Fix GameCube poll thread shutdown and backoff

Reviewed-on: #54
Co-authored-by: Álex Román Núñez <eirexe@eirteam.moe>

.gitignore

@@ -10,3 +10,7 @@ imported_assets
 *_old.glb
 /replay.json
 *.replay.tmp
+
+# Python debugger formatter tests
+__pycache__/
+*.pyc

README.md

@@ -2,6 +2,15 @@
 
 Fancy heavily advanced platform fighting game
 
+## Debugging fixed-point values with lldb
+
+If using CodeLLDB:
+```json
+"preRunCommands": [
+    "command script import ${workspaceFolder}/tools/lldb_fixed.py"
+]
+```
+
 ## Direct P2P Debugging
 
 ```text
@@ -16,18 +25,9 @@ cargo run -- --debug-match --players 2 --local-port 7001 \
 
 ## Production Build
 
-Production builds use the `production` Cargo profile and do not dynamically
-link Bevy or Rust. Development builds retain Bevy dynamic linking for faster
-iteration. Cargo stores the production profile under `target/production`,
-separate from development artifacts under `target/debug`.
-
 ```sh
 cargo run --locked \
   --bin process-assets --no-default-features --features debug_features
 cargo build --locked \
   --profile production --no-default-features --features debug_features
 ```
-
-The asset preprocessing command must be run from the repository root. It
-populates `imported_assets/Default`, which is then consumed by the production
-game without running the asset processor at startup.

src/fighter/baked_animation/mod.rs

@@ -4,8 +4,8 @@ mod asset_baking;
 mod runtime;
 mod visual_binding;
 
-pub use asset_baking::{BakedAnimationAssetProcessingPlugin, BakedAnimationPlugin};
 pub use crate::math::fixed_transform::FixedMat4;
+pub use asset_baking::{BakedAnimationAssetProcessingPlugin, BakedAnimationPlugin};
 pub use runtime::{
     BakedAnimationClip, BakedFighterAnimations, FighterBoneIndexMap, FighterBoneMatrices,
     update_fighter_bone_matrices,
@@ -164,6 +164,20 @@ mod tests {
         );
     }
 
+    #[test]
+    fn repeated_pose_updates_reuse_scratch_and_output_buffers() {
+        let mut matrices = FighterBoneMatrices::default();
+        let names = ["root".into(), "hand".into()];
+        let parents = [None, Some(0)];
+        let pose = [FixedMat4::IDENTITY, FixedMat4::IDENTITY];
+
+        matrices.set_pose(&names, &parents, &pose, FGi32::ONE);
+        let capacities = matrices.buffer_capacities();
+        matrices.set_pose(&names, &parents, &pose, FGi32::ONE);
+
+        assert_eq!(capacities, matrices.buffer_capacities());
+    }
+
     #[test]
     fn model_scale_affects_gameplay_bones_without_changing_visual_locals() {
         let mut root = FixedMat4::IDENTITY;

src/fighter/baked_animation/runtime.rs

@@ -3,7 +3,7 @@ use std::collections::HashMap;
 use bevy::prelude::*;
 use serde::{Deserialize, Serialize};
 
-use super::{BAKED_ANIMATION_FPS};
+use super::BAKED_ANIMATION_FPS;
 
 use crate::{
     fighter::{
@@ -12,8 +12,8 @@ use crate::{
         manifest::FighterManifest,
         visual::FighterAnimations,
     },
+    math::fixed_transform::FixedMat4,
     math::int::FGi32,
-    math::fixed_transform::FixedMat4
 };
 
 #[derive(Clone, Debug, Serialize, Deserialize)]
@@ -70,12 +70,24 @@ pub struct FighterBoneMatrices {
     previous_frame_matrices: Vec<FixedMat4>,
     local_matrices: Vec<FixedMat4>,
     previous_local_matrices: Vec<FixedMat4>,
+    model_matrices: Vec<Option<FixedMat4>>,
 }
 
 #[derive(Component, Clone, Debug, Default)]
 pub struct FighterBoneIndexMap(pub HashMap<String, usize>);
 
 impl FighterBoneMatrices {
+    #[cfg(test)]
+    pub(super) fn buffer_capacities(&self) -> [usize; 5] {
+        [
+            self.matrices.capacity(),
+            self.local_matrices.capacity(),
+            self.previous_frame_matrices.capacity(),
+            self.previous_local_matrices.capacity(),
+            self.model_matrices.capacity(),
+        ]
+    }
+
     pub fn get(&self, bone: &str) -> Option<(FixedMat4, FixedMat4)> {
         let index = self.bone_names.iter().position(|name| name == bone)?;
         Some((
@@ -142,13 +154,19 @@ impl FighterBoneMatrices {
             assert_eq!(self.bone_names, bone_names, "baked bone names changed");
             assert_eq!(self.parents, parents, "baked bone parents changed");
         }
+        self.matrices.reserve(local.len());
+        self.previous_frame_matrices.reserve(local.len());
+        self.local_matrices.reserve(local.len());
+        self.previous_local_matrices.reserve(local.len());
+        self.model_matrices.reserve(local.len());
         std::mem::swap(&mut self.matrices, &mut self.previous_frame_matrices);
         std::mem::swap(&mut self.local_matrices, &mut self.previous_local_matrices);
         self.local_matrices.clear();
         self.local_matrices.extend_from_slice(local);
-        let mut model = vec![None; local.len()];
+        self.model_matrices.resize(local.len(), None);
+        self.model_matrices.fill(None);
         for index in 0..local.len() {
-            resolve_model_transform(index, parents, local, &mut model)
+            resolve_model_transform(index, parents, local, &mut self.model_matrices)
                 .expect("baked bone hierarchy should be valid");
         }
         let model_scale = FixedMat4 {
@@ -159,10 +177,12 @@ impl FighterBoneMatrices {
                 [FGi32::ZERO, FGi32::ZERO, FGi32::ZERO, FGi32::ONE],
             ],
         };
-        self.matrices = model
-            .into_iter()
-            .map(|matrix| model_scale.mul(matrix.expect("baked bone hierarchy should be valid")))
-            .collect();
+        self.matrices.clear();
+        self.matrices.extend(
+            self.model_matrices.iter().map(|matrix| {
+                model_scale.mul(matrix.expect("baked bone hierarchy should be valid"))
+            }),
+        );
     }
 }
 

src/fighter/collision.rs

@@ -50,11 +50,13 @@ pub fn air_collide_with_stage(
         translation.0 + ecb.get_bottom_point(),
     );
 
-    let mut intersect_results = vec![];
-
-    for (poly_idx, poly) in stage_collision.stage_polys.iter().enumerate() {
-        if let Some(intersect_result) = poly.intersect_ray(ray_segment) {
-            intersect_results.push((
+    stage_collision
+        .stage_polys
+        .iter()
+        .enumerate()
+        .filter_map(|(poly_idx, poly)| {
+            poly.intersect_ray(ray_segment).map(|intersect_result| {
+                (
                     AirCollisionWithStageResult {
                         line_id: {
                             StageLineID {
@@ -68,13 +70,9 @@ pub fn air_collide_with_stage(
                     intersect_result
                         .position
                         .distance_squared(ray_segment.point2()),
-            ));
-        }
-    }
-    intersect_results.sort_by(|(_, a), (_, b)| a.cmp(b));
-
-    intersect_results
-        .iter()
-        .last()
-        .map(|(val, _)| val.to_owned().clone())
+                )
+            })
+        })
+        .max_by(|(_, a), (_, b)| a.cmp(b))
+        .map(|(result, _)| result)
 }

src/input/gamecube/poll.rs

@@ -1,6 +1,8 @@
 use std::panic::{self, AssertUnwindSafe};
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex};
+use std::thread::JoinHandle;
+use std::time::{Duration, Instant};
 
 use bevy::prelude::*;
 use gc_adapter_neo::{Controller, GcAdapter};
@@ -55,10 +57,11 @@ impl GcPortState {
 /// Shared, `Send + Sync` handle to the latest snapshot from the poll
 /// thread. Safe to store as an ordinary [`Resource`] (no `NonSend` needed)
 /// because the `GcAdapter` itself never leaves its thread.
-#[derive(Resource, Clone)]
+#[derive(Resource)]
 pub struct GcAdapterSnapshot {
     ports: Arc<Mutex<[GcPortState; 4]>>,
     shutdown: Arc<AtomicBool>,
+    poll_thread: Option<JoinHandle<()>>,
 }
 
 impl GcAdapterSnapshot {
@@ -69,13 +72,37 @@ impl GcAdapterSnapshot {
 
 impl Drop for GcAdapterSnapshot {
     fn drop(&mut self) {
-        // Only actually signals shutdown once the last clone (this resource
-        // is never cloned in practice, but be defensive) is dropped.
-        if Arc::strong_count(&self.shutdown) <= 1 {
-            self.shutdown.store(true, Ordering::Relaxed);
+        self.shutdown.store(true, Ordering::Release);
+
+        if let Some(poll_thread) = self.poll_thread.take() {
+            if let Err(payload) = poll_thread.join() {
+                error!(
+                    "GameCube Controller Adapter poll thread panicked during shutdown: {payload:?}"
+                );
             }
         }
     }
+}
+
+const INITIAL_ERROR_BACKOFF: Duration = Duration::from_millis(1);
+const MAX_ERROR_BACKOFF: Duration = Duration::from_millis(100);
+
+fn next_error_backoff(backoff: Duration) -> Duration {
+    backoff.saturating_mul(2).min(MAX_ERROR_BACKOFF)
+}
+
+/// Wait for a retry while still allowing the owner to shut the poll thread down promptly.
+fn wait_for_retry(shutdown: &AtomicBool, delay: Duration) -> bool {
+    let deadline = Instant::now() + delay;
+    while !shutdown.load(Ordering::Acquire) {
+        let remaining = deadline.saturating_duration_since(Instant::now());
+        if remaining.is_zero() {
+            return true;
+        }
+        std::thread::sleep(remaining.min(Duration::from_millis(10)));
+    }
+    false
+}
 
 /// Connects to the first GameCube adapter found on the USB bus and starts
 /// polling it on a dedicated thread. Returns `None` (after logging a
@@ -94,7 +121,7 @@ pub fn spawn_poll_thread() -> Result<GcAdapterSnapshot, gc_adapter_neo::UsbError
 
     let thread_ports = ports.clone();
     let thread_shutdown = shutdown.clone();
-    std::thread::Builder::new()
+    let poll_thread = std::thread::Builder::new()
         .name("gc-adapter-poll".into())
         .spawn(move || {
             // Flush whatever the adapter had buffered before we started
@@ -107,17 +134,27 @@ pub fn spawn_poll_thread() -> Result<GcAdapterSnapshot, gc_adapter_neo::UsbError
             let mut rate_window_start = std::time::Instant::now();
             #[cfg(debug_assertions)]
             let mut rate_window_count: u32 = 0;
+            let mut error_backoff = INITIAL_ERROR_BACKOFF;
 
-            while !thread_shutdown.load(Ordering::Relaxed) {
+            while !thread_shutdown.load(Ordering::Acquire) {
                 let result = panic::catch_unwind(AssertUnwindSafe(|| adapter.read_controllers()));
 
                 let controllers = match result {
-                    Ok(Ok(controllers)) => controllers,
+                    Ok(Ok(controllers)) => {
+                        error_backoff = INITIAL_ERROR_BACKOFF;
+                        controllers
+                    }
                     // Ignore this, for some reason we get a bunch of these when we start reading
                     Ok(Err(
                         gc_adapter_neo::AdapterError::Parse(_)
                         | gc_adapter_neo::AdapterError::ShortRead(_),
-                    )) => continue,
+                    )) => {
+                        if !wait_for_retry(&thread_shutdown, error_backoff) {
+                            break;
+                        }
+                        error_backoff = next_error_backoff(error_backoff);
+                        continue;
+                    }
                     Ok(Err(gc_adapter_neo::AdapterError::Usb(err))) => {
                         error!(
                             "GameCube Controller Adapter USB read failed ({err:?}); stopping \
@@ -160,5 +197,32 @@ pub fn spawn_poll_thread() -> Result<GcAdapterSnapshot, gc_adapter_neo::UsbError
         })
         .expect("failed to spawn gc-adapter poll thread");
 
-    Ok(GcAdapterSnapshot { ports, shutdown })
+    Ok(GcAdapterSnapshot {
+        ports,
+        shutdown,
+        poll_thread: Some(poll_thread),
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn error_backoff_is_capped() {
+        let mut backoff = INITIAL_ERROR_BACKOFF;
+        for _ in 0..16 {
+            backoff = next_error_backoff(backoff);
+        }
+
+        assert_eq!(backoff, MAX_ERROR_BACKOFF);
+        assert_eq!(next_error_backoff(MAX_ERROR_BACKOFF), MAX_ERROR_BACKOFF);
+    }
+
+    #[test]
+    fn retry_wait_stops_when_shutdown_is_requested() {
+        let shutdown = AtomicBool::new(true);
+
+        assert!(!wait_for_retry(&shutdown, Duration::from_secs(1)));
+    }
 }

src/menus/character_select/mod.rs

@@ -241,7 +241,7 @@ pub fn copy_cursor_transform_to_token(
     character_boxes: Query<(&CharacterBox, &ComputedNode, &UiGlobalTransform)>,
     match_config: Res<MenuMatchConfig>,
     cursors: Query<&UiGlobalTransform, With<FGMenuCursor>>,
-    cam: Single<&Camera, With<IsDefaultUiCamera>>,
+    cam: Single<&Camera>,
     ui_scale: Res<UiScale>,
 ) -> Result {
     let camera = cam.into_inner();

src/menus/cursor.rs

@@ -181,7 +181,7 @@ pub fn cursor_input(
 }
 
 pub fn update_cursor_transform(
-    camera: Single<&Camera, With<IsDefaultUiCamera>>,
+    camera: Single<&Camera>,
     query: Query<(&mut Node, &PointerLocation), With<FGMenuCursor>>,
     ui_scale: Res<UiScale>,
 ) {

src/menus/mod.rs

@@ -25,6 +25,8 @@ pub mod style;
 
 #[derive(Component, Clone, Default)]
 pub struct MenuMarker {}
+#[derive(Component, Clone, Default)]
+pub struct MenuCameraMarker {}
 
 pub struct MenuPlugin;
 
@@ -38,6 +40,7 @@ pub fn wrap_menu(menu: impl Scene) -> impl Scene {
     bsn! {
         #MenuRoot
         MenuMarker
+        Transform
         Node {
             width: percent(100),
             height: percent(100),
@@ -46,6 +49,11 @@ pub fn wrap_menu(menu: impl Scene) -> impl Scene {
             flex_direction: FlexDirection::Column,
         }
         Children [
+            (
+                #MenuCamera
+                Camera
+                Camera2d
+            ),
             (
                 #MenuContainer
                 Node {
@@ -65,15 +73,18 @@ pub fn wrap_menu(menu: impl Scene) -> impl Scene {
 
 pub fn despawn_menu(
     existing_menu: Option<Single<Entity, With<MenuMarker>>>,
+    existing_menu_camera: Option<Single<Entity, With<MenuCameraMarker>>>,
     mut commands: Commands,
 ) {
     if let Some(entity) = existing_menu {
         commands
             .entity(entity.into_inner())
-            .remove::<Camera2d>()
-            .remove::<Camera>()
             .despawn();
     }
+
+    if let Some(menu_cam) = existing_menu_camera {
+        commands.entity(*menu_cam).despawn();
+    }
 }
 
 pub fn spawn_menu(
@@ -84,8 +95,6 @@ pub fn spawn_menu(
     if let Some(entity) = existing_menu {
         commands
             .entity(entity.into_inner())
-            .remove::<Camera2d>()
-            .remove::<Camera>()
             .despawn();
     }
     commands.queue_spawn_scene(wrap_menu(menu));
@@ -113,16 +122,7 @@ impl Plugin for MenuPlugin {
     fn build(&self, app: &mut App) {
         app.add_systems(
             OnEnter(AppState::MainMenu),
-            (build_menu::<MainMenu>, |mut commands: Commands| {
-                commands.spawn((Camera2d, IsDefaultUiCamera));
-                commands.spawn((
-                    Camera2d,
-                    Camera {
-                        order: 1,
-                        ..default()
-                    },
-                ));
-            }),
+            build_menu::<MainMenu>,
         )
         .add_message::<character_select::PlayerSlotAssigned>()
         .init_resource::<navigation::UINavigationActionState>()

src/replay.rs

@@ -152,6 +152,20 @@ fn validate(replay: &Replay) -> Result<(), String> {
     {
         return Err("replay frames must be strictly ordered".into());
     }
+    if replay
+        .frames
+        .windows(2)
+        .any(|frames| frames[0].frame.checked_add(1) != Some(frames[1].frame))
+    {
+        return Err("replay frames must be contiguous".into());
+    }
+    if replay
+        .checksums
+        .windows(2)
+        .any(|checksums| checksums[0].frame >= checksums[1].frame)
+    {
+        return Err("replay checksums must be strictly ordered".into());
+    }
     if replay
         .frames
         .iter()
@@ -173,6 +187,21 @@ impl Replay {
         handles.sort_unstable();
         handles != (0..handles.len()).collect::<Vec<_>>()
     }
+
+    fn frame(&self, frame: i32) -> Option<&ReplayFrame> {
+        let first_frame = self.frames.first()?.frame;
+        let index = frame.checked_sub(first_frame)? as usize;
+        self.frames
+            .get(index)
+            .filter(|recorded| recorded.frame == frame)
+    }
+
+    fn checksum(&self, frame: i32) -> Option<u128> {
+        self.checksums
+            .binary_search_by_key(&frame, |checksum| checksum.frame)
+            .ok()
+            .map(|index| self.checksums[index].checksum)
+    }
 }
 
 fn start_replay(mut commands: Commands, args: Res<Args>, loaded: Option<Res<LoadedReplay>>) {
@@ -210,11 +239,7 @@ fn replay_inputs(
                 .insert(frame.0, inputs.iter().map(|(input, _)| *input).collect());
         }
         ReplayMode::Playback { replay, mismatch } if !*mismatch => {
-            let Some(recorded) = replay
-                .frames
-                .iter()
-                .find(|recorded| recorded.frame == frame.0)
-            else {
+            let Some(recorded) = replay.frame(frame.0) else {
                 error!("Replay has no input for frame {}", frame.0);
                 *mismatch = true;
                 return;
@@ -235,14 +260,10 @@ fn record_checksum(
     let Some(mut runtime) = runtime else { return };
     if matches!(&runtime.mode, ReplayMode::Record { .. }) {
         runtime.checksums.insert(frame.0, checksum.0);
-    } else if let ReplayMode::Playback { replay, mismatch } = &mut runtime.mode {
-        if let Some(expected) = replay
-            .checksums
-            .iter()
-            .find(|value| value.frame == frame.0)
-            .map(|value| value.checksum)
+    } else if let ReplayMode::Playback { replay, mismatch } = &mut runtime.mode
+        && let Some(expected) = replay.checksum(frame.0)
+        && expected != checksum.0
     {
-            if expected != checksum.0 {
         error!(
             "Replay desync at frame {}: expected {:X}, got {:X}",
             frame.0, expected, checksum.0
@@ -250,8 +271,6 @@ fn record_checksum(
         *mismatch = true;
     }
 }
-    }
-}
 
 fn stop_recording(
     mut commands: Commands,
@@ -407,4 +426,41 @@ mod tests {
             "unsupported replay version 1"
         );
     }
+
+    #[test]
+    fn playback_lookups_use_frame_offsets_and_support_sparse_checksums() {
+        let mut replay = sample();
+        replay.frames[0].frame = 10;
+        replay.frames.push(ReplayFrame {
+            frame: 11,
+            inputs: replay.frames[0].inputs.clone(),
+        });
+        replay.checksums.push(ReplayChecksum {
+            frame: 11,
+            checksum: 84,
+        });
+        replay.checksums[0].frame = 10;
+        validate(&replay).unwrap();
+
+        assert_eq!(replay.frame(10).unwrap().frame, 10);
+        assert_eq!(replay.frame(11).unwrap().frame, 11);
+        assert!(replay.frame(9).is_none());
+        assert_eq!(replay.checksum(10), Some(42));
+        assert_eq!(replay.checksum(11), Some(84));
+        assert_eq!(replay.checksum(12), None);
+    }
+
+    #[test]
+    fn noncontiguous_input_frames_are_rejected() {
+        let mut replay = sample();
+        replay.frames.push(ReplayFrame {
+            frame: 3,
+            inputs: replay.frames[0].inputs.clone(),
+        });
+
+        assert_eq!(
+            validate(&replay).unwrap_err(),
+            "replay frames must be contiguous"
+        );
+    }
 }

tools/lldb_fixed.py

@@ -0,0 +1,123 @@
+"""LLDB summaries for Rust's `fixed` crate.
+
+Load this file from LLDB with:
+
+    command script import /path/to/shinespark/tools/lldb_fixed.py
+
+The implementation does not use floating-point arithmetic, so displayed values
+are exact even for FixedI128/FixedU128 values.
+"""
+
+import re
+
+try:
+    import lldb
+except ImportError:
+    # Keep the pure parsing and formatting helpers testable without LLDB.
+    lldb = None
+
+
+_FIXED_TYPE_RE = re.compile(r"(?:^|::)Fixed([IU])(8|16|32|64|128)<(.+)>$")
+_DIRECT_TYPENUM_RE = re.compile(r"(?:^|::)U(\d+)$")
+_TYPENUM_BIT_RE = re.compile(r"(?:^|::)B([01])(?=\s*[,>])")
+
+
+def parse_fixed_type(type_name):
+    """Return (signed, storage_bits, fractional_bits), or None."""
+    if not type_name:
+        return None
+
+    match = _FIXED_TYPE_RE.search(type_name.replace(" ", ""))
+    if match is None:
+        return None
+
+    signed = match.group(1) == "I"
+    storage_bits = int(match.group(2))
+    fractional_type = match.group(3)
+
+    direct = _DIRECT_TYPENUM_RE.search(fractional_type)
+    if direct is not None:
+        fractional_bits = int(direct.group(1))
+    else:
+        # typenum represents UInt<N, B> as a binary tree. Its textual Rust
+        # type lists the bits from most significant to least significant.
+        digits = _TYPENUM_BIT_RE.findall(fractional_type)
+        if not digits:
+            return None
+        fractional_bits = int("".join(digits), 2)
+
+    if fractional_bits > storage_bits:
+        return None
+    return signed, storage_bits, fractional_bits
+
+
+def normalize_bits(raw_bits, signed, storage_bits):
+    """Interpret a possibly unsigned LLDB integer using the fixed type's width."""
+    mask = (1 << storage_bits) - 1
+    raw_bits &= mask
+    if signed and raw_bits >= 1 << (storage_bits - 1):
+        raw_bits -= 1 << storage_bits
+    return raw_bits
+
+
+def format_fixed(raw_bits, fractional_bits):
+    """Format a scaled integer exactly as a decimal string."""
+    if fractional_bits == 0:
+        return str(raw_bits)
+
+    negative = raw_bits < 0
+    magnitude = -raw_bits if negative else raw_bits
+    whole = magnitude >> fractional_bits
+    remainder = magnitude & ((1 << fractional_bits) - 1)
+
+    if remainder == 0:
+        result = str(whole)
+    else:
+        # remainder / 2^n == (remainder * 5^n) / 10^n, which gives a finite,
+        # exact decimal representation without converting through a float.
+        decimal = str(remainder * 5**fractional_bits).zfill(fractional_bits)
+        result = f"{whole}.{decimal.rstrip('0')}"
+
+    return f"-{result}" if negative else result
+
+
+def _parse_lldb_integer(value):
+    text = value.GetValue()
+    if text is not None:
+        try:
+            return int(text, 0)
+        except ValueError:
+            pass
+
+    # GetValueAsUnsigned is also useful on LLDB versions that do not render
+    # primitive values through GetValue. It is sufficient for all <= 64-bit
+    # fixed types; current LLDB versions render i128/u128 through GetValue.
+    return value.GetValueAsUnsigned()
+
+
+def fixed_summary(value, _internal_dict):
+    layout = parse_fixed_type(value.GetTypeName())
+    if layout is None:
+        return None
+
+    signed, storage_bits, fractional_bits = layout
+    bits = value.GetChildMemberWithName("bits")
+    if not bits.IsValid():
+        return None
+
+    raw_bits = _parse_lldb_integer(bits)
+    raw_bits = normalize_bits(raw_bits, signed, storage_bits)
+    return format_fixed(raw_bits, fractional_bits)
+
+
+def __lldb_init_module(debugger, _internal_dict):
+    # LLDB's type-name regex sees the concrete fixed type rather than project
+    # aliases such as FGi32 and FGWide.
+    debugger.HandleCommand(
+        "type summary add --python-function lldb_fixed.fixed_summary "
+        "--category Shinespark --regex "
+        "'^fixed::Fixed(I|U)(8|16|32|64|128)<.+>$'"
+    )
+    # A dedicated category makes the formatter work even when CodeLLDB has not
+    # enabled rustc's standard `Rust` formatter category yet.
+    debugger.HandleCommand("type category enable Shinespark")

tools/test_lldb_fixed.py

@@ -0,0 +1,58 @@
+import unittest
+
+import lldb_fixed
+
+
+class ParseFixedTypeTests(unittest.TestCase):
+    def test_direct_typenum_alias(self):
+        self.assertEqual(
+            lldb_fixed.parse_fixed_type("fixed::FixedI32<typenum::uint::U16>"),
+            (True, 32, 16),
+        )
+
+    def test_expanded_typenum(self):
+        type_name = (
+            "fixed::FixedI32<"
+            "typenum::uint::UInt<"
+            "typenum::uint::UInt<"
+            "typenum::uint::UInt<"
+            "typenum::uint::UInt<"
+            "typenum::uint::UInt<typenum::uint::UTerm, typenum::bit::B1>, "
+            "typenum::bit::B0>, typenum::bit::B0>, typenum::bit::B0>, "
+            "typenum::bit::B0>>"
+        )
+        self.assertEqual(lldb_fixed.parse_fixed_type(type_name), (True, 32, 16))
+
+    def test_unsigned_type(self):
+        self.assertEqual(
+            lldb_fixed.parse_fixed_type("fixed::FixedU64<typenum::uint::U24>"),
+            (False, 64, 24),
+        )
+
+    def test_unrelated_type(self):
+        self.assertIsNone(lldb_fixed.parse_fixed_type("core::primitive::i32"))
+
+
+class FormatFixedTests(unittest.TestCase):
+    def test_q16_16(self):
+        self.assertEqual(lldb_fixed.format_fixed(3 << 15, 16), "1.5")
+        self.assertEqual(lldb_fixed.format_fixed(-(3 << 15), 16), "-1.5")
+        self.assertEqual(lldb_fixed.format_fixed(1, 16), "0.0000152587890625")
+
+    def test_integer_value_has_no_decimal_suffix(self):
+        self.assertEqual(lldb_fixed.format_fixed(12 << 16, 16), "12")
+
+    def test_q96_32(self):
+        raw = (1 << 100) + (1 << 31)
+        self.assertEqual(
+            lldb_fixed.format_fixed(raw, 32),
+            "295147905179352825856.5",
+        )
+
+    def test_twos_complement_normalization(self):
+        self.assertEqual(lldb_fixed.normalize_bits(0xFFFF8000, True, 32), -32768)
+        self.assertEqual(lldb_fixed.normalize_bits(0xFFFF8000, False, 32), 0xFFFF8000)
+
+
+if __name__ == "__main__":
+    unittest.main()