How I build in Rust — and why.

/// Generate polar diagram as SVG string
#[uniffi::export]
pub fn generate_polar_svg(ldt: &Eulumdat, width: f64, height: f64, theme: SvgThemeType) -> String {
    let core_ldt = to_core_eulumdat(ldt);
    let polar = PolarDiagram::from_eulumdat(&core_ldt);
    polar.to_svg(width, height, &theme.to_core())
}

#[uniffi::export] generates the Swift and Kotlin side; the record is converted to the core type first.

fn gldf_to_xml(arguments: &mut [ZVal]) -> phper::Result<String> {
    let path = arguments[0].expect_z_str()?.to_str()?;
    let loaded: GldfProduct = GldfProduct::load_gldf(path).unwrap();
    Ok(loaded.to_xml().unwrap())
}
⋯
#[php_get_module]
pub fn get_module() -> Module {
    // New `Module` with extension info.
    let mut module = Module::new(
        env!("CARGO_CRATE_NAME"),
        env!("CARGO_PKG_VERSION"),
        env!("CARGO_PKG_AUTHORS"),
    );
⋯
    module
        .add_function("gldf_to_xml", gldf_to_xml)
        .argument(Argument::by_val("path"));
    module
        .add_function("gldf_to_json", gldf_to_json)
        .argument(Argument::by_val("path"));
⋯
    module
}

#[php_get_module] generates the extension's C entry point; each PHP function is a few lines over the gldf-rs API.

#[no_mangle]
pub unsafe extern "C" fn eulumdat_polar_svg(
    handle: *const EulumdatHandle,
    width: f64,
    height: f64,
    theme: i32,
) -> *mut c_char {
    if handle.is_null() {
        return ptr::null_mut();
    }

    let ldt = &(*handle).inner;
    let svg_theme = if theme == 1 {
        SvgTheme::dark()
    } else {
        SvgTheme::light()
    };

    let polar = PolarDiagram::from_eulumdat(ldt);
    let svg = polar.to_svg(width, height, &svg_theme);
    string_to_c(&svg)
}

Plain C types for the Cangjie side: a null check, an opaque handle, a string the caller frees.

/// Generate SVG from file content
fn generate_svg(content: &str, width: f64, height: f64) -> Result<String, String> {
    // Try LDT first, then IES
    let ldt = eulumdat::Eulumdat::parse(content)
        .or_else(|_| eulumdat::IesParser::parse(content))
        .map_err(|e| e.to_string())?;

    let polar = eulumdat::diagram::PolarDiagram::from_eulumdat(&ldt);
    let theme = eulumdat::diagram::SvgTheme::light();
    Ok(polar.to_svg(width, height, &theme))
}

The preview pane tries LDT first, then IES — and draws with the same two calls.

fn apply_json(&mut self, action_json: &str) -> PyResult<()> {
    let action: gldf_rs_editor::GldfAction = serde_json::from_str(action_json)
        .map_err(|e| PyValueError::new_err(format!("parse action: {}", e)))?;
    self.inner.apply(action);
    if let Some(err) = self.inner.last_error.as_deref() {
        return Err(PyValueError::new_err(err.to_string()));
    }
    Ok(())
}

Python sends JSON, Rust parses and applies — the reducer's error becomes a ValueError.

#[wasm_bindgen::prelude::wasm_bindgen(js_name = gldf_apply_action_json)]
pub fn apply_action_json(json: &str) -> String {
    let action: GldfAction = match serde_json::from_str(json) {
        Ok(a) => a,
        Err(e) => return format!("parse: {}", e),
    };
    let mut result = String::new();
    GLDF_CTX.with(|cell| {
        match cell.get() {
            Some(ctx) => {
                ctx.update(|s| {
                    s.apply(action);
                    if let Some(err) = &s.last_error {
                        result = format!("apply: {}", err);
                    }
                });
            }
            None => result = "GldfContext not yet initialised".to_string(),
        }
    });
    result
}

The same parse-and-apply, inside a Leptos signal update so the UI re-renders.

//! UI translation language — picked from the viewer's chrome, independent
//! of the document's locale. Persisted via a frontend-supplied store so
//! the state crate stays free of browser- and filesystem-specific calls.
⋯
/// Storage adapter for the user's UI language preference. The WASM
/// frontend persists to `localStorage`; the TUI persists to a config file
/// under `$XDG_CONFIG_HOME`; tests use [`NullLangStore`] which does
/// nothing.
pub trait UiLanguageStore: Send + Sync {
    /// Read the last-chosen UI language, if any.
    fn load(&self) -> Option<String>;
    /// Persist the chosen UI language.
    fn store(&self, lang: &str);
}

localStorage, a config file or nothing: the front end decides, the state crate stays pure.

/// Rewrite rc.4-canonical spellings back to their rc.3 typo'd forms.
///
/// The rc.4 schema kept both spellings valid via `<xs:choice>` wrappers
/// and deprecated-form enum aliases, so this rewrite is needed only for
/// consumers that haven't bumped to rc.4 yet. Pure string replacement —
/// the substrings we replace don't appear anywhere except as element
/// names (`<RatedChromaticityCoordinateValues>` open/close tags) and as
/// the literal enum values inside `<Cie97LampType>...</Cie97LampType>`
/// element bodies, so global replace is safe.
fn downconvert_rc4_to_rc3(xml: &str) -> String {
    xml
        // Element name (rc.4 only added this; rc.3 only knew the typo'd form)
        .replace(
            "RatedChromaticityCoordinateValues",
            "RatedChromacityCoordinateValues",
        )
        // Cie97LampType enum values
        .replace("Fluorescent Triphosphor", "Flourescent Triphosphor")
        .replace("Fluorescent Halophosphate", "Flourescent Halophosphate")
}

A plain string rewrite — and the doc comment says why it is safe.

/// True for the bit patterns vendors use to mean "not known".
///
/// Normally that is a NaN written little-endian like every other field
/// (ams OSRAM: `01 00 C0 7F`). Lumileds LUXEON files instead write the
/// sentinel **byte-swapped** (`7F 80 00 01`), which read little-endian is not
/// a NaN at all but the denormal 2.36e-38 — small enough to look like a real
/// measurement and poison anything derived from it. The ray data in those same
/// files is ordinary little-endian, so this is a quirk of the sentinel only.
///
/// Matched exactly, never by bit class: a value is "unknown" only if it is a
/// real NaN or precisely that one swapped pattern.
fn is_unknown(v: f32) -> bool {
    // Exact patterns only. An earlier version asked "would the swapped bytes
    // be a NaN?", which also matched ~0.4 % of ordinary positive values and
    // would have silently zeroed real measurements.
    const BYTE_SWAPPED_SENTINEL: u32 = 0x0100_807F;
    v.is_nan() || v.to_bits() == BYTE_SWAPPED_SENTINEL
}

One exact bit pattern, no clever classification — the comment records the version that was wrong.

/// Zero-copy view over a ray block.
#[derive(Clone, Debug)]
pub struct RayView<'a> {
    layout: RayLayout,
    data: &'a [u8],
    len: usize,
}
⋯
    /// Raw bytes of record `i`.
    pub fn raw(&self, i: usize) -> Option<&'a [u8]> {
        if i >= self.len {
            return None;
        }
        let s = i * self.layout.record_size;
        Some(&self.data[s..s + self.layout.record_size])
    }

    pub fn get(&self, i: usize) -> Option<Ray> {
        self.raw(i).map(|r| self.layout.decode(r))
    }
⋯
    /// The whole block as bytes (for uploading to a GPU buffer as-is).
    pub fn bytes(&self) -> &'a [u8] {
        &self.data[..self.len * self.layout.record_size]
    }

A view borrows the file's bytes; records are sliced on demand, and the GPU gets the block as-is.

/// The city image (`make_image`) sits in the last flash sectors, outside both program slots, so a
/// program update leaves it alone: flash it once with
/// `probe-rs download --binary-format bin --base-address 0x080C0000 geodb.fw`.
const IMAGE_ADDR: usize = 0x080C_0000;
const IMAGE_MAX: usize = 0x14_0000;
⋯
/// The image in flash, when it parses (its header names the length); else the placeholder.
fn flash_image() -> &'static [u8] {
    if !ota::UPDATING_IMAGE.load(core::sync::atomic::Ordering::Relaxed) {
        let len = unsafe { ((IMAGE_ADDR + 60) as *const u32).read_volatile() } as usize;
        let bytes =
            unsafe { core::slice::from_raw_parts(IMAGE_ADDR as *const u8, len.min(IMAGE_MAX)) };
        if FwImage::parse(bytes).is_ok() {
            return bytes;
        }
    }
    PLACEHOLDER
}

The image is read in place from flash — and only used if it parses.

//! The board's screen in the browser: `geodb-fw-core` on the firmware image
//! (`geodb.fw`), the same `ui::draw` the STM32F769I-DISCO runs, and the
//! board's main loop (touch, flick, spin, quick and full redraws).
//!
//! No wasm-bindgen: a handful of plain exports, driven by `web/index.html`.
⋯
/// A buffer of `len` bytes for the image; the page writes `geodb.fw` into it.
#[no_mangle]
pub extern "C" fn image_alloc(len: usize) -> *mut u8 {
    let buf: &'static mut [u8] = Box::leak(vec![0u8; len].into_boxed_slice());
    let ptr = buf.as_mut_ptr();
    IMAGE.with(|i| *i.borrow_mut() = Some(buf));
    ptr
}
⋯
/// Parses the image and draws the first screen: the number of cities, or -1
/// (no image), -2 (not a geodb firmware image), -3 (other version), -4 (damaged).
#[no_mangle]
pub extern "C" fn start() -> i32 {
    let Some(bytes) = IMAGE.with(|i| i.borrow_mut().take()) else {
        return -1;
    };
    let bytes: &'static [u8] = bytes;
    let img = match FwImage::parse(bytes) {
        Ok(img) => img,
        Err(geodb_fw_core::ImageError::Magic) => return -2,
        Err(geodb_fw_core::ImageError::Version) => return -3,
        Err(geodb_fw_core::ImageError::Layout) => return -4,
    };

The page writes geodb.fw into a leaked buffer; from there it is the same FwImage::parse.

/// Calls `f(city, haversine)` for every city within `radius_km` of
/// (lat, lon) (degrees), in geoid order; the haversine sin²(d / 2R)
/// orders like the distance. Returns how many cities it tested.
pub fn radius_index(
    &self,
    lat: f32,
    lon: f32,
    radius_km: f32,
    mut f: impl FnMut(u32, f32),
) -> usize {
    let limit = hav_of_km(radius_km);
    let cos_q = cos(lat * DEG_TO_RAD);
    let half = 0.5 * DEG_TO_RAD;
    let rg = crate::geo::ranges(lat, lon, radius_km);
    let mut tested = 0;
    for &(a, b) in rg.as_slice() {
        let (lo, hi) = (self.lower_bound(a), self.upper_bound(b));
        for i in lo..hi {
            tested += 1;
            let (la, lo) = to_deg(self.geoid(i));
            let s_lat = sin((la - lat) * half);
            let s_lon = sin((lo - lon) * half);
            let h = s_lat * s_lat + cos_q * cos(la * DEG_TO_RAD) * s_lon * s_lon;
            if h <= limit {
                f(i as u32, h);
            }
        }
    }
    tested
}

Ranges of the sort order, two binary searches each, then the haversine.

fn push_segments(&self, out: &mut Vec<[u32; 4]>, q: u32, center: u64, radius_km: f64) {
    for (start, end) in self.index_ranges(center, radius_km) {
        let mut at = start;
        while at < end {
            let len = (end - at).min(WORKGROUP);
            out.push([q, at, len, 0]);
            at += len;
        }
    }
}

The same ranges, cut into segments that fit one workgroup.

// One query, indexed: workgroup = segment, thread = city of the segment.
@compute @workgroup_size(256)
fn radius_single_seg(
    @builtin(workgroup_id) wid: vec3<u32>,
    @builtin(local_invocation_index) li: u32,
) {
    let s = wid.y * GRID + wid.x;
    if (s >= p.nseg) {
        return;
    }
    let seg = segments[s];
    if (li >= seg.z) {
        return;
    }
    let i = seg.y + li;
    if (hav(split(cities[i]), split(p.center)) <= p.h) {
        let k = atomicAdd(&counters[0], 1u);
        if (k < p.cap) {
            hits[k] = i;
        }
    }
}

Workgroup = segment, thread = city. Hits are appended with one atomic counter.

/// What one block of the globe needs from the view, computed once for a
/// tilt and zoom: the texture row and the longitude offset (fixed point),
/// and the shading. Turning the globe (spinning) changes none of it.
#[derive(Clone, Copy)]
pub struct LutCell {
    /// Longitude offset from the view centre, in texels x 256.
    du: i32,
    /// Texture row x 32 ([`EMPTY`] = the block is outside the disc; 1024 rows still fit a u16).
    v: u16,
    /// Brightness x 128.
    shade: u8,
    /// Strength of the blue rim, 0..255.
    rim: u8,
}
⋯
                let u = (centre + c.du).rem_euclid(wrap);
                let rgb = sample_fixed(tex, u, i32::from(c.v), rows);
                let (shade, rim) = (u32::from(c.shade), u32::from(c.rim));
                let mut out = [0u8; 3];
                for k in 0..3 {
                    out[k] = (((rgb[k] * shade) >> 7) + ((GLOW[k] * rim) >> 8)).min(255) as u8;
                }
                let color = rgb565(out[0], out[1], out[2]);

Eight bytes per block, computed once per view; the per-frame loop is shifts and multiplies.

// A name's folded form, and where a transliteration pads syllables
// with spaces also the form typed without them ("Dong Jing" and
// "dongjing" for 東京).
let add = |f: &mut Vec<String>, s: &str| {
    f.push(folder.fold(s));
    f.extend(folder.compact(s));
};

Folded, and compacted without spaces: “Dong Jing” and “dongjing”.

let gs = gateway::gears(p, &st.ids);
let mut out = Out::default();
let dali_topic = format!("plantworks/{GATEWAY_ID}/dali");
{
    let ctx = Ctx::new(p, &gs, st.ids);
    if msg.topic == dali_topic {
        // raw bus access from the console: {"fwd":[a,d]} or {"evt":[b0,b1,b2]}
        let v: serde_json::Value = serde_json::from_str(&msg.payload).unwrap_or_default();
        let bytes = |k: &str| -> Vec<u8> {
            v.get(k).and_then(|a| a.as_array()).map(|a| a.iter().filter_map(|x| x.as_u64()).map(|x| x as u8).collect()).unwrap_or_default()
        };
        let fwd = bytes("fwd");
        let evt = bytes("evt");
        if fwd.len() == 2 {
            gateway::exec_forward(&ctx, st, &mut out, [fwd[0], fwd[1]]);
        } else if evt.len() == 3 {
            gateway::exec_event_frame(&ctx, st, &mut out, [evt[0], evt[1], evt[2]]);
        } else {
            emit_ack(&msg.topic, false, "dali message needs {\"fwd\":[a,d]} or {\"evt\":[b0,b1,b2]}");
            return;
        }
    } else {
        gateway::exec_mqtt_in(&ctx, st, &mut out, &msg.topic, &msg.payload);
    }
}

Raw frames from the console or MQTT messages: both end in the shared executor.

run_local(&move |ctx, s, out| match c {
    Composed::Fwd(f) => gateway::exec_forward(ctx, s, out, f),
    Composed::Evt(f) => gateway::exec_event_frame(ctx, s, out, f),
});
⋯
run_local(&move |ctx, s, out| gateway::exec_mqtt_in(ctx, s, out, &t, &pl));

The same three calls, from a Leptos view.

/// Address byte of a 16-bit forward frame (Part 102 §7.2):
/// short `0AAAAAAS`, group `100GGGGS`, broadcast `1111111S`; `S` = 1 for a
/// command, 0 for direct arc power (DAPC).
pub fn address_byte(t: Target, command: bool) -> u8 {
    let s = command as u8;
    match t {
        Target::Short(a) => ((a & 0x3F) << 1) | s,
        Target::Group(g) => 0x80 | ((g & 0x0F) << 1) | s,
        Target::Broadcast => 0xFE | s,
    }
}

/// Direct Arc Power Control: set `level` (0 = off, 1..=254, 255 = MASK).
pub fn dapc(t: Target, level: u8) -> [u8; 2] {
    [address_byte(t, false), level]
}

/// Addressed command with an opcode from [`opcode`].
pub fn command(t: Target, op: u8) -> [u8; 2] {
    [address_byte(t, true), op]
}
⋯
/// Logarithmic dimming curve (Part 102 §9.3): level 1 → 0.1 %, 254 → 100 %.
pub fn level_to_percent(level: u8) -> f64 {
    match level {
        0 => 0.0,
        255 => f64::NAN,
        l => 10f64.powf((l as f64 - 1.0) / (253.0 / 3.0) - 1.0),
    }
}

Bit layouts straight from the standard, with the section numbers in the docs.

let mut next_tick = Instant::now() + Duration::from_millis(TICK_MS);
let mut last_ping = Instant::now();
loop {
    let sock = link.sock.as_mut().unwrap();
    match select(sock.read(&mut buf), Timer::at(next_tick)).await {
        Either::First(Ok(0)) => return Err("broker closed the connection"),
        Either::First(Ok(got)) => {
            inbox.extend_from_slice(&buf[..got]);
            while let Some((first, body)) = mqtt::take_packet(&mut inbox) {
                if let Some(p) = mqtt::parse_publish(first, &body) {
                    if let Some(pk) = p.pkid {
                        link.sock.as_mut().unwrap().write_all(&mqtt::puback_packet(pk)).await.map_err(|_| "tcp write")?;
                    }
                    let payload = String::from_utf8_lossy(&p.payload).into_owned();
                    handle(&mut link, gw, &p.topic, &payload).await?;
                }
            }
        }
        Either::First(Err(_)) => return Err("tcp read"),
        Either::Second(()) => {
            next_tick += Duration::from_millis(TICK_MS);
            led_ok.toggle();
            tick(&mut link, gw, net).await?;
            if last_ping.elapsed() >= Duration::from_secs((KEEPALIVE_S / 2) as u64) {
                link.sock.as_mut().unwrap().write_all(&mqtt::pingreq_packet()).await.map_err(|_| "tcp write")?;
                last_ping = Instant::now();
            }
        }
    }
}

select() over a socket read and a deadline: no threads, no drift.

/// Returns the input unchanged (borrowed) when it contains no escape character.
pub fn unescape<'a>(text: &'a str, enc: Encoding) -> Cow<'a, str> {
    let esc = enc.escape as char;
    if !text.contains(esc) {
        return Cow::Borrowed(text);
    }
    let mut out = String::with_capacity(text.len());
    let mut rest = text;
    while let Some(start) = rest.find(esc) {
        out.push_str(&rest[..start]);
        let after = &rest[start + esc.len_utf8()..];
        match after.find(esc) {
            None => {
                out.push_str(&rest[start..]);
                rest = "";
                break;
            }
            Some(end) => {
                let seq = &after[..end];
                match decode_sequence(seq, enc) {
                    Some(s) => out.push_str(&s),
                    None => {
                        out.push(esc);
                        out.push_str(seq);
                        out.push(esc);
                    }
                }
                rest = &after[end + esc.len_utf8()..];
            }
        }
    }
    out.push_str(rest);
    Cow::Owned(out)
}

The common case returns the borrowed input; only real escapes allocate.

    /// `None` when either side is absent.
    pub fn matches(&self) -> Option<bool> {
        Some(self.dicom.as_deref()? == self.hl7.as_deref()?)
    }
⋯
    /// The two keys disagree with each other: both sides carry both a
    /// study UID and an accession number, one pair matches and the other
    /// does not. `None` when they agree or when either key is absent on
    /// either side.
    pub fn key_conflict(&self) -> Option<KeyConflict> {
        match (self.study_uid.matches(), self.accession.matches()) {
            (Some(true), Some(false)) => Some(KeyConflict::AccessionDiffers),
            (Some(false), Some(true)) => Some(KeyConflict::StudyUidDiffers),
            _ => None,
        }
    }
⋯
/// DICOM string values are space-padded to even length and UIDs NUL-padded;
/// HL7 values may carry stray whitespace. Compare after trimming both.
fn clean(v: Option<&str>) -> Option<String> {
    let s = v?.trim_end_matches('\0').trim();
    (!s.is_empty()).then(|| s.to_string())
}

Two Option<bool>s, one match — absent, equal and conflicting stay distinct.

//! Three lookup paths, tried in order; first non-`Other` wins:
//!
//! 1. **Concrete IFC type name** — works for IFC4+ files that use
//!    `IfcCableSegment` / `IfcPipeSegment` / `IfcSpaceHeater` etc.
//! 2. **Defining IFC TypeObject** — IFC2x3 exporters (MagiCAD,
//!    Plancal) leave the instance Name null and attach the
//!    discipline-revealing class on `IfcRelDefinesByType →
//!    IfcDuctSegmentType` etc. The TUI scene module already does
//!    this; the classifier here is the rule it consults.
//! 3. **Instance Name keyword** — Revit-style exports name things
//!    helpfully ("Rectangular Duct", "Pipe Types: Waste", "Troffer
//!    Light…"). Last-resort when neither type-class layer matches.
⋯
pub fn classify_by_type_name(type_class_upper: &str, type_name: Option<&str>) -> Discipline {
    match type_class_upper {
        "IFCDUCTSEGMENTTYPE"
        | "IFCDUCTFITTINGTYPE"
⋯
        | "IFCSPACEHEATERTYPE" => return Discipline::Hvac,
        "IFCPIPESEGMENTTYPE"
⋯
        | "IFCTANKTYPE" => return Discipline::Plumbing,
        "IFCCABLESEGMENTTYPE"
⋯
        | "IFCOUTLETTYPE" => return Discipline::Electrical,
        "IFCLIGHTFIXTURETYPE" | "IFCLAMPTYPE" => return Discipline::Lighting,
        _ => {}
    }
    // Type class wasn't conclusive — try the type object's Name.
    if let Some(n) = type_name {
        return classify_by_name(n);
    }
    Discipline::Other
}

The module doc is the design: three lookups, first non-Other wins.

/// Find the end of an entity (semicolon), handling quoted strings
fn find_entity_end(&mut self) -> Option<usize> {
    let bytes = self.content.as_bytes();
    let mut in_string = false;

    while self.pos < bytes.len() {
        match bytes[self.pos] {
            b'\'' => {
                // Check for escaped quote ''
                if in_string && self.pos + 1 < bytes.len() && bytes[self.pos + 1] == b'\'' {
                    self.pos += 2;
                    continue;
                }
                in_string = !in_string;
            }
            b';' if !in_string => {
                self.pos += 1;
                return Some(self.pos);
            }
            _ => {}
        }
        self.pos += 1;
    }

    None
}

A byte loop that knows about quotes — and about '' inside them.

/// Pretrained u2netp weights, converted to SafeTensors and embedded in the
/// binary. Run `scripts/convert_weights.py` to (re)generate this file.
static WEIGHTS: &[u8] = include_bytes!("../weights/u2netp.safetensors");
⋯
/// Build the model and load the embedded pretrained weights.
pub fn load_model(device: &<Backend as burn::tensor::backend::Backend>::Device) -> U2NetP<Backend> {
    let mut model = U2NetP::<Backend>::new(device);

    let result = model.apply(
        snapshots(),
        None,
        Some(Box::new(PyTorchToBurnAdapter)),
        false,
    );
⋯
    // Every model parameter must have been filled; missing params would mean the
    // remapping is broken and inference would be garbage.
    assert!(
        !result.applied.is_empty() && result.missing.is_empty(),
        "weight load incomplete: {} params missing",
        result.missing.len()
    );

    model
}

include_bytes! puts the model in the binary; the assert keeps a bad mapping from shipping.

// Build a planar CHW f32 buffer with ImageNet normalization.
// Reference divides by max; for 8-bit input max is 255, so /255.
let mut chw = vec![0f32; 3 * n];
for i in 0..n {
    for c in 0..3 {
        let v = rgba[i * 4 + c] as f32 / 255.0;
        chw[c * n + i] = (v - MEAN[c]) / STD[c];
    }
}

let input = Tensor::<Backend, 1>::from_data(
    TensorData::new(chw, [3 * n]),
    &self.device,
)
.reshape([1, 3, size, size]);

// Forward pass → sigmoid saliency map in [0, 1], shape [1,1,H,W].
let mask = model.forward(input);

// Read once (async, GPU-safe) then min-max normalize on the CPU —
// matches the reference `normPRED`. Avoids blocking GPU scalar reads.
let data = mask.into_data_async().await.expect("read mask data");
let values: Vec<f32> = data.to_vec().expect("mask to vec");
⋯
let denom = (max - min).max(1e-8);

values
    .into_iter()
    .map(|v| (((v - min) / denom).clamp(0.0, 1.0) * 255.0 + 0.5) as u8)
    .collect()

RGBA to a normalized CHW tensor, one forward pass, one await.

// Cards and sections return AnyView: erasing the types keeps the page's view type shallow
// (the fully nested type overflows rustc's query depth in release SSR builds).
fn demo_card(d: &'static Demo) -> AnyView {
⋯
    .into_any()
}

AnyView trades a little static dispatch for a view type rustc can still handle in release builds.

// The reel answers at /landing-page/ (canonical) and /landing-page, both without a
// redirect: browsers cache 308s, and an old one pointing the other way would loop.
<Route path=(StaticSegment("landing-page"), StaticSegment("/")) view=ReelPage/>
<Route path=StaticSegment("landing-page") view=ReelPage/>

Two routes, one page, no redirect — learned the hard way from a cached 308.

// Identifiers: keyword, macro, type, function, or plain
if is_ident_start(c) {
    let n = b.iter().take_while(|&&ch| is_ident(ch)).count();
    let word = &rest[..n];
    if lang.keywords().contains(&word) {
        return (Some("kw"), n);
    }
    if lang == Lang::Rust && b.get(n) == Some(&b'!') && b.get(n + 1) != Some(&b'=') {
        return (Some("mc"), n + 1);
    }
    if lang.is_type(word) {
        return (Some("ty"), n);
    }
    if rest[n..].trim_start_matches(' ').starts_with('(') {
        return (Some("fn"), n);
    }
    return (None, n);
}

One pass, no regex: an identifier becomes a keyword, macro, type or function name by looking one token ahead.