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Diffstat (limited to 'crates/typst-library/src/text/shaping.rs')
| -rw-r--r-- | crates/typst-library/src/text/shaping.rs | 973 |
1 files changed, 973 insertions, 0 deletions
diff --git a/crates/typst-library/src/text/shaping.rs b/crates/typst-library/src/text/shaping.rs new file mode 100644 index 00000000..ec8812fe --- /dev/null +++ b/crates/typst-library/src/text/shaping.rs @@ -0,0 +1,973 @@ +use std::borrow::Cow; +use std::ops::Range; +use std::str::FromStr; + +use az::SaturatingAs; +use rustybuzz::{Feature, Tag, UnicodeBuffer}; +use typst::font::{Font, FontStyle, FontVariant}; +use typst::util::SliceExt; +use unicode_script::{Script, UnicodeScript}; + +use super::{decorate, FontFamily, NumberType, NumberWidth, TextElem}; +use crate::layout::SpanMapper; +use crate::prelude::*; + +/// The result of shaping text. +/// +/// This type contains owned or borrowed shaped text runs, which can be +/// measured, used to reshape substrings more quickly and converted into a +/// frame. +pub struct ShapedText<'a> { + /// The start of the text in the full paragraph. + pub base: usize, + /// The text that was shaped. + pub text: &'a str, + /// The text direction. + pub dir: Dir, + /// The text language. + pub lang: Lang, + /// The text region. + pub region: Option<Region>, + /// The text's style properties. + pub styles: StyleChain<'a>, + /// The font variant. + pub variant: FontVariant, + /// The font size. + pub size: Abs, + /// The width of the text's bounding box. + pub width: Abs, + /// The shaped glyphs. + pub glyphs: Cow<'a, [ShapedGlyph]>, +} + +/// A single glyph resulting from shaping. +#[derive(Debug, Clone)] +pub struct ShapedGlyph { + /// The font the glyph is contained in. + pub font: Font, + /// The glyph's index in the font. + pub glyph_id: u16, + /// The advance width of the glyph. + pub x_advance: Em, + /// The horizontal offset of the glyph. + pub x_offset: Em, + /// The vertical offset of the glyph. + pub y_offset: Em, + /// The adjustability of the glyph. + pub adjustability: Adjustability, + /// The byte range of this glyph's cluster in the full paragraph. A cluster + /// is a sequence of one or multiple glyphs that cannot be separated and + /// must always be treated as a union. + /// + /// The range values of the glyphs in a [`ShapedText`] should not + /// overlap with each other, and they should be monotonically + /// increasing (for left-to-right or top-to-bottom text) or + /// monotonically decreasing (for right-to-left or bottom-to-top + /// text). + pub range: Range<usize>, + /// Whether splitting the shaping result before this glyph would yield the + /// same results as shaping the parts to both sides of `text_index` + /// separately. + pub safe_to_break: bool, + /// The first char in this glyph's cluster. + pub c: char, + /// The source code location of the glyph and its byte offset within it. + pub span: (Span, u16), +} + +#[derive(Debug, Clone, Default)] +pub struct Adjustability { + /// The left and right strechability + pub stretchability: (Em, Em), + /// The left and right shrinkability + pub shrinkability: (Em, Em), +} + +impl ShapedGlyph { + /// Whether the glyph is a space. + pub fn is_space(&self) -> bool { + matches!(self.c, ' ' | '\u{00A0}' | ' ') + } + + /// Whether the glyph is justifiable. + pub fn is_justifiable(&self) -> bool { + // GB style is not relevant here. + self.is_space() + || self.is_cjk_script() + || self.is_cjk_left_aligned_punctuation(true) + || self.is_cjk_right_aligned_punctuation() + || self.is_cjk_center_aligned_punctuation(true) + } + + pub fn is_cjk_script(&self) -> bool { + use Script::*; + // U+30FC: Katakana-Hiragana Prolonged Sound Mark + matches!(self.c.script(), Hiragana | Katakana | Han) || self.c == '\u{30FC}' + } + + pub fn is_cjk_punctuation(&self) -> bool { + self.is_cjk_left_aligned_punctuation(true) + || self.is_cjk_right_aligned_punctuation() + || self.is_cjk_center_aligned_punctuation(true) + } + + /// See <https://www.w3.org/TR/clreq/#punctuation_width_adjustment> + pub fn is_cjk_left_aligned_punctuation(&self, gb_style: bool) -> bool { + // CJK quotation marks shares codepoints with latin quotation marks. + // But only the CJK ones have full width. + if matches!(self.c, '”' | '’') + && self.x_advance + self.stretchability().1 == Em::one() + { + return true; + } + + if gb_style && matches!(self.c, '，' | '。' | '、' | '：' | '；') { + return true; + } + + matches!(self.c, '》' | '）' | '』' | '」') + } + + /// See <https://www.w3.org/TR/clreq/#punctuation_width_adjustment> + pub fn is_cjk_right_aligned_punctuation(&self) -> bool { + // CJK quotation marks shares codepoints with latin quotation marks. + // But only the CJK ones have full width. + if matches!(self.c, '“' | '‘') + && self.x_advance + self.stretchability().0 == Em::one() + { + return true; + } + + matches!(self.c, '《' | '（' | '『' | '「') + } + + /// See <https://www.w3.org/TR/clreq/#punctuation_width_adjustment> + pub fn is_cjk_center_aligned_punctuation(&self, gb_style: bool) -> bool { + if !gb_style && matches!(self.c, '，' | '。' | '、' | '：' | '；') { + return true; + } + + // U+30FB: Katakana Middle Dot + matches!(self.c, '\u{30FB}') + } + + pub fn base_adjustability(&self, gb_style: bool) -> Adjustability { + let width = self.x_advance; + if self.is_space() { + Adjustability { + // The number for spaces is from Knuth-Plass' paper + stretchability: (Em::zero(), width / 2.0), + shrinkability: (Em::zero(), width / 3.0), + } + } else if self.is_cjk_left_aligned_punctuation(gb_style) { + Adjustability { + stretchability: (Em::zero(), Em::zero()), + shrinkability: (Em::zero(), width / 2.0), + } + } else if self.is_cjk_right_aligned_punctuation() { + Adjustability { + stretchability: (Em::zero(), Em::zero()), + shrinkability: (width / 2.0, Em::zero()), + } + } else if self.is_cjk_center_aligned_punctuation(gb_style) { + Adjustability { + stretchability: (Em::zero(), Em::zero()), + shrinkability: (width / 4.0, width / 4.0), + } + } else { + Adjustability::default() + } + } + + /// The stretchability of the character. + pub fn stretchability(&self) -> (Em, Em) { + self.adjustability.stretchability + } + + /// The shrinkability of the character. + pub fn shrinkability(&self) -> (Em, Em) { + self.adjustability.shrinkability + } + + /// Shrink the width of glyph on the left side. + pub fn shrink_left(&mut self, amount: Em) { + self.x_offset -= amount; + self.x_advance -= amount; + self.adjustability.shrinkability.0 -= amount; + self.adjustability.stretchability.0 += amount; + } + + /// Shrink the width of glyph on the right side. + pub fn shrink_right(&mut self, amount: Em) { + self.x_advance -= amount; + self.adjustability.shrinkability.1 -= amount; + self.adjustability.stretchability.1 += amount; + } +} + +/// A side you can go toward. +enum Side { + /// To the left-hand side. + Left, + /// To the right-hand side. + Right, +} + +impl<'a> ShapedText<'a> { + /// Build the shaped text's frame. + /// + /// The `justification` defines how much extra advance width each + /// [justifiable glyph](ShapedGlyph::is_justifiable) will get. + pub fn build( + &self, + vt: &Vt, + justification_ratio: f64, + extra_justification: Abs, + ) -> Frame { + let (top, bottom) = self.measure(vt); + let size = Size::new(self.width, top + bottom); + + let mut offset = Abs::zero(); + let mut frame = Frame::new(size); + frame.set_baseline(top); + + let shift = TextElem::baseline_in(self.styles); + let lang = TextElem::lang_in(self.styles); + let decos = TextElem::deco_in(self.styles); + let fill = TextElem::fill_in(self.styles); + + for ((font, y_offset), group) in + self.glyphs.as_ref().group_by_key(|g| (g.font.clone(), g.y_offset)) + { + let mut range = group[0].range.clone(); + for glyph in group { + range.start = range.start.min(glyph.range.start); + range.end = range.end.max(glyph.range.end); + } + + let pos = Point::new(offset, top + shift - y_offset.at(self.size)); + let glyphs = group + .iter() + .map(|glyph| { + let adjustability_left = if justification_ratio < 0.0 { + glyph.shrinkability().0 + } else { + glyph.stretchability().0 + }; + let adjustability_right = if justification_ratio < 0.0 { + glyph.shrinkability().1 + } else { + glyph.stretchability().1 + }; + + let justification_left = adjustability_left * justification_ratio; + let mut justification_right = + adjustability_right * justification_ratio; + if glyph.is_justifiable() { + justification_right += + Em::from_length(extra_justification, self.size) + } + + frame.size_mut().x += justification_left.at(self.size) + + justification_right.at(self.size); + + Glyph { + id: glyph.glyph_id, + x_advance: glyph.x_advance + + justification_left + + justification_right, + x_offset: glyph.x_offset + justification_left, + range: (glyph.range.start - range.start).saturating_as() + ..(glyph.range.end - range.start).saturating_as(), + span: glyph.span, + } + }) + .collect(); + + let item = TextItem { + font, + size: self.size, + lang, + fill: fill.clone(), + text: self.text[range.start - self.base..range.end - self.base].into(), + glyphs, + }; + + let layer = frame.layer(); + let width = item.width(); + + // Apply line decorations. + for deco in &decos { + decorate(&mut frame, deco, &item, shift, pos, width); + } + + frame.insert(layer, pos, FrameItem::Text(item)); + offset += width; + } + + // Apply metadata. + frame.meta(self.styles, false); + + frame + } + + /// Measure the top and bottom extent of this text. + fn measure(&self, vt: &Vt) -> (Abs, Abs) { + let mut top = Abs::zero(); + let mut bottom = Abs::zero(); + + let top_edge = TextElem::top_edge_in(self.styles); + let bottom_edge = TextElem::bottom_edge_in(self.styles); + + // Expand top and bottom by reading the font's vertical metrics. + let mut expand = |font: &Font| { + let metrics = font.metrics(); + top.set_max(top_edge.resolve(self.styles, metrics)); + bottom.set_max(-bottom_edge.resolve(self.styles, metrics)); + }; + + if self.glyphs.is_empty() { + // When there are no glyphs, we just use the vertical metrics of the + // first available font. + let world = vt.world; + for family in families(self.styles) { + if let Some(font) = world + .book() + .select(family.as_str(), self.variant) + .and_then(|id| world.font(id)) + { + expand(&font); + break; + } + } + } else { + for g in self.glyphs.iter() { + expand(&g.font); + } + } + + (top, bottom) + } + + /// How many glyphs are in the text where we can insert additional + /// space when encountering underfull lines. + pub fn justifiables(&self) -> usize { + self.glyphs.iter().filter(|g| g.is_justifiable()).count() + } + + /// Whether the last glyph is a CJK character which should not be justified + /// on line end. + pub fn cjk_justifiable_at_last(&self) -> bool { + self.glyphs + .last() + .map(|g| g.is_cjk_script() || g.is_cjk_punctuation()) + .unwrap_or(false) + } + + /// The stretchability of the text. + pub fn stretchability(&self) -> Abs { + self.glyphs + .iter() + .map(|g| g.stretchability().0 + g.stretchability().1) + .sum::<Em>() + .at(self.size) + } + + /// The shrinkability of the text + pub fn shrinkability(&self) -> Abs { + self.glyphs + .iter() + .map(|g| g.shrinkability().0 + g.shrinkability().1) + .sum::<Em>() + .at(self.size) + } + + /// Reshape a range of the shaped text, reusing information from this + /// shaping process if possible. + /// + /// The text `range` is relative to the whole paragraph. + pub fn reshape( + &'a self, + vt: &Vt, + spans: &SpanMapper, + text_range: Range<usize>, + ) -> ShapedText<'a> { + let text = &self.text[text_range.start - self.base..text_range.end - self.base]; + if let Some(glyphs) = self.slice_safe_to_break(text_range.clone()) { + #[cfg(debug_assertions)] + assert_all_glyphs_in_range(glyphs, text, text_range.clone()); + Self { + base: text_range.start, + text, + dir: self.dir, + lang: self.lang, + region: self.region, + styles: self.styles, + size: self.size, + variant: self.variant, + width: glyphs.iter().map(|g| g.x_advance).sum::<Em>().at(self.size), + glyphs: Cow::Borrowed(glyphs), + } + } else { + shape( + vt, + text_range.start, + text, + spans, + self.styles, + self.dir, + self.lang, + self.region, + ) + } + } + + /// Push a hyphen to end of the text. + pub fn push_hyphen(&mut self, vt: &Vt) { + families(self.styles).find_map(|family| { + let world = vt.world; + let font = world + .book() + .select(family.as_str(), self.variant) + .and_then(|id| world.font(id))?; + let ttf = font.ttf(); + let glyph_id = ttf.glyph_index('-')?; + let x_advance = font.to_em(ttf.glyph_hor_advance(glyph_id)?); + let range = self + .glyphs + .last() + .map(|g| g.range.end..g.range.end) + .unwrap_or_default(); + self.width += x_advance.at(self.size); + self.glyphs.to_mut().push(ShapedGlyph { + font, + glyph_id: glyph_id.0, + x_advance, + x_offset: Em::zero(), + y_offset: Em::zero(), + adjustability: Adjustability::default(), + range, + safe_to_break: true, + c: '-', + span: (Span::detached(), 0), + }); + Some(()) + }); + } + + /// Find the subslice of glyphs that represent the given text range if both + /// sides are safe to break. + fn slice_safe_to_break(&self, text_range: Range<usize>) -> Option<&[ShapedGlyph]> { + let Range { mut start, mut end } = text_range; + if !self.dir.is_positive() { + std::mem::swap(&mut start, &mut end); + } + + let left = self.find_safe_to_break(start, Side::Left)?; + let right = self.find_safe_to_break(end, Side::Right)?; + Some(&self.glyphs[left..right]) + } + + /// Find the glyph offset matching the text index that is most towards the + /// given side and safe-to-break. + fn find_safe_to_break(&self, text_index: usize, towards: Side) -> Option<usize> { + let ltr = self.dir.is_positive(); + + // Handle edge cases. + let len = self.glyphs.len(); + if text_index == self.base { + return Some(if ltr { 0 } else { len }); + } else if text_index == self.base + self.text.len() { + return Some(if ltr { len } else { 0 }); + } + + // Find any glyph with the text index. + let mut idx = self + .glyphs + .binary_search_by(|g| { + let ordering = g.range.start.cmp(&text_index); + if ltr { + ordering + } else { + ordering.reverse() + } + }) + .ok()?; + + let next = match towards { + Side::Left => usize::checked_sub, + Side::Right => usize::checked_add, + }; + + // Search for the outermost glyph with the text index. + while let Some(next) = next(idx, 1) { + if self.glyphs.get(next).map_or(true, |g| g.range.start != text_index) { + break; + } + idx = next; + } + + // RTL needs offset one because the left side of the range should be + // exclusive and the right side inclusive, contrary to the normal + // behaviour of ranges. + self.glyphs[idx].safe_to_break.then_some(idx + usize::from(!ltr)) + } +} + +impl Debug for ShapedText<'_> { + fn fmt(&self, f: &mut Formatter) -> fmt::Result { + self.text.fmt(f) + } +} + +/// Holds shaping results and metadata common to all shaped segments. +struct ShapingContext<'a, 'v> { + vt: &'a Vt<'v>, + spans: &'a SpanMapper, + glyphs: Vec<ShapedGlyph>, + used: Vec<Font>, + styles: StyleChain<'a>, + size: Abs, + variant: FontVariant, + tags: Vec<rustybuzz::Feature>, + fallback: bool, + dir: Dir, +} + +/// Shape text into [`ShapedText`]. +#[allow(clippy::too_many_arguments)] +pub fn shape<'a>( + vt: &Vt, + base: usize, + text: &'a str, + spans: &SpanMapper, + styles: StyleChain<'a>, + dir: Dir, + lang: Lang, + region: Option<Region>, +) -> ShapedText<'a> { + let size = TextElem::size_in(styles); + let mut ctx = ShapingContext { + vt, + spans, + size, + glyphs: vec![], + used: vec![], + styles, + variant: variant(styles), + tags: tags(styles), + fallback: TextElem::fallback_in(styles), + dir, + }; + + if !text.is_empty() { + shape_segment(&mut ctx, base, text, families(styles)); + } + + track_and_space(&mut ctx); + calculate_adjustability(&mut ctx, lang, region); + + #[cfg(debug_assertions)] + assert_all_glyphs_in_range(&ctx.glyphs, text, base..(base + text.len())); + #[cfg(debug_assertions)] + assert_glyph_ranges_in_order(&ctx.glyphs, dir); + + ShapedText { + base, + text, + dir, + lang, + region, + styles, + variant: ctx.variant, + size, + width: ctx.glyphs.iter().map(|g| g.x_advance).sum::<Em>().at(size), + glyphs: Cow::Owned(ctx.glyphs), + } +} + +/// Shape text with font fallback using the `families` iterator. +fn shape_segment( + ctx: &mut ShapingContext, + base: usize, + text: &str, + mut families: impl Iterator<Item = FontFamily> + Clone, +) { + // Fonts dont have newlines and tabs. + if text.chars().all(|c| c == '\n' || c == '\t') { + return; + } + + // Find the next available family. + let world = ctx.vt.world; + let book = world.book(); + let mut selection = families.find_map(|family| { + book.select(family.as_str(), ctx.variant) + .and_then(|id| world.font(id)) + .filter(|font| !ctx.used.contains(font)) + }); + + // Do font fallback if the families are exhausted and fallback is enabled. + if selection.is_none() && ctx.fallback { + let first = ctx.used.first().map(Font::info); + selection = book + .select_fallback(first, ctx.variant, text) + .and_then(|id| world.font(id)) + .filter(|font| !ctx.used.contains(font)); + } + + // Extract the font id or shape notdef glyphs if we couldn't find any font. + let Some(font) = selection else { + if let Some(font) = ctx.used.first().cloned() { + shape_tofus(ctx, base, text, font); + } + return; + }; + + ctx.used.push(font.clone()); + + // Fill the buffer with our text. + let mut buffer = UnicodeBuffer::new(); + buffer.push_str(text); + buffer.set_language(language(ctx.styles)); + buffer.set_direction(match ctx.dir { + Dir::LTR => rustybuzz::Direction::LeftToRight, + Dir::RTL => rustybuzz::Direction::RightToLeft, + _ => unimplemented!("vertical text layout"), + }); + + // Shape! + let buffer = rustybuzz::shape(font.rusty(), &ctx.tags, buffer); + let infos = buffer.glyph_infos(); + let pos = buffer.glyph_positions(); + let ltr = ctx.dir.is_positive(); + + // Collect the shaped glyphs, doing fallback and shaping parts again with + // the next font if necessary. + let mut i = 0; + while i < infos.len() { + let info = &infos[i]; + let cluster = info.cluster as usize; + + // Add the glyph to the shaped output. + if info.glyph_id != 0 { + // Determine the text range of the glyph. + let start = base + cluster; + let end = base + + if ltr { i.checked_add(1) } else { i.checked_sub(1) } + .and_then(|last| infos.get(last)) + .map_or(text.len(), |info| info.cluster as usize); + + ctx.glyphs.push(ShapedGlyph { + font: font.clone(), + glyph_id: info.glyph_id as u16, + // TODO: Don't ignore y_advance. + x_advance: font.to_em(pos[i].x_advance), + x_offset: font.to_em(pos[i].x_offset), + y_offset: font.to_em(pos[i].y_offset), + adjustability: Adjustability::default(), + range: start..end, + safe_to_break: !info.unsafe_to_break(), + c: text[cluster..].chars().next().unwrap(), + span: ctx.spans.span_at(start), + }); + } else { + // First, search for the end of the tofu sequence. + let k = i; + while infos.get(i + 1).map_or(false, |info| info.glyph_id == 0) { + i += 1; + } + + // Then, determine the start and end text index for the tofu + // sequence. + // + // Examples: + // Everything is shown in visual order. Tofus are written as "_". + // We want to find out that the tofus span the text `2..6`. + // Note that the clusters are longer than 1 char. + // + // Left-to-right: + // Text: h a l i h a l l o + // Glyphs: A _ _ C E + // Clusters: 0 2 4 6 8 + // k=1 i=2 + // + // Right-to-left: + // Text: O L L A H I L A H + // Glyphs: E C _ _ A + // Clusters: 8 6 4 2 0 + // k=2 i=3 + let start = infos[if ltr { k } else { i }].cluster as usize; + let end = if ltr { i.checked_add(1) } else { k.checked_sub(1) } + .and_then(|last| infos.get(last)) + .map_or(text.len(), |info| info.cluster as usize); + + // Trim half-baked cluster. + let remove = base + start..base + end; + while ctx.glyphs.last().map_or(false, |g| remove.contains(&g.range.start)) { + ctx.glyphs.pop(); + } + + // Recursively shape the tofu sequence with the next family. + shape_segment(ctx, base + start, &text[start..end], families.clone()); + } + + i += 1; + } + + ctx.used.pop(); +} + +/// Shape the text with tofus from the given font. +fn shape_tofus(ctx: &mut ShapingContext, base: usize, text: &str, font: Font) { + let x_advance = font.advance(0).unwrap_or_default(); + let add_glyph = |(cluster, c): (usize, char)| { + let start = base + cluster; + let end = start + c.len_utf8(); + ctx.glyphs.push(ShapedGlyph { + font: font.clone(), + glyph_id: 0, + x_advance, + x_offset: Em::zero(), + y_offset: Em::zero(), + adjustability: Adjustability::default(), + range: start..end, + safe_to_break: true, + c, + span: ctx.spans.span_at(start), + }); + }; + if ctx.dir.is_positive() { + text.char_indices().for_each(add_glyph); + } else { + text.char_indices().rev().for_each(add_glyph); + } +} + +/// Apply tracking and spacing to the shaped glyphs. +fn track_and_space(ctx: &mut ShapingContext) { + let tracking = Em::from_length(TextElem::tracking_in(ctx.styles), ctx.size); + let spacing = + TextElem::spacing_in(ctx.styles).map(|abs| Em::from_length(abs, ctx.size)); + + let mut glyphs = ctx.glyphs.iter_mut().peekable(); + while let Some(glyph) = glyphs.next() { + // Make non-breaking space same width as normal space. + if glyph.c == '\u{00A0}' { + glyph.x_advance -= nbsp_delta(&glyph.font).unwrap_or_default(); + } + + if glyph.is_space() { + glyph.x_advance = spacing.relative_to(glyph.x_advance); + } + + if glyphs + .peek() + .map_or(false, |next| glyph.range.start != next.range.start) + { + glyph.x_advance += tracking; + } + } +} + +pub fn is_gb_style(lang: Lang, region: Option<Region>) -> bool { + // Most CJK variants, including zh-CN, ja-JP, zh-SG, zh-MY use GB-style punctuation, + // while zh-HK and zh-TW use alternative style. We default to use GB-style. + !(lang == Lang::CHINESE + && matches!(region.as_ref().map(Region::as_str), Some("TW" | "HK"))) +} + +/// Calculate stretchability and shrinkability of each glyph, +/// and CJK punctuation adjustments according to Chinese Layout Requirements. +fn calculate_adjustability(ctx: &mut ShapingContext, lang: Lang, region: Option<Region>) { + let gb_style = is_gb_style(lang, region); + + for glyph in &mut ctx.glyphs { + glyph.adjustability = glyph.base_adjustability(gb_style); + } + + let mut glyphs = ctx.glyphs.iter_mut().peekable(); + while let Some(glyph) = glyphs.next() { + // Only GB style needs further adjustment. + if glyph.is_cjk_punctuation() && !gb_style { + continue; + } + + // Now we apply consecutive punctuation adjustment, specified in Chinese Layout + // Requirements, section 3.1.6.1 Punctuation Adjustment Space, and Japanese Layout + // Requirements, section 3.1 Line Composition Rules for Punctuation Marks + let Some(next) = glyphs.peek_mut() else { continue }; + let width = glyph.x_advance; + let delta = width / 2.0; + if glyph.is_cjk_punctuation() + && next.is_cjk_punctuation() + && (glyph.shrinkability().1 + next.shrinkability().0) >= delta + { + let left_delta = glyph.shrinkability().1.min(delta); + glyph.shrink_right(left_delta); + next.shrink_left(delta - left_delta); + } + } +} + +/// Difference between non-breaking and normal space. +fn nbsp_delta(font: &Font) -> Option<Em> { + let space = font.ttf().glyph_index(' ')?.0; + let nbsp = font.ttf().glyph_index('\u{00A0}')?.0; + Some(font.advance(nbsp)? - font.advance(space)?) +} + +/// Resolve the font variant. +pub fn variant(styles: StyleChain) -> FontVariant { + let mut variant = FontVariant::new( + TextElem::style_in(styles), + TextElem::weight_in(styles), + TextElem::stretch_in(styles), + ); + + let delta = TextElem::delta_in(styles); + variant.weight = variant + .weight + .thicken(delta.clamp(i16::MIN as i64, i16::MAX as i64) as i16); + + if TextElem::emph_in(styles) { + variant.style = match variant.style { + FontStyle::Normal => FontStyle::Italic, + FontStyle::Italic => FontStyle::Normal, + FontStyle::Oblique => FontStyle::Normal, + } + } + + variant +} + +/// Resolve a prioritized iterator over the font families. +pub fn families(styles: StyleChain) -> impl Iterator<Item = FontFamily> + Clone { + const FALLBACKS: &[&str] = &[ + "linux libertine", + "twitter color emoji", + "noto color emoji", + "apple color emoji", + "segoe ui emoji", + ]; + + let tail = if TextElem::fallback_in(styles) { FALLBACKS } else { &[] }; + TextElem::font_in(styles) + .into_iter() + .chain(tail.iter().copied().map(FontFamily::new)) +} + +/// Collect the tags of the OpenType features to apply. +fn tags(styles: StyleChain) -> Vec<Feature> { + let mut tags = vec![]; + let mut feat = |tag, value| { + tags.push(Feature::new(Tag::from_bytes(tag), value, ..)); + }; + + // Features that are on by default in Harfbuzz are only added if disabled. + if !TextElem::kerning_in(styles) { + feat(b"kern", 0); + } + + // Features that are off by default in Harfbuzz are only added if enabled. + if TextElem::smallcaps_in(styles) { + feat(b"smcp", 1); + } + + if TextElem::alternates_in(styles) { + feat(b"salt", 1); + } + + let storage; + if let Some(set) = TextElem::stylistic_set_in(styles) { + storage = [b's', b's', b'0' + set.get() / 10, b'0' + set.get() % 10]; + feat(&storage, 1); + } + + if !TextElem::ligatures_in(styles) { + feat(b"liga", 0); + feat(b"clig", 0); + } + + if TextElem::discretionary_ligatures_in(styles) { + feat(b"dlig", 1); + } + + if TextElem::historical_ligatures_in(styles) { + feat(b"hilg", 1); + } + + match TextElem::number_type_in(styles) { + Smart::Auto => {} + Smart::Custom(NumberType::Lining) => feat(b"lnum", 1), + Smart::Custom(NumberType::OldStyle) => feat(b"onum", 1), + } + + match TextElem::number_width_in(styles) { + Smart::Auto => {} + Smart::Custom(NumberWidth::Proportional) => feat(b"pnum", 1), + Smart::Custom(NumberWidth::Tabular) => feat(b"tnum", 1), + } + + if TextElem::slashed_zero_in(styles) { + feat(b"zero", 1); + } + + if TextElem::fractions_in(styles) { + feat(b"frac", 1); + } + + for (tag, value) in TextElem::features_in(styles).0 { + tags.push(Feature::new(tag, value, ..)) + } + + tags +} + +/// Process the language and and region of a style chain into a +/// rustybuzz-compatible BCP 47 language. +fn language(styles: StyleChain) -> rustybuzz::Language { + let mut bcp: EcoString = TextElem::lang_in(styles).as_str().into(); + if let Some(region) = TextElem::region_in(styles) { + bcp.push('-'); + bcp.push_str(region.as_str()); + } + rustybuzz::Language::from_str(&bcp).unwrap() +} + +/// Returns true if all glyphs in `glyphs` have ranges within the range `range`. +#[cfg(debug_assertions)] +fn assert_all_glyphs_in_range(glyphs: &[ShapedGlyph], text: &str, range: Range<usize>) { + if glyphs + .iter() + .any(|g| g.range.start < range.start || g.range.end > range.end) + { + panic!("one or more glyphs in {text:?} fell out of range"); + } +} + +/// Asserts that the ranges of `glyphs` is in the proper order according to `dir`. +/// +/// This asserts instead of returning a bool in order to provide a more informative message when the invariant is violated. +#[cfg(debug_assertions)] +fn assert_glyph_ranges_in_order(glyphs: &[ShapedGlyph], dir: Dir) { + if glyphs.is_empty() { + return; + } + + // Iterator::is_sorted and friends are unstable as of Rust 1.70.0 + for i in 0..(glyphs.len() - 1) { + let a = &glyphs[i]; + let b = &glyphs[i + 1]; + let ord = a.range.start.cmp(&b.range.start); + let ord = if dir.is_positive() { ord } else { ord.reverse() }; + if ord == std::cmp::Ordering::Greater { + panic!( + "glyph ranges should be monotonically {}, \ + but found glyphs out of order:\n\n\ + first: {a:#?}\nsecond: {b:#?}", + if dir.is_positive() { "increasing" } else { "decreasing" }, + ); + } + } +} |