + UpperHex
         + Send
         + Sync
@@ -209,8 +213,8 @@ impl<T: Number> Widget for NumberEdit<'_, T> {
         let from_string = |val: &str| {
             if self.hex {
                 let bytes = val.as_bytes();
-                let (result, consumed) = T::from_radix_16(bytes);
-                (consumed == bytes.len()).then_some(result)
+                let (result, consumed) = atoi::Integer::<T>::from_radix_16(bytes);
+                (consumed == bytes.len()).then_some(result.0)
             } else {
                 val.parse::<T>().ok()
             }
@@ -409,3 +413,51 @@ impl ResponseExt for Response {
         self.clicked() || self.dragged()
     }
 }
+
+pub struct UiData<T> {
+    current: T,
+    prev: T,
+    loaded: bool,
+}
+
+impl<T> UiData<T>
+where
+    T: Default + PartialEq + SerializableAny,
+{
+    pub fn new() -> Self {
+        Self {
+            current: T::default(),
+            prev: T::default(),
+            loaded: false,
+        }
+    }
+
+    pub fn load(&mut self, ui: &Ui) {
+        if !self.loaded {
+            self.current = ui
+                .data_mut(|d| d.get_persisted(ui.id()))
+                .unwrap_or_default();
+            self.loaded = true;
+        }
+    }
+
+    pub fn save(&mut self, ui: &Ui) {
+        if self.current != self.prev {
+            ui.data_mut(|d| d.insert_persisted(ui.id(), self.current.clone()));
+            self.prev = self.current.clone();
+        }
+    }
+}
+
+impl<T> Deref for UiData<T> {
+    type Target = T;
+    fn deref(&self) -> &Self::Target {
+        &self.current
+    }
+}
+
+impl<T> DerefMut for UiData<T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.current
+    }
+}

src/window/vip/bgmap.rs

@@ -2,9 +2,10 @@ use std::sync::Arc;
 
 use egui::{
     Align, CentralPanel, Checkbox, Color32, ComboBox, Image, ScrollArea, Slider, TextEdit,
-    TextureOptions, Ui, ViewportBuilder, ViewportId,
+    TextureOptions, Ui, ViewportBuilder,
 };
 use egui_extras::{Column, Size, StripBuilder, TableBuilder};
+use serde::{Deserialize, Serialize};
 
 use crate::{
     emulator::SimId,
@@ -12,36 +13,56 @@ use crate::{
     memory::{MemoryClient, MemoryView},
     window::{
         AppWindow,
-        utils::{NumberEdit, UiExt},
+        utils::{NumberEdit, UiData, UiExt},
     },
 };
 
 use super::utils::{self, CellData, CharacterGrid};
 
+#[derive(Clone, PartialEq, Serialize, Deserialize)]
+struct State {
+    cell_index: usize,
+    generic_palette: bool,
+    scale: f32,
+    show_grid: bool,
+}
+impl Default for State {
+    fn default() -> Self {
+        Self {
+            cell_index: 0,
+            generic_palette: false,
+            scale: 1.0,
+            show_grid: false,
+        }
+    }
+}
+
 pub struct BgMapWindow {
     sim_id: SimId,
     memory: Arc<MemoryClient>,
     bgmaps: MemoryView,
-    cell_index: usize,
-    generic_palette: bool,
     params: ImageParams<BgMapParams>,
-    scale: f32,
-    show_grid: bool,
+    state: UiData<State>,
 }
 
 impl BgMapWindow {
     pub fn new(sim_id: SimId, memory: &Arc<MemoryClient>, images: &ImageTextureLoader) -> Self {
+        let state: UiData<State> = UiData::new();
         let renderer = BgMapRenderer::new(sim_id, memory);
-        let params = images.add(sim_id, renderer, BgMapParams::default());
+        let params = images.add(
+            sim_id,
+            renderer,
+            BgMapParams {
+                cell_index: state.cell_index,
+                generic_palette: state.generic_palette,
+            },
+        );
         Self {
             sim_id,
             memory: memory.clone(),
             bgmaps: memory.watch(sim_id, 0x00020000, 0x20000),
-            cell_index: params.cell_index,
-            generic_palette: params.generic_palette,
             params,
-            scale: 1.0,
-            show_grid: false,
+            state,
         }
     }
 
@@ -57,10 +78,11 @@ impl BgMapWindow {
                             ui.label("Map");
                         });
                         row.col(|ui| {
-                            let mut bgmap_index = self.cell_index / 4096;
+                            let mut bgmap_index = self.state.cell_index / 4096;
                             ui.add(NumberEdit::new(&mut bgmap_index).range(0..16));
-                            if bgmap_index != self.cell_index / 4096 {
-                                self.cell_index = (bgmap_index * 4096) + (self.cell_index % 4096);
+                            if bgmap_index != self.state.cell_index / 4096 {
+                                self.state.cell_index =
+                                    (bgmap_index * 4096) + (self.state.cell_index % 4096);
                             }
                         });
                     });
@@ -69,7 +91,7 @@ impl BgMapWindow {
                             ui.label("Cell");
                         });
                         row.col(|ui| {
-                            ui.add(NumberEdit::new(&mut self.cell_index).range(0..16 * 4096));
+                            ui.add(NumberEdit::new(&mut self.state.cell_index).range(0..16 * 4096));
                         });
                     });
                     body.row(row_height, |mut row| {
@@ -77,7 +99,7 @@ impl BgMapWindow {
                             ui.label("Address");
                         });
                         row.col(|ui| {
-                            let address = 0x00020000 + (self.cell_index * 2);
+                            let address = 0x00020000 + (self.state.cell_index * 2);
                             let mut address_str = format!("{address:08x}");
                             ui.add_enabled(
                                 false,
@@ -91,7 +113,7 @@ impl BgMapWindow {
                 .texture_options(TextureOptions::NEAREST);
             ui.add(image);
             ui.section("Cell", |ui| {
-                let mut data = self.bgmaps.borrow().read::<u16>(self.cell_index);
+                let mut data = self.bgmaps.borrow().read::<u16>(self.state.cell_index);
                 let mut cell = CellData::parse(data);
                 TableBuilder::new(ui)
                     .column(Column::remainder())
@@ -134,7 +156,7 @@ impl BgMapWindow {
                         });
                     });
                 if cell.update(&mut data) {
-                    let address = 0x00020000 + (self.cell_index * 2);
+                    let address = 0x00020000 + (self.state.cell_index * 2);
                     self.memory.write(self.sim_id, address as u32, &data);
                 }
             });
@@ -142,48 +164,45 @@ impl BgMapWindow {
                 ui.horizontal(|ui| {
                     ui.label("Scale");
                     ui.spacing_mut().slider_width = ui.available_width();
-                    let slider = Slider::new(&mut self.scale, 1.0..=10.0)
+                    let slider = Slider::new(&mut self.state.scale, 1.0..=10.0)
                         .step_by(1.0)
                         .show_value(false);
                     ui.add(slider);
                 });
-                ui.checkbox(&mut self.show_grid, "Show grid");
-                ui.checkbox(&mut self.generic_palette, "Generic palette");
+                ui.checkbox(&mut self.state.show_grid, "Show grid");
+                ui.checkbox(&mut self.state.generic_palette, "Generic palette");
             });
         });
         self.params.write(BgMapParams {
-            cell_index: self.cell_index,
-            generic_palette: self.generic_palette,
+            cell_index: self.state.cell_index,
+            generic_palette: self.state.generic_palette,
         });
     }
 
     fn show_bgmap(&mut self, ui: &mut Ui) {
         let grid = CharacterGrid::new(self.image_url("bgmap"))
-            .with_scale(self.scale)
-            .with_grid(self.show_grid)
-            .with_selected(self.cell_index % 4096);
+            .with_scale(self.state.scale)
+            .with_grid(self.state.show_grid)
+            .with_selected(self.state.cell_index % 4096);
         if let Some(selected) = grid.show(ui) {
-            self.cell_index = (self.cell_index / 4096 * 4096) + selected;
+            self.state.cell_index = (self.state.cell_index / 4096 * 4096) + selected;
         }
     }
 }
 
 impl AppWindow for BgMapWindow {
-    fn viewport_id(&self) -> ViewportId {
-        ViewportId::from_hash_of(format!("bgmap-{}", self.sim_id))
-    }
-
-    fn sim_id(&self) -> SimId {
-        self.sim_id
+    fn sim_id(&self) -> Option<SimId> {
+        Some(self.sim_id)
     }
 
     fn initial_viewport(&self) -> ViewportBuilder {
         ViewportBuilder::default()
-            .with_title(format!("BG Map Data ({})", self.sim_id))
+            .with_title("BG Map Data")
             .with_inner_size((640.0, 480.0))
     }
 
     fn show(&mut self, ui: &mut Ui) {
+        self.state.load(ui);
         CentralPanel::default().show_inside(ui, |ui| {
             ui.horizontal_top(|ui| {
                 StripBuilder::new(ui)
@@ -199,6 +218,7 @@ impl AppWindow for BgMapWindow {
                     })
             });
         });
+        self.state.save(ui);
     }
 }
 

src/window/vip/chardata.rs

@@ -2,7 +2,7 @@ use std::fmt::Display;
 
 use egui::{
     Align, CentralPanel, Color32, ComboBox, Image, ScrollArea, Slider, TextEdit, TextureOptions,
-    Ui, Vec2, ViewportBuilder, ViewportId,
+    Ui, Vec2, ViewportBuilder,
 };
 use egui_extras::{Column, Size, StripBuilder, TableBuilder};
 use serde::{Deserialize, Serialize};
@@ -13,7 +13,7 @@ use crate::{
     memory::{MemoryClient, MemoryView},
     window::{
         AppWindow,
-        utils::{NumberEdit, UiExt as _},
+        utils::{NumberEdit, UiData, UiExt as _},
     },
 };
 
@@ -79,30 +79,50 @@ impl Display for Palette {
     }
 }
 
+#[derive(Clone, PartialEq, Serialize, Deserialize)]
+struct State {
+    palette: Palette,
+    index: usize,
+    scale: f32,
+    show_grid: bool,
+}
+impl Default for State {
+    fn default() -> Self {
+        Self {
+            palette: Palette::default(),
+            index: 0,
+            scale: 4.0,
+            show_grid: true,
+        }
+    }
+}
+
 pub struct CharacterDataWindow {
     sim_id: SimId,
     brightness: MemoryView,
     palettes: MemoryView,
-    palette: Palette,
-    index: usize,
     params: ImageParams<CharDataParams>,
-    scale: f32,
-    show_grid: bool,
+    state: UiData<State>,
 }
 
 impl CharacterDataWindow {
     pub fn new(sim_id: SimId, memory: &MemoryClient, images: &ImageTextureLoader) -> Self {
+        let state: UiData<State> = UiData::new();
         let renderer = CharDataRenderer::new(sim_id, memory);
-        let params = images.add(sim_id, renderer, CharDataParams::default());
+        let params = images.add(
+            sim_id,
+            renderer,
+            CharDataParams {
+                palette: state.palette,
+                index: state.index,
+            },
+        );
         Self {
             sim_id,
             brightness: memory.watch(sim_id, 0x0005f824, 8),
             palettes: memory.watch(sim_id, 0x0005f860, 16),
-            palette: params.palette,
-            index: params.index,
             params,
-            scale: 4.0,
-            show_grid: true,
+            state,
         }
     }
 
@@ -118,7 +138,7 @@ impl CharacterDataWindow {
                             ui.label("Index");
                         });
                         row.col(|ui| {
-                            ui.add(NumberEdit::new(&mut self.index).range(0..2048));
+                            ui.add(NumberEdit::new(&mut self.state.index).range(0..2048));
                         });
                     });
                     body.row(row_height, |mut row| {
@@ -126,11 +146,11 @@ impl CharacterDataWindow {
                             ui.label("Address");
                         });
                         row.col(|ui| {
-                            let address = match self.index {
-                                0x000..0x200 => 0x00060000 + self.index * 16,
-                                0x200..0x400 => 0x000e0000 + (self.index - 0x200) * 16,
-                                0x400..0x600 => 0x00160000 + (self.index - 0x400) * 16,
-                                0x600..0x800 => 0x001e0000 + (self.index - 0x600) * 16,
+                            let address = match self.state.index {
+                                0x000..0x200 => 0x00060000 + self.state.index * 16,
+                                0x200..0x400 => 0x000e0000 + (self.state.index - 0x200) * 16,
+                                0x400..0x600 => 0x00160000 + (self.state.index - 0x400) * 16,
+                                0x600..0x800 => 0x001e0000 + (self.state.index - 0x600) * 16,
                                 _ => unreachable!("can't happen"),
                             };
                             let mut address_str = format!("{address:08x}");
@@ -145,7 +165,7 @@ impl CharacterDataWindow {
                             ui.label("Mirror");
                         });
                         row.col(|ui| {
-                            let mirror = 0x00078000 + (self.index * 16);
+                            let mirror = 0x00078000 + (self.state.index * 16);
                             let mut mirror_str = format!("{mirror:08x}");
                             ui.add_enabled(
                                 false,
@@ -162,12 +182,12 @@ impl CharacterDataWindow {
                 ui.horizontal(|ui| {
                     ui.label("Palette");
                     ComboBox::from_id_salt("palette")
-                        .selected_text(self.palette.to_string())
+                        .selected_text(self.state.palette.to_string())
                         .width(ui.available_width())
                         .show_ui(ui, |ui| {
                             for palette in Palette::values() {
                                 ui.selectable_value(
-                                    &mut self.palette,
+                                    &mut self.state.palette,
                                     palette,
                                     palette.to_string(),
                                 );
@@ -194,23 +214,23 @@ impl CharacterDataWindow {
                 ui.horizontal(|ui| {
                     ui.label("Scale");
                     ui.spacing_mut().slider_width = ui.available_width();
-                    let slider = Slider::new(&mut self.scale, 1.0..=10.0)
+                    let slider = Slider::new(&mut self.state.scale, 1.0..=10.0)
                         .step_by(1.0)
                         .show_value(false);
                     ui.add(slider);
                 });
-                ui.checkbox(&mut self.show_grid, "Show grid");
+                ui.checkbox(&mut self.state.show_grid, "Show grid");
             });
         });
 
         self.params.write(CharDataParams {
-            palette: self.palette,
-            index: self.index,
+            palette: self.state.palette,
+            index: self.state.index,
         });
     }
 
     fn load_palette_colors(&self) -> [Color32; 4] {
-        let Some(offset) = self.palette.offset() else {
+        let Some(offset) = self.state.palette.offset() else {
             return utils::generic_palette(Color32::RED);
         };
         let palette = self.palettes.borrow().read(offset);
@@ -221,31 +241,28 @@ impl CharacterDataWindow {
 
     fn show_chardata(&mut self, ui: &mut Ui) {
         let grid = CharacterGrid::new(self.image_url("chardata"))
-            .with_scale(self.scale)
-            .with_grid(self.show_grid)
-            .with_selected(self.index);
+            .with_scale(self.state.scale)
+            .with_grid(self.state.show_grid)
+            .with_selected(self.state.index);
         if let Some(selected) = grid.show(ui) {
-            self.index = selected;
+            self.state.index = selected;
         }
     }
 }
 
 impl AppWindow for CharacterDataWindow {
-    fn viewport_id(&self) -> ViewportId {
-        ViewportId::from_hash_of(format!("chardata-{}", self.sim_id))
-    }
-
-    fn sim_id(&self) -> SimId {
-        self.sim_id
+    fn sim_id(&self) -> Option<SimId> {
+        Some(self.sim_id)
     }
 
     fn initial_viewport(&self) -> ViewportBuilder {
         ViewportBuilder::default()
-            .with_title(format!("Character Data ({})", self.sim_id))
+            .with_title("Character Data")
             .with_inner_size((640.0, 480.0))
     }
 
     fn show(&mut self, ui: &mut Ui) {
+        self.state.load(ui);
         CentralPanel::default().show_inside(ui, |ui| {
             ui.horizontal_top(|ui| {
                 StripBuilder::new(ui)
@@ -261,10 +278,11 @@ impl AppWindow for CharacterDataWindow {
                     });
             });
         });
+        self.state.save(ui);
     }
 }
 
-#[derive(Clone, Default, PartialEq, Eq)]
+#[derive(Clone, PartialEq, Eq)]
 struct CharDataParams {
     palette: Palette,
     index: usize,

src/window/vip/framebuffer.rs

@@ -1,8 +1,9 @@
 use egui::{
     Align, CentralPanel, Color32, Image, ScrollArea, Slider, TextEdit, TextureOptions, Ui,
-    ViewportBuilder, ViewportId,
+    ViewportBuilder,
 };
 use egui_extras::{Column, Size, StripBuilder, TableBuilder};
+use serde::{Deserialize, Serialize};
 
 use crate::{
     emulator::SimId,
@@ -10,42 +11,58 @@ use crate::{
     memory::{MemoryClient, MemoryView},
     window::{
         AppWindow,
-        utils::{NumberEdit, UiExt as _},
+        utils::{NumberEdit, UiData, UiExt as _},
     },
 };
 
 use super::utils;
 
-pub struct FrameBufferWindow {
-    sim_id: SimId,
+#[derive(Clone, PartialEq, Serialize, Deserialize)]
+struct State {
     index: usize,
     left: bool,
     right: bool,
     generic_palette: bool,
-    params: ImageParams<FrameBufferParams>,
     scale: f32,
 }
-
-impl FrameBufferWindow {
-    pub fn new(sim_id: SimId, memory: &MemoryClient, images: &ImageTextureLoader) -> Self {
-        let initial_params = FrameBufferParams {
+impl Default for State {
+    fn default() -> Self {
+        Self {
             index: 0,
             left: true,
             right: true,
             generic_palette: false,
+            scale: 2.0,
+        }
+    }
+}
+
+pub struct FrameBufferWindow {
+    sim_id: SimId,
+    params: ImageParams<FrameBufferParams>,
+    state: UiData<State>,
+}
+
+impl FrameBufferWindow {
+    pub fn new(sim_id: SimId, memory: &MemoryClient, images: &ImageTextureLoader) -> Self {
+        let state: UiData<State> = UiData::new();
+        let renderer = FrameBufferRenderer::new(sim_id, memory);
+        let params = images.add(
+            sim_id,
+            renderer,
+            FrameBufferParams {
+                index: state.index,
+                left: state.left,
+                right: state.right,
+                generic_palette: state.generic_palette,
                 left_color: Color32::from_rgb(0xff, 0x00, 0x00),
                 right_color: Color32::from_rgb(0x00, 0xc6, 0xf0),
-        };
-        let renderer = FrameBufferRenderer::new(sim_id, memory);
-        let params = images.add(sim_id, renderer, initial_params);
+            },
+        );
         Self {
             sim_id,
-            index: params.index,
-            left: params.left,
-            right: params.right,
-            generic_palette: params.generic_palette,
             params,
-            scale: 2.0,
+            state,
         }
     }
 
@@ -61,7 +78,7 @@ impl FrameBufferWindow {
                             ui.label("Index");
                         });
                         row.col(|ui| {
-                            ui.add(NumberEdit::new(&mut self.index).range(0..2));
+                            ui.add(NumberEdit::new(&mut self.state.index).range(0..2));
                         });
                     });
                     body.row(row_height, |mut row| {
@@ -69,7 +86,7 @@ impl FrameBufferWindow {
                             ui.label("Left");
                         });
                         row.col(|ui| {
-                            let address = self.index * 0x00008000;
+                            let address = self.state.index * 0x00008000;
                             let mut address_str = format!("{address:08x}");
                             ui.add_enabled(
                                 false,
@@ -82,7 +99,7 @@ impl FrameBufferWindow {
                             ui.label("Right");
                         });
                         row.col(|ui| {
-                            let address = self.index * 0x00008000 + 0x00010000;
+                            let address = self.state.index * 0x00008000 + 0x00010000;
                             let mut address_str = format!("{address:08x}");
                             ui.add_enabled(
                                 false,
@@ -95,7 +112,7 @@ impl FrameBufferWindow {
                 ui.horizontal(|ui| {
                     ui.label("Scale");
                     ui.spacing_mut().slider_width = ui.available_width();
-                    let slider = Slider::new(&mut self.scale, 1.0..=10.0)
+                    let slider = Slider::new(&mut self.state.scale, 1.0..=10.0)
                         .step_by(1.0)
                         .show_value(false);
                     ui.add(slider);
@@ -105,50 +122,47 @@ impl FrameBufferWindow {
                     .body(|mut body| {
                         body.row(row_height, |mut row| {
                             row.col(|ui| {
-                                ui.checkbox(&mut self.left, "Left");
+                                ui.checkbox(&mut self.state.left, "Left");
                             });
                             row.col(|ui| {
-                                ui.checkbox(&mut self.right, "Right");
+                                ui.checkbox(&mut self.state.right, "Right");
                             });
                         });
                     });
-                ui.checkbox(&mut self.generic_palette, "Generic colors");
+                ui.checkbox(&mut self.state.generic_palette, "Generic colors");
             });
         });
 
         self.params.write(FrameBufferParams {
-            index: self.index,
-            left: self.left,
-            right: self.right,
-            generic_palette: self.generic_palette,
+            index: self.state.index,
+            left: self.state.left,
+            right: self.state.right,
+            generic_palette: self.state.generic_palette,
             ..*self.params
         });
     }
 
     fn show_buffers(&mut self, ui: &mut Ui) {
         let image = Image::new(self.image_url("buffer"))
-            .fit_to_original_size(self.scale)
+            .fit_to_original_size(self.state.scale)
             .texture_options(TextureOptions::NEAREST);
         ui.add(image);
     }
 }
 
 impl AppWindow for FrameBufferWindow {
-    fn viewport_id(&self) -> ViewportId {
-        ViewportId::from_hash_of(format!("framebuffer-{}", self.sim_id))
-    }
-
-    fn sim_id(&self) -> SimId {
-        self.sim_id
+    fn sim_id(&self) -> Option<SimId> {
+        Some(self.sim_id)
     }
 
     fn initial_viewport(&self) -> ViewportBuilder {
         ViewportBuilder::default()
-            .with_title(format!("Frame Buffers ({})", self.sim_id))
+            .with_title("Frame Buffers")
             .with_inner_size((640.0, 480.0))
     }
 
     fn show(&mut self, ui: &mut Ui) {
+        self.state.load(ui);
         CentralPanel::default().show_inside(ui, |ui| {
             ui.horizontal_top(|ui| {
                 StripBuilder::new(ui)
@@ -164,6 +178,7 @@ impl AppWindow for FrameBufferWindow {
                     });
             });
         });
+        self.state.save(ui);
     }
 }
 

src/window/vip/object.rs

@@ -2,9 +2,10 @@ use std::sync::Arc;
 
 use egui::{
     Align, CentralPanel, Checkbox, Color32, ComboBox, Image, ScrollArea, Slider, TextEdit,
-    TextureOptions, Ui, ViewportBuilder, ViewportId,
+    TextureOptions, Ui, ViewportBuilder,
 };
 use egui_extras::{Column, Size, StripBuilder, TableBuilder};
+use serde::{Deserialize, Serialize};
 
 use crate::{
     emulator::SimId,
@@ -12,40 +13,56 @@ use crate::{
     memory::{MemoryClient, MemoryView},
     window::{
         AppWindow,
-        utils::{NumberEdit, UiExt as _},
+        utils::{NumberEdit, UiData, UiExt as _},
     },
 };
 
 use super::utils::{self, Object};
 
+#[derive(Clone, PartialEq, Serialize, Deserialize)]
+struct State {
+    index: usize,
+    generic_palette: bool,
+    scale: f32,
+}
+impl Default for State {
+    fn default() -> Self {
+        Self {
+            index: 0,
+            generic_palette: false,
+            scale: 1.0,
+        }
+    }
+}
+
 pub struct ObjectWindow {
     sim_id: SimId,
     memory: Arc<MemoryClient>,
     objects: MemoryView,
-    index: usize,
-    generic_palette: bool,
     params: ImageParams<ObjectParams>,
-    scale: f32,
+    state: UiData<State>,
 }
 
 impl ObjectWindow {
     pub fn new(sim_id: SimId, memory: &Arc<MemoryClient>, images: &ImageTextureLoader) -> Self {
-        let initial_params = ObjectParams {
-            index: 0,
-            generic_palette: false,
+        let state: UiData<State> = UiData::new();
+        let renderer = ObjectRenderer::new(sim_id, memory);
+        let params = images.add(
+            sim_id,
+            renderer,
+            ObjectParams {
+                index: state.index,
+                generic_palette: state.generic_palette,
                 left_color: Color32::from_rgb(0xff, 0x00, 0x00),
                 right_color: Color32::from_rgb(0x00, 0xc6, 0xf0),
-        };
-        let renderer = ObjectRenderer::new(sim_id, memory);
-        let params = images.add(sim_id, renderer, initial_params);
+            },
+        );
         Self {
             sim_id,
             memory: memory.clone(),
             objects: memory.watch(sim_id, 0x0003e000, 0x2000),
-            index: params.index,
-            generic_palette: params.generic_palette,
             params,
-            scale: 1.0,
+            state,
         }
     }
 
@@ -61,7 +78,7 @@ impl ObjectWindow {
                             ui.label("Index");
                         });
                         row.col(|ui| {
-                            ui.add(NumberEdit::new(&mut self.index).range(0..1024));
+                            ui.add(NumberEdit::new(&mut self.state.index).range(0..1024));
                         });
                     });
                     body.row(row_height, |mut row| {
@@ -69,7 +86,7 @@ impl ObjectWindow {
                             ui.label("Address");
                         });
                         row.col(|ui| {
-                            let address = 0x3e000 + self.index * 8;
+                            let address = 0x3e000 + self.state.index * 8;
                             let mut address_str = format!("{address:08x}");
                             ui.add_enabled(
                                 false,
@@ -83,7 +100,7 @@ impl ObjectWindow {
                 .texture_options(TextureOptions::NEAREST);
             ui.add(image);
             ui.section("Properties", |ui| {
-                let mut object = self.objects.borrow().read::<[u16; 4]>(self.index);
+                let mut object = self.objects.borrow().read::<[u16; 4]>(self.state.index);
                 let mut obj = Object::parse(object);
                 TableBuilder::new(ui)
                     .column(Column::remainder())
@@ -158,7 +175,7 @@ impl ObjectWindow {
                         });
                     });
                 if obj.update(&mut object) {
-                    let address = 0x3e000 + self.index * 8;
+                    let address = 0x3e000 + self.state.index * 8;
                     self.memory.write(self.sim_id, address as u32, &object);
                 }
             });
@@ -166,45 +183,42 @@ impl ObjectWindow {
                 ui.horizontal(|ui| {
                     ui.label("Scale");
                     ui.spacing_mut().slider_width = ui.available_width();
-                    let slider = Slider::new(&mut self.scale, 1.0..=10.0)
+                    let slider = Slider::new(&mut self.state.scale, 1.0..=10.0)
                         .step_by(1.0)
                         .show_value(false);
                     ui.add(slider);
                 });
-                ui.checkbox(&mut self.generic_palette, "Generic palette");
+                ui.checkbox(&mut self.state.generic_palette, "Generic palette");
             });
         });
         self.params.write(ObjectParams {
-            index: self.index,
-            generic_palette: self.generic_palette,
+            index: self.state.index,
+            generic_palette: self.state.generic_palette,
             ..*self.params
         });
     }
 
     fn show_object(&mut self, ui: &mut Ui) {
         let image = Image::new(self.image_url("object-full"))
-            .fit_to_original_size(self.scale)
+            .fit_to_original_size(self.state.scale)
             .texture_options(TextureOptions::NEAREST);
         ui.add(image);
     }
 }
 
 impl AppWindow for ObjectWindow {
-    fn viewport_id(&self) -> egui::ViewportId {
-        ViewportId::from_hash_of(format!("object-{}", self.sim_id))
-    }
-
-    fn sim_id(&self) -> SimId {
-        self.sim_id
+    fn sim_id(&self) -> Option<SimId> {
+        Some(self.sim_id)
     }
 
     fn initial_viewport(&self) -> ViewportBuilder {
         ViewportBuilder::default()
-            .with_title(format!("Object Data ({})", self.sim_id))
+            .with_title("Object Data")
             .with_inner_size((640.0, 500.0))
     }
 
     fn show(&mut self, ui: &mut Ui) {
+        self.state.load(ui);
         CentralPanel::default().show_inside(ui, |ui| {
             ui.horizontal_top(|ui| {
                 StripBuilder::new(ui)
@@ -220,6 +234,7 @@ impl AppWindow for ObjectWindow {
                     });
             });
         });
+        self.state.save(ui);
     }
 }
 

src/window/vip/registers.rs

@@ -2,7 +2,7 @@ use std::sync::Arc;
 
 use egui::{
     Align, Button, CentralPanel, Checkbox, Color32, Direction, Label, Layout, ScrollArea, TextEdit,
-    Ui, ViewportBuilder, ViewportId,
+    Ui, ViewportBuilder,
 };
 use egui_extras::{Column, Size, StripBuilder, TableBuilder};
 
@@ -630,17 +630,13 @@ fn read_address<T: MemoryValue>(registers: &MemoryRef, address: usize) -> T {
 }
 
 impl AppWindow for RegisterWindow {
-    fn viewport_id(&self) -> ViewportId {
-        ViewportId::from_hash_of(format!("registers-{}", self.sim_id))
-    }
-
-    fn sim_id(&self) -> SimId {
-        self.sim_id
+    fn sim_id(&self) -> Option<SimId> {
+        Some(self.sim_id)
     }
 
     fn initial_viewport(&self) -> ViewportBuilder {
         ViewportBuilder::default()
-            .with_title(format!("Registers ({})", self.sim_id))
+            .with_title("Registers")
             .with_inner_size((800.0, 480.0))
     }
 

src/window/vip/world.rs

@@ -2,7 +2,7 @@ use std::{fmt::Display, sync::Arc};
 
 use egui::{
     Align, CentralPanel, Checkbox, Color32, ComboBox, Image, ScrollArea, Slider, TextEdit,
-    TextureOptions, Ui, ViewportBuilder, ViewportId,
+    TextureOptions, Ui, ViewportBuilder,
 };
 use egui_extras::{Column, Size, StripBuilder, TableBuilder};
 use fixed::{
@@ -11,6 +11,7 @@ use fixed::{
 };
 use num_derive::{FromPrimitive, ToPrimitive};
 use num_traits::{FromPrimitive, ToPrimitive};
+use serde::{Deserialize, Serialize};
 
 use crate::{
     emulator::SimId,
@@ -18,46 +19,62 @@ use crate::{
     memory::{MemoryClient, MemoryRef, MemoryView},
     window::{
         AppWindow,
-        utils::{NumberEdit, UiExt as _},
+        utils::{NumberEdit, UiData, UiExt as _},
     },
 };
 
 use super::utils::{self, CellData, Object, shade};
 
+#[derive(Clone, PartialEq, Serialize, Deserialize)]
+struct State {
+    index: usize,
+    param_index: usize,
+    generic_palette: bool,
+    show_extents: bool,
+    scale: f32,
+}
+impl Default for State {
+    fn default() -> Self {
+        Self {
+            index: 31,
+            param_index: 0,
+            generic_palette: false,
+            show_extents: false,
+            scale: 1.0,
+        }
+    }
+}
+
 pub struct WorldWindow {
     sim_id: SimId,
     memory: Arc<MemoryClient>,
     worlds: MemoryView,
     bgmaps: MemoryView,
-    index: usize,
-    param_index: usize,
-    generic_palette: bool,
-    show_extents: bool,
     params: ImageParams<WorldParams>,
-    scale: f32,
+    state: UiData<State>,
 }
 
 impl WorldWindow {
     pub fn new(sim_id: SimId, memory: &Arc<MemoryClient>, images: &ImageTextureLoader) -> Self {
-        let initial_params = WorldParams {
-            index: 31,
-            generic_palette: false,
+        let state: UiData<State> = UiData::new();
+        let renderer = WorldRenderer::new(sim_id, memory);
+        let params = images.add(
+            sim_id,
+            renderer,
+            WorldParams {
+                index: state.index,
+                generic_palette: state.generic_palette,
                 left_color: Color32::from_rgb(0xff, 0x00, 0x00),
                 right_color: Color32::from_rgb(0x00, 0xc6, 0xf0),
-        };
-        let renderer = WorldRenderer::new(sim_id, memory);
-        let params = images.add(sim_id, renderer, initial_params);
+            },
+        );
         Self {
             sim_id,
             memory: memory.clone(),
             worlds: memory.watch(sim_id, 0x0003d800, 0x400),
             bgmaps: memory.watch(sim_id, 0x00020000, 0x20000),
-            index: params.index,
-            param_index: 0,
-            generic_palette: params.generic_palette,
-            show_extents: false,
             params,
-            scale: 1.0,
+            state,
         }
     }
 
@@ -73,7 +90,7 @@ impl WorldWindow {
                             ui.label("Index");
                         });
                         row.col(|ui| {
-                            ui.add(NumberEdit::new(&mut self.index).range(0..32));
+                            ui.add(NumberEdit::new(&mut self.state.index).range(0..32));
                         });
                     });
                     body.row(row_height, |mut row| {
@@ -81,7 +98,7 @@ impl WorldWindow {
                             ui.label("Address");
                         });
                         row.col(|ui| {
-                            let address = 0x0003d800 + self.index * 32;
+                            let address = 0x0003d800 + self.state.index * 32;
                             let mut address_str = format!("{address:08x}");
                             ui.add_enabled(
                                 false,
@@ -92,7 +109,7 @@ impl WorldWindow {
                 });
             let mut data = {
                 let worlds = self.worlds.borrow();
-                worlds.read(self.index)
+                worlds.read(self.state.index)
             };
             let mut world = World::parse(&data);
             ui.section("Properties", |ui| {
@@ -272,7 +289,7 @@ impl WorldWindow {
                     });
             });
             if world.update(&mut data) {
-                let address = 0x0003d800 + self.index * 32;
+                let address = 0x0003d800 + self.state.index * 32;
                 self.memory.write(self.sim_id, address as u32, &data);
             }
             if world.header.mode == WorldMode::HBias {
@@ -287,10 +304,12 @@ impl WorldWindow {
                                 });
                                 row.col(|ui| {
                                     let max = world.height.max(8) as usize;
-                                    ui.add(NumberEdit::new(&mut self.param_index).range(0..max));
+                                    ui.add(
+                                        NumberEdit::new(&mut self.state.param_index).range(0..max),
+                                    );
                                 });
                             });
-                            let base = (world.param_base + self.param_index * 2) & 0x1ffff;
+                            let base = (world.param_base + self.state.param_index * 2) & 0x1ffff;
                             let mut param = HBiasParam::load(&self.bgmaps.borrow(), base);
                             body.row(row_height, |mut row| {
                                 row.col(|ui| {
@@ -337,10 +356,12 @@ impl WorldWindow {
                                 });
                                 row.col(|ui| {
                                     let max = world.height.max(1) as usize;
-                                    ui.add(NumberEdit::new(&mut self.param_index).range(0..max));
+                                    ui.add(
+                                        NumberEdit::new(&mut self.state.param_index).range(0..max),
+                                    );
                                 });
                             });
-                            let base = (world.param_base + self.param_index * 8) & 0x1ffff;
+                            let base = (world.param_base + self.state.param_index * 8) & 0x1ffff;
                             let mut param = AffineParam::load(&self.bgmaps.borrow(), base);
                             body.row(row_height, |mut row| {
                                 row.col(|ui| {
@@ -400,49 +421,49 @@ impl WorldWindow {
                         });
                 });
             } else {
-                self.param_index = 0;
+                self.state.param_index = 0;
             }
             ui.section("Display", |ui| {
                 ui.horizontal(|ui| {
                     ui.label("Scale");
                     ui.spacing_mut().slider_width = ui.available_width();
-                    let slider = Slider::new(&mut self.scale, 1.0..=10.0)
+                    let slider = Slider::new(&mut self.state.scale, 1.0..=10.0)
                         .step_by(1.0)
                         .show_value(false);
                     ui.add(slider);
                 });
-                ui.checkbox(&mut self.generic_palette, "Generic palette");
-                ui.checkbox(&mut self.show_extents, "Show extents");
+                ui.checkbox(&mut self.state.generic_palette, "Generic palette");
+                ui.checkbox(&mut self.state.show_extents, "Show extents");
             });
         });
         self.params.write(WorldParams {
-            index: self.index,
-            generic_palette: self.generic_palette,
+            index: self.state.index,
+            generic_palette: self.state.generic_palette,
             ..*self.params
         });
     }
 
     fn show_world(&mut self, ui: &mut Ui) {
         let image = Image::new(self.image_url("world"))
-            .fit_to_original_size(self.scale)
+            .fit_to_original_size(self.state.scale)
             .texture_options(TextureOptions::NEAREST);
         let res = ui.add(image);
-        if self.show_extents {
+        if self.state.show_extents {
             let world = {
                 let worlds = self.worlds.borrow();
-                let data = worlds.read(self.index);
+                let data = worlds.read(self.state.index);
                 World::parse(&data)
             };
             if world.header.mode == WorldMode::Object {
                 return;
             }
 
-            let lx1 = (world.dst_x - world.dst_parallax) as f32 * self.scale;
-            let lx2 = lx1 + world.width as f32 * self.scale;
-            let rx1 = (world.dst_x + world.dst_parallax) as f32 * self.scale;
-            let rx2 = rx1 + world.width as f32 * self.scale;
-            let y1 = world.dst_y as f32 * self.scale;
-            let y2 = y1 + world.height as f32 * self.scale;
+            let lx1 = (world.dst_x - world.dst_parallax) as f32 * self.state.scale;
+            let lx2 = lx1 + world.width as f32 * self.state.scale;
+            let rx1 = (world.dst_x + world.dst_parallax) as f32 * self.state.scale;
+            let rx2 = rx1 + world.width as f32 * self.state.scale;
+            let y1 = world.dst_y as f32 * self.state.scale;
+            let y2 = y1 + world.height as f32 * self.state.scale;
 
             let left_color = self.params.left_color;
             let right_color = self.params.right_color;
@@ -506,21 +527,18 @@ impl WorldWindow {
 }
 
 impl AppWindow for WorldWindow {
-    fn viewport_id(&self) -> ViewportId {
-        ViewportId::from_hash_of(format!("world-{}", self.sim_id))
-    }
-
-    fn sim_id(&self) -> SimId {
-        self.sim_id
+    fn sim_id(&self) -> Option<SimId> {
+        Some(self.sim_id)
     }
 
     fn initial_viewport(&self) -> ViewportBuilder {
         ViewportBuilder::default()
-            .with_title(format!("Worlds ({})", self.sim_id))
+            .with_title("Worlds")
             .with_inner_size((640.0, 520.0))
     }
 
     fn show(&mut self, ui: &mut Ui) {
+        self.state.load(ui);
         CentralPanel::default().show_inside(ui, |ui| {
             ui.horizontal_top(|ui| {
                 StripBuilder::new(ui)
@@ -536,6 +554,7 @@ impl AppWindow for WorldWindow {
                     });
             });
         });
+        self.state.save(ui);
     }
 }
 
@@ -1062,8 +1081,8 @@ impl<'a> SourceCoordCalculator<'a> {
                 (sx, sy)
             }
             SourceParam::Affine(affine) => {
-                let sx = affine_coord(affine.src_x, x, affine.dx, affine.src_parallax.min(0));
-                let sy = affine_coord(affine.src_y, x, affine.dy, affine.src_parallax.min(0));
+                let sx = affine_coord(affine.src_x, x, affine.dx, -(affine.src_parallax.min(0)));
+                let sy = affine_coord(affine.src_y, x, affine.dy, -(affine.src_parallax.min(0)));
                 (sx, sy)
             }
         }