cranpose_render_common/

software_text_raster.rs

use ab_glyph::{
    point, Font, FontArc, FontVec, Glyph, GlyphId, OutlinedGlyph, PxScale, ScaleFont, VariableFont,
};
use cranpose_core::hash::default as default_hash;
use cranpose_ui::text::{
    AnnotatedString, FontFamily, FontStyle, FontSynthesis, FontWeight, RangeStyle, RenderString,
    Shadow, SpanStyle, TextDrawStyle, TextMotion, TextShaping, TextStyle,
};
use cranpose_ui::text_layout_result::{GlyphLayout, LineLayout, TextLayoutData, TextLayoutResult};
use cranpose_ui::{TextLinePrefixWidths, TextMeasurer, TextMetrics};
use cranpose_ui_graphics::{Color, ImageBitmap, Rect};
use std::hash::{Hash, Hasher};
use std::rc::Rc;
use std::sync::{Arc, Mutex, MutexGuard};
use tiny_skia::{LineCap, LineJoin, Paint, Path, PathBuilder, Pixmap, Stroke, Transform};

use crate::bounded_lru_cache::BoundedLruCache;
use crate::brush_sampling::{color_to_rgba, sample_brush_rgba};
#[cfg(test)]
use crate::font_layout::layout_line_glyphs;
use crate::font_layout::{
    align_glyph_to_pixel_grid, line_advance_width, pixel_bounds_from_outlined, vertical_metrics,
    GlyphPixelBounds,
};
use crate::gpos_kerning::KernedFont;
#[cfg(feature = "text-hyphenation")]
use crate::text_hyphenation::HyphenationDictionaryError;
use crate::text_hyphenation::HyphenationDictionaryStore;
use crate::Brush;

const COMPOSE_STROKE_MITER_LIMIT: f32 = 4.0;
const SHADOW_SIGMA_SCALE: f32 = 0.57735;
const SHADOW_SIGMA_BIAS: f32 = 0.5;
const MAX_GAUSSIAN_KERNEL_HALF: i32 = 128;
const SOFTWARE_TEXT_GLYPH_METRICS_CACHE_CAPACITY: usize = 8_192;
const SOFTWARE_TEXT_KERN_METRICS_CACHE_CAPACITY: usize = 16_384;
const SOFTWARE_TEXT_PREFIX_WIDTH_CACHE_CAPACITY: usize = 512;
#[cfg(feature = "embedded-default-font")]
#[doc(hidden)]
pub const DEFAULT_SOFTWARE_TEXT_FONT_BYTES: &[u8] = include_bytes!("../assets/NotoSansMerged.ttf");

#[derive(Clone, Copy, Debug, Eq, PartialEq, thiserror::Error)]
pub enum SoftwareTextFontError {
    #[error("invalid software text font bytes")]
    InvalidFont,
    #[error("embedded default font disabled (feature `embedded-default-font` is off)")]
    EmbeddedFontDisabled,
}

#[derive(Clone)]
pub struct SoftwareTextFont {
    font: KernedFont,
    metadata: SoftwareTextFontMetadata,
    score: TextFontScore,
    content_hash: u64,
}

#[derive(Clone)]
struct SoftwareTextFontMetadata {
    families: Arc<[String]>,
    registered_family: Option<FontFamilyKey>,
    weight: FontWeight,
    style: FontStyle,
    ab_glyph_scale_factor: f32,
}

/// Identity an app-supplied face was registered under.
///
/// `FontFamily::FileBacked` and `FontFamily::LoadedTypeface` name a face by its
/// files rather than by a name inside the font, so resolution cannot compare
/// strings from the `name` table. Hashing the `FontFamily` value once at
/// registration and once per resolve keeps the two sides in step without
/// walking path lists on every frame.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
pub struct FontFamilyKey(u64);

impl FontFamilyKey {
    pub fn of(family: &FontFamily) -> Self {
        let mut state = default_hash::new();
        family.hash(&mut state);
        Self(state.finish())
    }
}

impl SoftwareTextFont {
    pub fn from_bytes(bytes: impl Into<Vec<u8>>) -> Result<Self, SoftwareTextFontError> {
        let bytes = bytes.into();
        let mut hasher = default_hash::new();
        bytes.hash(&mut hasher);
        let content_hash = hasher.finish();
        let metadata = software_text_font_metadata(bytes.as_slice());
        let kerning = KernedFont::read_kerning(bytes.as_slice(), &[]);
        let font = FontArc::try_from_vec(bytes).map_err(|_| SoftwareTextFontError::InvalidFont)?;
        let score =
            text_font_score_from_parts(&font, metadata.ab_glyph_scale_factor, metadata.weight);
        Ok(Self {
            font: KernedFont::new(font, kerning),
            metadata,
            score,
            content_hash,
        })
    }

    /// Parse `bytes` as a face an app registered under `family`, declaring
    /// `weight` and `style` for it.
    ///
    /// The declaration wins over the face's own `OS/2` values, the way a
    /// Compose `Font(resId, FontWeight.Medium)` entry does, and a variable face
    /// is instanced on its `wght`/`ital` axes so one file can back a whole
    /// family. That last part is what makes Android's `sans-serif` reachable:
    /// the platform ships a single variable `Roboto-Regular.ttf` and describes
    /// every weight of the family as an axis position on it.
    pub fn from_registered_bytes(
        family: &FontFamily,
        weight: FontWeight,
        style: FontStyle,
        bytes: impl Into<Vec<u8>>,
    ) -> Result<Self, SoftwareTextFontError> {
        let bytes = bytes.into();
        let mut hasher = default_hash::new();
        bytes.hash(&mut hasher);
        let mut metadata = software_text_font_metadata(bytes.as_slice());
        metadata.registered_family = Some(FontFamilyKey::of(family));
        metadata.weight = weight;
        metadata.style = style;

        let mut font =
            FontVec::try_from_vec(bytes).map_err(|_| SoftwareTextFontError::InvalidFont)?;
        // Two instances of one variable file draw different outlines, so the
        // axis values have to reach `content_hash` — it is the glyph atlas key.
        let variations = apply_declared_variations(&mut font, weight, style);
        for (tag, value) in &variations {
            tag.hash(&mut hasher);
            value.to_bits().hash(&mut hasher);
        }
        let content_hash = hasher.finish();

        // Read the kerning at the SAME axis position the outlines were
        // instanced at. Roboto's GPOS pair values carry `VariationIndex`
        // deltas worth up to 136 font units between wght 400 and wght 700, so
        // a table read at the default instance would kern a Medium run as if
        // it were Regular.
        let kerning = KernedFont::read_kerning(font.font_data(), &variations);

        let font = FontArc::from(font);
        let score = text_font_score_from_parts(&font, metadata.ab_glyph_scale_factor, weight);
        Ok(Self {
            font: KernedFont::new(font, kerning),
            metadata,
            score,
            content_hash,
        })
    }

    pub fn family_names(&self) -> &[String] {
        &self.metadata.families
    }

    /// The family an app registered this face under, if any.
    pub fn registered_family(&self) -> Option<FontFamilyKey> {
        self.metadata.registered_family
    }

    pub fn weight(&self) -> FontWeight {
        self.metadata.weight
    }

    pub fn style(&self) -> FontStyle {
        self.metadata.style
    }

    fn ab_glyph_px_size(&self, logical_font_size: f32) -> f32 {
        logical_font_size * self.metadata.ab_glyph_scale_factor
    }

    /// Stable hash of the font binary — cache-key component wherever
    /// rasterized output depends on which font served the run.
    pub fn content_hash(&self) -> u64 {
        self.content_hash
    }
}

pub fn try_default_software_text_font() -> Result<SoftwareTextFont, SoftwareTextFontError> {
    #[cfg(feature = "embedded-default-font")]
    {
        SoftwareTextFont::from_bytes(DEFAULT_SOFTWARE_TEXT_FONT_BYTES.to_vec())
    }
    #[cfg(not(feature = "embedded-default-font"))]
    {
        Err(SoftwareTextFontError::EmbeddedFontDisabled)
    }
}

pub fn default_software_text_font() -> Option<SoftwareTextFont> {
    try_default_software_text_font().ok()
}

#[derive(Clone)]
pub struct SoftwareTextFontSet {
    fonts: Arc<[SoftwareTextFont]>,
    registered_families: Arc<[FontFamilyKey]>,
    default_index: Option<usize>,
}

impl SoftwareTextFontSet {
    pub fn empty() -> Self {
        Self::from_faces(Vec::new())
    }

    pub fn from_font(font: SoftwareTextFont) -> Self {
        Self::from_faces(vec![font])
    }

    /// Build a set from already-parsed faces, keeping the default-face choice
    /// and the registered-family index in one place.
    pub fn from_faces(fonts: Vec<SoftwareTextFont>) -> Self {
        let mut registered_families: Vec<FontFamilyKey> = Vec::new();
        for family in fonts.iter().filter_map(SoftwareTextFont::registered_family) {
            if !registered_families.contains(&family) {
                registered_families.push(family);
            }
        }
        let default_index = (!fonts.is_empty()).then(|| default_font_index(&fonts));
        Self {
            fonts: Arc::from(fonts),
            registered_families: Arc::from(registered_families),
            default_index,
        }
    }

    pub fn from_fonts_or_default(fonts: &[&[u8]]) -> Self {
        let mut parsed = Vec::with_capacity(fonts.len().max(1));
        for font in fonts {
            if let Ok(candidate) = SoftwareTextFont::from_bytes((*font).to_vec()) {
                parsed.push(candidate);
            }
        }
        if parsed.is_empty() {
            if let Some(default_font) = default_software_text_font() {
                parsed.push(default_font);
            }
        }

        Self::from_faces(parsed)
    }

    pub fn default_font(&self) -> Option<&SoftwareTextFont> {
        self.default_index.and_then(|index| self.fonts.get(index))
    }

    /// Every face in the set, in registration order.
    pub fn faces(&self) -> &[SoftwareTextFont] {
        &self.fonts
    }

    /// Whether any face in the set was registered under `family`.
    pub fn has_registered_family(&self, family: &FontFamily) -> bool {
        self.registered_families
            .contains(&FontFamilyKey::of(family))
    }

    pub fn resolve(&self, style: &TextStyle) -> Option<&SoftwareTextFont> {
        let target_weight = style.span_style.font_weight.unwrap_or_default();
        let target_style = style.span_style.font_style.unwrap_or_default();
        let request = FontFamilyRequest::resolve(
            style.span_style.font_family.as_ref(),
            &self.registered_families,
        );

        let mut best: Option<(usize, u32)> = None;
        for (index, font) in self.fonts.iter().enumerate() {
            let Some(score) = font_match_score(font, target_weight, target_style, request) else {
                continue;
            };
            if best.is_none_or(|(_, best_score)| score < best_score) {
                best = Some((index, score));
            }
        }

        let index = best.map(|(index, _)| index).or(self.default_index);
        index.and_then(|index| self.fonts.get(index))
    }
}

pub fn software_text_font_from_fonts_or_default(fonts: &[&[u8]]) -> Option<SoftwareTextFont> {
    SoftwareTextFontSet::from_fonts_or_default(fonts)
        .default_font()
        .cloned()
}

pub fn software_text_font_set_from_fonts_or_default(fonts: &[&[u8]]) -> SoftwareTextFontSet {
    SoftwareTextFontSet::from_fonts_or_default(fonts)
}

#[derive(Clone, Copy)]
struct TextFontScore {
    supported_latin_chars: usize,
    latin_sample_width: f32,
}

impl TextFontScore {
    fn is_complete_default_face(self) -> bool {
        const LATIN_SAMPLE_CHAR_COUNT: usize = 21;
        self.supported_latin_chars == LATIN_SAMPLE_CHAR_COUNT && self.latin_sample_width > 1.0
    }

    fn is_better_than(self, other: Self) -> bool {
        self.supported_latin_chars > other.supported_latin_chars
            || (self.supported_latin_chars == other.supported_latin_chars
                && self.latin_sample_width > other.latin_sample_width)
    }
}

fn text_font_score(font: &SoftwareTextFont) -> TextFontScore {
    font.score
}

fn text_font_score_from_parts(
    font: &FontArc,
    ab_glyph_scale_factor: f32,
    weight: FontWeight,
) -> TextFontScore {
    const SAMPLE: &str = "UNDER The quick brown fox";
    let glyph_font_size = 18.0 * ab_glyph_scale_factor;
    let scaled_font = font.as_scaled(PxScale::from(glyph_font_size));
    let supported_latin_chars = SAMPLE
        .chars()
        .filter(|ch| !ch.is_whitespace())
        .filter(|ch| scaled_font.glyph_id(*ch).0 != 0)
        .count();
    let latin_sample_width = measure_text_impl(
        SAMPLE,
        &TextStyle::default(),
        18.0,
        glyph_font_size,
        font,
        FontStyle::Normal,
        weight,
    )
    .width;
    TextFontScore {
        supported_latin_chars,
        latin_sample_width,
    }
}

fn default_font_index(fonts: &[SoftwareTextFont]) -> usize {
    let mut best: Option<(usize, TextFontScore)> = None;
    for (index, font) in fonts.iter().enumerate() {
        let score = text_font_score(font);
        if font.style() == FontStyle::Normal
            && font.weight() == FontWeight::NORMAL
            && score.is_complete_default_face()
        {
            return index;
        }
        if best
            .as_ref()
            .is_none_or(|(_, best_score)| score.is_better_than(*best_score))
        {
            best = Some((index, score));
        }
    }
    best.map(|(index, _)| index).unwrap_or(0)
}

/// How a `TextStyle`'s font family narrows the faces a resolve may pick from.
///
/// Both measurement and rasterization go through `SoftwareTextFontSet::resolve`,
/// so deriving the constraint here is what keeps the two from disagreeing.
#[derive(Clone, Copy)]
enum FontFamilyRequest<'a> {
    /// No family was named, or a generic family nothing was registered under.
    /// Every face is eligible and weight/style alone decide, which is the
    /// behaviour generic families had before app-supplied fonts existed.
    Any,
    /// A face qualifies by carrying `name` in its `name` table, or by having
    /// been registered under `FontFamily::Named(name)`.
    Named { name: &'a str, key: FontFamilyKey },
    /// Only faces registered under exactly this family value qualify.
    Registered(FontFamilyKey),
}

impl<'a> FontFamilyRequest<'a> {
    fn resolve(font_family: Option<&'a FontFamily>, registered: &[FontFamilyKey]) -> Self {
        match font_family {
            None | Some(FontFamily::Default) => Self::Any,
            Some(FontFamily::Named(name)) => Self::Named {
                name: name.as_str(),
                key: FontFamilyKey::of(&FontFamily::Named(name.clone())),
            },
            Some(family @ (FontFamily::FileBacked(_) | FontFamily::LoadedTypeface(_))) => {
                Self::Registered(FontFamilyKey::of(family))
            }
            Some(family) => {
                // Generic families (`SansSerif`, `Serif`, …) only constrain the
                // set once an app has registered a face for one; otherwise they
                // would strip the weight matching they used to allow.
                let key = FontFamilyKey::of(family);
                if registered.contains(&key) {
                    Self::Registered(key)
                } else {
                    Self::Any
                }
            }
        }
    }

    fn matches(self, font: &SoftwareTextFont) -> bool {
        match self {
            Self::Any => true,
            Self::Named { name, key } => {
                font_family_matches(font, name) || font.registered_family() == Some(key)
            }
            Self::Registered(key) => font.registered_family() == Some(key),
        }
    }
}

fn font_match_score(
    font: &SoftwareTextFont,
    target_weight: FontWeight,
    target_style: FontStyle,
    request: FontFamilyRequest<'_>,
) -> Option<u32> {
    if !request.matches(font) {
        return None;
    }
    let style_penalty = if font.style() == target_style {
        0
    } else {
        10_000
    };
    let weight_penalty = (i32::from(font.weight().0) - i32::from(target_weight.0)).unsigned_abs();
    let coverage_penalty =
        (21usize.saturating_sub(text_font_score(font).supported_latin_chars) as u32) * 1_000;

    Some(style_penalty + weight_penalty + coverage_penalty)
}

fn font_family_matches(font: &SoftwareTextFont, requested: &str) -> bool {
    font.family_names()
        .iter()
        .any(|family| family.eq_ignore_ascii_case(requested))
}

/// Instance a variable face at the weight and slant the app declared for it.
///
/// Returns the axis values actually applied so they can join the face's content
/// hash: two instances of one file share bytes but not outlines, and
/// `content_hash` is what keys the glyph mask cache and the glyph atlas.
fn apply_declared_variations(
    font: &mut FontVec,
    weight: FontWeight,
    style: FontStyle,
) -> Vec<([u8; 4], f32)> {
    // Faces spell italic either as `ital` (0..1) or as `slnt`, a counter-
    // clockwise angle where a right-leaning oblique is negative. The angle
    // matches the slant `TextStyleSynthesis` would shear in, so a face that
    // carries the axis lands where a synthesized one would.
    const OBLIQUE_DEGREES: f32 = -12.0;

    let mut applied = Vec::new();
    for axis in font.variations() {
        let requested = match &axis.tag {
            b"wght" => f32::from(weight.value()),
            b"ital" if style == FontStyle::Italic => 1.0,
            b"slnt" if style == FontStyle::Italic => OBLIQUE_DEGREES,
            _ => continue,
        };
        let value = requested.clamp(axis.min_value, axis.max_value);
        if font.set_variation(&axis.tag, value) {
            applied.push((axis.tag, value));
        }
    }
    applied
}

fn software_text_font_metadata(bytes: &[u8]) -> SoftwareTextFontMetadata {
    let Some(face) = ttf_parser::Face::parse(bytes, 0).ok() else {
        return SoftwareTextFontMetadata {
            families: Arc::from(Vec::<String>::new()),
            registered_family: None,
            weight: FontWeight::NORMAL,
            style: FontStyle::Normal,
            ab_glyph_scale_factor: 1.0,
        };
    };

    let mut families = Vec::new();
    for name in face.names() {
        if matches!(
            name.name_id,
            ttf_parser::name_id::TYPOGRAPHIC_FAMILY | ttf_parser::name_id::FAMILY
        ) {
            if let Some(value) = name.to_string().filter(|value| !value.is_empty()) {
                if !families
                    .iter()
                    .any(|existing: &String| existing.eq_ignore_ascii_case(&value))
                {
                    families.push(value);
                }
            }
        }
    }
    let weight = FontWeight::try_new(face.weight().to_number()).unwrap_or(FontWeight::NORMAL);
    let style = if face.is_italic() {
        FontStyle::Italic
    } else {
        FontStyle::Normal
    };
    let units_per_em = face.units_per_em() as f32;
    let height = (face.ascender() as f32 - face.descender() as f32).abs();
    let ab_glyph_scale_factor =
        if units_per_em.is_finite() && units_per_em > 0.0 && height.is_finite() && height > 0.0 {
            height / units_per_em
        } else {
            1.0
        };

    SoftwareTextFontMetadata {
        families: Arc::from(families),
        registered_family: None,
        weight,
        style,
        ab_glyph_scale_factor,
    }
}

#[derive(Clone)]
struct TextMetricsKey {
    text: Rc<str>,
    font_size_bits: u32,
    style_hash: u64,
    span_styles_hash: u64,
}

impl PartialEq for TextMetricsKey {
    fn eq(&self, other: &Self) -> bool {
        (Rc::ptr_eq(&self.text, &other.text) || *self.text == *other.text)
            && self.font_size_bits == other.font_size_bits
            && self.style_hash == other.style_hash
            && self.span_styles_hash == other.span_styles_hash
    }
}

impl Eq for TextMetricsKey {}

impl Hash for TextMetricsKey {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.text.hash(state);
        self.font_size_bits.hash(state);
        self.style_hash.hash(state);
        self.span_styles_hash.hash(state);
    }
}

struct SoftwareTextMetricsCache {
    map: BoundedLruCache<TextMetricsKey, TextMetrics>,
    line_prefix_widths: BoundedLruCache<LinePrefixWidthsKey, TextLinePrefixWidths>,
    glyph_metrics: SoftwareTextGlyphMetricsCache,
}

impl SoftwareTextMetricsCache {
    fn new(capacity: usize) -> Self {
        Self {
            map: BoundedLruCache::with_capacity_at_least_one(capacity),
            line_prefix_widths: BoundedLruCache::with_capacity_at_least_one(
                capacity.max(SOFTWARE_TEXT_PREFIX_WIDTH_CACHE_CAPACITY),
            ),
            glyph_metrics: SoftwareTextGlyphMetricsCache::new(),
        }
    }

    fn get_or_measure(
        &mut self,
        fonts: &SoftwareTextFontSet,
        text: &AnnotatedString,
        style: &TextStyle,
    ) -> TextMetrics {
        let font_size = resolve_font_size(style);
        let key = TextMetricsKey {
            text: Rc::from(text.text.as_str()),
            font_size_bits: font_size.to_bits(),
            style_hash: style.measurement_hash(),
            span_styles_hash: text.span_styles_hash(),
        };
        if let Some(metrics) = self.map.get(&key).copied() {
            return metrics;
        }

        let metrics =
            measure_annotated_text_with_font_set_cached(text, style, font_size, fonts, self);
        self.map.put(key, metrics);
        metrics
    }

    fn get_or_measure_line_prefix_widths(
        &mut self,
        fonts: &SoftwareTextFontSet,
        text: &AnnotatedString,
        line_range: std::ops::Range<usize>,
        style: &TextStyle,
    ) -> Option<TextLinePrefixWidths> {
        let key = line_prefix_widths_key(text, line_range.clone(), style)?;
        if let Some(widths) = self.line_prefix_widths.get(&key) {
            return Some(widths.clone());
        }

        let widths = annotated_line_prefix_widths_with_font_set_cached(
            text, line_range, style, fonts, self,
        )?;
        self.line_prefix_widths.put(key, widths.clone());
        Some(widths)
    }

    fn get_or_measure_line_width(
        &mut self,
        fonts: &SoftwareTextFontSet,
        text: &AnnotatedString,
        line_range: std::ops::Range<usize>,
        style: &TextStyle,
    ) -> Option<f32> {
        let key = line_prefix_widths_key(text, line_range.clone(), style)?;
        if let Some(widths) = self.line_prefix_widths.get(&key) {
            return widths.width_for_char_range(0, widths.char_count());
        }

        let widths = annotated_line_prefix_widths_with_font_set_cached(
            text, line_range, style, fonts, self,
        )?;
        let width = widths.width_for_char_range(0, widths.char_count());
        self.line_prefix_widths.put(key, widths);
        width
    }
}

#[derive(Clone)]
struct LinePrefixWidthsKey {
    text: Rc<str>,
    start: usize,
    end: usize,
    style_hash: u64,
    span_styles_hash: u64,
}

impl PartialEq for LinePrefixWidthsKey {
    fn eq(&self, other: &Self) -> bool {
        (Rc::ptr_eq(&self.text, &other.text) || *self.text == *other.text)
            && self.start == other.start
            && self.end == other.end
            && self.style_hash == other.style_hash
            && self.span_styles_hash == other.span_styles_hash
    }
}

impl Eq for LinePrefixWidthsKey {}

impl Hash for LinePrefixWidthsKey {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.text.hash(state);
        self.start.hash(state);
        self.end.hash(state);
        self.style_hash.hash(state);
        self.span_styles_hash.hash(state);
    }
}

fn line_prefix_widths_key(
    text: &AnnotatedString,
    line_range: std::ops::Range<usize>,
    style: &TextStyle,
) -> Option<LinePrefixWidthsKey> {
    if !style_allows_prefix_widths(style)
        || line_range.start > line_range.end
        || line_range.end > text.text.len()
        || !text.text.is_char_boundary(line_range.start)
        || !text.text.is_char_boundary(line_range.end)
        || text.text[line_range.clone()].contains('\n')
    {
        return None;
    }

    Some(LinePrefixWidthsKey {
        text: Rc::from(text.text.as_str()),
        start: line_range.start,
        end: line_range.end,
        style_hash: style.measurement_hash(),
        span_styles_hash: text.span_styles_hash(),
    })
}

/// A glyph's advance, in font units.
///
/// Font units rather than pixels, because everything ab_glyph reports for a
/// scaled font is the unscaled value times one horizontal scale factor. Caching
/// the scaled number buys nothing and costs the key: the font size has to join
/// it, and text whose size moves -- a scaling list, a zoom, a spring on a font
/// size -- then misses on every glyph of every frame and re-reads the font
/// tables for all of them. In font units such a page pays for each glyph once
/// and multiplies from then on.
#[derive(Clone, Copy, Debug)]
struct CachedGlyphMetrics {
    glyph_id: GlyphId,
    advance_unscaled: f32,
}

#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
struct GlyphMetricsKey {
    font_hash: u64,
    ch: char,
}

#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
struct KernMetricsKey {
    font_hash: u64,
    previous_id: u32,
    glyph_id: u32,
}

#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
struct SoftwareTextGlyphMetricsStats {
    glyph_hits: u64,
    glyph_misses: u64,
    kern_hits: u64,
    kern_misses: u64,
}

struct SoftwareTextGlyphMetricsCache {
    glyphs: BoundedLruCache<GlyphMetricsKey, CachedGlyphMetrics>,
    kerns: BoundedLruCache<KernMetricsKey, f32>,
    stats: SoftwareTextGlyphMetricsStats,
}

impl SoftwareTextGlyphMetricsCache {
    fn new() -> Self {
        Self {
            glyphs: BoundedLruCache::with_capacity_at_least_one(
                SOFTWARE_TEXT_GLYPH_METRICS_CACHE_CAPACITY,
            ),
            kerns: BoundedLruCache::with_capacity_at_least_one(
                SOFTWARE_TEXT_KERN_METRICS_CACHE_CAPACITY,
            ),
            stats: SoftwareTextGlyphMetricsStats::default(),
        }
    }

    #[cfg(test)]
    fn stats(&self) -> SoftwareTextGlyphMetricsStats {
        self.stats
    }

    /// Glyph id and advance in font units. Multiply the advance by the run's
    /// horizontal scale factor, which is what ab_glyph would have done.
    fn glyph_metrics<F, S>(
        &mut self,
        font: &SoftwareTextFont,
        scaled_font: &S,
        ch: char,
    ) -> CachedGlyphMetrics
    where
        F: Font,
        S: ScaleFont<F>,
    {
        let key = GlyphMetricsKey {
            font_hash: font.content_hash(),
            ch,
        };
        if let Some(metrics) = self.glyphs.get(&key).copied() {
            self.stats.glyph_hits = self.stats.glyph_hits.saturating_add(1);
            return metrics;
        }

        let glyph_id = scaled_font.font().glyph_id(ch);
        let metrics = CachedGlyphMetrics {
            glyph_id,
            advance_unscaled: scaled_font.font().h_advance_unscaled(glyph_id).max(0.0),
        };
        self.glyphs.put(key, metrics);
        self.stats.glyph_misses = self.stats.glyph_misses.saturating_add(1);
        metrics
    }

    /// Kerning between two glyphs in font units, scaled by the caller like the
    /// advance beside it.
    fn kern<F, S>(
        &mut self,
        font: &SoftwareTextFont,
        scaled_font: &S,
        previous_id: GlyphId,
        glyph_id: GlyphId,
    ) -> f32
    where
        F: Font,
        S: ScaleFont<F>,
    {
        let key = KernMetricsKey {
            font_hash: font.content_hash(),
            previous_id: previous_id.0.into(),
            glyph_id: glyph_id.0.into(),
        };
        if let Some(kern) = self.kerns.get(&key).copied() {
            self.stats.kern_hits = self.stats.kern_hits.saturating_add(1);
            return kern;
        }

        let kern = scaled_font.font().kern_unscaled(previous_id, glyph_id);
        self.kerns.put(key, kern);
        self.stats.kern_misses = self.stats.kern_misses.saturating_add(1);
        kern
    }
}

pub struct SoftwareTextMeasurer {
    fonts: SoftwareTextFontSet,
    cache: Mutex<SoftwareTextMetricsCache>,
    hyphenation: HyphenationDictionaryStore,
}

impl SoftwareTextMeasurer {
    pub fn new(font: SoftwareTextFont, cache_capacity: usize) -> Self {
        Self::from_font_set(SoftwareTextFontSet::from_font(font), cache_capacity)
    }

    pub fn from_font_set(fonts: SoftwareTextFontSet, cache_capacity: usize) -> Self {
        Self {
            fonts,
            cache: Mutex::new(SoftwareTextMetricsCache::new(cache_capacity)),
            hyphenation: HyphenationDictionaryStore::new(),
        }
    }

    pub fn from_fonts_or_default(fonts: &[&[u8]], cache_capacity: usize) -> Self {
        Self::from_font_set(
            software_text_font_set_from_fonts_or_default(fonts),
            cache_capacity,
        )
    }

    fn lock_cache(&self) -> MutexGuard<'_, SoftwareTextMetricsCache> {
        self.cache
            .lock()
            .unwrap_or_else(|poisoned| poisoned.into_inner())
    }

    #[cfg(feature = "text-hyphenation")]
    pub fn register_hyphenation_dictionary_path(
        &self,
        locale: &str,
        path: impl AsRef<std::path::Path>,
    ) -> Result<(), HyphenationDictionaryError> {
        self.hyphenation.register_dictionary_path(locale, path)
    }

    #[cfg(feature = "text-hyphenation")]
    pub fn register_hyphenation_dictionary_reader(
        &self,
        locale: &str,
        reader: &mut impl std::io::Read,
    ) -> Result<(), HyphenationDictionaryError> {
        self.hyphenation.register_dictionary_reader(locale, reader)
    }
}

impl TextMeasurer for SoftwareTextMeasurer {
    fn measure(&self, text: &cranpose_ui::text::AnnotatedString, style: &TextStyle) -> TextMetrics {
        self.lock_cache().get_or_measure(&self.fonts, text, style)
    }

    fn measure_subsequence(
        &self,
        text: &cranpose_ui::text::AnnotatedString,
        range: std::ops::Range<usize>,
        style: &TextStyle,
    ) -> TextMetrics {
        let text = text.subsequence(range);
        self.lock_cache().get_or_measure(&self.fonts, &text, style)
    }

    fn measure_line_prefix_widths(
        &self,
        text: &cranpose_ui::text::AnnotatedString,
        line_range: std::ops::Range<usize>,
        style: &TextStyle,
    ) -> Option<TextLinePrefixWidths> {
        self.lock_cache()
            .get_or_measure_line_prefix_widths(&self.fonts, text, line_range, style)
    }

    fn measure_line_width(
        &self,
        text: &cranpose_ui::text::AnnotatedString,
        line_range: std::ops::Range<usize>,
        style: &TextStyle,
    ) -> Option<f32> {
        self.lock_cache()
            .get_or_measure_line_width(&self.fonts, text, line_range, style)
    }

    fn line_height(&self, text: &cranpose_ui::text::AnnotatedString, style: &TextStyle) -> f32 {
        let font_size = resolve_font_size(style);
        max_line_height_for_annotated_text_with_resolver(text, style, font_size, &self.fonts)
    }

    fn glyph_line_box(&self, style: &TextStyle) -> Option<(f32, f32)> {
        let font = self.fonts.resolve(style)?;
        let font_size = resolve_font_size(style);
        let metrics = crate::font_layout::vertical_metrics(&font.font, font_size);
        let asked = line_height_for_render_style(style, font_size);
        let resolved = line_box_for(style, metrics, asked, measure_grid());
        // Glyph rows sit in the slot the line box gives them; the tight box is
        // the font's own ascent+descent extent, clamped to the slot.
        let height = metrics.natural_line_height.min(resolved.height).max(1.0);
        Some((((resolved.height - height) * 0.5).max(0.0), height))
    }

    fn first_baseline(&self, style: &TextStyle) -> Option<f32> {
        let font = self.fonts.resolve(style)?;
        let font_size = resolve_font_size(style);
        // Metrics must be read at the font's own px size, not the logical one:
        // this is the very expression `collect_text_segment_solid_atlas_glyphs`
        // places glyph origins with, so a baseline-anchored draw lands on the
        // row the rasterizer will use. (`glyph_line_box` deliberately keeps its
        // own, coarser box for selection chrome.)
        let metrics =
            crate::font_layout::vertical_metrics(&font.font, font.ab_glyph_px_size(font_size));
        // A measurer works in layout points, so the line box rounds on the
        // device grid the app is running at rather than on whole points.
        Some(baseline_y_for_line_box(
            style,
            metrics,
            line_height_for_render_style(style, font_size),
            measure_grid(),
        ))
    }

    fn get_offset_for_position(
        &self,
        text: &cranpose_ui::text::AnnotatedString,
        style: &TextStyle,
        x: f32,
        y: f32,
    ) -> usize {
        if let Some(font) = self.fonts.resolve(style) {
            text_offset_for_position_with_font(text.text.as_str(), style, x, y, font)
        } else {
            fallback_text_offset_for_position(text.text.as_str(), style, x, y)
        }
    }

    fn get_cursor_x_for_offset(
        &self,
        text: &cranpose_ui::text::AnnotatedString,
        style: &TextStyle,
        offset: usize,
    ) -> f32 {
        if let Some(font) = self.fonts.resolve(style) {
            cursor_x_for_offset_with_font(text.text.as_str(), style, offset, font)
        } else {
            fallback_cursor_x_for_offset(text.text.as_str(), style, offset)
        }
    }

    fn layout(
        &self,
        text: &cranpose_ui::text::AnnotatedString,
        style: &TextStyle,
    ) -> TextLayoutResult {
        if let Some(font) = self.fonts.resolve(style) {
            layout_text_with_font(text.text.as_str(), style, font)
        } else {
            fallback_layout_text(text.text.as_str(), style)
        }
    }

    fn choose_auto_hyphen_break(
        &self,
        line: &str,
        style: &TextStyle,
        segment_start_char: usize,
        measured_break_char: usize,
    ) -> Option<usize> {
        self.hyphenation.choose_auto_hyphen_break(
            line,
            style,
            segment_start_char,
            measured_break_char,
        )
    }
}

pub fn software_text_content_hash(text: &cranpose_ui::text::AnnotatedString) -> u64 {
    let mut state = default_hash::new();
    text.text.hash(&mut state);
    text.span_styles_hash().hash(&mut state);
    state.finish()
}

#[derive(Clone, Copy)]
enum GlyphRasterStyle {
    Fill,
    Stroke { width_px: f32 },
}

#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
pub struct SoftwareGlyphAtlasKey {
    pub font_hash: u64,
    pub glyph_id: u32,
    pub scale_x_bits: u32,
    pub scale_y_bits: u32,
    pub embolden_px_bits: u32,
    pub slant_bits: u32,
}

#[derive(Clone)]
pub struct SoftwareGlyphAtlasMask {
    pub alpha: Arc<[f32]>,
    pub width: usize,
    pub height: usize,
}

#[derive(Clone)]
pub struct SoftwareGlyphAtlasGlyph {
    pub key: SoftwareGlyphAtlasKey,
    pub mask: SoftwareGlyphAtlasMask,
    pub x: i32,
    pub y: i32,
    pub color: Color,
}

#[derive(Clone, Copy)]
pub struct SoftwareGlyphAtlasPlacement {
    pub key: SoftwareGlyphAtlasKey,
    pub x: i32,
    pub y: i32,
    pub width: usize,
    pub height: usize,
    pub color: Color,
}

#[derive(Clone)]
pub enum SoftwareGlyphAtlasRunGlyph {
    Cached(SoftwareGlyphAtlasPlacement),
    New(SoftwareGlyphAtlasGlyph),
}

impl SoftwareGlyphAtlasRunGlyph {
    pub fn placement(&self) -> SoftwareGlyphAtlasPlacement {
        match self {
            Self::Cached(placement) => *placement,
            Self::New(glyph) => SoftwareGlyphAtlasPlacement {
                key: glyph.key,
                x: glyph.x,
                y: glyph.y,
                width: glyph.mask.width,
                height: glyph.mask.height,
                color: glyph.color,
            },
        }
    }
}

#[derive(Clone)]
struct GlyphMask {
    alpha: Arc<[f32]>,
    width: usize,
    height: usize,
    origin_x: i32,
    origin_y: i32,
}

#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub struct SoftwareGlyphRasterCacheStats {
    pub entries: usize,
    pub hits: u64,
    pub misses: u64,
}

const RUN_GLYPH_METRICS_CACHE_LIMIT: usize = 64;

#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
enum GlyphRasterStyleKey {
    Fill,
    Stroke { width_px_bits: u32 },
}

impl GlyphRasterStyleKey {
    fn from_style(style: GlyphRasterStyle) -> Self {
        match style {
            GlyphRasterStyle::Fill => Self::Fill,
            GlyphRasterStyle::Stroke { width_px } => Self::Stroke {
                width_px_bits: width_px.to_bits(),
            },
        }
    }
}

#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
struct GlyphMaskCacheKey {
    font_hash: u64,
    glyph_id: u32,
    scale_x_bits: u32,
    scale_y_bits: u32,
    raster_style: GlyphRasterStyleKey,
    embolden_px_bits: u32,
    slant_bits: u32,
}

#[derive(Clone)]
struct CachedGlyphMask {
    alpha: Arc<[f32]>,
    width: usize,
    height: usize,
    origin_offset_x: i32,
    origin_offset_y: i32,
}

impl CachedGlyphMask {
    fn from_mask(mask: GlyphMask, glyph: &Glyph) -> Self {
        let (glyph_x, glyph_y) = static_glyph_pixel_origin(glyph);
        Self {
            alpha: mask.alpha,
            width: mask.width,
            height: mask.height,
            origin_offset_x: mask.origin_x - glyph_x,
            origin_offset_y: mask.origin_y - glyph_y,
        }
    }

    fn instantiate(&self, glyph: &Glyph) -> GlyphMask {
        let (glyph_x, glyph_y) = static_glyph_pixel_origin(glyph);
        GlyphMask {
            alpha: Arc::clone(&self.alpha),
            width: self.width,
            height: self.height,
            origin_x: glyph_x + self.origin_offset_x,
            origin_y: glyph_y + self.origin_offset_y,
        }
    }

    fn placement(&self, glyph: &Glyph) -> (i32, i32, usize, usize) {
        let (glyph_x, glyph_y) = static_glyph_pixel_origin(glyph);
        (
            glyph_x + self.origin_offset_x,
            glyph_y + self.origin_offset_y,
            self.width,
            self.height,
        )
    }

    fn atlas_metrics(&self, key: SoftwareGlyphAtlasKey) -> CachedAtlasGlyphMetrics {
        CachedAtlasGlyphMetrics {
            key,
            width: self.width,
            height: self.height,
            origin_offset_x: self.origin_offset_x,
            origin_offset_y: self.origin_offset_y,
        }
    }
}

#[derive(Clone, Copy)]
struct CachedAtlasGlyphMetrics {
    key: SoftwareGlyphAtlasKey,
    width: usize,
    height: usize,
    origin_offset_x: i32,
    origin_offset_y: i32,
}

impl CachedAtlasGlyphMetrics {
    fn placement(self, glyph: &Glyph, color: Color) -> SoftwareGlyphAtlasPlacement {
        let (glyph_x, glyph_y) = static_glyph_pixel_origin(glyph);
        SoftwareGlyphAtlasPlacement {
            key: self.key,
            x: glyph_x + self.origin_offset_x,
            y: glyph_y + self.origin_offset_y,
            width: self.width,
            height: self.height,
            color,
        }
    }
}

pub struct SoftwareGlyphRasterCache {
    masks: BoundedLruCache<GlyphMaskCacheKey, CachedGlyphMask>,
    hits: u64,
    misses: u64,
}

impl SoftwareGlyphRasterCache {
    pub fn with_capacity_at_least_one(capacity: usize) -> Self {
        Self {
            masks: BoundedLruCache::with_capacity_at_least_one(capacity),
            hits: 0,
            misses: 0,
        }
    }

    pub fn stats(&self) -> SoftwareGlyphRasterCacheStats {
        SoftwareGlyphRasterCacheStats {
            entries: self.masks.len(),
            hits: self.hits,
            misses: self.misses,
        }
    }

    fn get(&mut self, key: &GlyphMaskCacheKey, glyph: &Glyph) -> Option<GlyphMask> {
        let mask = self.masks.get(key)?.instantiate(glyph);
        self.hits = self.hits.saturating_add(1);
        Some(mask)
    }

    fn get_atlas_placement(
        &mut self,
        key: &GlyphMaskCacheKey,
        glyph: &Glyph,
    ) -> Option<(SoftwareGlyphAtlasKey, i32, i32, usize, usize)> {
        let atlas_key = glyph_atlas_key_from_mask_key(*key)?;
        let (x, y, width, height) = self.masks.get(key)?.placement(glyph);
        self.hits = self.hits.saturating_add(1);
        Some((atlas_key, x, y, width, height))
    }

    fn get_atlas_metrics(&mut self, key: &GlyphMaskCacheKey) -> Option<CachedAtlasGlyphMetrics> {
        let atlas_key = glyph_atlas_key_from_mask_key(*key)?;
        let metrics = self.masks.get(key)?.atlas_metrics(atlas_key);
        self.hits = self.hits.saturating_add(1);
        Some(metrics)
    }

    pub fn atlas_glyph_for_placement(
        &mut self,
        placement: &SoftwareGlyphAtlasPlacement,
    ) -> Option<SoftwareGlyphAtlasGlyph> {
        let key = GlyphMaskCacheKey {
            font_hash: placement.key.font_hash,
            glyph_id: placement.key.glyph_id,
            scale_x_bits: placement.key.scale_x_bits,
            scale_y_bits: placement.key.scale_y_bits,
            raster_style: GlyphRasterStyleKey::Fill,
            embolden_px_bits: placement.key.embolden_px_bits,
            slant_bits: placement.key.slant_bits,
        };
        let mask = self.masks.get(&key)?;
        self.hits = self.hits.saturating_add(1);
        Some(SoftwareGlyphAtlasGlyph {
            key: placement.key,
            mask: SoftwareGlyphAtlasMask {
                alpha: Arc::clone(&mask.alpha),
                width: mask.width,
                height: mask.height,
            },
            x: placement.x,
            y: placement.y,
            color: placement.color,
        })
    }

    fn put(&mut self, key: GlyphMaskCacheKey, glyph: &Glyph, mask: GlyphMask) -> GlyphMask {
        let cached = CachedGlyphMask::from_mask(mask, glyph);
        let mask = cached.instantiate(glyph);
        self.masks.put(key, cached);
        self.misses = self.misses.saturating_add(1);
        mask
    }
}

struct RasterFontRef<'a, F> {
    font: &'a F,
    ab_glyph_scale_factor: f32,
    weight: FontWeight,
    style: FontStyle,
}

#[derive(Clone, Copy)]
struct TextWeightSynthesis {
    embolden_px: f32,
    advance_scale: f32,
}

impl TextWeightSynthesis {
    fn none() -> Self {
        Self {
            embolden_px: 0.0,
            advance_scale: 1.0,
        }
    }

    fn for_style(
        style: &TextStyle,
        resolved_weight: FontWeight,
        font_size: f32,
        scale: f32,
    ) -> Self {
        let requested_weight = style.span_style.font_weight.unwrap_or_default();
        if requested_weight <= resolved_weight {
            return Self::none();
        }

        let synthesis = style
            .span_style
            .font_synthesis
            .unwrap_or(FontSynthesis::All);
        if !matches!(synthesis, FontSynthesis::All | FontSynthesis::Weight) {
            return Self::none();
        }

        let weight_delta = (requested_weight.value() - resolved_weight.value()) as f32;
        let strength = (weight_delta / 300.0).clamp(0.0, 1.5);
        Self {
            embolden_px: (font_size * scale * 0.055 * strength).clamp(0.0, 3.0 * scale),
            advance_scale: 1.0 + 0.085 * strength.min(1.0),
        }
    }

    fn apply_width(self, width: f32) -> f32 {
        width * self.advance_scale
    }
}

#[derive(Clone, Copy)]
struct TextStyleSynthesis {
    slant: f32,
    font_size: f32,
    scale: f32,
}

impl TextStyleSynthesis {
    fn none() -> Self {
        Self {
            slant: 0.0,
            font_size: 0.0,
            scale: 1.0,
        }
    }

    fn for_style(style: &TextStyle, resolved_style: FontStyle, font_size: f32, scale: f32) -> Self {
        let requested_style = style.span_style.font_style.unwrap_or_default();
        if requested_style != FontStyle::Italic || resolved_style == FontStyle::Italic {
            return Self::none();
        }

        let synthesis = style
            .span_style
            .font_synthesis
            .unwrap_or(FontSynthesis::All);
        if !matches!(synthesis, FontSynthesis::All | FontSynthesis::Style) {
            return Self::none();
        }

        Self {
            slant: 0.22,
            font_size,
            scale,
        }
    }

    fn visual_overhang_px(self) -> f32 {
        if self.slant <= 0.0 || !self.font_size.is_finite() || !self.scale.is_finite() {
            return 0.0;
        }
        (self.font_size * self.scale * self.slant).ceil().max(0.0)
    }
}

pub fn rasterize_text_to_image(
    text: &str,
    rect: Rect,
    style: &TextStyle,
    fallback_color: Color,
    font_size: f32,
    scale: f32,
    font: &SoftwareTextFont,
) -> Option<ImageBitmap> {
    rasterize_text_to_image_impl(
        TextRasterImageRequest {
            text,
            rect,
            style,
            fallback_color,
            font_size,
            scale,
        },
        RasterFontRef {
            font: &font.font,
            ab_glyph_scale_factor: font.metadata.ab_glyph_scale_factor,
            weight: font.weight(),
            style: font.style(),
        },
        font.content_hash(),
        None,
    )
}

#[allow(clippy::too_many_arguments)]
pub fn rasterize_text_to_image_with_glyph_cache(
    text: &str,
    rect: Rect,
    style: &TextStyle,
    fallback_color: Color,
    font_size: f32,
    scale: f32,
    font: &SoftwareTextFont,
    glyph_cache: &mut SoftwareGlyphRasterCache,
) -> Option<ImageBitmap> {
    rasterize_text_to_image_impl(
        TextRasterImageRequest {
            text,
            rect,
            style,
            fallback_color,
            font_size,
            scale,
        },
        RasterFontRef {
            font: &font.font,
            ab_glyph_scale_factor: font.metadata.ab_glyph_scale_factor,
            weight: font.weight(),
            style: font.style(),
        },
        font.content_hash(),
        Some(glyph_cache),
    )
}

/// The slice of a text payload that solid-run rasterization reads: content
/// plus span styles. Borrowable from both an [`AnnotatedString`] (UI-side
/// text) and a [`RenderString`] (a lowered scene's link-handler-free view),
/// so the run collectors serve both without copying either.
#[derive(Clone, Copy)]
pub struct StyledTextRef<'a> {
    pub text: &'a str,
    pub span_styles: &'a [RangeStyle<SpanStyle>],
}

impl StyledTextRef<'_> {
    fn is_empty(&self) -> bool {
        self.text.is_empty()
    }

    /// Mirrors [`AnnotatedString::span_boundaries`].
    fn span_boundaries(&self) -> Vec<usize> {
        let mut boundaries = vec![0, self.text.len()];
        for span in self.span_styles {
            boundaries.push(span.range.start);
            boundaries.push(span.range.end);
        }
        boundaries.sort_unstable();
        boundaries.dedup();
        boundaries
            .into_iter()
            .filter(|&b| b <= self.text.len() && self.text.is_char_boundary(b))
            .collect()
    }
}

impl<'a> From<&'a AnnotatedString> for StyledTextRef<'a> {
    fn from(text: &'a AnnotatedString) -> Self {
        Self {
            text: text.text.as_str(),
            span_styles: &text.span_styles,
        }
    }
}

impl<'a> From<&'a RenderString> for StyledTextRef<'a> {
    fn from(text: &'a RenderString) -> Self {
        Self {
            text: text.text.as_str(),
            span_styles: &text.span_styles,
        }
    }
}

/// The x each line of an annotated block starts at, relative to the block's
/// left edge, once `TextAlign` has had its say.
///
/// The block's own offset inside its parent is the scene builder's job; this
/// is the other half, and Compose needs both — a `TextAlign` applies to every
/// line of the paragraph, so a wrapped continuation line is centred in its own
/// right and does not simply start where the first line started. See
/// `scene_builder::text_align_fraction` for why the two telescope.
///
/// This walks the same span/newline segmentation the collectors below walk,
/// and adds up advances with the same kern-plus-letter-spacing rule the glyph
/// loops use, so the widths it aligns against are the widths that get drawn.
/// `None` when there is nothing to do: start-aligned, or a single line.
fn annotated_line_alignment_offsets(
    text: &StyledTextRef<'_>,
    style: &TextStyle,
    font_size: f32,
    scale: f32,
    fonts: &SoftwareTextFontSet,
) -> Option<Vec<f32>> {
    let align_fraction = crate::scene_builder::text_align_fraction(style, text.text);
    if align_fraction == 0.0 || !text.text.contains('\n') {
        return None;
    }

    let mut advances = vec![0.0f32];
    for range in annotated_segment_boundaries(text).windows(2) {
        let (start, end) = (range[0], range[1]);
        if start == end {
            continue;
        }
        let segment_style = effective_style_for_range(text.span_styles, style, start, end);
        for part in text.text[start..end].split_inclusive('\n') {
            let has_newline = part.ends_with('\n');
            let content = if has_newline {
                &part[..part.len().saturating_sub(1)]
            } else {
                part
            };
            if !content.is_empty() {
                let segment_font_size = segment_style.resolve_font_size(font_size);
                let font = fonts.resolve(&segment_style)?;
                let font_px_size = font.ab_glyph_px_size(segment_font_size) * scale;
                let letter_spacing =
                    resolve_letter_spacing(&segment_style, segment_font_size) * scale;
                if let Some(last) = advances.last_mut() {
                    *last += segment_advance_px(&font.font, content, font_px_size, letter_spacing);
                }
            }
            if has_newline {
                advances.push(0.0);
            }
        }
    }

    let block = advances.iter().copied().fold(0.0f32, f32::max);
    Some(
        advances
            .iter()
            .map(|advance| ((block - advance) * align_fraction).max(0.0))
            .collect(),
    )
}

/// Where an annotated block changes style or breaks a line — every offset the
/// collectors below cut a segment at.
fn annotated_segment_boundaries(text: &StyledTextRef<'_>) -> Vec<usize> {
    let mut boundaries = text.span_boundaries();
    for (offset, ch) in text.text.char_indices() {
        if ch == '\n' {
            boundaries.push(offset);
            boundaries.push(offset + ch.len_utf8());
        }
    }
    boundaries.sort_unstable();
    boundaries.dedup();
    boundaries.retain(|offset| *offset <= text.text.len() && text.text.is_char_boundary(*offset));
    boundaries
}

/// One line's advance, walked exactly as the glyph loops walk it.
fn segment_advance_px(
    font: &impl Font,
    content: &str,
    font_px_size: f32,
    letter_spacing: f32,
) -> f32 {
    let scaled_font = font.as_scaled(PxScale::from(font_px_size));
    let mut caret = 0.0f32;
    let mut previous = None;
    for ch in content.chars() {
        let glyph_id = scaled_font.glyph_id(ch);
        if let Some(previous_id) = previous {
            caret += scaled_font.kern(previous_id, glyph_id);
        }
        // One letter space PER CHARACTER, not per gap -- see `run_tracking`.
        caret += letter_spacing + scaled_font.h_advance(glyph_id);
        previous = Some(glyph_id);
    }
    caret.max(0.0)
}

#[allow(clippy::too_many_arguments)]
pub fn rasterize_annotated_text_to_image_with_glyph_cache<'a>(
    text: impl Into<StyledTextRef<'a>>,
    rect: Rect,
    style: &TextStyle,
    fallback_color: Color,
    font_size: f32,
    scale: f32,
    fonts: &SoftwareTextFontSet,
    glyph_cache: &mut SoftwareGlyphRasterCache,
) -> Option<ImageBitmap> {
    let text: StyledTextRef<'a> = text.into();
    if text.span_styles.is_empty() {
        let font = fonts.resolve(style)?;
        return rasterize_text_to_image_with_glyph_cache(
            text.text,
            rect,
            style,
            fallback_color,
            font_size,
            scale,
            font,
            glyph_cache,
        );
    }
    if text.is_empty()
        || rect.width <= 0.0
        || rect.height <= 0.0
        || !font_size.is_finite()
        || font_size <= 0.0
        || !scale.is_finite()
        || scale <= 0.0
    {
        return None;
    }

    let width = rect.width.ceil().max(1.0) as u32;
    let height = rect.height.ceil().max(1.0) as u32;
    let boundaries = text.span_boundaries();
    let mut segment_plan = Vec::with_capacity(boundaries.len().saturating_sub(1));
    for window in boundaries.windows(2) {
        let start = window[0];
        let end = window[1];
        if start == end {
            continue;
        }
        let segment_style = effective_style_for_range(text.span_styles, style, start, end);
        if !style_can_rasterize_direct_solid(&segment_style) {
            return None;
        }
        let static_text_motion = segment_style
            .paragraph_style
            .text_motion
            .unwrap_or(TextMotion::Static)
            == TextMotion::Static;
        if !static_text_motion {
            return None;
        }
        segment_plan.push((start, end, segment_style));
    }

    let mut canvas = vec![0_u8; (width as usize) * (height as usize) * 4];
    let base_line_height = line_height_for_render_style(style, font_size);
    let mut current_line_height = base_line_height;
    // Each line of the block is aligned in its own right; see
    // `annotated_line_alignment_offsets`.
    let line_offsets = annotated_line_alignment_offsets(&text, style, font_size, scale, fonts);
    let mut line_idx = 0usize;
    let mut cursor_x = rect.x + line_offset(&line_offsets, 0);
    let mut cursor_y = rect.y;

    for (start, end, segment_style) in segment_plan {
        let segment = &text.text[start..end];
        for part in segment.split_inclusive('\n') {
            let has_newline = part.ends_with('\n');
            let content = if has_newline {
                &part[..part.len().saturating_sub(1)]
            } else {
                part
            };

            if !content.is_empty() {
                let segment_font_size = segment_style.resolve_font_size(font_size);
                if let Some(font) = fonts.resolve(&segment_style) {
                    let local_rect = Rect {
                        x: (cursor_x - rect.x).round(),
                        y: (cursor_y - rect.y).round(),
                        width: width as f32,
                        height: height as f32,
                    };
                    let color = segment_style.resolve_text_color(fallback_color);
                    let advance_px = draw_text_segment_solid_to_rgba(
                        &mut canvas,
                        width,
                        height,
                        content,
                        local_rect,
                        &segment_style,
                        color,
                        segment_font_size,
                        scale,
                        font,
                        glyph_cache,
                    );
                    cursor_x += advance_px;
                    current_line_height = current_line_height.max(line_height_for_render_style(
                        &segment_style,
                        segment_font_size,
                    ));
                }
            }

            if has_newline {
                line_idx += 1;
                cursor_x = rect.x + line_offset(&line_offsets, line_idx);
                cursor_y += current_line_height * scale;
                current_line_height = base_line_height;
            }
        }
    }

    ImageBitmap::from_rgba8(width, height, canvas).ok()
}

#[allow(clippy::too_many_arguments)]
pub fn collect_solid_text_atlas_glyphs(
    text: &AnnotatedString,
    rect: Rect,
    style: &TextStyle,
    fallback_color: Color,
    font_size: f32,
    scale: f32,
    fonts: &SoftwareTextFontSet,
    glyph_cache: &mut SoftwareGlyphRasterCache,
    out: &mut Vec<SoftwareGlyphAtlasGlyph>,
) -> Option<()> {
    if text.is_empty()
        || rect.width <= 0.0
        || rect.height <= 0.0
        || !font_size.is_finite()
        || font_size <= 0.0
        || !scale.is_finite()
        || scale <= 0.0
    {
        return Some(());
    }

    let base_line_height = line_height_for_render_style(style, font_size);
    let mut current_line_height = base_line_height;
    // Each line of the block is aligned in its own right; see
    // `annotated_line_alignment_offsets`.
    let line_offsets = annotated_line_alignment_offsets(
        &StyledTextRef::from(text),
        style,
        font_size,
        scale,
        fonts,
    );
    let mut line_idx = 0usize;
    let mut cursor_x = rect.x + line_offset(&line_offsets, 0);
    let mut cursor_y = rect.y;
    let initial_len = out.len();

    let mut boundaries = text.span_boundaries();
    for (offset, ch) in text.text.char_indices() {
        if ch == '\n' {
            boundaries.push(offset);
            boundaries.push(offset + ch.len_utf8());
        }
    }
    boundaries.sort_unstable();
    boundaries.dedup();
    boundaries.retain(|offset| *offset <= text.text.len() && text.text.is_char_boundary(*offset));

    for range in boundaries.windows(2) {
        let start = range[0];
        let end = range[1];
        if start == end {
            continue;
        }
        let segment_style = effective_style_for_range(&text.span_styles, style, start, end);
        if !style_can_atlas_solid_fill(&segment_style) {
            out.truncate(initial_len);
            return None;
        }
        let static_text_motion = segment_style
            .paragraph_style
            .text_motion
            .unwrap_or(TextMotion::Static)
            == TextMotion::Static;
        if !static_text_motion {
            out.truncate(initial_len);
            return None;
        }

        let segment = &text.text[start..end];
        for part in segment.split_inclusive('\n') {
            let has_newline = part.ends_with('\n');
            let content = if has_newline {
                &part[..part.len().saturating_sub(1)]
            } else {
                part
            };

            if !content.is_empty() {
                let segment_font_size = segment_style.resolve_font_size(font_size);
                let Some(font) = fonts.resolve(&segment_style) else {
                    out.truncate(initial_len);
                    return None;
                };
                let local_rect = Rect {
                    x: (cursor_x - rect.x).round(),
                    y: (cursor_y - rect.y).round(),
                    width: rect.width,
                    height: rect.height,
                };
                let color = segment_style.resolve_text_color(fallback_color);
                let advance_px = collect_text_segment_solid_atlas_glyphs(
                    content,
                    local_rect,
                    &segment_style,
                    color,
                    segment_font_size,
                    scale,
                    font,
                    glyph_cache,
                    out,
                )?;
                cursor_x += advance_px;
                current_line_height = current_line_height.max(line_height_for_render_style(
                    &segment_style,
                    segment_font_size,
                ));
            }

            if has_newline {
                line_idx += 1;
                cursor_x = rect.x + line_offset(&line_offsets, line_idx);
                cursor_y += current_line_height * scale;
                current_line_height = base_line_height;
            }
        }
    }

    Some(())
}

#[allow(clippy::too_many_arguments)]
pub fn collect_cached_solid_text_atlas_placements(
    text: &AnnotatedString,
    rect: Rect,
    style: &TextStyle,
    fallback_color: Color,
    font_size: f32,
    scale: f32,
    fonts: &SoftwareTextFontSet,
    glyph_cache: &mut SoftwareGlyphRasterCache,
    out: &mut Vec<SoftwareGlyphAtlasPlacement>,
) -> Option<()> {
    if text.is_empty()
        || rect.width <= 0.0
        || rect.height <= 0.0
        || !font_size.is_finite()
        || font_size <= 0.0
        || !scale.is_finite()
        || scale <= 0.0
    {
        return Some(());
    }

    let base_line_height = line_height_for_render_style(style, font_size);
    let mut current_line_height = base_line_height;
    // Each line of the block is aligned in its own right; see
    // `annotated_line_alignment_offsets`.
    let line_offsets = annotated_line_alignment_offsets(
        &StyledTextRef::from(text),
        style,
        font_size,
        scale,
        fonts,
    );
    let mut line_idx = 0usize;
    let mut cursor_x = rect.x + line_offset(&line_offsets, 0);
    let mut cursor_y = rect.y;
    let initial_len = out.len();

    let mut boundaries = text.span_boundaries();
    for (offset, ch) in text.text.char_indices() {
        if ch == '\n' {
            boundaries.push(offset);
            boundaries.push(offset + ch.len_utf8());
        }
    }
    boundaries.sort_unstable();
    boundaries.dedup();
    boundaries.retain(|offset| *offset <= text.text.len() && text.text.is_char_boundary(*offset));

    for range in boundaries.windows(2) {
        let start = range[0];
        let end = range[1];
        if start == end {
            continue;
        }
        let segment_style = effective_style_for_range(&text.span_styles, style, start, end);
        if !style_can_atlas_solid_fill(&segment_style) {
            out.truncate(initial_len);
            return None;
        }
        let static_text_motion = segment_style
            .paragraph_style
            .text_motion
            .unwrap_or(TextMotion::Static)
            == TextMotion::Static;
        if !static_text_motion {
            out.truncate(initial_len);
            return None;
        }

        let segment = &text.text[start..end];
        for part in segment.split_inclusive('\n') {
            let has_newline = part.ends_with('\n');
            let content = if has_newline {
                &part[..part.len().saturating_sub(1)]
            } else {
                part
            };

            if !content.is_empty() {
                let segment_font_size = segment_style.resolve_font_size(font_size);
                let Some(font) = fonts.resolve(&segment_style) else {
                    out.truncate(initial_len);
                    return None;
                };
                let local_rect = Rect {
                    x: (cursor_x - rect.x).round(),
                    y: (cursor_y - rect.y).round(),
                    width: rect.width,
                    height: rect.height,
                };
                let color = segment_style.resolve_text_color(fallback_color);
                let advance_px = collect_text_segment_cached_solid_atlas_placements(
                    content,
                    local_rect,
                    &segment_style,
                    color,
                    segment_font_size,
                    scale,
                    font,
                    glyph_cache,
                    out,
                )?;
                cursor_x += advance_px;
                current_line_height = current_line_height.max(line_height_for_render_style(
                    &segment_style,
                    segment_font_size,
                ));
            }

            if has_newline {
                line_idx += 1;
                cursor_x = rect.x + line_offset(&line_offsets, line_idx);
                cursor_y += current_line_height * scale;
                current_line_height = base_line_height;
            }
        }
    }

    Some(())
}

#[allow(clippy::too_many_arguments)]
pub fn collect_solid_text_atlas_run<'a>(
    text: impl Into<StyledTextRef<'a>>,
    rect: Rect,
    style: &TextStyle,
    fallback_color: Color,
    font_size: f32,
    scale: f32,
    fonts: &SoftwareTextFontSet,
    glyph_cache: &mut SoftwareGlyphRasterCache,
    out: &mut Vec<SoftwareGlyphAtlasRunGlyph>,
) -> Option<()> {
    let text: StyledTextRef<'a> = text.into();
    if text.is_empty()
        || rect.width <= 0.0
        || rect.height <= 0.0
        || !font_size.is_finite()
        || font_size <= 0.0
        || !scale.is_finite()
        || scale <= 0.0
    {
        return Some(());
    }

    let base_line_height = line_height_for_render_style(style, font_size);
    let mut current_line_height = base_line_height;
    // Each line of the block is aligned in its own right; see
    // `annotated_line_alignment_offsets`.
    let line_offsets = annotated_line_alignment_offsets(&text, style, font_size, scale, fonts);
    let mut line_idx = 0usize;
    let mut cursor_x = rect.x + line_offset(&line_offsets, 0);
    let mut cursor_y = rect.y;
    let initial_len = out.len();

    let mut boundaries = text.span_boundaries();
    for (offset, ch) in text.text.char_indices() {
        if ch == '\n' {
            boundaries.push(offset);
            boundaries.push(offset + ch.len_utf8());
        }
    }
    boundaries.sort_unstable();
    boundaries.dedup();
    boundaries.retain(|offset| *offset <= text.text.len() && text.text.is_char_boundary(*offset));

    for range in boundaries.windows(2) {
        let start = range[0];
        let end = range[1];
        if start == end {
            continue;
        }
        let segment_style = effective_style_for_range(text.span_styles, style, start, end);
        if !style_can_atlas_solid_fill(&segment_style) {
            out.truncate(initial_len);
            return None;
        }
        let static_text_motion = segment_style
            .paragraph_style
            .text_motion
            .unwrap_or(TextMotion::Static)
            == TextMotion::Static;
        if !static_text_motion {
            out.truncate(initial_len);
            return None;
        }

        let segment = &text.text[start..end];
        for part in segment.split_inclusive('\n') {
            let has_newline = part.ends_with('\n');
            let content = if has_newline {
                &part[..part.len().saturating_sub(1)]
            } else {
                part
            };

            if !content.is_empty() {
                let segment_font_size = segment_style.resolve_font_size(font_size);
                let Some(font) = fonts.resolve(&segment_style) else {
                    out.truncate(initial_len);
                    return None;
                };
                let local_rect = Rect {
                    x: (cursor_x - rect.x).round(),
                    y: (cursor_y - rect.y).round(),
                    width: rect.width,
                    height: rect.height,
                };
                let color = segment_style.resolve_text_color(fallback_color);
                let advance_px = collect_text_segment_solid_atlas_run(
                    content,
                    local_rect,
                    &segment_style,
                    color,
                    segment_font_size,
                    scale,
                    font,
                    glyph_cache,
                    out,
                )?;
                cursor_x += advance_px;
                current_line_height = current_line_height.max(line_height_for_render_style(
                    &segment_style,
                    segment_font_size,
                ));
            }

            if has_newline {
                line_idx += 1;
                cursor_x = rect.x + line_offset(&line_offsets, line_idx);
                cursor_y += current_line_height * scale;
                current_line_height = base_line_height;
            }
        }
    }

    Some(())
}

pub fn measure_text_with_font(
    text: &str,
    style: &TextStyle,
    font_size: f32,
    font: &SoftwareTextFont,
) -> TextMetrics {
    measure_text_impl(
        text,
        style,
        font_size,
        font.ab_glyph_px_size(font_size),
        &font.font,
        font.style(),
        font.weight(),
    )
}

fn measure_text_with_font_cached(
    text: &str,
    style: &TextStyle,
    font_size: f32,
    font: &SoftwareTextFont,
    cache: &mut SoftwareTextMetricsCache,
) -> TextMetrics {
    measure_text_impl_cached(text, style, font_size, font, cache)
}

pub fn measure_annotated_text_with_font(
    text: &AnnotatedString,
    style: &TextStyle,
    font_size: f32,
    font: &SoftwareTextFont,
) -> TextMetrics {
    if text.span_styles.is_empty() {
        return measure_text_with_font(text.text.as_str(), style, font_size, font);
    }
    measure_annotated_text_with_resolver(
        text,
        style,
        font_size,
        &SoftwareTextFontSet::from_font(font.clone()),
        None,
    )
}

pub fn measure_annotated_text_with_font_set(
    text: &AnnotatedString,
    style: &TextStyle,
    font_size: f32,
    fonts: &SoftwareTextFontSet,
) -> TextMetrics {
    if text.span_styles.is_empty() {
        if let Some(font) = fonts.resolve(style) {
            return measure_text_with_font(text.text.as_str(), style, font_size, font);
        }
        return fallback_text_metrics(text.text.as_str(), style, font_size);
    }
    measure_annotated_text_with_resolver(text, style, font_size, fonts, None)
}

fn measure_annotated_text_with_font_set_cached(
    text: &AnnotatedString,
    style: &TextStyle,
    font_size: f32,
    fonts: &SoftwareTextFontSet,
    cache: &mut SoftwareTextMetricsCache,
) -> TextMetrics {
    if text.span_styles.is_empty() {
        if let Some(font) = fonts.resolve(style) {
            return measure_text_with_font_cached(
                text.text.as_str(),
                style,
                font_size,
                font,
                cache,
            );
        }
        return fallback_text_metrics(text.text.as_str(), style, font_size);
    }
    measure_annotated_text_with_resolver(text, style, font_size, fonts, Some(cache))
}

pub fn text_offset_for_position_with_font(
    text: &str,
    style: &TextStyle,
    x: f32,
    y: f32,
    font: &SoftwareTextFont,
) -> usize {
    if text.is_empty() {
        return 0;
    }

    let font_size = resolve_font_size(style);
    let glyph_font_size = font.ab_glyph_px_size(font_size);
    let line_height = resolve_line_height(style, font_size * 1.4);

    let line_index = (y / line_height).floor().max(0.0) as usize;
    let lines: Vec<&str> = text.split('\n').collect();
    let target_line = line_index.min(lines.len().saturating_sub(1));

    let mut line_start_byte = 0;
    for line in lines.iter().take(target_line) {
        line_start_byte += line.len() + 1;
    }

    let line_text = lines.get(target_line).unwrap_or(&"");
    if line_text.is_empty() {
        return line_start_byte;
    }

    let mut best_offset = 0;
    let mut best_distance = f32::INFINITY;
    let mut current_byte_offset = 0;

    for c in line_text.chars() {
        let prefix = &line_text[..current_byte_offset];
        let glyph_x = measure_text_impl(
            prefix,
            style,
            font_size,
            glyph_font_size,
            &font.font,
            font.style(),
            font.weight(),
        )
        .width;

        let char_str = &line_text[current_byte_offset..current_byte_offset + c.len_utf8()];
        let char_width = measure_text_impl(
            char_str,
            style,
            font_size,
            glyph_font_size,
            &font.font,
            font.style(),
            font.weight(),
        )
        .width
        .max(font_size * 0.5);

        let left_dist = (x - glyph_x).abs();
        if left_dist < best_distance {
            best_distance = left_dist;
            best_offset = current_byte_offset;
        }

        let right_x = glyph_x + char_width;
        let right_dist = (x - right_x).abs();
        if right_dist < best_distance {
            best_distance = right_dist;
            best_offset = current_byte_offset + c.len_utf8();
        }

        current_byte_offset += c.len_utf8();
    }

    let total_width = measure_text_impl(
        line_text,
        style,
        font_size,
        glyph_font_size,
        &font.font,
        font.style(),
        font.weight(),
    )
    .width;
    let end_dist = (x - total_width).abs();
    if end_dist < best_distance {
        best_offset = line_text.len();
    }

    line_start_byte + best_offset.min(line_text.len())
}

pub fn cursor_x_for_offset_with_font(
    text: &str,
    style: &TextStyle,
    offset: usize,
    font: &SoftwareTextFont,
) -> f32 {
    let clamped_offset = clamp_to_char_boundary(text, offset.min(text.len()));
    if clamped_offset == 0 {
        return 0.0;
    }

    let font_size = resolve_font_size(style);
    measure_text_impl(
        &text[..clamped_offset],
        style,
        font_size,
        font.ab_glyph_px_size(font_size),
        &font.font,
        font.style(),
        font.weight(),
    )
    .width
}

pub fn layout_text_with_font(
    text: &str,
    style: &TextStyle,
    font: &SoftwareTextFont,
) -> TextLayoutResult {
    let font_size = resolve_font_size(style);
    let glyph_font_size = font.ab_glyph_px_size(font_size);
    let resolved_weight = font.weight();
    let resolved_style = font.style();
    let weight_synthesis = TextWeightSynthesis::for_style(style, resolved_weight, font_size, 1.0);
    let font = &font.font;
    let line_height = resolve_line_height(style, font_size * 1.4);
    let letter_spacing = resolve_letter_spacing(style, font_size);
    let scaled_font = font.as_scaled(PxScale::from(glyph_font_size));

    let mut glyph_x_positions = Vec::new();
    let mut char_to_byte = Vec::new();
    let mut glyph_layouts = Vec::new();
    let mut lines = Vec::new();
    let mut current_x = 0.0f32;
    let mut line_start = 0;
    let mut y = 0.0f32;

    let mut iter = text.char_indices().peekable();
    while let Some((byte_offset, c)) = iter.next() {
        glyph_x_positions.push(current_x);
        char_to_byte.push(byte_offset);

        if c == '\n' {
            lines.push(LineLayout {
                start_offset: line_start,
                end_offset: byte_offset,
                y,
                height: line_height,
            });
            line_start = byte_offset + 1;
            y += line_height;
            current_x = 0.0;
        } else {
            let glyph_id = scaled_font.glyph_id(c);
            let glyph_width =
                weight_synthesis.apply_width(scaled_font.h_advance(glyph_id).max(0.0));
            let glyph_end = byte_offset + c.len_utf8();
            if glyph_end > byte_offset {
                glyph_layouts.push(GlyphLayout {
                    line_index: lines.len(),
                    start_offset: byte_offset,
                    end_offset: glyph_end,
                    x: current_x,
                    y,
                    width: glyph_width,
                    height: line_height,
                });
            }
            current_x += glyph_width;
            if let Some((_, next)) = iter.peek() {
                if *next != '\n' {
                    current_x += letter_spacing;
                }
            }
        }
    }

    glyph_x_positions.push(current_x);
    char_to_byte.push(text.len());

    lines.push(LineLayout {
        start_offset: line_start,
        end_offset: text.len(),
        y,
        height: line_height,
    });

    let metrics = measure_text_impl(
        text,
        style,
        font_size,
        glyph_font_size,
        font,
        resolved_style,
        resolved_weight,
    );
    TextLayoutResult::new(
        text,
        TextLayoutData {
            width: metrics.width,
            height: metrics.height,
            line_height,
            glyph_x_positions,
            char_to_byte,
            lines,
            glyph_layouts,
        },
    )
}

pub fn rasterize_text_to_image_with_font(
    text: &str,
    rect: Rect,
    style: &TextStyle,
    fallback_color: Color,
    font_size: f32,
    scale: f32,
    font: &impl Font,
) -> Option<ImageBitmap> {
    rasterize_text_to_image_impl(
        TextRasterImageRequest {
            text,
            rect,
            style,
            fallback_color,
            font_size,
            scale,
        },
        RasterFontRef {
            font,
            ab_glyph_scale_factor: 1.0,
            weight: FontWeight::NORMAL,
            style: FontStyle::Normal,
        },
        0,
        None,
    )
}

struct TextRasterImageRequest<'a> {
    text: &'a str,
    rect: Rect,
    style: &'a TextStyle,
    fallback_color: Color,
    font_size: f32,
    scale: f32,
}

fn rasterize_text_to_image_impl(
    request: TextRasterImageRequest<'_>,
    font_ref: RasterFontRef<'_, impl Font>,
    font_cache_key: u64,
    mut glyph_cache: Option<&mut SoftwareGlyphRasterCache>,
) -> Option<ImageBitmap> {
    let TextRasterImageRequest {
        text,
        rect,
        style,
        fallback_color,
        font_size,
        scale,
    } = request;

    if text.is_empty()
        || rect.width <= 0.0
        || rect.height <= 0.0
        || !font_size.is_finite()
        || font_size <= 0.0
        || !scale.is_finite()
        || scale <= 0.0
    {
        return None;
    }

    let width = rect.width.ceil().max(1.0) as u32;
    let height = rect.height.ceil().max(1.0) as u32;

    let fallback_brush = Brush::solid(fallback_color);
    let (brush, brush_alpha_multiplier) = match style.span_style.brush.as_ref() {
        Some(brush) => (brush, style.span_style.alpha.unwrap_or(1.0).clamp(0.0, 1.0)),
        None => (&fallback_brush, 1.0),
    };
    let raster_style = match style.span_style.draw_style.unwrap_or(TextDrawStyle::Fill) {
        TextDrawStyle::Fill => GlyphRasterStyle::Fill,
        TextDrawStyle::Stroke { width } => {
            if width.is_finite() && width > 0.0 {
                GlyphRasterStyle::Stroke {
                    width_px: width * scale,
                }
            } else {
                GlyphRasterStyle::Fill
            }
        }
    };
    let shadow = style
        .span_style
        .shadow
        .filter(|shadow| shadow.color.3 > 0.0);
    let static_text_motion = style
        .paragraph_style
        .text_motion
        .unwrap_or(TextMotion::Static)
        == TextMotion::Static;

    let origin_x = if static_text_motion {
        0.0
    } else {
        rect.x.fract()
    };
    let origin_y = if static_text_motion {
        0.0
    } else {
        rect.y.fract()
    };

    let font = font_ref.font;
    let font_px_size = font_size * scale * font_ref.ab_glyph_scale_factor;
    let letter_spacing = resolve_letter_spacing(style, font_size) * scale;
    let align_fraction = crate::scene_builder::text_align_fraction(style, text);
    let weight_synthesis = TextWeightSynthesis::for_style(style, font_ref.weight, font_size, scale);
    let style_synthesis = TextStyleSynthesis::for_style(style, font_ref.style, font_size, scale);
    let metrics = vertical_metrics(font, font_px_size);
    // Everything here is already in raster device pixels, so the line
    // box rounds on a grid of 1.
    let line_box = line_box_for(
        style,
        metrics,
        (style.resolve_line_height(14.0, font_size * 1.4) * scale).max(1.0),
        1.0,
    );
    let line_height = line_box.height;
    let first_baseline_y = line_box.baseline;

    if let Brush::Solid(color) = brush {
        if shadow.is_none() {
            let color = color_to_rgba(*color);
            let mut rgba = vec![0u8; (width * height * 4) as usize];
            visit_text_glyph_masks(
                text,
                font,
                font_cache_key,
                font_px_size,
                line_height,
                first_baseline_y,
                origin_x,
                origin_y,
                letter_spacing,
                align_fraction,
                static_text_motion,
                raster_style,
                weight_synthesis,
                style_synthesis,
                glyph_cache.as_deref_mut(),
                |mask| {
                    draw_mask_glyph_solid_u8(
                        &mut rgba,
                        width,
                        height,
                        mask,
                        color,
                        brush_alpha_multiplier,
                    );
                },
            );

            return ImageBitmap::from_rgba8(width, height, rgba).ok();
        }
    }

    let mut canvas = vec![[0.0f32; 4]; (width * height) as usize];
    visit_text_glyph_masks(
        text,
        font,
        font_cache_key,
        font_px_size,
        line_height,
        first_baseline_y,
        origin_x,
        origin_y,
        letter_spacing,
        align_fraction,
        static_text_motion,
        raster_style,
        weight_synthesis,
        style_synthesis,
        glyph_cache,
        |mask| {
            if let Some(shadow) = shadow {
                draw_shadow_mask(
                    &mut canvas,
                    width,
                    height,
                    mask,
                    shadow,
                    scale,
                    static_text_motion,
                );
            }

            draw_mask_glyph(
                &mut canvas,
                width,
                height,
                mask,
                brush,
                brush_alpha_multiplier,
                rect,
            );
        },
    );

    let mut rgba = vec![0u8; canvas.len() * 4];
    for (index, pixel) in canvas.iter().enumerate() {
        let base = index * 4;
        rgba[base] = (pixel[0].clamp(0.0, 1.0) * 255.0).round() as u8;
        rgba[base + 1] = (pixel[1].clamp(0.0, 1.0) * 255.0).round() as u8;
        rgba[base + 2] = (pixel[2].clamp(0.0, 1.0) * 255.0).round() as u8;
        rgba[base + 3] = (pixel[3].clamp(0.0, 1.0) * 255.0).round() as u8;
    }

    ImageBitmap::from_rgba8(width, height, rgba).ok()
}

fn style_can_rasterize_direct_solid(style: &TextStyle) -> bool {
    if style
        .span_style
        .shadow
        .is_some_and(|shadow| shadow.color.3 > 0.0)
    {
        return false;
    }
    matches!(
        style.span_style.brush.as_ref(),
        None | Some(Brush::Solid(_))
    )
}

fn style_can_atlas_solid_fill(style: &TextStyle) -> bool {
    if style
        .span_style
        .shadow
        .is_some_and(|shadow| shadow.color.3 > 0.0)
    {
        return false;
    }
    if !matches!(
        style.span_style.brush.as_ref(),
        None | Some(Brush::Solid(_))
    ) {
        return false;
    }
    match style.span_style.draw_style.unwrap_or(TextDrawStyle::Fill) {
        TextDrawStyle::Fill => true,
        TextDrawStyle::Stroke { width } => !width.is_finite() || width <= 0.0,
    }
}

#[allow(clippy::too_many_arguments)]
fn draw_text_segment_solid_to_rgba(
    canvas: &mut [u8],
    canvas_width: u32,
    canvas_height: u32,
    text: &str,
    local_rect: Rect,
    style: &TextStyle,
    color: Color,
    font_size: f32,
    scale: f32,
    font: &SoftwareTextFont,
    glyph_cache: &mut SoftwareGlyphRasterCache,
) -> f32 {
    if text.is_empty()
        || local_rect.width <= 0.0
        || local_rect.height <= 0.0
        || !font_size.is_finite()
        || font_size <= 0.0
        || !scale.is_finite()
        || scale <= 0.0
    {
        return 0.0;
    }

    let raster_style = match style.span_style.draw_style.unwrap_or(TextDrawStyle::Fill) {
        TextDrawStyle::Fill => GlyphRasterStyle::Fill,
        TextDrawStyle::Stroke { width } => {
            if width.is_finite() && width > 0.0 {
                GlyphRasterStyle::Stroke {
                    width_px: width * scale,
                }
            } else {
                GlyphRasterStyle::Fill
            }
        }
    };
    let text_motion_static = style
        .paragraph_style
        .text_motion
        .unwrap_or(TextMotion::Static)
        == TextMotion::Static;
    let font_px_size = font.ab_glyph_px_size(font_size) * scale;
    let letter_spacing = resolve_letter_spacing(style, font_size) * scale;
    let align_fraction = crate::scene_builder::text_align_fraction(style, text);
    let weight_synthesis = TextWeightSynthesis::for_style(style, font.weight(), font_size, scale);
    let style_synthesis = TextStyleSynthesis::for_style(style, font.style(), font_size, scale);
    let metrics = vertical_metrics(&font.font, font_px_size);
    // Everything here is already in raster device pixels, so the line
    // box rounds on a grid of 1.
    let line_box = line_box_for(
        style,
        metrics,
        (style.resolve_line_height(14.0, font_size * 1.4) * scale).max(1.0),
        1.0,
    );
    let line_height = line_box.height;
    let first_baseline_y = local_rect.y + line_box.baseline;
    let origin_x = if text_motion_static {
        local_rect.x.round()
    } else {
        local_rect.x + local_rect.x.fract()
    };
    let color = color_to_rgba(color);

    visit_text_glyph_masks(
        text,
        &font.font,
        font.content_hash(),
        font_px_size,
        line_height,
        first_baseline_y,
        origin_x,
        0.0,
        letter_spacing,
        align_fraction,
        text_motion_static,
        raster_style,
        weight_synthesis,
        style_synthesis,
        Some(glyph_cache),
        |mask| draw_mask_glyph_solid_u8(canvas, canvas_width, canvas_height, mask, color, 1.0),
    )
}

#[allow(clippy::too_many_arguments)]
fn collect_text_segment_solid_atlas_glyphs(
    text: &str,
    local_rect: Rect,
    style: &TextStyle,
    color: Color,
    font_size: f32,
    scale: f32,
    font: &SoftwareTextFont,
    glyph_cache: &mut SoftwareGlyphRasterCache,
    out: &mut Vec<SoftwareGlyphAtlasGlyph>,
) -> Option<f32> {
    if text.is_empty()
        || local_rect.width <= 0.0
        || local_rect.height <= 0.0
        || !font_size.is_finite()
        || font_size <= 0.0
        || !scale.is_finite()
        || scale <= 0.0
    {
        return Some(0.0);
    }
    if !style_can_atlas_solid_fill(style) {
        return None;
    }

    let text_motion_static = style
        .paragraph_style
        .text_motion
        .unwrap_or(TextMotion::Static)
        == TextMotion::Static;
    if !text_motion_static {
        return None;
    }

    let font_px_size = font.ab_glyph_px_size(font_size) * scale;
    let letter_spacing = resolve_letter_spacing(style, font_size) * scale;
    let align_fraction = crate::scene_builder::text_align_fraction(style, text);
    let weight_synthesis = TextWeightSynthesis::for_style(style, font.weight(), font_size, scale);
    let style_synthesis = TextStyleSynthesis::for_style(style, font.style(), font_size, scale);
    let metrics = vertical_metrics(&font.font, font_px_size);
    // Everything here is already in raster device pixels, so the line
    // box rounds on a grid of 1.
    let line_box = line_box_for(
        style,
        metrics,
        (style.resolve_line_height(14.0, font_size * 1.4) * scale).max(1.0),
        1.0,
    );
    let line_height = line_box.height;
    let first_baseline_y = local_rect.y + line_box.baseline;
    let origin_x = local_rect.x.round();
    let initial_len = out.len();

    let advance = visit_text_glyph_masks_with_key(
        text,
        &font.font,
        font.content_hash(),
        font_px_size,
        line_height,
        first_baseline_y,
        origin_x,
        0.0,
        letter_spacing,
        align_fraction,
        true,
        GlyphRasterStyle::Fill,
        weight_synthesis,
        style_synthesis,
        Some(glyph_cache),
        |key, mask| {
            if mask.width == 0 || mask.height == 0 {
                return;
            }
            out.push(SoftwareGlyphAtlasGlyph {
                key,
                mask: SoftwareGlyphAtlasMask {
                    alpha: Arc::clone(&mask.alpha),
                    width: mask.width,
                    height: mask.height,
                },
                x: mask.origin_x,
                y: mask.origin_y,
                color,
            });
        },
    );

    if advance.is_finite() {
        Some(advance)
    } else {
        out.truncate(initial_len);
        None
    }
}

#[allow(clippy::too_many_arguments)]
fn collect_text_segment_cached_solid_atlas_placements(
    text: &str,
    local_rect: Rect,
    style: &TextStyle,
    color: Color,
    font_size: f32,
    scale: f32,
    font: &SoftwareTextFont,
    glyph_cache: &mut SoftwareGlyphRasterCache,
    out: &mut Vec<SoftwareGlyphAtlasPlacement>,
) -> Option<f32> {
    if text.is_empty()
        || local_rect.width <= 0.0
        || local_rect.height <= 0.0
        || !font_size.is_finite()
        || font_size <= 0.0
        || !scale.is_finite()
        || scale <= 0.0
    {
        return Some(0.0);
    }
    if !style_can_atlas_solid_fill(style) {
        return None;
    }

    let text_motion_static = style
        .paragraph_style
        .text_motion
        .unwrap_or(TextMotion::Static)
        == TextMotion::Static;
    if !text_motion_static {
        return None;
    }

    let font_px_size = font.ab_glyph_px_size(font_size) * scale;
    let letter_spacing = resolve_letter_spacing(style, font_size) * scale;
    let align_fraction = crate::scene_builder::text_align_fraction(style, text);
    let weight_synthesis = TextWeightSynthesis::for_style(style, font.weight(), font_size, scale);
    let style_synthesis = TextStyleSynthesis::for_style(style, font.style(), font_size, scale);
    let metrics = vertical_metrics(&font.font, font_px_size);
    // Everything here is already in raster device pixels, so the line
    // box rounds on a grid of 1.
    let line_box = line_box_for(
        style,
        metrics,
        (style.resolve_line_height(14.0, font_size * 1.4) * scale).max(1.0),
        1.0,
    );
    let line_height = line_box.height;
    let first_baseline_y = local_rect.y + line_box.baseline;
    let origin_x = local_rect.x.round();
    let initial_len = out.len();

    let advance = visit_cached_text_glyph_atlas_placements(
        text,
        &font.font,
        font.content_hash(),
        font_px_size,
        line_height,
        first_baseline_y,
        origin_x,
        0.0,
        letter_spacing,
        align_fraction,
        GlyphRasterStyle::Fill,
        weight_synthesis,
        style_synthesis,
        glyph_cache,
        |placement| {
            if placement.width == 0 || placement.height == 0 {
                return;
            }
            out.push(SoftwareGlyphAtlasPlacement { color, ..placement });
        },
    );

    if advance.is_finite() {
        Some(advance)
    } else {
        out.truncate(initial_len);
        None
    }
}

#[allow(clippy::too_many_arguments)]
fn collect_text_segment_solid_atlas_run(
    text: &str,
    local_rect: Rect,
    style: &TextStyle,
    color: Color,
    font_size: f32,
    scale: f32,
    font: &SoftwareTextFont,
    glyph_cache: &mut SoftwareGlyphRasterCache,
    out: &mut Vec<SoftwareGlyphAtlasRunGlyph>,
) -> Option<f32> {
    if text.is_empty()
        || local_rect.width <= 0.0
        || local_rect.height <= 0.0
        || !font_size.is_finite()
        || font_size <= 0.0
        || !scale.is_finite()
        || scale <= 0.0
    {
        return Some(0.0);
    }
    if !style_can_atlas_solid_fill(style) {
        return None;
    }

    let text_motion_static = style
        .paragraph_style
        .text_motion
        .unwrap_or(TextMotion::Static)
        == TextMotion::Static;
    if !text_motion_static {
        return None;
    }

    let font_px_size = font.ab_glyph_px_size(font_size) * scale;
    let letter_spacing = resolve_letter_spacing(style, font_size) * scale;
    let align_fraction = crate::scene_builder::text_align_fraction(style, text);
    let weight_synthesis = TextWeightSynthesis::for_style(style, font.weight(), font_size, scale);
    let style_synthesis = TextStyleSynthesis::for_style(style, font.style(), font_size, scale);
    let metrics = vertical_metrics(&font.font, font_px_size);
    // Everything here is already in raster device pixels, so the line
    // box rounds on a grid of 1.
    let line_box = line_box_for(
        style,
        metrics,
        (style.resolve_line_height(14.0, font_size * 1.4) * scale).max(1.0),
        1.0,
    );
    let line_height = line_box.height;
    let first_baseline_y = local_rect.y + line_box.baseline;
    let origin_x = local_rect.x.round();
    let initial_len = out.len();

    let advance = visit_text_glyph_atlas_run(
        text,
        &font.font,
        font.content_hash(),
        font_px_size,
        line_height,
        first_baseline_y,
        origin_x,
        0.0,
        letter_spacing,
        align_fraction,
        GlyphRasterStyle::Fill,
        weight_synthesis,
        style_synthesis,
        glyph_cache,
        |run_glyph| {
            let run_glyph = match run_glyph {
                SoftwareGlyphAtlasRunGlyph::Cached(mut placement) => {
                    if placement.width == 0 || placement.height == 0 {
                        return;
                    }
                    placement.color = color;
                    SoftwareGlyphAtlasRunGlyph::Cached(placement)
                }
                SoftwareGlyphAtlasRunGlyph::New(mut glyph) => {
                    if glyph.mask.width == 0 || glyph.mask.height == 0 {
                        return;
                    }
                    glyph.color = color;
                    SoftwareGlyphAtlasRunGlyph::New(glyph)
                }
            };
            out.push(run_glyph);
        },
    );

    if advance.is_finite() {
        Some(advance)
    } else {
        out.truncate(initial_len);
        None
    }
}

fn resolve_font_size(style: &TextStyle) -> f32 {
    style.resolve_font_size(14.0)
}

/// The line box a style asks for, in the unit `metrics` and `line_height` are
/// already in.
///
/// `grid` is how many device pixels one of those units is worth — `1.0` on the
/// raster paths, where everything has already been multiplied by the render
/// scale, and the density on the measure paths, which work in layout points.
///
/// A style that leaves `line_height_style` unset — every style in the framework
/// but the Wear ones — comes back through the same arithmetic this function
/// used before it took a style at all.
fn line_box_for(
    style: &TextStyle,
    metrics: crate::font_layout::FontVerticalMetrics,
    line_height: f32,
    grid: f32,
) -> cranpose_ui::text::LineBox {
    cranpose_ui::text::line_box(
        style,
        cranpose_ui::text::FontExtent::new(metrics.ascent, -metrics.descent, metrics.line_gap),
        line_height,
        grid,
    )
}

/// The device grid a measurement in layout points rounds on.
///
/// A measurer runs inside an app context in the running app, but the offline
/// raster paths and this file's own tests call it without one, and asking for
/// the ambient density there is a panic rather than a default. Those callers
/// are all working at one pixel per point by definition.
fn measure_grid() -> f32 {
    if cranpose_ui::has_current_app_context() {
        cranpose_ui::current_density()
    } else {
        1.0
    }
}

fn baseline_y_for_line_box(
    style: &TextStyle,
    metrics: crate::font_layout::FontVerticalMetrics,
    line_height: f32,
    grid: f32,
) -> f32 {
    line_box_for(style, metrics, line_height, grid).baseline
}

fn resolve_line_height(style: &TextStyle, font_size: f32) -> f32 {
    style.resolve_line_height(14.0, font_size)
}

fn line_height_for_render_style(style: &TextStyle, font_size: f32) -> f32 {
    resolve_line_height(style, font_size * 1.4).max(1.0)
}

fn resolve_letter_spacing(style: &TextStyle, font_size: f32) -> f32 {
    let _ = font_size;
    style.resolve_letter_spacing(14.0)
}

/// How much width `char_count` characters of tracking add to a run.
///
/// **A run of `n` characters carries `n` letter spaces, not `n - 1`.** Android
/// resolves `letterSpacing` in Minikin, which distributes it as HALF a letter
/// space on each side of every cluster: `LayoutCore.cpp` adds
/// `letterSpaceHalf` to the pen before the first glyph of a script run, a full
/// `letterSpace` at each cluster boundary, and `letterSpaceHalf` again after
/// the last glyph. Every character therefore ends up carrying exactly one
/// letter space in `mAdvances[]`, which is what `StaticLayout` sums to get a
/// line's width. (Compose reaches that code by putting the value on the paint:
/// `LetterSpacingSpanPx` divides the px value by `textSize * textScaleX` and
/// assigns `TextPaint.letterSpacing`, and `TextPaintExtensions.android.kt`
/// does the same for a paragraph-level `Sp` tracking.)
///
/// The trailing half is real on the platform this is measured against — the
/// `sdk_gwear` emulator runs Android 14, whose `Layout.cpp` has no letter
/// spacing code at all. The edge-trimming that removes the two half spaces
/// (`adjustAdvanceLetterSpacingEdge`) only arrives in Android 15, and is
/// opt-in per run there.
///
/// An empty run carries none: the loop that adds them never runs.
fn run_tracking(char_count: usize, letter_spacing: f32) -> f32 {
    char_count as f32 * letter_spacing
}

/// The lead-in before a run's first glyph: half a letter space, or nothing at
/// all for an empty run. See [`run_tracking`].
fn run_lead_in(char_count: usize, letter_spacing: f32) -> f32 {
    if char_count == 0 {
        0.0
    } else {
        letter_spacing * 0.5
    }
}

fn fallback_char_width(font_size: f32) -> f32 {
    font_size.max(1.0) * 0.55
}

fn fallback_line_height(style: &TextStyle, font_size: f32) -> f32 {
    resolve_line_height(style, font_size.max(1.0) * 1.2)
}

fn fallback_line_heights(text: &str, style: &TextStyle, font_size: f32) -> Vec<f32> {
    let line_count = text.split('\n').count().max(1);
    vec![fallback_line_height(style, font_size); line_count]
}

fn fallback_text_metrics(text: &str, style: &TextStyle, font_size: f32) -> TextMetrics {
    let line_height = fallback_line_height(style, font_size);
    let char_width = fallback_char_width(font_size);
    let letter_spacing = resolve_letter_spacing(style, font_size);
    let mut line_count = 0usize;
    let mut max_width = 0.0f32;

    for line in text.split('\n') {
        line_count += 1;
        let char_count = line.chars().count();
        let spacing = run_tracking(char_count, letter_spacing);
        max_width = max_width.max(char_count as f32 * char_width + spacing);
    }

    let line_count = line_count.max(1);
    TextMetrics {
        width: max_width,
        height: line_count as f32 * line_height,
        line_height,
        line_count,
    }
}

fn fallback_cursor_x_for_offset(text: &str, style: &TextStyle, offset: usize) -> f32 {
    let font_size = resolve_font_size(style);
    let clamped = clamp_to_char_boundary(text, offset.min(text.len()));
    let line_start = text[..clamped].rfind('\n').map_or(0, |index| index + 1);
    let char_count = text[line_start..clamped].chars().count();
    // The caret after `k` characters sits at the sum of their advances, and
    // every character's advance carries a whole letter space (`run_tracking`).
    let spacing = run_tracking(char_count, resolve_letter_spacing(style, font_size));
    char_count as f32 * fallback_char_width(font_size) + spacing
}

fn fallback_text_offset_for_position(text: &str, style: &TextStyle, x: f32, y: f32) -> usize {
    if text.is_empty() {
        return 0;
    }

    let font_size = resolve_font_size(style);
    let line_height = fallback_line_height(style, font_size);
    let line_index = (y / line_height).floor().max(0.0) as usize;
    let lines: Vec<&str> = text.split('\n').collect();
    let target_line = line_index.min(lines.len().saturating_sub(1));

    let mut line_start_byte = 0;
    for line in lines.iter().take(target_line) {
        line_start_byte += line.len() + 1;
    }

    let line_text = lines.get(target_line).copied().unwrap_or("");
    if line_text.is_empty() {
        return line_start_byte;
    }

    let advance =
        (fallback_char_width(font_size) + resolve_letter_spacing(style, font_size)).max(1.0);
    let target_char = (x / advance).round().max(0.0) as usize;
    line_start_byte + byte_offset_for_char_index(line_text, target_char)
}

fn fallback_layout_text(text: &str, style: &TextStyle) -> TextLayoutResult {
    let font_size = resolve_font_size(style);
    let line_height = fallback_line_height(style, font_size);
    let char_width = fallback_char_width(font_size);
    let letter_spacing = resolve_letter_spacing(style, font_size);

    let mut glyph_x_positions = Vec::new();
    let mut char_to_byte = Vec::new();
    let mut glyph_layouts = Vec::new();
    let mut lines = Vec::new();
    let mut current_x = 0.0f32;
    let mut line_start = 0;
    let mut y = 0.0f32;

    let mut iter = text.char_indices().peekable();
    while let Some((byte_offset, ch)) = iter.next() {
        glyph_x_positions.push(current_x);
        char_to_byte.push(byte_offset);

        if ch == '\n' {
            lines.push(LineLayout {
                start_offset: line_start,
                end_offset: byte_offset,
                y,
                height: line_height,
            });
            line_start = byte_offset + 1;
            y += line_height;
            current_x = 0.0;
        } else {
            glyph_layouts.push(GlyphLayout {
                line_index: lines.len(),
                start_offset: byte_offset,
                end_offset: byte_offset + ch.len_utf8(),
                x: current_x,
                y,
                width: char_width,
                height: line_height,
            });
            current_x += char_width;
            if let Some((_, next)) = iter.peek() {
                if *next != '\n' {
                    current_x += letter_spacing;
                }
            }
        }
    }

    glyph_x_positions.push(current_x);
    char_to_byte.push(text.len());
    lines.push(LineLayout {
        start_offset: line_start,
        end_offset: text.len(),
        y,
        height: line_height,
    });

    let metrics = fallback_text_metrics(text, style, font_size);
    TextLayoutResult::new(
        text,
        TextLayoutData {
            width: metrics.width,
            height: metrics.height,
            line_height,
            glyph_x_positions,
            char_to_byte,
            glyph_layouts,
            lines,
        },
    )
}

fn style_allows_prefix_widths(style: &TextStyle) -> bool {
    !matches!(
        style
            .paragraph_style
            .platform_style
            .and_then(|platform| platform.shaping),
        Some(TextShaping::Advanced)
    )
}

fn cached_line_advance_width(
    font: &SoftwareTextFont,
    text: &str,
    glyph_font_size: f32,
    glyph_metrics: &mut SoftwareTextGlyphMetricsCache,
) -> f32 {
    let scaled_font = font.font.as_scaled(PxScale::from(glyph_font_size));
    // One scale factor for the whole run: the cache keeps font units, and this
    // is the multiply ab_glyph would have applied per lookup.
    let h_scale = scaled_font.h_scale_factor();
    let mut width = 0.0f32;
    let mut previous = None;

    for ch in text.chars() {
        let metrics = glyph_metrics.glyph_metrics(font, &scaled_font, ch);
        if let Some(previous_id) = previous {
            width +=
                glyph_metrics.kern(font, &scaled_font, previous_id, metrics.glyph_id) * h_scale;
        }
        width += metrics.advance_unscaled * h_scale;
        previous = Some(metrics.glyph_id);
    }

    width.max(0.0)
}

fn annotated_line_prefix_widths_with_font_set_cached(
    text: &AnnotatedString,
    line_range: std::ops::Range<usize>,
    style: &TextStyle,
    fonts: &SoftwareTextFontSet,
    cache: &mut SoftwareTextMetricsCache,
) -> Option<TextLinePrefixWidths> {
    let mut boundaries = text.span_boundaries();
    boundaries.push(line_range.start);
    boundaries.push(line_range.end);
    boundaries.sort_unstable();
    boundaries.dedup();
    boundaries.retain(|offset| {
        *offset >= line_range.start
            && *offset <= line_range.end
            && text.text.is_char_boundary(*offset)
    });

    let char_count = text.text[line_range.clone()].chars().count();
    let mut prefix_widths = Vec::with_capacity(char_count + 1);
    let mut separator_before = Vec::with_capacity(char_count);
    let non_empty_overhang = {
        let mut sink = PrefixWidthSegmentSink {
            prefix_widths: &mut prefix_widths,
            separator_before: &mut separator_before,
            width: 0.0,
            non_empty_overhang: 0.0,
        };
        sink.prefix_widths.push(sink.width);

        for range in boundaries.windows(2) {
            let start = range[0];
            let end = range[1];
            if start >= end {
                continue;
            }
            let segment = &text.text[start..end];
            let segment_style = effective_style_for_range(&text.span_styles, style, start, end);
            append_prefix_width_segment_cached(segment, &segment_style, fonts, cache, &mut sink);
        }

        sink.non_empty_overhang
    };

    TextLinePrefixWidths::from_parts(prefix_widths, separator_before, non_empty_overhang)
}

struct PrefixWidthSegmentSink<'a> {
    prefix_widths: &'a mut Vec<f32>,
    separator_before: &'a mut Vec<f32>,
    width: f32,
    non_empty_overhang: f32,
}

fn append_prefix_width_segment_cached(
    segment: &str,
    style: &TextStyle,
    fonts: &SoftwareTextFontSet,
    cache: &mut SoftwareTextMetricsCache,
    sink: &mut PrefixWidthSegmentSink<'_>,
) {
    if segment.is_empty() {
        return;
    }

    let font_size = resolve_font_size(style);
    if let Some(font) = fonts.resolve(style) {
        append_font_prefix_width_segment_cached(segment, style, font_size, font, cache, sink);
    } else {
        append_fallback_prefix_width_segment(segment, style, font_size, sink);
    }
}

fn append_font_prefix_width_segment_cached(
    segment: &str,
    style: &TextStyle,
    font_size: f32,
    font: &SoftwareTextFont,
    cache: &mut SoftwareTextMetricsCache,
    sink: &mut PrefixWidthSegmentSink<'_>,
) {
    let glyph_font_size = font.ab_glyph_px_size(font_size);
    let scaled_font = font.font.as_scaled(PxScale::from(glyph_font_size));
    let letter_spacing = resolve_letter_spacing(style, font_size);
    let weight_synthesis = TextWeightSynthesis::for_style(style, font.weight(), font_size, 1.0);
    let style_synthesis = TextStyleSynthesis::for_style(style, font.style(), font_size, 1.0);
    sink.non_empty_overhang = sink
        .non_empty_overhang
        .max(style_synthesis.visual_overhang_px());

    let mut previous = None;
    // One scale factor for the whole run: the cache keeps font units.
    let h_scale = scaled_font.h_scale_factor();

    for (index, ch) in segment.chars().enumerate() {
        let metrics = cache.glyph_metrics.glyph_metrics(font, &scaled_font, ch);
        // `separator_before` is the KERN alone. The letter space belongs to
        // the character rather than to the gap before it (`run_tracking`), so
        // it goes into `width` unconditionally -- and a line that starts
        // mid-string, which drops `separator_before[start]`, still keeps one
        // letter space for every character it contains.
        let separator = if index == 0 {
            0.0
        } else {
            previous
                .map(|previous_id| {
                    weight_synthesis.apply_width(
                        cache
                            .glyph_metrics
                            .kern(font, &scaled_font, previous_id, metrics.glyph_id)
                            * h_scale,
                    )
                })
                .unwrap_or(0.0)
        };
        sink.separator_before.push(separator);
        sink.width += separator
            + letter_spacing
            + weight_synthesis.apply_width(metrics.advance_unscaled * h_scale);
        sink.prefix_widths.push(sink.width.max(0.0));
        previous = Some(metrics.glyph_id);
    }
}

fn append_fallback_prefix_width_segment(
    segment: &str,
    style: &TextStyle,
    font_size: f32,
    sink: &mut PrefixWidthSegmentSink<'_>,
) {
    let char_width = fallback_char_width(font_size);
    let letter_spacing = resolve_letter_spacing(style, font_size);
    for _ in segment.chars() {
        // No kerning in the fallback, so nothing is dropped at a line's
        // leading edge; the letter space rides the character (`run_tracking`).
        sink.separator_before.push(0.0);
        sink.width += letter_spacing + char_width;
        sink.prefix_widths.push(sink.width.max(0.0));
    }
}

fn byte_offset_for_char_index(text: &str, char_index: usize) -> usize {
    text.char_indices()
        .map(|(index, _)| index)
        .nth(char_index)
        .unwrap_or(text.len())
}

fn measure_text_impl(
    text: &str,
    style: &TextStyle,
    font_size: f32,
    glyph_font_size: f32,
    font: &impl Font,
    resolved_style: FontStyle,
    resolved_weight: FontWeight,
) -> TextMetrics {
    let line_height = line_box_for(
        style,
        vertical_metrics(font, glyph_font_size),
        resolve_line_height(style, font_size * 1.4),
        measure_grid(),
    )
    .height;
    let letter_spacing = resolve_letter_spacing(style, font_size);
    let weight_synthesis = TextWeightSynthesis::for_style(style, resolved_weight, font_size, 1.0);
    let style_synthesis = TextStyleSynthesis::for_style(style, resolved_style, font_size, 1.0);

    let lines: Vec<&str> = text.split('\n').collect();
    let line_count = lines.len().max(1);

    let mut max_width: f32 = 0.0;
    for line in &lines {
        let line_width = line_advance_width(font, line, glyph_font_size);
        let char_spacing = run_tracking(line.chars().count(), letter_spacing);
        let line_width = (weight_synthesis.apply_width(line_width) + char_spacing).max(0.0);
        let line_width = if line.is_empty() {
            line_width
        } else {
            line_width + style_synthesis.visual_overhang_px()
        };
        max_width = max_width.max(line_width);
    }

    TextMetrics {
        width: max_width,
        height: line_count as f32 * line_height,
        line_height,
        line_count,
    }
}

fn measure_text_impl_cached(
    text: &str,
    style: &TextStyle,
    font_size: f32,
    font: &SoftwareTextFont,
    cache: &mut SoftwareTextMetricsCache,
) -> TextMetrics {
    let letter_spacing = resolve_letter_spacing(style, font_size);
    let weight_synthesis = TextWeightSynthesis::for_style(style, font.weight(), font_size, 1.0);
    let style_synthesis = TextStyleSynthesis::for_style(style, font.style(), font_size, 1.0);
    let glyph_font_size = font.ab_glyph_px_size(font_size);
    let line_height = line_box_for(
        style,
        vertical_metrics(&font.font, glyph_font_size),
        resolve_line_height(style, font_size * 1.4),
        measure_grid(),
    )
    .height;

    let lines: Vec<&str> = text.split('\n').collect();
    let line_count = lines.len().max(1);

    let mut max_width: f32 = 0.0;
    for line in &lines {
        let line_width =
            cached_line_advance_width(font, line, glyph_font_size, &mut cache.glyph_metrics);
        let char_spacing = run_tracking(line.chars().count(), letter_spacing);
        let line_width = (weight_synthesis.apply_width(line_width) + char_spacing).max(0.0);
        let line_width = if line.is_empty() {
            line_width
        } else {
            line_width + style_synthesis.visual_overhang_px()
        };
        max_width = max_width.max(line_width);
    }

    TextMetrics {
        width: max_width,
        height: line_count as f32 * line_height,
        line_height,
        line_count,
    }
}

fn measure_annotated_text_with_resolver(
    text: &AnnotatedString,
    style: &TextStyle,
    font_size: f32,
    fonts: &SoftwareTextFontSet,
    mut cache: Option<&mut SoftwareTextMetricsCache>,
) -> TextMetrics {
    let Some(base_font) = fonts.resolve(style) else {
        return fallback_text_metrics(text.text.as_str(), style, font_size);
    };
    let base_line_height = line_height_for_style(style, font_size, base_font);
    let mut boundaries = text.span_boundaries();
    for (offset, ch) in text.text.char_indices() {
        if ch == '\n' {
            boundaries.push(offset);
            boundaries.push(offset + ch.len_utf8());
        }
    }
    boundaries.sort_unstable();
    boundaries.dedup();
    boundaries.retain(|offset| *offset <= text.text.len() && text.text.is_char_boundary(*offset));

    let mut line_count = 1usize;
    let mut max_width = 0.0f32;
    let mut current_line_width = 0.0f32;

    for range in boundaries.windows(2) {
        let start = range[0];
        let end = range[1];
        if start == end {
            continue;
        }
        let segment = &text.text[start..end];
        let segment_style = effective_style_for_range(&text.span_styles, style, start, end);
        let segment_font_size = resolve_font_size(&segment_style);
        let Some(segment_font) = fonts.resolve(&segment_style) else {
            let mut remaining = segment;
            loop {
                if let Some(newline_offset) = remaining.find('\n') {
                    let before_newline = &remaining[..newline_offset];
                    if !before_newline.is_empty() {
                        current_line_width += fallback_text_metrics(
                            before_newline,
                            &segment_style,
                            segment_font_size,
                        )
                        .width;
                    }
                    max_width = max_width.max(current_line_width);
                    current_line_width = 0.0;
                    line_count += 1;
                    remaining = &remaining[newline_offset + 1..];
                    if remaining.is_empty() {
                        break;
                    }
                } else {
                    if !remaining.is_empty() {
                        current_line_width +=
                            fallback_text_metrics(remaining, &segment_style, segment_font_size)
                                .width;
                    }
                    break;
                }
            }
            continue;
        };

        let mut remaining = segment;
        loop {
            if let Some(newline_offset) = remaining.find('\n') {
                let before_newline = &remaining[..newline_offset];
                if !before_newline.is_empty() {
                    let metrics = if let Some(cache) = cache.as_deref_mut() {
                        measure_text_with_font_cached(
                            before_newline,
                            &segment_style,
                            segment_font_size,
                            segment_font,
                            cache,
                        )
                    } else {
                        measure_text_with_font(
                            before_newline,
                            &segment_style,
                            segment_font_size,
                            segment_font,
                        )
                    };
                    current_line_width += metrics.width;
                }
                max_width = max_width.max(current_line_width);
                current_line_width = 0.0;
                line_count += 1;
                remaining = &remaining[newline_offset + 1..];
                if remaining.is_empty() {
                    break;
                }
            } else {
                if !remaining.is_empty() {
                    let metrics = if let Some(cache) = cache.as_deref_mut() {
                        measure_text_with_font_cached(
                            remaining,
                            &segment_style,
                            segment_font_size,
                            segment_font,
                            cache,
                        )
                    } else {
                        measure_text_with_font(
                            remaining,
                            &segment_style,
                            segment_font_size,
                            segment_font,
                        )
                    };
                    current_line_width += metrics.width;
                }
                break;
            }
        }
    }

    max_width = max_width.max(current_line_width);

    let line_heights = annotated_line_heights_with_resolver(text, style, font_size, fonts);
    let total_height = line_heights.iter().sum();
    let max_line_height = line_heights.into_iter().fold(base_line_height, f32::max);

    TextMetrics {
        width: max_width,
        height: total_height,
        line_height: max_line_height,
        line_count,
    }
}

fn annotated_line_heights_with_resolver(
    text: &AnnotatedString,
    style: &TextStyle,
    font_size: f32,
    fonts: &SoftwareTextFontSet,
) -> Vec<f32> {
    let Some(base_font) = fonts.resolve(style) else {
        return fallback_line_heights(text.text.as_str(), style, font_size);
    };
    let base_line_height = line_height_for_style(style, font_size, base_font);
    let mut line_heights = vec![base_line_height];
    let mut boundaries = text.span_boundaries();
    for (offset, ch) in text.text.char_indices() {
        if ch == '\n' {
            boundaries.push(offset);
            boundaries.push(offset + ch.len_utf8());
        }
    }
    boundaries.sort_unstable();
    boundaries.dedup();
    boundaries.retain(|offset| *offset <= text.text.len() && text.text.is_char_boundary(*offset));

    let mut line_index = 0usize;
    for range in boundaries.windows(2) {
        let start = range[0];
        let end = range[1];
        if start == end {
            continue;
        }
        let segment = &text.text[start..end];
        let segment_style = effective_style_for_range(&text.span_styles, style, start, end);
        let segment_font_size = resolve_font_size(&segment_style);
        let segment_line_height = if let Some(segment_font) = fonts.resolve(&segment_style) {
            line_height_for_style(&segment_style, segment_font_size, segment_font)
        } else {
            fallback_line_height(&segment_style, segment_font_size)
        };
        for ch in segment.chars() {
            line_heights[line_index] = line_heights[line_index].max(segment_line_height);
            if ch == '\n' {
                line_index += 1;
                if line_heights.len() <= line_index {
                    line_heights.push(base_line_height);
                }
            }
        }
    }

    line_heights
}

fn max_line_height_for_annotated_text_with_resolver(
    text: &AnnotatedString,
    style: &TextStyle,
    font_size: f32,
    fonts: &SoftwareTextFontSet,
) -> f32 {
    let base_line_height = fonts
        .resolve(style)
        .map(|font| line_height_for_style(style, font_size, font))
        .unwrap_or_else(|| fallback_line_height(style, font_size));
    if text.span_styles.is_empty() {
        return base_line_height;
    }

    let mut max_line_height = base_line_height;
    for range in text.span_boundaries().windows(2) {
        let start = range[0];
        let end = range[1];
        if start == end {
            continue;
        }
        let segment_style = effective_style_for_range(&text.span_styles, style, start, end);
        let segment_font_size = resolve_font_size(&segment_style);
        let segment_line_height = fonts
            .resolve(&segment_style)
            .map(|font| line_height_for_style(&segment_style, segment_font_size, font))
            .unwrap_or_else(|| fallback_line_height(&segment_style, segment_font_size));
        max_line_height = max_line_height.max(segment_line_height);
    }
    max_line_height
}

fn effective_style_for_range(
    span_styles: &[RangeStyle<SpanStyle>],
    style: &TextStyle,
    start: usize,
    end: usize,
) -> TextStyle {
    let mut effective = style.clone();
    for span in span_styles {
        if span.range.start < end && span.range.end > start {
            effective.span_style = effective.span_style.merge(&span.item);
        }
    }
    effective
}

/// The line advance a style asks for on a given font, in layout points.
///
/// The font used to be discarded here, which is why the "natural" line height
/// was a flat `font_size * 1.4` guess. A style that asks for a line-height
/// policy needs the font's real ascent and descent, and reading them at the
/// font's own pixel size is what makes them em-relative rather than a restated
/// `font_size`.
fn line_height_for_style(style: &TextStyle, font_size: f32, font: &SoftwareTextFont) -> f32 {
    let asked = resolve_line_height(style, font_size * 1.4);
    if style.paragraph_style.line_height_style.is_none() {
        return asked;
    }
    let metrics =
        crate::font_layout::vertical_metrics(&font.font, font.ab_glyph_px_size(font_size));
    line_box_for(style, metrics, asked, measure_grid()).height
}

fn clamp_to_char_boundary(text: &str, mut offset: usize) -> usize {
    offset = offset.min(text.len());
    while offset > 0 && !text.is_char_boundary(offset) {
        offset -= 1;
    }
    offset
}

fn align_glyph_for_text_motion(glyph: Glyph, static_text_motion: bool) -> Glyph {
    align_glyph_to_pixel_grid(glyph, static_text_motion)
}

fn static_glyph_pixel_origin(glyph: &Glyph) -> (i32, i32) {
    (
        glyph.position.x.round() as i32,
        glyph.position.y.round() as i32,
    )
}

fn glyph_mask_cache_key(
    font_hash: u64,
    glyph: &Glyph,
    raster_style: GlyphRasterStyle,
    weight_synthesis: TextWeightSynthesis,
    style_synthesis: TextStyleSynthesis,
) -> GlyphMaskCacheKey {
    GlyphMaskCacheKey {
        font_hash,
        glyph_id: u32::from(glyph.id.0),
        scale_x_bits: glyph.scale.x.to_bits(),
        scale_y_bits: glyph.scale.y.to_bits(),
        raster_style: GlyphRasterStyleKey::from_style(raster_style),
        embolden_px_bits: weight_synthesis.embolden_px.to_bits(),
        slant_bits: style_synthesis.slant.to_bits(),
    }
}

fn glyph_atlas_key_from_mask_key(key: GlyphMaskCacheKey) -> Option<SoftwareGlyphAtlasKey> {
    if !matches!(key.raster_style, GlyphRasterStyleKey::Fill) {
        return None;
    }
    Some(SoftwareGlyphAtlasKey {
        font_hash: key.font_hash,
        glyph_id: key.glyph_id,
        scale_x_bits: key.scale_x_bits,
        scale_y_bits: key.scale_y_bits,
        embolden_px_bits: key.embolden_px_bits,
        slant_bits: key.slant_bits,
    })
}

fn build_complete_glyph_mask(
    font: &impl Font,
    glyph: &Glyph,
    raster_style: GlyphRasterStyle,
    weight_synthesis: TextWeightSynthesis,
    style_synthesis: TextStyleSynthesis,
) -> Option<GlyphMask> {
    let (outlined, bounds) = outline_glyph_with_bounds(font, glyph)?;
    let mask = build_glyph_mask(font, glyph, &outlined, bounds, raster_style)?;
    let mask = synthesize_glyph_weight(mask, weight_synthesis);
    Some(synthesize_glyph_style(mask, style_synthesis))
}

fn cached_static_glyph_mask_with_key(
    cache: &mut SoftwareGlyphRasterCache,
    font_hash: u64,
    font: &impl Font,
    glyph: &Glyph,
    raster_style: GlyphRasterStyle,
    weight_synthesis: TextWeightSynthesis,
    style_synthesis: TextStyleSynthesis,
) -> Option<(GlyphMaskCacheKey, GlyphMask)> {
    let key = glyph_mask_cache_key(
        font_hash,
        glyph,
        raster_style,
        weight_synthesis,
        style_synthesis,
    );
    if let Some(mask) = cache.get(&key, glyph) {
        return Some((key, mask));
    }
    let mask =
        build_complete_glyph_mask(font, glyph, raster_style, weight_synthesis, style_synthesis)?;
    Some((key, cache.put(key, glyph, mask)))
}

fn cached_static_glyph_mask(
    cache: &mut SoftwareGlyphRasterCache,
    font_hash: u64,
    font: &impl Font,
    glyph: &Glyph,
    raster_style: GlyphRasterStyle,
    weight_synthesis: TextWeightSynthesis,
    style_synthesis: TextStyleSynthesis,
) -> Option<GlyphMask> {
    cached_static_glyph_mask_with_key(
        cache,
        font_hash,
        font,
        glyph,
        raster_style,
        weight_synthesis,
        style_synthesis,
    )
    .map(|(_, mask)| mask)
}

/// Where each line of a paragraph starts, relative to the block's own left
/// edge, once `TextAlign` has had its say.
///
/// A `TextAlign` is a property of the paragraph and it applies to **every
/// line**: Compose centres each line in the paragraph's width. Every glyph
/// loop below used to start each line at `origin_x`, which centres a
/// single-line paragraph correctly — the scene builder offsets the whole block
/// — and leaves every wrapped continuation line jammed under the start of the
/// first. On the Credits screen that is the difference between
/// `"Designed and built for Wear" / "OS."` centred and `"OS."` hard against
/// the left of the block.
///
/// The offsets are measured against the widest line rather than against the
/// parent's width, because the block offset already covers the rest; see
/// `scene_builder::text_align_fraction`. `None` for the start-aligned case, so
/// the common path does not measure anything twice.
fn line_alignment_offsets<F: Font, S: ScaleFont<F>>(
    scaled_font: &S,
    text: &str,
    letter_spacing: f32,
    align_fraction: f32,
) -> Option<Vec<f32>> {
    if align_fraction == 0.0 || !text.contains('\n') {
        return None;
    }
    let advances: Vec<f32> = text
        .split('\n')
        .map(|line| {
            let mut advance = 0.0f32;
            let mut previous = None;
            for ch in line.chars() {
                let glyph_id = scaled_font.glyph_id(ch);
                if let Some(previous_id) = previous {
                    advance += scaled_font.kern(previous_id, glyph_id);
                }
                // One letter space PER CHARACTER -- see `run_tracking`. An
                // empty line gets none, which is why a blank line between two
                // tracked paragraphs no longer aligns as though it were a
                // character wide.
                advance += letter_spacing + scaled_font.h_advance(glyph_id);
                previous = Some(glyph_id);
            }
            advance.max(0.0)
        })
        .collect();
    let block = advances.iter().copied().fold(0.0f32, f32::max);
    Some(
        advances
            .iter()
            .map(|advance| ((block - advance) * align_fraction).max(0.0))
            .collect(),
    )
}

fn line_offset(offsets: &Option<Vec<f32>>, line_idx: usize) -> f32 {
    offsets
        .as_ref()
        .and_then(|offsets| offsets.get(line_idx).copied())
        .unwrap_or(0.0)
}

#[allow(clippy::too_many_arguments)]
fn visit_text_glyph_masks(
    text: &str,
    font: &impl Font,
    font_hash: u64,
    font_px_size: f32,
    line_height: f32,
    first_baseline_y: f32,
    origin_x: f32,
    origin_y: f32,
    letter_spacing: f32,
    align_fraction: f32,
    static_text_motion: bool,
    raster_style: GlyphRasterStyle,
    weight_synthesis: TextWeightSynthesis,
    style_synthesis: TextStyleSynthesis,
    mut glyph_cache: Option<&mut SoftwareGlyphRasterCache>,
    mut visit: impl FnMut(&GlyphMask),
) -> f32 {
    let scale = PxScale::from(font_px_size);
    let scaled_font = font.as_scaled(scale);
    let line_offsets = line_alignment_offsets(&scaled_font, text, letter_spacing, align_fraction);
    let mut max_advance = 0.0f32;
    for (line_idx, line) in text.split('\n').enumerate() {
        let baseline_y = first_baseline_y + line_idx as f32 * line_height + origin_y;
        // Half a letter space of lead-in before the first glyph, and half
        // again after the last -- see `run_tracking`.
        let lead_in = run_lead_in(line.chars().count(), letter_spacing);
        let mut caret_x = origin_x + line_offset(&line_offsets, line_idx) + lead_in;
        let mut previous = None;
        for ch in line.chars() {
            let glyph_id = scaled_font.glyph_id(ch);
            if let Some(previous_id) = previous {
                caret_x += scaled_font.kern(previous_id, glyph_id) + letter_spacing;
            }
            let glyph = glyph_id.with_scale_and_position(scale, point(caret_x, baseline_y));
            caret_x += scaled_font.h_advance(glyph_id);
            previous = Some(glyph_id);
            let glyph = align_glyph_for_text_motion(glyph, static_text_motion);
            let Some(mask) = (if static_text_motion {
                glyph_cache.as_deref_mut().and_then(|cache| {
                    cached_static_glyph_mask(
                        cache,
                        font_hash,
                        font,
                        &glyph,
                        raster_style,
                        weight_synthesis,
                        style_synthesis,
                    )
                })
            } else {
                None
            })
            .or_else(|| {
                build_complete_glyph_mask(
                    font,
                    &glyph,
                    raster_style,
                    weight_synthesis,
                    style_synthesis,
                )
            }) else {
                continue;
            };
            visit(&mask);
        }
        max_advance = max_advance.max((caret_x - origin_x + lead_in).max(0.0));
    }
    max_advance
}

#[allow(clippy::too_many_arguments)]
fn visit_text_glyph_masks_with_key(
    text: &str,
    font: &impl Font,
    font_hash: u64,
    font_px_size: f32,
    line_height: f32,
    first_baseline_y: f32,
    origin_x: f32,
    origin_y: f32,
    letter_spacing: f32,
    align_fraction: f32,
    static_text_motion: bool,
    raster_style: GlyphRasterStyle,
    weight_synthesis: TextWeightSynthesis,
    style_synthesis: TextStyleSynthesis,
    mut glyph_cache: Option<&mut SoftwareGlyphRasterCache>,
    mut visit: impl FnMut(SoftwareGlyphAtlasKey, &GlyphMask),
) -> f32 {
    if !static_text_motion {
        return 0.0;
    }

    let scale = PxScale::from(font_px_size);
    let scaled_font = font.as_scaled(scale);
    let line_offsets = line_alignment_offsets(&scaled_font, text, letter_spacing, align_fraction);
    let mut max_advance = 0.0f32;
    for (line_idx, line) in text.split('\n').enumerate() {
        let baseline_y = first_baseline_y + line_idx as f32 * line_height + origin_y;
        // Half a letter space of lead-in before the first glyph, and half
        // again after the last -- see `run_tracking`.
        let lead_in = run_lead_in(line.chars().count(), letter_spacing);
        let mut caret_x = origin_x + line_offset(&line_offsets, line_idx) + lead_in;
        let mut previous = None;
        for ch in line.chars() {
            let glyph_id = scaled_font.glyph_id(ch);
            if let Some(previous_id) = previous {
                caret_x += scaled_font.kern(previous_id, glyph_id) + letter_spacing;
            }
            let glyph = glyph_id.with_scale_and_position(scale, point(caret_x, baseline_y));
            caret_x += scaled_font.h_advance(glyph_id);
            previous = Some(glyph_id);
            let glyph = align_glyph_for_text_motion(glyph, true);
            let Some((cache_key, mask)) = glyph_cache.as_deref_mut().and_then(|cache| {
                cached_static_glyph_mask_with_key(
                    cache,
                    font_hash,
                    font,
                    &glyph,
                    raster_style,
                    weight_synthesis,
                    style_synthesis,
                )
            }) else {
                continue;
            };
            let Some(atlas_key) = glyph_atlas_key_from_mask_key(cache_key) else {
                continue;
            };
            visit(atlas_key, &mask);
        }
        max_advance = max_advance.max((caret_x - origin_x + lead_in).max(0.0));
    }
    max_advance
}

#[allow(clippy::too_many_arguments)]
fn visit_cached_text_glyph_atlas_placements(
    text: &str,
    font: &impl Font,
    font_hash: u64,
    font_px_size: f32,
    line_height: f32,
    first_baseline_y: f32,
    origin_x: f32,
    origin_y: f32,
    letter_spacing: f32,
    align_fraction: f32,
    raster_style: GlyphRasterStyle,
    weight_synthesis: TextWeightSynthesis,
    style_synthesis: TextStyleSynthesis,
    glyph_cache: &mut SoftwareGlyphRasterCache,
    mut visit: impl FnMut(SoftwareGlyphAtlasPlacement),
) -> f32 {
    let scale = PxScale::from(font_px_size);
    let scaled_font = font.as_scaled(scale);
    let line_offsets = line_alignment_offsets(&scaled_font, text, letter_spacing, align_fraction);
    let mut max_advance = 0.0f32;
    for (line_idx, line) in text.split('\n').enumerate() {
        let baseline_y = first_baseline_y + line_idx as f32 * line_height + origin_y;
        // Half a letter space of lead-in before the first glyph, and half
        // again after the last -- see `run_tracking`.
        let lead_in = run_lead_in(line.chars().count(), letter_spacing);
        let mut caret_x = origin_x + line_offset(&line_offsets, line_idx) + lead_in;
        let mut previous = None;
        for ch in line.chars() {
            let glyph_id = scaled_font.glyph_id(ch);
            if let Some(previous_id) = previous {
                caret_x += scaled_font.kern(previous_id, glyph_id) + letter_spacing;
            }
            let glyph = glyph_id.with_scale_and_position(scale, point(caret_x, baseline_y));
            caret_x += scaled_font.h_advance(glyph_id);
            previous = Some(glyph_id);
            let glyph = align_glyph_for_text_motion(glyph, true);
            let cache_key = glyph_mask_cache_key(
                font_hash,
                &glyph,
                raster_style,
                weight_synthesis,
                style_synthesis,
            );
            let Some((key, x, y, width, height)) =
                glyph_cache.get_atlas_placement(&cache_key, &glyph)
            else {
                if font.outline(glyph.id).is_none() {
                    continue;
                }
                return f32::NAN;
            };
            visit(SoftwareGlyphAtlasPlacement {
                key,
                x,
                y,
                width,
                height,
                color: Color::WHITE,
            });
        }
        max_advance = max_advance.max((caret_x - origin_x + lead_in).max(0.0));
    }
    max_advance
}

#[allow(clippy::too_many_arguments)]
fn visit_text_glyph_atlas_run(
    text: &str,
    font: &impl Font,
    font_hash: u64,
    font_px_size: f32,
    line_height: f32,
    first_baseline_y: f32,
    origin_x: f32,
    origin_y: f32,
    letter_spacing: f32,
    align_fraction: f32,
    raster_style: GlyphRasterStyle,
    weight_synthesis: TextWeightSynthesis,
    style_synthesis: TextStyleSynthesis,
    glyph_cache: &mut SoftwareGlyphRasterCache,
    mut visit: impl FnMut(SoftwareGlyphAtlasRunGlyph),
) -> f32 {
    let scale = PxScale::from(font_px_size);
    let scaled_font = font.as_scaled(scale);
    let line_offsets = line_alignment_offsets(&scaled_font, text, letter_spacing, align_fraction);
    let mut max_advance = 0.0f32;
    let mut run_metrics_cache: Vec<(GlyphMaskCacheKey, CachedAtlasGlyphMetrics)> = Vec::new();
    for (line_idx, line) in text.split('\n').enumerate() {
        let baseline_y = first_baseline_y + line_idx as f32 * line_height + origin_y;
        // Half a letter space of lead-in before the first glyph, and half
        // again after the last -- see `run_tracking`.
        let lead_in = run_lead_in(line.chars().count(), letter_spacing);
        let mut caret_x = origin_x + line_offset(&line_offsets, line_idx) + lead_in;
        let mut previous = None;
        for ch in line.chars() {
            let glyph_id = scaled_font.glyph_id(ch);
            if let Some(previous_id) = previous {
                caret_x += scaled_font.kern(previous_id, glyph_id) + letter_spacing;
            }
            let glyph = glyph_id.with_scale_and_position(scale, point(caret_x, baseline_y));
            caret_x += scaled_font.h_advance(glyph_id);
            previous = Some(glyph_id);
            let glyph = align_glyph_for_text_motion(glyph, true);
            let cache_key = glyph_mask_cache_key(
                font_hash,
                &glyph,
                raster_style,
                weight_synthesis,
                style_synthesis,
            );
            if let Some((_, metrics)) = run_metrics_cache
                .iter()
                .find(|(cached_key, _)| *cached_key == cache_key)
            {
                visit(SoftwareGlyphAtlasRunGlyph::Cached(
                    metrics.placement(&glyph, Color::WHITE),
                ));
                continue;
            }
            if let Some(metrics) = glyph_cache.get_atlas_metrics(&cache_key) {
                if run_metrics_cache.len() < RUN_GLYPH_METRICS_CACHE_LIMIT {
                    run_metrics_cache.push((cache_key, metrics));
                }
                visit(SoftwareGlyphAtlasRunGlyph::Cached(
                    metrics.placement(&glyph, Color::WHITE),
                ));
                continue;
            }

            if font.outline(glyph.id).is_none() {
                continue;
            }
            let Some(mask) = build_complete_glyph_mask(
                font,
                &glyph,
                raster_style,
                weight_synthesis,
                style_synthesis,
            ) else {
                continue;
            };
            let mask = glyph_cache.put(cache_key, &glyph, mask);
            let Some(key) = glyph_atlas_key_from_mask_key(cache_key) else {
                continue;
            };
            let (glyph_x, glyph_y) = static_glyph_pixel_origin(&glyph);
            if run_metrics_cache.len() < RUN_GLYPH_METRICS_CACHE_LIMIT {
                run_metrics_cache.push((
                    cache_key,
                    CachedAtlasGlyphMetrics {
                        key,
                        width: mask.width,
                        height: mask.height,
                        origin_offset_x: mask.origin_x - glyph_x,
                        origin_offset_y: mask.origin_y - glyph_y,
                    },
                ));
            }
            visit(SoftwareGlyphAtlasRunGlyph::New(SoftwareGlyphAtlasGlyph {
                key,
                mask: SoftwareGlyphAtlasMask {
                    alpha: Arc::clone(&mask.alpha),
                    width: mask.width,
                    height: mask.height,
                },
                x: mask.origin_x,
                y: mask.origin_y,
                color: Color::WHITE,
            }));
        }
        max_advance = max_advance.max((caret_x - origin_x + lead_in).max(0.0));
    }
    max_advance
}

fn blend_src_over(dst: &mut [f32; 4], src: [f32; 4]) {
    let src_alpha = src[3].clamp(0.0, 1.0);
    if src_alpha <= 0.0 {
        return;
    }

    let dst_alpha = dst[3].clamp(0.0, 1.0);
    let out_alpha = src_alpha + dst_alpha * (1.0 - src_alpha);

    if out_alpha <= f32::EPSILON {
        *dst = [0.0, 0.0, 0.0, 0.0];
        return;
    }

    for channel in 0..3 {
        let src_premult = src[channel].clamp(0.0, 1.0) * src_alpha;
        let dst_premult = dst[channel].clamp(0.0, 1.0) * dst_alpha;
        dst[channel] =
            ((src_premult + dst_premult * (1.0 - src_alpha)) / out_alpha).clamp(0.0, 1.0);
    }
    dst[3] = out_alpha;
}

fn draw_mask_glyph(
    canvas: &mut [[f32; 4]],
    width: u32,
    height: u32,
    mask: &GlyphMask,
    brush: &Brush,
    brush_alpha_multiplier: f32,
    brush_rect: Rect,
) {
    for y in 0..mask.height {
        let py = mask.origin_y + y as i32;
        if py < 0 || py >= height as i32 {
            continue;
        }

        for x in 0..mask.width {
            let px = mask.origin_x + x as i32;
            if px < 0 || px >= width as i32 {
                continue;
            }

            let coverage = mask.alpha[y * mask.width + x];
            if coverage <= 0.0 {
                continue;
            }

            let sample = sample_brush_rgba(
                brush,
                brush_rect,
                brush_rect.x + px as f32 + 0.5,
                brush_rect.y + py as f32 + 0.5,
            );
            let alpha = coverage * sample[3] * brush_alpha_multiplier;
            if alpha <= 0.0 {
                continue;
            }
            let idx = (py as u32 * width + px as u32) as usize;
            blend_src_over(
                &mut canvas[idx],
                [sample[0], sample[1], sample[2], alpha.clamp(0.0, 1.0)],
            );
        }
    }
}

fn blend_src_over_u8(dst: &mut [u8], src: [f32; 4]) {
    let src_alpha = src[3].clamp(0.0, 1.0);
    if src_alpha <= 0.0 {
        return;
    }

    let dst_alpha = dst[3] as f32 / 255.0;
    if dst_alpha <= 0.0 {
        dst[0] = (src[0].clamp(0.0, 1.0) * 255.0).round() as u8;
        dst[1] = (src[1].clamp(0.0, 1.0) * 255.0).round() as u8;
        dst[2] = (src[2].clamp(0.0, 1.0) * 255.0).round() as u8;
        dst[3] = (src_alpha * 255.0).round() as u8;
        return;
    }

    let out_alpha = src_alpha + dst_alpha * (1.0 - src_alpha);
    if out_alpha <= f32::EPSILON {
        dst.fill(0);
        return;
    }

    for channel in 0..3 {
        let src_premult = src[channel].clamp(0.0, 1.0) * src_alpha;
        let dst_premult = (dst[channel] as f32 / 255.0) * dst_alpha;
        dst[channel] =
            ((src_premult + dst_premult * (1.0 - src_alpha)) / out_alpha * 255.0).round() as u8;
    }
    dst[3] = (out_alpha.clamp(0.0, 1.0) * 255.0).round() as u8;
}

fn draw_mask_glyph_solid_u8(
    canvas: &mut [u8],
    width: u32,
    height: u32,
    mask: &GlyphMask,
    color: [f32; 4],
    alpha_multiplier: f32,
) {
    let red = (color[0].clamp(0.0, 1.0) * 255.0).round() as u8;
    let green = (color[1].clamp(0.0, 1.0) * 255.0).round() as u8;
    let blue = (color[2].clamp(0.0, 1.0) * 255.0).round() as u8;
    let alpha_scale = color[3].clamp(0.0, 1.0) * alpha_multiplier.clamp(0.0, 1.0);
    if alpha_scale <= 0.0 {
        return;
    }

    for y in 0..mask.height {
        let py = mask.origin_y + y as i32;
        if py < 0 || py >= height as i32 {
            continue;
        }

        for x in 0..mask.width {
            let px = mask.origin_x + x as i32;
            if px < 0 || px >= width as i32 {
                continue;
            }

            let coverage = mask.alpha[y * mask.width + x];
            if coverage <= 0.0 {
                continue;
            }

            let alpha = (coverage * alpha_scale).clamp(0.0, 1.0);
            let alpha_u8 = (alpha * 255.0).round() as u8;
            if alpha_u8 == 0 {
                continue;
            }
            let idx = ((py as u32 * width + px as u32) * 4) as usize;
            let dst = &mut canvas[idx..idx + 4];
            if dst[3] == 0 {
                dst[0] = red;
                dst[1] = green;
                dst[2] = blue;
                dst[3] = alpha_u8;
            } else {
                blend_src_over_u8(dst, [color[0], color[1], color[2], alpha]);
            }
        }
    }
}

fn draw_shadow_mask(
    canvas: &mut [[f32; 4]],
    width: u32,
    height: u32,
    mask: &GlyphMask,
    shadow: Shadow,
    text_scale: f32,
    static_text_motion: bool,
) {
    if mask.width == 0 || mask.height == 0 {
        return;
    }

    let shadow_dx = shadow.offset.x * text_scale;
    let shadow_dy = shadow.offset.y * text_scale;
    let blur_radius = (shadow.blur_radius * text_scale).max(0.0);
    let sigma = shadow_blur_sigma(blur_radius);
    let blur_margin = if sigma > 0.0 {
        (sigma * 3.0).ceil() as i32
    } else {
        0
    };

    let padded_width = mask.width + (blur_margin as usize) * 2;
    let padded_height = mask.height + (blur_margin as usize) * 2;
    let mut padded_mask = vec![0.0f32; padded_width * padded_height];

    for y in 0..mask.height {
        let src_offset = y * mask.width;
        let dst_offset = (y + blur_margin as usize) * padded_width + blur_margin as usize;
        padded_mask[dst_offset..dst_offset + mask.width]
            .copy_from_slice(&mask.alpha[src_offset..src_offset + mask.width]);
    }

    let blurred = if sigma > 0.0 {
        gaussian_blur_alpha(&padded_mask, padded_width, padded_height, sigma)
    } else {
        padded_mask
    };

    let shadow_rgba = color_to_rgba(shadow.color);
    let shadow_origin_x = mask.origin_x - blur_margin;
    let shadow_origin_y = mask.origin_y - blur_margin;

    for y in 0..padded_height {
        for x in 0..padded_width {
            let alpha = blurred[y * padded_width + x] * shadow_rgba[3];
            if alpha <= 0.0 {
                continue;
            }

            let target_x = shadow_origin_x as f32 + x as f32 + shadow_dx;
            let target_y = shadow_origin_y as f32 + y as f32 + shadow_dy;
            if static_text_motion {
                blend_shadow_pixel(
                    canvas,
                    width,
                    height,
                    target_x.round() as i32,
                    target_y.round() as i32,
                    shadow_rgba,
                    alpha.clamp(0.0, 1.0),
                );
            } else {
                blend_shadow_pixel_subpixel(
                    canvas,
                    width,
                    height,
                    target_x,
                    target_y,
                    shadow_rgba,
                    alpha.clamp(0.0, 1.0),
                );
            }
        }
    }
}

fn blend_shadow_pixel(
    canvas: &mut [[f32; 4]],
    width: u32,
    height: u32,
    px: i32,
    py: i32,
    color: [f32; 4],
    alpha: f32,
) {
    if px < 0 || py < 0 || px >= width as i32 || py >= height as i32 || alpha <= 0.0 {
        return;
    }
    let idx = (py as u32 * width + px as u32) as usize;
    blend_src_over(
        &mut canvas[idx],
        [color[0], color[1], color[2], alpha.clamp(0.0, 1.0)],
    );
}

fn blend_shadow_pixel_subpixel(
    canvas: &mut [[f32; 4]],
    width: u32,
    height: u32,
    x: f32,
    y: f32,
    color: [f32; 4],
    alpha: f32,
) {
    if alpha <= 0.0 {
        return;
    }

    let base_x = x.floor();
    let base_y = y.floor();
    let frac_x = x - base_x;
    let frac_y = y - base_y;
    let base_x_i32 = base_x as i32;
    let base_y_i32 = base_y as i32;
    let weights = [
        ((1.0 - frac_x) * (1.0 - frac_y), 0i32, 0i32),
        (frac_x * (1.0 - frac_y), 1, 0),
        ((1.0 - frac_x) * frac_y, 0, 1),
        (frac_x * frac_y, 1, 1),
    ];

    for (weight, dx, dy) in weights {
        if weight <= 0.0 {
            continue;
        }
        blend_shadow_pixel(
            canvas,
            width,
            height,
            base_x_i32 + dx,
            base_y_i32 + dy,
            color,
            alpha * weight,
        );
    }
}

fn shadow_blur_sigma(blur_radius: f32) -> f32 {
    if blur_radius <= 0.0 {
        0.0
    } else {
        (blur_radius * SHADOW_SIGMA_SCALE + SHADOW_SIGMA_BIAS).max(0.5)
    }
}

fn gaussian_blur_alpha(src: &[f32], width: usize, height: usize, sigma: f32) -> Vec<f32> {
    let kernel = gaussian_kernel_1d(sigma);
    if kernel.len() == 1 {
        return src.to_vec();
    }
    let half = (kernel.len() / 2) as i32;

    let mut horizontal = vec![0.0f32; src.len()];
    for y in 0..height {
        for x in 0..width {
            let mut sum = 0.0f32;
            for (index, weight) in kernel.iter().enumerate() {
                let offset = index as i32 - half;
                let sample_x = (x as i32 + offset).clamp(0, width as i32 - 1) as usize;
                sum += src[y * width + sample_x] * *weight;
            }
            horizontal[y * width + x] = sum;
        }
    }

    let mut output = vec![0.0f32; src.len()];
    for y in 0..height {
        for x in 0..width {
            let mut sum = 0.0f32;
            for (index, weight) in kernel.iter().enumerate() {
                let offset = index as i32 - half;
                let sample_y = (y as i32 + offset).clamp(0, height as i32 - 1) as usize;
                sum += horizontal[sample_y * width + x] * *weight;
            }
            output[y * width + x] = sum;
        }
    }

    output
}

fn gaussian_kernel_1d(sigma: f32) -> Vec<f32> {
    let half = ((sigma * 3.0).ceil() as i32).clamp(1, MAX_GAUSSIAN_KERNEL_HALF);
    if half <= 0 {
        return vec![1.0];
    }

    let mut kernel = Vec::with_capacity((half * 2 + 1) as usize);
    let mut sum = 0.0f32;
    for offset in -half..=half {
        let distance = offset as f32;
        let weight = (-0.5 * (distance / sigma).powi(2)).exp();
        kernel.push(weight);
        sum += weight;
    }

    if sum > f32::EPSILON {
        for weight in &mut kernel {
            *weight /= sum;
        }
    }

    kernel
}

fn outline_glyph_with_bounds(
    font: &impl Font,
    glyph: &Glyph,
) -> Option<(OutlinedGlyph, GlyphPixelBounds)> {
    let outlined = font.outline_glyph(glyph.clone())?;
    let bounds = pixel_bounds_from_outlined(&outlined);
    Some((outlined, bounds))
}

fn build_glyph_mask(
    font: &impl Font,
    glyph: &Glyph,
    outlined: &OutlinedGlyph,
    bounds: GlyphPixelBounds,
    style: GlyphRasterStyle,
) -> Option<GlyphMask> {
    match style {
        GlyphRasterStyle::Fill => build_fill_mask(outlined, bounds),
        GlyphRasterStyle::Stroke { width_px } => {
            build_stroke_mask(font, glyph, outlined, bounds, width_px)
        }
    }
}

fn build_fill_mask(outlined: &OutlinedGlyph, bounds: GlyphPixelBounds) -> Option<GlyphMask> {
    let mask_width = bounds.width();
    let mask_height = bounds.height();
    if mask_width == 0 || mask_height == 0 {
        return None;
    }

    let mut alpha = vec![0.0f32; mask_width * mask_height];
    outlined.draw(|gx, gy, value| {
        let idx = gy as usize * mask_width + gx as usize;
        alpha[idx] = value;
    });

    Some(GlyphMask {
        alpha: Arc::from(alpha),
        width: mask_width,
        height: mask_height,
        origin_x: bounds.min_x,
        origin_y: bounds.min_y,
    })
}

fn build_stroke_mask(
    font: &impl Font,
    glyph: &Glyph,
    outlined: &OutlinedGlyph,
    bounds: GlyphPixelBounds,
    stroke_width_px: f32,
) -> Option<GlyphMask> {
    if !stroke_width_px.is_finite() || stroke_width_px <= 0.0 {
        return build_fill_mask(outlined, bounds);
    }

    let mask_width = bounds.max_x - bounds.min_x;
    let mask_height = bounds.max_y - bounds.min_y;
    if mask_width <= 0 || mask_height <= 0 {
        return None;
    }

    let half_width = stroke_width_px * 0.5;
    let miter_pad = (half_width * COMPOSE_STROKE_MITER_LIMIT).ceil();
    let pad = miter_pad.max(1.0) as i32 + 1;
    let path = build_outline_path(font, glyph, bounds, pad)?;
    let raster_width = mask_width + pad * 2;
    let raster_height = mask_height + pad * 2;
    if raster_width <= 0 || raster_height <= 0 {
        return None;
    }

    let mut pixmap = Pixmap::new(raster_width as u32, raster_height as u32)?;
    let mut paint = Paint::default();
    paint.set_color_rgba8(255, 255, 255, 255);
    paint.anti_alias = true;

    let stroke = Stroke {
        width: stroke_width_px,
        line_cap: LineCap::Butt,
        line_join: LineJoin::Miter,
        miter_limit: COMPOSE_STROKE_MITER_LIMIT,
        ..Stroke::default()
    };

    pixmap.stroke_path(&path, &paint, &stroke, Transform::identity(), None);

    let alpha: Vec<f32> = pixmap
        .data()
        .chunks_exact(4)
        .map(|pixel| pixel[3] as f32 / 255.0)
        .collect();

    Some(GlyphMask {
        alpha: Arc::from(alpha),
        width: raster_width as usize,
        height: raster_height as usize,
        origin_x: bounds.min_x - pad,
        origin_y: bounds.min_y - pad,
    })
}

fn synthesize_glyph_weight(mask: GlyphMask, synthesis: TextWeightSynthesis) -> GlyphMask {
    let horizontal_shift = synthetic_weight_shift_px(synthesis.embolden_px);
    if horizontal_shift == 0 || mask.width == 0 || mask.height == 0 {
        return mask;
    }

    let vertical_shift = (horizontal_shift / 2).min(1);
    let output_width = mask.width + horizontal_shift;
    let output_height = mask.height + vertical_shift * 2;
    let mut alpha = vec![0.0f32; output_width * output_height];
    for y in 0..mask.height {
        for x in 0..mask.width {
            let coverage = mask.alpha[y * mask.width + x];
            if coverage <= 0.0 {
                continue;
            }
            for dy in 0..=(vertical_shift * 2) {
                let output_y = y + dy;
                for dx in 0..=horizontal_shift {
                    let output_x = x + dx;
                    let output_index = output_y * output_width + output_x;
                    if coverage > alpha[output_index] {
                        alpha[output_index] = coverage;
                    }
                }
            }
        }
    }

    GlyphMask {
        alpha: Arc::from(alpha),
        width: output_width,
        height: output_height,
        origin_x: mask.origin_x,
        origin_y: mask.origin_y - vertical_shift as i32,
    }
}

fn synthesize_glyph_style(mask: GlyphMask, synthesis: TextStyleSynthesis) -> GlyphMask {
    if synthesis.slant <= 0.0 || mask.width == 0 || mask.height == 0 {
        return mask;
    }

    let max_shift = ((mask.height.saturating_sub(1)) as f32 * synthesis.slant).ceil() as usize;
    if max_shift == 0 {
        return mask;
    }

    let output_width = mask.width + max_shift + 1;
    let mut alpha = vec![0.0f32; output_width * mask.height];
    for y in 0..mask.height {
        let shift = (mask.height.saturating_sub(1) - y) as f32 * synthesis.slant;
        let shift_floor = shift.floor() as usize;
        let shift_fraction = shift - shift.floor();
        for x in 0..mask.width {
            let coverage = mask.alpha[y * mask.width + x];
            if coverage <= 0.0 {
                continue;
            }

            let output_x = x + shift_floor;
            let left_index = y * output_width + output_x;
            let left_coverage = coverage * (1.0 - shift_fraction);
            if left_coverage > alpha[left_index] {
                alpha[left_index] = left_coverage;
            }

            if shift_fraction > 0.0 {
                let right_index = left_index + 1;
                let right_coverage = coverage * shift_fraction;
                if right_coverage > alpha[right_index] {
                    alpha[right_index] = right_coverage;
                }
            }
        }
    }

    GlyphMask {
        alpha: Arc::from(alpha),
        width: output_width,
        height: mask.height,
        origin_x: mask.origin_x,
        origin_y: mask.origin_y,
    }
}

fn synthetic_weight_shift_px(embolden_px: f32) -> usize {
    if !embolden_px.is_finite() || embolden_px < 0.35 {
        return 0;
    }
    embolden_px.ceil().max(1.0) as usize
}

fn build_outline_path(
    font: &impl Font,
    glyph: &Glyph,
    bounds: GlyphPixelBounds,
    pad: i32,
) -> Option<Path> {
    let outline = font.outline(glyph.id)?;
    let scale_factor = font.as_scaled(glyph.scale).scale_factor();
    let mut builder = PathBuilder::new();
    let mut has_segments = false;
    let mut current_end = None;
    let mut subpath_start = None;

    for curve in outline.curves {
        match curve {
            ab_glyph::OutlineCurve::Line(p0, p1) => {
                let start = transform_outline_point(p0, scale_factor, glyph, bounds, pad);
                let end = transform_outline_point(p1, scale_factor, glyph, bounds, pad);
                if current_end != Some(start) {
                    if current_end.is_some() {
                        builder.close();
                    }
                    builder.move_to(start.0, start.1);
                    subpath_start = Some(start);
                }
                builder.line_to(end.0, end.1);
                if subpath_start == Some(end) {
                    builder.close();
                    current_end = None;
                    subpath_start = None;
                } else {
                    current_end = Some(end);
                }
            }
            ab_glyph::OutlineCurve::Quad(p0, p1, p2) => {
                let start = transform_outline_point(p0, scale_factor, glyph, bounds, pad);
                let control = transform_outline_point(p1, scale_factor, glyph, bounds, pad);
                let end = transform_outline_point(p2, scale_factor, glyph, bounds, pad);
                if current_end != Some(start) {
                    if current_end.is_some() {
                        builder.close();
                    }
                    builder.move_to(start.0, start.1);
                    subpath_start = Some(start);
                }
                builder.quad_to(control.0, control.1, end.0, end.1);
                if subpath_start == Some(end) {
                    builder.close();
                    current_end = None;
                    subpath_start = None;
                } else {
                    current_end = Some(end);
                }
            }
            ab_glyph::OutlineCurve::Cubic(p0, p1, p2, p3) => {
                let start = transform_outline_point(p0, scale_factor, glyph, bounds, pad);
                let control1 = transform_outline_point(p1, scale_factor, glyph, bounds, pad);
                let control2 = transform_outline_point(p2, scale_factor, glyph, bounds, pad);
                let end = transform_outline_point(p3, scale_factor, glyph, bounds, pad);
                if current_end != Some(start) {
                    if current_end.is_some() {
                        builder.close();
                    }
                    builder.move_to(start.0, start.1);
                    subpath_start = Some(start);
                }
                builder.cubic_to(control1.0, control1.1, control2.0, control2.1, end.0, end.1);
                if subpath_start == Some(end) {
                    builder.close();
                    current_end = None;
                    subpath_start = None;
                } else {
                    current_end = Some(end);
                }
            }
        }
        has_segments = true;
    }

    if !has_segments {
        return None;
    }

    if current_end.is_some() {
        builder.close();
    }

    builder.finish()
}

fn transform_outline_point(
    point: ab_glyph::Point,
    scale_factor: ab_glyph::PxScaleFactor,
    glyph: &Glyph,
    bounds: GlyphPixelBounds,
    pad: i32,
) -> (f32, f32) {
    (
        point.x * scale_factor.horizontal + glyph.position.x - bounds.min_x as f32 + pad as f32,
        point.y * -scale_factor.vertical + glyph.position.y - bounds.min_y as f32 + pad as f32,
    )
}

#[cfg(test)]
mod tests {
    use super::*;
    use cranpose_ui::text::{RangeStyle, SpanStyle};
    use cranpose_ui_graphics::Point;

    fn count_ink_pixels(image: &ImageBitmap) -> usize {
        image
            .pixels()
            .chunks_exact(4)
            .filter(|px| px[3] > 0)
            .count()
    }

    #[test]
    fn software_glyph_raster_cache_reuses_static_masks_across_positions() {
        let font = default_software_text_font().expect("bundled default font");
        let style = TextStyle::default();
        let rect = Rect {
            x: 0.0,
            y: 0.0,
            width: 160.0,
            height: 32.0,
        };
        let mut cache = SoftwareGlyphRasterCache::with_capacity_at_least_one(64);

        let uncached = rasterize_text_to_image(
            "aaaa",
            rect,
            &style,
            Color(1.0, 1.0, 1.0, 1.0),
            18.0,
            1.0,
            &font,
        )
        .expect("uncached image");
        let cached = rasterize_text_to_image_with_glyph_cache(
            "aaaa",
            rect,
            &style,
            Color(1.0, 1.0, 1.0, 1.0),
            18.0,
            1.0,
            &font,
            &mut cache,
        )
        .expect("cached image");

        assert_eq!(cached.pixels(), uncached.pixels());
        let stats = cache.stats();
        assert_eq!(stats.entries, 1);
        assert_eq!(stats.misses, 1);
        assert_eq!(stats.hits, 3);

        let shifted_rect = Rect {
            x: 24.0,
            y: 17.0,
            ..rect
        };
        let _ = rasterize_text_to_image_with_glyph_cache(
            "aaaa",
            shifted_rect,
            &style,
            Color(1.0, 1.0, 1.0, 1.0),
            18.0,
            1.0,
            &font,
            &mut cache,
        )
        .expect("cached shifted image");

        let shifted_stats = cache.stats();
        assert_eq!(shifted_stats.entries, 1);
        assert_eq!(shifted_stats.misses, 1);
        assert_eq!(shifted_stats.hits, 7);
    }

    #[test]
    fn annotated_solid_text_direct_raster_matches_plain_text_pixels() {
        let font = default_software_text_font().expect("bundled default font");
        let font_set = SoftwareTextFontSet::from_font(font.clone());
        let style = TextStyle::default();
        let rect = Rect {
            x: 0.0,
            y: 0.0,
            width: 240.0,
            height: 40.0,
        };
        let color = Color(1.0, 1.0, 1.0, 1.0);
        let annotated = AnnotatedString {
            text: "plain link".to_string(),
            span_styles: vec![RangeStyle {
                item: SpanStyle {
                    color: Some(color),
                    ..Default::default()
                },
                range: 0..10,
            }],
            ..Default::default()
        };
        let mut cache = SoftwareGlyphRasterCache::with_capacity_at_least_one(64);

        let plain = rasterize_text_to_image(
            annotated.text.as_str(),
            rect,
            &style,
            color,
            18.0,
            1.0,
            &font,
        )
        .expect("plain text image");
        let direct = rasterize_annotated_text_to_image_with_glyph_cache(
            &annotated, rect, &style, color, 18.0, 1.0, &font_set, &mut cache,
        )
        .expect("annotated text image");

        assert_eq!(direct.pixels(), plain.pixels());
    }

    #[test]
    fn solid_annotated_text_collects_atlas_glyphs_with_stable_keys() {
        let font = default_software_text_font().expect("bundled default font");
        let font_set = SoftwareTextFontSet::from_font(font);
        let style = TextStyle::default();
        let rect = Rect {
            x: 12.0,
            y: 4.0,
            width: 260.0,
            height: 48.0,
        };
        let annotated = AnnotatedString {
            text: "markdown link".to_string(),
            span_styles: vec![RangeStyle {
                item: SpanStyle {
                    color: Some(Color(0.4, 0.7, 1.0, 1.0)),
                    ..Default::default()
                },
                range: 9..13,
            }],
            ..Default::default()
        };
        let mut cache = SoftwareGlyphRasterCache::with_capacity_at_least_one(64);
        let mut glyphs = Vec::new();

        collect_solid_text_atlas_glyphs(
            &annotated,
            rect,
            &style,
            Color::WHITE,
            18.0,
            1.0,
            &font_set,
            &mut cache,
            &mut glyphs,
        )
        .expect("solid styled text is atlas-eligible");

        assert!(!glyphs.is_empty());
        assert!(glyphs.iter().all(|glyph| glyph.mask.width > 0));
        assert!(glyphs.iter().all(|glyph| glyph.mask.height > 0));
        assert!(glyphs
            .iter()
            .any(|glyph| glyph.color == Color(0.4, 0.7, 1.0, 1.0)));
        assert!(cache.stats().entries > 0);
    }

    #[test]
    fn cached_atlas_placements_reuse_existing_glyph_masks_without_payloads() {
        let font = default_software_text_font().expect("bundled default font");
        let font_set = SoftwareTextFontSet::from_font(font);
        let style = TextStyle::default();
        let rect = Rect {
            x: 12.0,
            y: 4.0,
            width: 260.0,
            height: 48.0,
        };
        let annotated = AnnotatedString {
            text: "markdown link".to_string(),
            span_styles: vec![RangeStyle {
                item: SpanStyle {
                    color: Some(Color(0.4, 0.7, 1.0, 1.0)),
                    ..Default::default()
                },
                range: 9..13,
            }],
            ..Default::default()
        };
        let mut cache = SoftwareGlyphRasterCache::with_capacity_at_least_one(64);
        let mut placements = Vec::new();

        assert!(
            collect_cached_solid_text_atlas_placements(
                &annotated,
                rect,
                &style,
                Color::WHITE,
                18.0,
                1.0,
                &font_set,
                &mut cache,
                &mut placements,
            )
            .is_none(),
            "placement-only collection requires retained glyph masks"
        );
        assert!(placements.is_empty());

        let mut glyphs = Vec::new();
        collect_solid_text_atlas_glyphs(
            &annotated,
            rect,
            &style,
            Color::WHITE,
            18.0,
            1.0,
            &font_set,
            &mut cache,
            &mut glyphs,
        )
        .expect("solid styled text is atlas-eligible");

        collect_cached_solid_text_atlas_placements(
            &annotated,
            rect,
            &style,
            Color::WHITE,
            18.0,
            1.0,
            &font_set,
            &mut cache,
            &mut placements,
        )
        .expect("cached masks provide placement-only atlas glyphs");

        assert_eq!(placements.len(), glyphs.len());
        assert!(placements
            .iter()
            .zip(glyphs.iter())
            .all(|(placement, glyph)| {
                placement.key == glyph.key
                    && placement.x == glyph.x
                    && placement.y == glyph.y
                    && placement.width == glyph.mask.width
                    && placement.height == glyph.mask.height
                    && placement.color == glyph.color
            }));
        let recovered = cache
            .atlas_glyph_for_placement(&placements[0])
            .expect("placement should recover retained mask payload");
        assert_eq!(recovered.key, glyphs[0].key);
        assert_eq!(recovered.x, glyphs[0].x);
        assert_eq!(recovered.y, glyphs[0].y);
        assert_eq!(recovered.mask.width, glyphs[0].mask.width);
        assert_eq!(recovered.mask.height, glyphs[0].mask.height);
        assert_eq!(recovered.mask.alpha, glyphs[0].mask.alpha);
        assert_eq!(recovered.color, glyphs[0].color);
    }

    #[test]
    fn atlas_glyph_collection_rejects_shadow_and_gradient_without_partial_output() {
        let font = default_software_text_font().expect("bundled default font");
        let font_set = SoftwareTextFontSet::from_font(font);
        let rect = Rect {
            x: 0.0,
            y: 0.0,
            width: 240.0,
            height: 40.0,
        };
        let mut cache = SoftwareGlyphRasterCache::with_capacity_at_least_one(64);
        let mut glyphs = Vec::new();
        glyphs.push(SoftwareGlyphAtlasGlyph {
            key: SoftwareGlyphAtlasKey {
                font_hash: 1,
                glyph_id: 1,
                scale_x_bits: 1,
                scale_y_bits: 1,
                embolden_px_bits: 0,
                slant_bits: 0,
            },
            mask: SoftwareGlyphAtlasMask {
                alpha: Arc::from([1.0f32]),
                width: 1,
                height: 1,
            },
            x: 0,
            y: 0,
            color: Color::WHITE,
        });
        let initial_len = glyphs.len();

        let shadow_style = TextStyle::from_span_style(SpanStyle {
            shadow: Some(Shadow {
                color: Color(0.0, 0.0, 0.0, 0.5),
                offset: Point::new(1.0, 1.0),
                blur_radius: 0.0,
            }),
            ..Default::default()
        });
        assert!(collect_solid_text_atlas_glyphs(
            &AnnotatedString::new("shadow".to_string()),
            rect,
            &shadow_style,
            Color::WHITE,
            18.0,
            1.0,
            &font_set,
            &mut cache,
            &mut glyphs,
        )
        .is_none());
        assert_eq!(glyphs.len(), initial_len);

        let gradient_style = TextStyle::from_span_style(SpanStyle {
            brush: Some(Brush::linear_gradient(vec![Color::WHITE, Color::BLACK])),
            ..Default::default()
        });
        assert!(collect_solid_text_atlas_glyphs(
            &AnnotatedString::new("gradient".to_string()),
            rect,
            &gradient_style,
            Color::WHITE,
            18.0,
            1.0,
            &font_set,
            &mut cache,
            &mut glyphs,
        )
        .is_none());
        assert_eq!(glyphs.len(), initial_len);
    }

    fn average_ink_rgb(
        image: &ImageBitmap,
        x_start: u32,
        x_end: u32,
        y_start: u32,
        y_end: u32,
    ) -> Option<[f32; 3]> {
        let width = image.width();
        let height = image.height();
        let mut sums = [0.0f32; 3];
        let mut count = 0usize;
        let pixels = image.pixels();

        let x_end = x_end.min(width);
        let y_end = y_end.min(height);
        for y in y_start.min(height)..y_end {
            for x in x_start.min(width)..x_end {
                let idx = ((y * width + x) * 4) as usize;
                let alpha = pixels[idx + 3];
                if alpha == 0 {
                    continue;
                }
                sums[0] += pixels[idx] as f32 / 255.0;
                sums[1] += pixels[idx + 1] as f32 / 255.0;
                sums[2] += pixels[idx + 2] as f32 / 255.0;
                count += 1;
            }
        }

        if count == 0 {
            return None;
        }
        Some([
            sums[0] / count as f32,
            sums[1] / count as f32,
            sums[2] / count as f32,
        ])
    }

    fn ink_x_range(image: &ImageBitmap) -> Option<(u32, u32)> {
        let width = image.width();
        let height = image.height();
        let pixels = image.pixels();
        let mut min_x = u32::MAX;
        let mut max_x = 0u32;
        let mut found = false;
        for y in 0..height {
            for x in 0..width {
                let idx = ((y * width + x) * 4) as usize;
                if pixels[idx + 3] > 0 {
                    min_x = min_x.min(x);
                    max_x = max_x.max(x + 1);
                    found = true;
                }
            }
        }
        found.then_some((min_x, max_x))
    }

    fn ink_y_range(image: &ImageBitmap) -> Option<(u32, u32)> {
        let width = image.width();
        let height = image.height();
        let pixels = image.pixels();
        let mut min_y = u32::MAX;
        let mut max_y = 0u32;
        let mut found = false;
        for y in 0..height {
            for x in 0..width {
                let idx = ((y * width + x) * 4) as usize;
                if pixels[idx + 3] > 0 {
                    min_y = min_y.min(y);
                    max_y = max_y.max(y + 1);
                    found = true;
                }
            }
        }
        found.then_some((min_y, max_y))
    }

    fn ink_centroid_x(image: &ImageBitmap, y_start: u32, y_end: u32) -> Option<f32> {
        let width = image.width();
        let height = image.height();
        let pixels = image.pixels();
        let mut weighted_x = 0.0f32;
        let mut total_alpha = 0.0f32;

        for y in y_start.min(height)..y_end.min(height) {
            for x in 0..width {
                let idx = ((y * width + x) * 4) as usize;
                let alpha = pixels[idx + 3] as f32 / 255.0;
                if alpha <= 0.0 {
                    continue;
                }
                weighted_x += x as f32 * alpha;
                total_alpha += alpha;
            }
        }

        (total_alpha > 0.0).then_some(weighted_x / total_alpha)
    }

    fn vertical_slant_delta(image: &ImageBitmap) -> f32 {
        let (top, bottom) = ink_y_range(image).expect("image should contain ink");
        let mid = top + (bottom - top).max(1) / 2;
        let top_x = ink_centroid_x(image, top, mid).expect("top ink centroid");
        let bottom_x = ink_centroid_x(image, mid, bottom).expect("bottom ink centroid");
        top_x - bottom_x
    }

    fn top_ink_row(image: &ImageBitmap) -> Option<u32> {
        let width = image.width();
        let height = image.height();
        let pixels = image.pixels();
        for y in 0..height {
            for x in 0..width {
                let idx = ((y * width + x) * 4) as usize;
                if pixels[idx + 3] > 0 {
                    return Some(y);
                }
            }
        }
        None
    }

    fn reference_dilation_offsets(radius: i32) -> Vec<(i32, i32)> {
        let mut offsets = Vec::new();
        let squared_radius = radius * radius;
        for dy in -radius..=radius {
            for dx in -radius..=radius {
                if dx * dx + dy * dy <= squared_radius {
                    offsets.push((dx, dy));
                }
            }
        }
        if offsets.is_empty() {
            offsets.push((0, 0));
        }
        offsets
    }

    fn reference_dilation_stroke_mask(fill: &GlyphMask, stroke_width: f32) -> GlyphMask {
        let radius = (stroke_width * 0.5).ceil() as i32;
        let offsets = reference_dilation_offsets(radius);
        let out_width = fill.width as i32 + radius * 2;
        let out_height = fill.height as i32 + radius * 2;
        let fill_width_i32 = fill.width as i32;
        let fill_height_i32 = fill.height as i32;
        let mut alpha = vec![0.0f32; (out_width * out_height) as usize];

        for out_y in 0..out_height {
            let oy = out_y - radius;
            for out_x in 0..out_width {
                let ox = out_x - radius;
                let base_alpha =
                    if ox >= 0 && oy >= 0 && ox < fill_width_i32 && oy < fill_height_i32 {
                        fill.alpha[oy as usize * fill.width + ox as usize]
                    } else {
                        0.0
                    };

                let mut dilated_alpha = 0.0f32;
                for (dx, dy) in &offsets {
                    let sx = ox + dx;
                    let sy = oy + dy;
                    if sx < 0 || sy < 0 || sx >= fill_width_i32 || sy >= fill_height_i32 {
                        continue;
                    }
                    let sample = fill.alpha[sy as usize * fill.width + sx as usize];
                    if sample > dilated_alpha {
                        dilated_alpha = sample;
                        if dilated_alpha >= 0.999 {
                            break;
                        }
                    }
                }
                alpha[out_y as usize * out_width as usize + out_x as usize] =
                    (dilated_alpha - base_alpha).max(0.0);
            }
        }

        GlyphMask {
            alpha: Arc::from(alpha),
            width: out_width as usize,
            height: out_height as usize,
            origin_x: fill.origin_x - radius,
            origin_y: fill.origin_y - radius,
        }
    }

    fn rasterize_reference_dilation_stroke(
        text: &str,
        rect: Rect,
        font_size: f32,
        stroke_width: f32,
        font: &impl Font,
    ) -> ImageBitmap {
        let width = rect.width.ceil().max(1.0) as u32;
        let height = rect.height.ceil().max(1.0) as u32;
        let mut canvas = vec![[0.0f32; 4]; (width * height) as usize];

        let metrics = vertical_metrics(font, font_size);
        let baseline =
            baseline_y_for_line_box(&TextStyle::default(), metrics, font_size * 1.4, 1.0);
        for glyph in layout_line_glyphs(font, text, font_size, point(0.0, baseline)) {
            let Some((outlined, bounds)) = outline_glyph_with_bounds(font, &glyph) else {
                continue;
            };
            let Some(fill) = build_fill_mask(&outlined, bounds) else {
                continue;
            };
            let reference = reference_dilation_stroke_mask(&fill, stroke_width);
            draw_mask_glyph(
                &mut canvas,
                width,
                height,
                &reference,
                &Brush::solid(Color::WHITE),
                1.0,
                rect,
            );
        }

        let mut rgba = vec![0u8; canvas.len() * 4];
        for (index, pixel) in canvas.iter().enumerate() {
            let base = index * 4;
            rgba[base] = (pixel[0].clamp(0.0, 1.0) * 255.0).round() as u8;
            rgba[base + 1] = (pixel[1].clamp(0.0, 1.0) * 255.0).round() as u8;
            rgba[base + 2] = (pixel[2].clamp(0.0, 1.0) * 255.0).round() as u8;
            rgba[base + 3] = (pixel[3].clamp(0.0, 1.0) * 255.0).round() as u8;
        }
        ImageBitmap::from_rgba8(width, height, rgba).expect("reference dilation image")
    }

    fn test_font() -> ab_glyph::FontRef<'static> {
        ab_glyph::FontRef::try_from_slice(include_bytes!("../assets/NotoSansMerged.ttf"))
            .expect("font")
    }

    fn test_software_font() -> SoftwareTextFont {
        SoftwareTextFont::from_bytes(include_bytes!("../assets/NotoSansMerged.ttf").to_vec())
            .expect("font")
    }

    #[test]
    fn software_text_font_rejects_invalid_bytes() {
        assert!(SoftwareTextFont::from_bytes(vec![0, 1, 2, 3]).is_err());
    }

    #[test]
    fn default_software_text_font_has_no_process_global_cache() {
        let source = include_str!("software_text_raster.rs");
        let once_lock = ["Once", "Lock"].concat();
        let cached_default = ["static ", "FONT"].concat();
        let default_font_fn = ["fn ", "default_font()"].concat();

        assert!(
            !source.contains(&cached_default)
                && !source.contains(&default_font_fn)
                && !source.contains(&once_lock),
            "default software text font construction must be explicit renderer/app-owned state, not a process-global cache"
        );
    }

    #[test]
    fn software_text_measurer_empty_font_set_uses_deterministic_fallback_without_panicking() {
        let measurer = SoftwareTextMeasurer::from_font_set(SoftwareTextFontSet::empty(), 4);
        let style = TextStyle {
            span_style: SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(20.0),
                ..Default::default()
            },
            ..Default::default()
        };
        let text = AnnotatedString::from("ab\nc");

        let metrics = measurer.measure(&text, &style);
        assert_eq!(metrics.line_count, 2);
        assert!(metrics.width > 0.0);
        assert!(metrics.height >= metrics.line_height * 2.0);

        let cursor_x = measurer.get_cursor_x_for_offset(&text, &style, 2);
        assert!(cursor_x > 0.0);
        let second_line_offset =
            measurer.get_offset_for_position(&text, &style, 0.0, metrics.line_height);
        assert!(
            second_line_offset >= "ab\n".len(),
            "fallback hit testing should resolve into the second line: {second_line_offset}"
        );

        let layout = measurer.layout(&text, &style);
        assert_eq!(layout.lines.len(), 2);
        assert_eq!(layout.glyph_layouts().len(), 3);
    }

    #[test]
    fn software_text_metrics_layout_and_cursor_share_font_backend() {
        let font = test_software_font();
        let style = TextStyle {
            span_style: SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(18.0),
                ..Default::default()
            },
            ..Default::default()
        };
        let text = "Text\nBackend";

        let metrics = measure_text_with_font(text, &style, 18.0, &font);
        let layout = layout_text_with_font(text, &style, &font);

        assert!(metrics.width > 0.0);
        assert_eq!(metrics.line_count, 2);
        assert_eq!(layout.lines.len(), 2);
        assert_eq!(layout.height, metrics.height);
        assert!(layout.glyph_layouts().len() >= "TextBackend".len());

        let offset =
            text_offset_for_position_with_font(text, &style, 0.0, metrics.line_height, &font);
        assert!(
            offset >= "Text\n".len(),
            "second-line hit testing should return a byte offset on the second line: {offset}"
        );
        let cursor_x = cursor_x_for_offset_with_font(text, &style, "Text".len(), &font);
        assert!(cursor_x > 0.0);
    }

    #[test]
    fn software_text_metrics_keep_requested_font_size_for_default_font() {
        let font = default_software_text_font().expect("bundled default test font");
        let style = TextStyle {
            span_style: SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(14.0),
                ..Default::default()
            },
            ..Default::default()
        };

        let metrics = measure_text_with_font("Counter App", &style, 14.0, &font);
        assert!(
            (metrics.width - 83.16).abs() < 0.05 && (metrics.height - 19.6).abs() < 0.05,
            "14sp demo text must use font em metrics, not ab_glyph height units: {metrics:?}"
        );
    }

    #[test]
    fn software_text_synthesizes_missing_bold_weight() {
        let font = test_software_font();
        let normal_style = TextStyle {
            span_style: SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(20.0),
                ..Default::default()
            },
            ..Default::default()
        };
        let bold_style = TextStyle {
            span_style: SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(20.0),
                font_weight: Some(FontWeight::BOLD),
                ..Default::default()
            },
            ..Default::default()
        };
        let no_synthesis_style = TextStyle {
            span_style: SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(20.0),
                font_weight: Some(FontWeight::BOLD),
                font_synthesis: Some(FontSynthesis::None),
                ..Default::default()
            },
            ..Default::default()
        };

        let normal = measure_text_with_font("Save Raster WebP", &normal_style, 20.0, &font);
        let synthesized = measure_text_with_font("Save Raster WebP", &bold_style, 20.0, &font);
        let disabled = measure_text_with_font("Save Raster WebP", &no_synthesis_style, 20.0, &font);

        assert!(
            synthesized.width > normal.width * 1.04,
            "bold fallback should synthesize heavier advances: normal={normal:?} synthesized={synthesized:?}"
        );
        assert!(
            (disabled.width - normal.width).abs() < 0.01,
            "explicit FontSynthesis::None should preserve regular metrics: normal={normal:?} disabled={disabled:?}"
        );
    }

    #[test]
    fn rasterized_synthetic_bold_adds_ink_without_changing_line_box() {
        let font = test_software_font();
        let normal_style = TextStyle {
            span_style: SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(20.0),
                ..Default::default()
            },
            ..Default::default()
        };
        let bold_style = TextStyle {
            span_style: SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(20.0),
                font_weight: Some(FontWeight::BOLD),
                ..Default::default()
            },
            ..Default::default()
        };
        let normal_metrics = measure_text_with_font("Composer", &normal_style, 20.0, &font);
        let bold_metrics = measure_text_with_font("Composer", &bold_style, 20.0, &font);

        let normal = rasterize_text_to_image(
            "Composer",
            Rect {
                x: 0.0,
                y: 0.0,
                width: normal_metrics.width.ceil(),
                height: normal_metrics.height.ceil(),
            },
            &normal_style,
            Color::WHITE,
            20.0,
            1.0,
            &font,
        )
        .expect("normal text image");
        let bold = rasterize_text_to_image(
            "Composer",
            Rect {
                x: 0.0,
                y: 0.0,
                width: bold_metrics.width.ceil(),
                height: bold_metrics.height.ceil(),
            },
            &bold_style,
            Color::WHITE,
            20.0,
            1.0,
            &font,
        )
        .expect("bold text image");

        assert_eq!(bold.height(), normal.height());
        assert!(
            count_ink_pixels(&bold) > count_ink_pixels(&normal),
            "synthetic bold should increase rasterized ink coverage"
        );
    }

    #[test]
    fn software_text_synthesizes_missing_italic_style() {
        let font = test_software_font();
        let normal_style = TextStyle {
            span_style: SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(36.0),
                ..Default::default()
            },
            ..Default::default()
        };
        let italic_style = TextStyle {
            span_style: SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(36.0),
                font_style: Some(FontStyle::Italic),
                ..Default::default()
            },
            ..Default::default()
        };
        let no_synthesis_style = TextStyle {
            span_style: SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(36.0),
                font_style: Some(FontStyle::Italic),
                font_synthesis: Some(FontSynthesis::None),
                ..Default::default()
            },
            ..Default::default()
        };

        let normal_metrics = measure_text_with_font("Italic", &normal_style, 36.0, &font);
        let italic_metrics = measure_text_with_font("Italic", &italic_style, 36.0, &font);
        let disabled_metrics = measure_text_with_font("Italic", &no_synthesis_style, 36.0, &font);

        assert!(
            italic_metrics.width > normal_metrics.width + 6.0,
            "italic fallback should reserve slanted visual overhang: normal={normal_metrics:?} italic={italic_metrics:?}"
        );
        assert!(
            (disabled_metrics.width - normal_metrics.width).abs() < 0.01,
            "explicit FontSynthesis::None should preserve regular metrics: normal={normal_metrics:?} disabled={disabled_metrics:?}"
        );

        let normal = rasterize_text_to_image(
            "Italic",
            Rect {
                x: 0.0,
                y: 0.0,
                width: normal_metrics.width.ceil(),
                height: normal_metrics.height.ceil(),
            },
            &normal_style,
            Color::WHITE,
            36.0,
            1.0,
            &font,
        )
        .expect("normal text image");
        let italic = rasterize_text_to_image(
            "Italic",
            Rect {
                x: 0.0,
                y: 0.0,
                width: italic_metrics.width.ceil(),
                height: italic_metrics.height.ceil(),
            },
            &italic_style,
            Color::WHITE,
            36.0,
            1.0,
            &font,
        )
        .expect("italic text image");
        let disabled = rasterize_text_to_image(
            "Italic",
            Rect {
                x: 0.0,
                y: 0.0,
                width: disabled_metrics.width.ceil(),
                height: disabled_metrics.height.ceil(),
            },
            &no_synthesis_style,
            Color::WHITE,
            36.0,
            1.0,
            &font,
        )
        .expect("disabled italic text image");

        assert_eq!(
            normal.pixels(),
            disabled.pixels(),
            "FontSynthesis::None must not synthesize oblique glyphs"
        );
        assert!(
            vertical_slant_delta(&italic) > vertical_slant_delta(&normal) + 2.0,
            "synthetic italic should visibly lean top ink to the right"
        );
    }

    #[test]
    fn rasterized_default_text_fills_expected_visual_height() {
        let font = default_software_text_font().expect("bundled default test font");
        let style = TextStyle {
            span_style: SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(14.0),
                ..Default::default()
            },
            ..Default::default()
        };
        let metrics = measure_text_with_font("Counter App", &style, 14.0, &font);
        let image = rasterize_text_to_image(
            "Counter App",
            Rect {
                x: 0.0,
                y: 0.0,
                width: metrics.width.ceil(),
                height: metrics.height.ceil(),
            },
            &style,
            Color::WHITE,
            14.0,
            1.0,
            &font,
        )
        .expect("text image");
        let (top, bottom) = ink_y_range(&image).expect("text should contain ink");
        let ink_height = bottom - top;

        assert!(
            ink_height >= 13,
            "14sp default text ink should keep visual height parity with the WGPU baseline: top={top} bottom={bottom} image={}x{}",
            image.width(),
            image.height()
        );
    }

    #[test]
    fn software_text_font_selection_preserves_first_complete_default_face() {
        let regular =
            SoftwareTextFont::from_bytes(include_bytes!("../assets/NotoSansMerged.ttf").to_vec())
                .expect("regular test font should load");
        let font = software_text_font_from_fonts_or_default(&[
            include_bytes!("../assets/NotoSansMerged.ttf"),
            include_bytes!("../assets/NotoSansBold.ttf"),
            include_bytes!("../assets/TwemojiMozilla.ttf"),
        ])
        .expect("font selection should resolve a test font");
        let style = TextStyle {
            span_style: SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(18.0),
                ..Default::default()
            },
            ..Default::default()
        };

        let regular_metrics = measure_text_with_font("UNDER", &style, 18.0, &regular);
        let metrics = measure_text_with_font("UNDER", &style, 18.0, &font);
        assert!(
            (metrics.width - regular_metrics.width).abs() < 0.01,
            "font selection should keep the declared regular face for default text: selected={metrics:?}, regular={regular_metrics:?}"
        );
    }

    #[test]
    fn software_text_font_resolution_reuses_cached_font_score() {
        let font = test_software_font();
        assert!(
            font.score.is_complete_default_face(),
            "test font should cache complete Latin coverage at load time: supported={} width={}",
            font.score.supported_latin_chars,
            font.score.latin_sample_width
        );

        let fonts = SoftwareTextFontSet::from_font(font.clone());
        let resolved = fonts
            .resolve(&TextStyle {
                span_style: SpanStyle {
                    font_weight: Some(FontWeight::BOLD),
                    ..Default::default()
                },
                ..Default::default()
            })
            .expect("font set should resolve a test font");

        assert_eq!(
            resolved.score.supported_latin_chars,
            font.score.supported_latin_chars
        );
        assert_eq!(
            resolved.score.latin_sample_width,
            font.score.latin_sample_width
        );
    }

    #[test]
    fn software_text_font_set_resolves_requested_weight() {
        let fonts = software_text_font_set_from_fonts_or_default(&[
            include_bytes!("../assets/NotoSansMerged.ttf"),
            include_bytes!("../assets/NotoSansBold.ttf"),
            include_bytes!("../assets/TwemojiMozilla.ttf"),
        ]);
        let regular = fonts
            .resolve(&TextStyle::default())
            .expect("font set should resolve regular test font");
        let bold_style = TextStyle {
            span_style: SpanStyle {
                font_weight: Some(FontWeight::BOLD),
                ..Default::default()
            },
            ..Default::default()
        };
        let bold = fonts
            .resolve(&bold_style)
            .expect("font set should resolve bold test font");

        assert_eq!(regular.weight(), FontWeight::NORMAL);
        assert_eq!(bold.weight(), FontWeight::BOLD);

        let regular_metrics =
            measure_text_with_font("Counter App", &TextStyle::default(), 18.0, regular);
        let bold_metrics = measure_text_with_font("Counter App", &bold_style, 18.0, bold);
        assert!(
            bold_metrics.width > regular_metrics.width,
            "bold face resolution should affect real text metrics: regular={regular_metrics:?} bold={bold_metrics:?}"
        );
    }

    fn registered_face(family: &FontFamily, weight: FontWeight) -> SoftwareTextFont {
        SoftwareTextFont::from_registered_bytes(
            family,
            weight,
            FontStyle::Normal,
            include_bytes!("../assets/NotoSansMerged.ttf").to_vec(),
        )
        .expect("registered test face")
    }

    fn style_naming(family: &FontFamily) -> TextStyle {
        TextStyle {
            span_style: SpanStyle {
                font_family: Some(family.clone()),
                ..Default::default()
            },
            ..Default::default()
        }
    }

    fn unregistered_face() -> SoftwareTextFont {
        SoftwareTextFont::from_bytes(include_bytes!("../assets/NotoSansBold.ttf").to_vec())
            .expect("unregistered test face")
    }

    #[test]
    fn a_named_family_resolves_the_face_registered_under_it() {
        // The file's own `name` table says Noto Sans; the app filed it as
        // "Game UI", and asking for that has to find it.
        let family = FontFamily::named("Game UI");
        let fonts = SoftwareTextFontSet::from_faces(vec![
            unregistered_face(),
            registered_face(&family, FontWeight::NORMAL),
        ]);

        let resolved = fonts
            .resolve(&style_naming(&family))
            .expect("registered face");
        assert_eq!(
            resolved.registered_family(),
            Some(FontFamilyKey::of(&family))
        );
    }

    #[test]
    fn a_file_backed_family_never_resolves_a_face_filed_under_another_one() {
        let mine = FontFamily::loaded_typeface_path("/fonts/Mine.ttf");
        let theirs = FontFamily::loaded_typeface_path("/fonts/Theirs.ttf");
        let fallback =
            SoftwareTextFont::from_bytes(include_bytes!("../assets/NotoSansMerged.ttf").to_vec())
                .expect("fallback test face");
        let theirs_face = SoftwareTextFont::from_registered_bytes(
            &theirs,
            FontWeight::BOLD,
            FontStyle::Normal,
            include_bytes!("../assets/NotoSansBold.ttf").to_vec(),
        )
        .expect("registered test face");
        let fonts = SoftwareTextFontSet::from_faces(vec![fallback.clone(), theirs_face]);

        assert_eq!(
            fonts
                .resolve(&style_naming(&mine))
                .expect("fallback face")
                .content_hash(),
            fallback.content_hash(),
            "an unregistered family must fall back rather than borrow someone else's face"
        );
        assert_eq!(
            fonts
                .resolve(&style_naming(&theirs))
                .expect("registered face")
                .registered_family(),
            Some(FontFamilyKey::of(&theirs)),
            "the family that was registered still resolves to its own face"
        );
    }

    #[test]
    fn a_generic_family_only_constrains_the_set_once_a_face_is_registered_for_it() {
        let bold_sans_serif = TextStyle {
            span_style: SpanStyle {
                font_family: Some(FontFamily::SansSerif),
                font_weight: Some(FontWeight::BOLD),
                ..Default::default()
            },
            ..Default::default()
        };

        // Nothing claims `sans-serif`, so weight matching still runs over the
        // whole set the way it did before app-supplied families existed.
        let unclaimed = software_text_font_set_from_fonts_or_default(&[
            include_bytes!("../assets/NotoSansMerged.ttf"),
            include_bytes!("../assets/NotoSansBold.ttf"),
        ]);
        assert_eq!(
            unclaimed
                .resolve(&bold_sans_serif)
                .expect("bold face")
                .weight(),
            FontWeight::BOLD
        );

        // Once a face is filed under `sans-serif` it wins, because that is what
        // the app said the alias means.
        let claimed = SoftwareTextFontSet::from_faces(vec![
            SoftwareTextFont::from_bytes(include_bytes!("../assets/NotoSansBold.ttf").to_vec())
                .expect("bold test face"),
            registered_face(&FontFamily::SansSerif, FontWeight::NORMAL),
        ]);
        let resolved = claimed.resolve(&bold_sans_serif).expect("system face");
        assert_eq!(
            resolved.registered_family(),
            Some(FontFamilyKey::of(&FontFamily::SansSerif))
        );
    }

    #[test]
    fn an_app_supplied_family_measures_once_and_is_served_from_the_metrics_cache() {
        let family = FontFamily::named("Game UI");
        let measurer = SoftwareTextMeasurer::from_font_set(
            SoftwareTextFontSet::from_faces(vec![registered_face(&family, FontWeight::NORMAL)]),
            64,
        );
        let style = style_naming(&family);
        let text = AnnotatedString::from("SCORE 1234");

        let first = measurer.measure(&text, &style);
        let stats_after_first = measurer.lock_cache().glyph_metrics.stats();
        for _ in 0..60 {
            assert_eq!(measurer.measure(&text, &style), first);
        }

        assert_eq!(
            measurer.lock_cache().glyph_metrics.stats(),
            stats_after_first,
            "repeat frames of an unchanged string must not re-shape against the app face"
        );
    }

    #[test]
    fn a_font_size_animation_measures_each_glyph_once_rather_than_once_per_size() {
        let font = default_software_text_font().expect("bundled default test font");
        let measurer = SoftwareTextMeasurer::new(font, 64);
        let text = AnnotatedString::from("Scaling list row");

        let sized = |size: f32| TextStyle {
            span_style: SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(size),
                ..Default::default()
            },
            ..Default::default()
        };

        // One size to fill the cache with this string's glyphs and pairs.
        let first = measurer.measure(&text, &sized(14.0));
        let after_first = measurer.lock_cache().glyph_metrics.stats();

        // A scaling list re-draws the same rows at a new size every frame. Font
        // metrics are linear in the size, so nothing here is new work: what the
        // cache holds is font units, and only the multiply changes.
        for step in 0..120 {
            let size = 14.0 + step as f32 * 0.137;
            let measured = measurer.measure(&text, &sized(size));
            assert!(
                measured.width > 0.0,
                "a scaled measurement must still produce a width"
            );
        }

        // Hits climb, which is the point. What must not move is the misses:
        // every one of those is a font-table read, and keying by size made them
        // grow with every frame a scaling list drew.
        let after_scaling = measurer.lock_cache().glyph_metrics.stats();
        assert_eq!(
            (after_scaling.glyph_misses, after_scaling.kern_misses),
            (after_first.glyph_misses, after_first.kern_misses),
            "measuring the same glyphs at a new size must not re-read the font: {after_scaling:?}"
        );
        assert!(
            after_scaling.glyph_hits > after_first.glyph_hits,
            "the scaled measurements must have come from the cache"
        );

        // And the scaling stays honest: twice the size is twice the advance.
        let single = measurer.measure(&AnnotatedString::from("W"), &sized(20.0));
        let double = measurer.measure(&AnnotatedString::from("W"), &sized(40.0));
        let ratio = double.width / single.width.max(f32::EPSILON);
        assert!(
            (ratio - 2.0).abs() < 0.01,
            "advances must scale with the font size: {single:?} -> {double:?} (ratio {ratio})"
        );
        let _ = first;
    }

    #[test]
    fn software_text_metrics_use_largest_annotated_span_font_size() {
        let font = default_software_text_font().expect("bundled default test font");
        let text = AnnotatedString::builder()
            .push_style(SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(30.0),
                ..Default::default()
            })
            .append("BIG ")
            .pop()
            .push_style(SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(10.0),
                ..Default::default()
            })
            .append("small")
            .pop()
            .to_annotated_string();

        let metrics = measure_annotated_text_with_font(&text, &TextStyle::default(), 14.0, &font);

        assert!(
            metrics.height >= 30.0,
            "rich text metrics must include the largest span height: {metrics:?}"
        );
        assert!(
            metrics.width > 48.0,
            "rich text metrics should measure run widths at their span sizes: {metrics:?}"
        );
    }

    #[test]
    fn software_text_line_height_matches_full_measurement_without_width_layout() {
        let measurer = SoftwareTextMeasurer::new(
            default_software_text_font().expect("bundled default test font"),
            8,
        );
        let text = AnnotatedString::builder()
            .append("normal ")
            .push_style(SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(32.0),
                ..Default::default()
            })
            .append("large")
            .pop()
            .append("\nsecond line")
            .to_annotated_string();
        let style = TextStyle::default();

        let measured = measurer.measure(&text, &style);
        let line_height = measurer.line_height(&text, &style);

        assert_eq!(line_height, measured.line_height);
        assert!(
            line_height > measurer.line_height(&AnnotatedString::from("normal"), &style),
            "span font size should affect fast line-height lookup"
        );
    }

    #[test]
    fn solid_text_atlas_line_advance_matches_measured_line_height() {
        let font = default_software_text_font().expect("bundled default test font");
        let fonts = SoftwareTextFontSet::from_font(font);
        let style = TextStyle::default();
        let text = AnnotatedString::from("A\nA\nA\nA");
        let font_size = style.resolve_font_size(14.0);
        let metrics = measure_annotated_text_with_font_set(&text, &style, font_size, &fonts);
        let rect = Rect {
            x: 0.0,
            y: 0.0,
            width: 120.0,
            height: metrics.height,
        };
        let mut glyph_cache = SoftwareGlyphRasterCache::with_capacity_at_least_one(16);
        let mut run = Vec::new();

        collect_solid_text_atlas_run(
            &text,
            rect,
            &style,
            Color(1.0, 1.0, 1.0, 1.0),
            font_size,
            1.0,
            &fonts,
            &mut glyph_cache,
            &mut run,
        )
        .expect("atlas-compatible text");

        let mut glyph_y: Vec<i32> = run.iter().map(|glyph| glyph.placement().y).collect();
        glyph_y.sort_unstable();
        glyph_y.dedup();
        assert_eq!(glyph_y.len(), 4);
        for window in glyph_y.windows(2) {
            let advance = (window[1] - window[0]) as f32;
            assert!(
                (advance - metrics.line_height).abs() <= 1.0,
                "glyph advance {advance} should match measured line height {}",
                metrics.line_height
            );
        }
    }

    #[test]
    fn software_text_metrics_cache_keys_include_span_styles() {
        let measurer = SoftwareTextMeasurer::new(
            default_software_text_font().expect("bundled default test font"),
            8,
        );
        let plain = AnnotatedString::from("BIG small");
        let rich = AnnotatedString::builder()
            .push_style(SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(30.0),
                ..Default::default()
            })
            .append("BIG ")
            .pop()
            .append("small")
            .to_annotated_string();

        let plain_metrics = measurer.measure(&plain, &TextStyle::default());
        let rich_metrics = measurer.measure(&rich, &TextStyle::default());

        assert!(
            rich_metrics.height > plain_metrics.height,
            "cached plain text metrics must not be reused for styled text: plain={plain_metrics:?} rich={rich_metrics:?}"
        );
    }

    #[test]
    fn software_text_metrics_cache_recovers_after_poison() {
        let measurer = SoftwareTextMeasurer::new(
            default_software_text_font().expect("bundled default test font"),
            8,
        );
        let text = AnnotatedString::from("Recovered text metrics");

        let poison_result = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
            let _guard = measurer
                .cache
                .lock()
                .unwrap_or_else(|poisoned| poisoned.into_inner());
            panic!("poison software text metrics cache for recovery test");
        }));

        assert!(poison_result.is_err());

        let metrics = measurer.measure(&text, &TextStyle::default());
        assert!(metrics.width > 0.0);
        assert!(metrics.height > 0.0);

        let subset =
            measurer.measure_subsequence(&text, 0.."Recovered".len(), &TextStyle::default());
        assert!(subset.width > 0.0);
        assert!(subset.width < metrics.width);
    }

    #[test]
    fn software_text_prefix_widths_match_subsequence_measurement() {
        let measurer = SoftwareTextMeasurer::new(
            default_software_text_font().expect("bundled default test font"),
            8,
        );
        let style = TextStyle {
            span_style: SpanStyle {
                font_size: cranpose_ui::text::TextUnit::Sp(18.0),
                ..Default::default()
            },
            ..Default::default()
        };
        let text = AnnotatedString::from("Hello Prefix Widths");
        let widths = measurer
            .measure_line_prefix_widths(&text, 0..text.text.len(), &style)
            .expect("uniform line should expose prefix widths");

        let start = "Hello ".len();
        let end = "Hello Prefix".len();
        let expected = measurer
            .measure_subsequence(&text, start..end, &style)
            .width;
        let actual = widths
            .width_for_char_range(6, 12)
            .expect("valid char range");

        assert!(
            (actual - expected).abs() < 0.01,
            "prefix width should match exact subsequence width: actual={actual}, expected={expected}"
        );
    }

    #[test]
    fn software_text_line_width_and_prefix_width_share_cached_plan() {
        let measurer = SoftwareTextMeasurer::new(
            default_software_text_font().expect("bundled default test font"),
            8,
        );
        let style = TextStyle::default();
        let text = AnnotatedString::from("shared prefix plan ".repeat(32).as_str());
        let line_range = 0..text.text.len();

        let width = measurer
            .measure_line_width(&text, line_range.clone(), &style)
            .expect("software text should expose a line width");
        let stats_after_width = {
            let cache = measurer.lock_cache();
            assert_eq!(cache.line_prefix_widths.len(), 1);
            cache.glyph_metrics.stats()
        };

        let widths = measurer
            .measure_line_prefix_widths(&text, line_range, &style)
            .expect("line width probe should cache the prefix plan");
        let stats_after_prefix = measurer.lock_cache().glyph_metrics.stats();

        assert_eq!(stats_after_prefix, stats_after_width);
        assert!(
            (width - widths.width_for_char_range(0, widths.char_count()).unwrap()).abs() < 0.01,
            "cached line-width probe and prefix plan must agree"
        );
    }

    #[test]
    fn software_text_glyph_metrics_cache_reuses_common_glyphs_across_unique_lines() {
        let measurer = SoftwareTextMeasurer::new(
            default_software_text_font().expect("bundled default test font"),
            8,
        );
        let style = TextStyle::default();
        let first = AnnotatedString::from("algorithm data structure ".repeat(24).as_str());
        let second =
            AnnotatedString::from("algorithmic structures repeat data ".repeat(24).as_str());

        measurer
            .measure_line_prefix_widths(&first, 0..first.text.len(), &style)
            .expect("first unique line should measure");
        let stats_after_first = measurer.lock_cache().glyph_metrics.stats();

        measurer
            .measure_line_prefix_widths(&second, 0..second.text.len(), &style)
            .expect("second unique line should measure");
        let stats_after_second = measurer.lock_cache().glyph_metrics.stats();

        assert!(
            stats_after_second.glyph_hits > stats_after_first.glyph_hits,
            "unique markdown rows should reuse retained glyph metrics: first={stats_after_first:?} second={stats_after_second:?}"
        );
        assert!(
            stats_after_second.kern_hits > stats_after_first.kern_hits,
            "unique markdown rows should reuse retained kerning metrics: first={stats_after_first:?} second={stats_after_second:?}"
        );
    }

    #[test]
    fn rasterized_gradient_text_shows_color_transition() {
        let font = test_font();
        // Use a gradient sized to the rendered text width so left=red, right=blue.
        // We first do a plain measurement pass to know the text width.
        let plain_style = TextStyle::default();
        let probe = rasterize_text_to_image_with_font(
            "MMMMMMMM",
            Rect {
                x: 0.0,
                y: 0.0,
                width: 320.0,
                height: 96.0,
            },
            &plain_style,
            Color::WHITE,
            48.0,
            1.0,
            &font,
        )
        .expect("probe image");
        let (ink_x_min, ink_x_max) = ink_x_range(&probe).expect("probe must contain ink");
        let gradient_end = ink_x_max as f32;

        let style = TextStyle {
            span_style: SpanStyle {
                brush: Some(Brush::linear_gradient_range(
                    vec![Color::RED, Color::BLUE],
                    Point::new(0.0, 0.0),
                    Point::new(gradient_end, 0.0),
                )),
                ..Default::default()
            },
            ..Default::default()
        };

        let image = rasterize_text_to_image_with_font(
            "MMMMMMMM",
            Rect {
                x: 0.0,
                y: 0.0,
                width: 320.0,
                height: 96.0,
            },
            &style,
            Color::WHITE,
            48.0,
            1.0,
            &font,
        )
        .expect("rasterized image");

        let ink_span = ink_x_max.saturating_sub(ink_x_min).max(1);
        let left_end = ink_x_min + ink_span * 3 / 10;
        let right_start = ink_x_max.saturating_sub(ink_span * 3 / 10);
        let left = average_ink_rgb(&image, ink_x_min, left_end, 8, 90).expect("left ink");
        let right = average_ink_rgb(&image, right_start, ink_x_max, 8, 90).expect("right ink");
        assert!(
            left[0] > left[2] * 1.1,
            "left region should be red dominant, got {left:?}"
        );
        assert!(
            right[2] > right[0] * 1.1,
            "right region should be blue dominant, got {right:?}"
        );
    }

    #[test]
    fn rasterized_stroke_and_fill_ink_coverage_differs() {
        let font = test_font();
        let fill_style = TextStyle::default();
        let stroke_style = TextStyle {
            span_style: SpanStyle {
                draw_style: Some(TextDrawStyle::Stroke { width: 6.0 }),
                ..Default::default()
            },
            ..Default::default()
        };
        let rect = Rect {
            x: 0.0,
            y: 0.0,
            width: 320.0,
            height: 96.0,
        };

        let fill = rasterize_text_to_image_with_font(
            "MMMMMMMM",
            rect,
            &fill_style,
            Color::WHITE,
            48.0,
            1.0,
            &font,
        )
        .expect("fill image");
        let stroke = rasterize_text_to_image_with_font(
            "MMMMMMMM",
            rect,
            &stroke_style,
            Color::WHITE,
            48.0,
            1.0,
            &font,
        )
        .expect("stroke image");

        let fill_ink = count_ink_pixels(&fill);
        let stroke_ink = count_ink_pixels(&stroke);
        assert_ne!(fill.pixels(), stroke.pixels());
        assert!(
            fill_ink.abs_diff(stroke_ink) > 300,
            "fill/stroke ink coverage should differ; fill={fill_ink}, stroke={stroke_ink}"
        );
    }

    #[test]
    fn stroke_path_uses_miter_join_for_acute_apexes() {
        let font = test_font();
        let fill_style = TextStyle::default();
        let stroke_width = 12.0;
        let stroke_style = TextStyle {
            span_style: SpanStyle {
                draw_style: Some(TextDrawStyle::Stroke {
                    width: stroke_width,
                }),
                ..Default::default()
            },
            ..Default::default()
        };
        let rect = Rect {
            x: 0.0,
            y: 0.0,
            width: 180.0,
            height: 140.0,
        };

        let fill = rasterize_text_to_image_with_font(
            "A",
            rect,
            &fill_style,
            Color::WHITE,
            110.0,
            1.0,
            &font,
        )
        .expect("fill image");
        let stroke = rasterize_text_to_image_with_font(
            "A",
            rect,
            &stroke_style,
            Color::WHITE,
            110.0,
            1.0,
            &font,
        )
        .expect("stroke image");

        let fill_top = top_ink_row(&fill).expect("fill top row");
        let stroke_top = top_ink_row(&stroke).expect("stroke top row");
        let reference_dilation =
            rasterize_reference_dilation_stroke("A", rect, 110.0, stroke_width, &font);
        let reference_top = top_ink_row(&reference_dilation).expect("reference top row");
        let extra_extension = fill_top.saturating_sub(stroke_top) as f32;
        let half_stroke = stroke_width * 0.5;
        assert!(
            extra_extension >= half_stroke - 0.25,
            "stroke apex should extend by roughly at least half stroke width; fill_top={fill_top}, stroke_top={stroke_top}, half_stroke={half_stroke:.2}"
        );
        assert!(
            stroke.pixels() != reference_dilation.pixels(),
            "path stroke should diverge from mask-dilation reference output"
        );
        assert!(
            stroke_top <= reference_top,
            "miter stroke should keep acute apex at least as extended as mask-dilation reference; stroke_top={stroke_top}, reference_top={reference_top}"
        );
    }

    #[test]
    fn shadow_blur_radius_changes_spread_for_shared_raster_path() {
        let font = test_font();
        let base_shadow = Shadow {
            color: Color(0.0, 0.0, 0.0, 0.9),
            offset: Point::new(5.5, 4.25),
            blur_radius: 0.0,
        };
        let hard_shadow_style = TextStyle {
            span_style: SpanStyle {
                shadow: Some(base_shadow),
                ..Default::default()
            },
            ..Default::default()
        };
        let blurred_shadow_style = TextStyle {
            span_style: SpanStyle {
                shadow: Some(Shadow {
                    blur_radius: 9.0,
                    ..base_shadow
                }),
                ..Default::default()
            },
            ..Default::default()
        };
        let rect = Rect {
            x: 0.0,
            y: 0.0,
            width: 320.0,
            height: 120.0,
        };

        let hard_shadow = rasterize_text_to_image_with_font(
            "Shared shadow",
            rect,
            &hard_shadow_style,
            Color::TRANSPARENT,
            48.0,
            1.0,
            &font,
        )
        .expect("hard shadow image");
        let blurred_shadow = rasterize_text_to_image_with_font(
            "Shared shadow",
            rect,
            &blurred_shadow_style,
            Color::TRANSPARENT,
            48.0,
            1.0,
            &font,
        )
        .expect("blurred shadow image");

        let hard_ink = count_ink_pixels(&hard_shadow);
        let blurred_ink = count_ink_pixels(&blurred_shadow);
        assert_ne!(
            hard_shadow.pixels(),
            blurred_shadow.pixels(),
            "blur radius should change rasterized shadow output"
        );
        assert!(
            blurred_ink > hard_ink,
            "blurred shadow should spread to more pixels; hard={hard_ink}, blurred={blurred_ink}"
        );
    }

    #[test]
    fn text_motion_changes_fractional_shadow_sampling() {
        let font = test_font();
        let base_shadow = Shadow {
            color: Color(0.0, 0.0, 0.0, 0.9),
            offset: Point::new(3.35, 2.65),
            blur_radius: 6.0,
        };
        let static_style = TextStyle {
            span_style: SpanStyle {
                shadow: Some(base_shadow),
                ..Default::default()
            },
            paragraph_style: cranpose_ui::text::ParagraphStyle {
                text_motion: Some(TextMotion::Static),
                ..Default::default()
            },
        };
        let animated_style = TextStyle {
            span_style: SpanStyle {
                shadow: Some(base_shadow),
                ..Default::default()
            },
            paragraph_style: cranpose_ui::text::ParagraphStyle {
                text_motion: Some(TextMotion::Animated),
                ..Default::default()
            },
        };
        let rect = Rect {
            x: 11.35,
            y: 7.65,
            width: 280.0,
            height: 120.0,
        };

        let static_image = rasterize_text_to_image_with_font(
            "Motion shadow",
            rect,
            &static_style,
            Color::TRANSPARENT,
            42.0,
            1.0,
            &font,
        )
        .expect("static image");
        let animated_image = rasterize_text_to_image_with_font(
            "Motion shadow",
            rect,
            &animated_style,
            Color::TRANSPARENT,
            42.0,
            1.0,
            &font,
        )
        .expect("animated image");

        assert_ne!(
            static_image.pixels(),
            animated_image.pixels(),
            "TextMotion::Static should quantize shadow placement while Animated keeps fractional sampling"
        );
    }

    #[test]
    fn static_text_motion_aligns_glyph_positions_to_pixel_grid() {
        let font = test_font();
        let base_glyph = layout_line_glyphs(&font, "A", 17.0, point(0.0, 13.37))
            .into_iter()
            .next()
            .expect("glyph");
        let static_aligned = align_glyph_for_text_motion(base_glyph, true);
        let static_position = static_aligned.position;
        assert!(
            (static_position.x - static_position.x.round()).abs() < f32::EPSILON,
            "static text should snap glyph x to pixel grid"
        );
        assert!(
            (static_position.y - static_position.y.round()).abs() < f32::EPSILON,
            "static text should snap glyph y to pixel grid"
        );

        let animated_source = layout_line_glyphs(&font, "A", 17.0, point(0.0, 13.37))
            .into_iter()
            .next()
            .expect("glyph");
        let animated_aligned = align_glyph_for_text_motion(animated_source, false);
        let animated_position = animated_aligned.position;
        assert!(
            (animated_position.y - 13.37).abs() < 1e-3,
            "animated text should preserve fractional glyph position"
        );
    }
}

#[cfg(test)]
mod line_alignment_tests {
    use super::*;
    use cranpose_ui::text::{ParagraphStyle, TextAlign};

    /// The x range of every non-transparent pixel on the rows a line occupies.
    fn ink_columns(image: &ImageBitmap, rows: std::ops::Range<u32>) -> Option<(u32, u32)> {
        let width = image.width();
        let pixels = image.pixels();
        let mut min = u32::MAX;
        let mut max = 0u32;
        for y in rows {
            for x in 0..width {
                let index = ((y * width + x) * 4 + 3) as usize;
                if pixels.get(index).copied().unwrap_or(0) > 0 {
                    min = min.min(x);
                    max = max.max(x);
                }
            }
        }
        (min != u32::MAX).then_some((min, max))
    }

    fn centred_style(align: TextAlign) -> TextStyle {
        TextStyle {
            paragraph_style: ParagraphStyle {
                text_align: align,
                ..ParagraphStyle::default()
            },
            ..TextStyle::default()
        }
    }

    #[test]
    fn a_wrapped_line_is_centred_under_the_one_above_it_not_left_under_it() {
        // `TextAlign` is a paragraph property and Compose applies it to every
        // line. The scene builder centres the block; without a per-line offset
        // as well, the short second line sits hard against the left of the
        // block -- which is exactly what the Credits screen's
        // "Designed and built for Wear / OS." showed.
        let font = default_software_text_font().expect("bundled default font");
        let rect = Rect {
            x: 0.0,
            y: 0.0,
            width: 400.0,
            height: 80.0,
        };
        let text = "wwwwwwwwwwww\nww";
        let image = rasterize_text_to_image(
            text,
            rect,
            &centred_style(TextAlign::Center),
            Color(1.0, 1.0, 1.0, 1.0),
            20.0,
            1.0,
            &font,
        )
        .expect("centred image");
        let long = ink_columns(&image, 0..(image.height() / 2)).expect("first line ink");
        let short =
            ink_columns(&image, (image.height() / 2)..image.height()).expect("second line ink");
        let long_centre = (long.0 + long.1) as f32 * 0.5;
        let short_centre = (short.0 + short.1) as f32 * 0.5;
        assert!(
            (long_centre - short_centre).abs() <= 2.0,
            "the two lines should share a centre: {long:?} vs {short:?}"
        );
        assert!(
            short.0 > long.0 + 4,
            "the short line must not start where the long one does: {long:?} vs {short:?}"
        );
    }

    #[test]
    fn the_atlas_run_centres_each_line_of_a_wrapped_block() {
        // The path an app on wgpu actually takes. It cuts the block into
        // segments at span boundaries AND at newlines and drives its own
        // cursor, so the per-line offset has to be applied there and not
        // inside the glyph loop -- a segment handed to the glyph loop never
        // contains a newline, so a rule written there never fires. This test
        // is the difference between the two: it was green against the glyph
        // loop and the watch still drew "OS." hard left.
        let font = default_software_text_font().expect("bundled default font");
        let fonts = SoftwareTextFontSet::from_font(font);
        let mut cache = SoftwareGlyphRasterCache::with_capacity_at_least_one(256);
        let rect = Rect {
            x: 0.0,
            y: 0.0,
            width: 400.0,
            height: 80.0,
        };
        let text = AnnotatedString::from("wwwwwwwwwwww\nww".to_string());

        let mut centred = Vec::new();
        collect_solid_text_atlas_run(
            &text,
            rect,
            &centred_style(TextAlign::Center),
            Color(1.0, 1.0, 1.0, 1.0),
            20.0,
            1.0,
            &fonts,
            &mut cache,
            &mut centred,
        )
        .expect("centred run");
        let mut flush = Vec::new();
        collect_solid_text_atlas_run(
            &text,
            rect,
            &centred_style(TextAlign::Start),
            Color(1.0, 1.0, 1.0, 1.0),
            20.0,
            1.0,
            &fonts,
            &mut cache,
            &mut flush,
        )
        .expect("start aligned run");

        let second_line_start = |glyphs: &[SoftwareGlyphAtlasRunGlyph]| {
            let placements: Vec<_> = glyphs.iter().map(|glyph| glyph.placement()).collect();
            let baseline = placements.iter().map(|p| p.y).max().expect("glyphs");
            placements
                .iter()
                .filter(|p| p.y == baseline)
                .map(|p| p.x)
                .min()
                .expect("second line")
        };
        assert_eq!(
            second_line_start(&flush),
            0,
            "a start-aligned second line begins at the block's left edge"
        );
        assert!(
            second_line_start(&centred) > 40,
            "a centred second line is indented by half the slack, was {}",
            second_line_start(&centred)
        );
    }

    #[test]
    fn a_start_aligned_paragraph_still_stacks_its_lines_flush_left() {
        let font = default_software_text_font().expect("bundled default font");
        let rect = Rect {
            x: 0.0,
            y: 0.0,
            width: 400.0,
            height: 80.0,
        };
        let image = rasterize_text_to_image(
            "wwwwwwwwwwww\nww",
            rect,
            &centred_style(TextAlign::Start),
            Color(1.0, 1.0, 1.0, 1.0),
            20.0,
            1.0,
            &font,
        )
        .expect("start aligned image");
        let long = ink_columns(&image, 0..(image.height() / 2)).expect("first line ink");
        let short =
            ink_columns(&image, (image.height() / 2)..image.height()).expect("second line ink");
        assert!(
            short.0.abs_diff(long.0) <= 1,
            "start-aligned lines share a left edge: {long:?} vs {short:?}"
        );
    }
}