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Use "subs" and "sups" font features for typographic scripts (#5777)

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Malo 2025-07-02 09:00:45 +01:00 committed by GitHub
parent 30ddc4a7ca
commit 09c831d3b3
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21 changed files with 450 additions and 197 deletions
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4
crates/typst-layout/src/inline/collect.rs
View File

@ -206,7 +206,7 @@ pub fn collect<'a>(
}
InlineItem::Frame(mut frame) => {
frame.modify(&FrameModifiers::get_in(styles));
apply_baseline_shift(&mut frame, styles);
apply_shift(&engine.world, &mut frame, styles);
collector.push_item(Item::Frame(frame));
}
}
@ -221,7 +221,7 @@ pub fn collect<'a>(
let mut frame = layout_and_modify(styles, |styles| {
layout_box(elem, engine, loc, styles, region)
})?;
apply_baseline_shift(&mut frame, styles);
apply_shift(&engine.world, &mut frame, styles);
collector.push_item(Item::Frame(frame));
}
} else if let Some(elem) = child.to_packed::<TagElem>() {

43
crates/typst-layout/src/inline/line.rs
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@ -5,7 +5,7 @@ use typst_library::engine::Engine;
use typst_library::introspection::{SplitLocator, Tag};
use typst_library::layout::{Abs, Dir, Em, Fr, Frame, FrameItem, Point};
use typst_library::model::ParLineMarker;
use typst_library::text::{Lang, TextElem};
use typst_library::text::{variant, Lang, TextElem};
use typst_utils::Numeric;
use super::*;
@ -330,7 +330,7 @@ fn adjust_cj_at_line_start(p: &Preparation, items: &mut Items) {
let glyph = shaped.glyphs.to_mut().first_mut().unwrap();
let shrink = glyph.shrinkability().0;
glyph.shrink_left(shrink);
shaped.width -= shrink.at(shaped.size);
shaped.width -= shrink.at(glyph.size);
} else if p.config.cjk_latin_spacing
&& glyph.is_cj_script()
&& glyph.x_offset > Em::zero()
@ -342,7 +342,7 @@ fn adjust_cj_at_line_start(p: &Preparation, items: &mut Items) {
glyph.x_advance -= shrink;
glyph.x_offset = Em::zero();
glyph.adjustability.shrinkability.0 = Em::zero();
shaped.width -= shrink.at(shaped.size);
shaped.width -= shrink.at(glyph.size);
}
}
@ -360,7 +360,7 @@ fn adjust_cj_at_line_end(p: &Preparation, items: &mut Items) {
let shrink = glyph.shrinkability().1;
let punct = shaped.glyphs.to_mut().last_mut().unwrap();
punct.shrink_right(shrink);
shaped.width -= shrink.at(shaped.size);
shaped.width -= shrink.at(punct.size);
} else if p.config.cjk_latin_spacing
&& glyph.is_cj_script()
&& (glyph.x_advance - glyph.x_offset) > Em::one()
@ -371,7 +371,7 @@ fn adjust_cj_at_line_end(p: &Preparation, items: &mut Items) {
let glyph = shaped.glyphs.to_mut().last_mut().unwrap();
glyph.x_advance -= shrink;
glyph.adjustability.shrinkability.1 = Em::zero();
shaped.width -= shrink.at(shaped.size);
shaped.width -= shrink.at(glyph.size);
}
}
@ -412,9 +412,30 @@ fn should_repeat_hyphen(pred_line: &Line, text: &str) -> bool {
}
}
/// Apply the current baseline shift to a frame.
pub fn apply_baseline_shift(frame: &mut Frame, styles: StyleChain) {
frame.translate(Point::with_y(TextElem::baseline_in(styles)));
/// Apply the current baseline shift and italic compensation to a frame.
pub fn apply_shift<'a>(
world: &Tracked<'a, dyn World + 'a>,
frame: &mut Frame,
styles: StyleChain,
) {
let mut baseline = TextElem::baseline_in(styles);
let mut compensation = Abs::zero();
if let Some(scripts) = TextElem::shift_settings_in(styles) {
let font_metrics = TextElem::font_in(styles)
.into_iter()
.find_map(|family| {
world
.book()
.select(family.as_str(), variant(styles))
.and_then(|id| world.font(id))
})
.map_or(*scripts.kind.default_metrics(), |f| {
*scripts.kind.read_metrics(f.metrics())
});
baseline -= scripts.shift.unwrap_or(font_metrics.vertical_offset).resolve(styles);
compensation += font_metrics.horizontal_offset.resolve(styles);
}
frame.translate(Point::new(compensation, baseline));
}
/// Commit to a line and build its frame.
@ -444,7 +465,7 @@ pub fn commit(
&& TextElem::overhang_in(text.styles)
&& (line.items.len() > 1 || text.glyphs.len() > 1)
{
let amount = overhang(glyph.c) * glyph.x_advance.at(text.size);
let amount = overhang(glyph.c) * glyph.x_advance.at(glyph.size);
offset -= amount;
remaining += amount;
}
@ -458,7 +479,7 @@ pub fn commit(
&& TextElem::overhang_in(text.styles)
&& (line.items.len() > 1 || text.glyphs.len() > 1)
{
let amount = overhang(glyph.c) * glyph.x_advance.at(text.size);
let amount = overhang(glyph.c) * glyph.x_advance.at(glyph.size);
remaining += amount;
}
}
@ -519,7 +540,7 @@ pub fn commit(
let mut frame = layout_and_modify(*styles, |styles| {
layout_box(elem, engine, loc.relayout(), styles, region)
})?;
apply_baseline_shift(&mut frame, *styles);
apply_shift(&engine.world, &mut frame, *styles);
push(&mut offset, frame, idx);
} else {
offset += amount;

6
crates/typst-layout/src/inline/linebreak.rs
View File

@ -927,9 +927,9 @@ impl Estimates {
let byte_len = g.range.len();
let stretch = g.stretchability().0 + g.stretchability().1;
let shrink = g.shrinkability().0 + g.shrinkability().1;
widths.push(byte_len, g.x_advance.at(shaped.size));
stretchability.push(byte_len, stretch.at(shaped.size));
shrinkability.push(byte_len, shrink.at(shaped.size));
widths.push(byte_len, g.x_advance.at(g.size));
stretchability.push(byte_len, stretch.at(g.size));
shrinkability.push(byte_len, shrink.at(g.size));
justifiables.push(byte_len, g.is_justifiable() as usize);
}
} else {

2
crates/typst-layout/src/inline/mod.rs
View File

@ -29,7 +29,7 @@ use typst_utils::{Numeric, SliceExt};
use self::collect::{collect, Item, Segment, SpanMapper};
use self::deco::decorate;
use self::finalize::finalize;
use self::line::{apply_baseline_shift, commit, line, Line};
use self::line::{apply_shift, commit, line, Line};
use self::linebreak::{linebreak, Breakpoint};
use self::prepare::{prepare, Preparation};
use self::shaping::{

4
crates/typst-layout/src/inline/prepare.rs
View File

@ -144,7 +144,7 @@ fn add_cjk_latin_spacing(items: &mut [(Range, Item)]) {
// The spacing is default to 1/4 em, and can be shrunk to 1/8 em.
glyph.x_advance += Em::new(0.25);
glyph.adjustability.shrinkability.1 += Em::new(0.125);
text.width += Em::new(0.25).at(text.size);
text.width += Em::new(0.25).at(glyph.size);
}
// Case 2: Latin followed by a CJ character
@ -152,7 +152,7 @@ fn add_cjk_latin_spacing(items: &mut [(Range, Item)]) {
glyph.x_advance += Em::new(0.25);
glyph.x_offset += Em::new(0.25);
glyph.adjustability.shrinkability.0 += Em::new(0.125);
text.width += Em::new(0.25).at(text.size);
text.width += Em::new(0.25).at(glyph.size);
}
prev = Some(glyph);

143
crates/typst-layout/src/inline/shaping.rs
View File

@ -3,14 +3,15 @@ use std::fmt::{self, Debug, Formatter};
use std::sync::Arc;
use az::SaturatingAs;
use rustybuzz::{BufferFlags, ShapePlan, UnicodeBuffer};
use rustybuzz::{BufferFlags, Feature, ShapePlan, UnicodeBuffer};
use ttf_parser::gsub::SubstitutionSubtable;
use ttf_parser::Tag;
use typst_library::engine::Engine;
use typst_library::foundations::{Smart, StyleChain};
use typst_library::layout::{Abs, Dir, Em, Frame, FrameItem, Point, Size};
use typst_library::text::{
families, features, is_default_ignorable, language, variant, Font, FontFamily,
FontVariant, Glyph, Lang, Region, TextEdgeBounds, TextElem, TextItem,
FontVariant, Glyph, Lang, Region, ShiftSettings, TextEdgeBounds, TextElem, TextItem,
};
use typst_library::World;
use typst_utils::SliceExt;
@ -41,8 +42,6 @@ pub struct ShapedText<'a> {
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.
@ -62,6 +61,8 @@ pub struct ShapedGlyph {
pub x_offset: Em,
/// The vertical offset of the glyph.
pub y_offset: Em,
/// The font size for the glyph.
pub size: Abs,
/// The adjustability of the glyph.
pub adjustability: Adjustability,
/// The byte range of this glyph's cluster in the full inline layout. A
@ -222,14 +223,17 @@ impl<'a> ShapedText<'a> {
let mut frame = Frame::soft(size);
frame.set_baseline(top);
let size = TextElem::size_in(self.styles);
let shift = TextElem::baseline_in(self.styles);
let decos = TextElem::deco_in(self.styles);
let fill = TextElem::fill_in(self.styles);
let stroke = TextElem::stroke_in(self.styles);
let span_offset = TextElem::span_offset_in(self.styles);
for ((font, y_offset), group) in
self.glyphs.as_ref().group_by_key(|g| (g.font.clone(), g.y_offset))
for ((font, y_offset, glyph_size), group) in self
.glyphs
.as_ref()
.group_by_key(|g| (g.font.clone(), g.y_offset, g.size))
{
let mut range = group[0].range.clone();
for glyph in group {
@ -237,7 +241,7 @@ impl<'a> ShapedText<'a> {
range.end = range.end.max(glyph.range.end);
}
let pos = Point::new(offset, top + shift - y_offset.at(self.size));
let pos = Point::new(offset, top + shift - y_offset.at(size));
let glyphs: Vec<Glyph> = group
.iter()
.map(|shaped: &ShapedGlyph| {
@ -257,11 +261,11 @@ impl<'a> ShapedText<'a> {
adjustability_right * justification_ratio;
if shaped.is_justifiable() {
justification_right +=
Em::from_length(extra_justification, self.size)
Em::from_abs(extra_justification, glyph_size)
}
frame.size_mut().x += justification_left.at(self.size)
+ justification_right.at(self.size);
frame.size_mut().x += justification_left.at(glyph_size)
+ justification_right.at(glyph_size);
// We may not be able to reach the offset completely if
// it exceeds u16, but better to have a roughly correct
@ -304,7 +308,7 @@ impl<'a> ShapedText<'a> {
let item = TextItem {
font,
size: self.size,
size: glyph_size,
lang: self.lang,
region: self.region,
fill: fill.clone(),
@ -336,12 +340,13 @@ impl<'a> ShapedText<'a> {
let mut top = Abs::zero();
let mut bottom = Abs::zero();
let size = TextElem::size_in(self.styles);
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, bounds: TextEdgeBounds| {
let (t, b) = font.edges(top_edge, bottom_edge, self.size, bounds);
let (t, b) = font.edges(top_edge, bottom_edge, size, bounds);
top.set_max(t);
bottom.set_max(b);
};
@ -388,18 +393,16 @@ impl<'a> ShapedText<'a> {
pub fn stretchability(&self) -> Abs {
self.glyphs
.iter()
.map(|g| g.stretchability().0 + g.stretchability().1)
.sum::<Em>()
.at(self.size)
.map(|g| (g.stretchability().0 + g.stretchability().1).at(g.size))
.sum()
}
/// 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)
.map(|g| (g.shrinkability().0 + g.shrinkability().1).at(g.size))
.sum()
}
/// Reshape a range of the shaped text, reusing information from this
@ -418,9 +421,8 @@ impl<'a> ShapedText<'a> {
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),
width: glyphs_width(glyphs),
glyphs: Cow::Borrowed(glyphs),
}
} else {
@ -484,13 +486,15 @@ impl<'a> ShapedText<'a> {
// that subtracting either of the endpoints by self.base doesn't
// underflow. See <https://github.com/typst/typst/issues/2283>.
.unwrap_or_else(|| self.base..self.base);
self.width += x_advance.at(self.size);
let size = TextElem::size_in(self.styles);
self.width += x_advance.at(size);
let glyph = ShapedGlyph {
font,
glyph_id: glyph_id.0,
x_advance,
x_offset: Em::zero(),
y_offset: Em::zero(),
size,
adjustability: Adjustability::default(),
range,
safe_to_break: true,
@ -666,6 +670,7 @@ fn shape<'a>(
region: Option<Region>,
) -> ShapedText<'a> {
let size = TextElem::size_in(styles);
let shift_settings = TextElem::shift_settings_in(styles);
let mut ctx = ShapingContext {
engine,
size,
@ -676,6 +681,7 @@ fn shape<'a>(
features: features(styles),
fallback: TextElem::fallback_in(styles),
dir,
shift_settings,
};
if !text.is_empty() {
@ -698,12 +704,17 @@ fn shape<'a>(
region,
styles,
variant: ctx.variant,
size,
width: ctx.glyphs.iter().map(|g| g.x_advance).sum::<Em>().at(size),
width: glyphs_width(&ctx.glyphs),
glyphs: Cow::Owned(ctx.glyphs),
}
}
/// Computes the width of a run of glyphs relative to the font size, accounting
/// for their individual scaling factors and other font metrics.
fn glyphs_width(glyphs: &[ShapedGlyph]) -> Abs {
glyphs.iter().map(|g| g.x_advance.at(g.size)).sum()
}
/// Holds shaping results and metadata common to all shaped segments.
struct ShapingContext<'a, 'v> {
engine: &'a Engine<'v>,
@ -715,6 +726,7 @@ struct ShapingContext<'a, 'v> {
features: Vec<rustybuzz::Feature>,
fallback: bool,
dir: Dir,
shift_settings: Option<ShiftSettings>,
}
/// Shape text with font fallback using the `families` iterator.
@ -789,6 +801,18 @@ fn shape_segment<'a>(
// text extraction.
buffer.set_flags(BufferFlags::REMOVE_DEFAULT_IGNORABLES);
let (script_shift, script_compensation, scale, shift_feature) = ctx
.shift_settings
.map_or((Em::zero(), Em::zero(), Em::one(), None), |settings| {
determine_shift(text, &font, settings)
});
let has_shift_feature = shift_feature.is_some();
if let Some(feat) = shift_feature {
// Temporarily push the feature.
ctx.features.push(feat)
}
// Prepare the shape plan. This plan depends on direction, script, language,
// and features, but is independent from the text and can thus be memoized.
let plan = create_shape_plan(
@ -799,6 +823,10 @@ fn shape_segment<'a>(
&ctx.features,
);
if has_shift_feature {
ctx.features.pop();
}
// Shape!
let buffer = rustybuzz::shape_with_plan(font.rusty(), &plan, buffer);
let infos = buffer.glyph_infos();
@ -869,8 +897,9 @@ fn shape_segment<'a>(
glyph_id: info.glyph_id as u16,
// TODO: Don't ignore y_advance.
x_advance,
x_offset: font.to_em(pos[i].x_offset),
y_offset: font.to_em(pos[i].y_offset),
x_offset: font.to_em(pos[i].x_offset) + script_compensation,
y_offset: font.to_em(pos[i].y_offset) + script_shift,
size: scale.at(ctx.size),
adjustability: Adjustability::default(),
range: start..end,
safe_to_break: !info.unsafe_to_break(),
@ -932,6 +961,64 @@ fn shape_segment<'a>(
ctx.used.pop();
}
/// Returns a `(script_shift, script_compensation, scale, feature)` quadruplet
/// describing how to produce scripts.
///
/// Those values determine how the rendered text should be transformed to
/// display sub-/super-scripts. If the OpenType feature can be used, the
/// rendered text should not be transformed in any way, and so those values are
/// neutral (`(0, 0, 1, None)`). If scripts should be synthesized, those values
/// determine how to transform the rendered text to display scripts as expected.
fn determine_shift(
text: &str,
font: &Font,
settings: ShiftSettings,
) -> (Em, Em, Em, Option<Feature>) {
settings
.typographic
.then(|| {
// If typographic scripts are enabled (i.e., we want to use the
// OpenType feature instead of synthesizing if possible), we add
// "subs"/"sups" to the feature list if supported by the font.
// In case of a problem, we just early exit
let gsub = font.rusty().tables().gsub?;
let subtable_index =
gsub.features.find(settings.kind.feature())?.lookup_indices.get(0)?;
let coverage = gsub
.lookups
.get(subtable_index)?
.subtables
.get::<SubstitutionSubtable>(0)?
.coverage();
text.chars()
.all(|c| {
font.rusty().glyph_index(c).is_some_and(|i| coverage.contains(i))
})
.then(|| {
// If we can use the OpenType feature, we can keep the text
// as is.
(
Em::zero(),
Em::zero(),
Em::one(),
Some(Feature::new(settings.kind.feature(), 1, ..)),
)
})
})
// Reunite the cases where `typographic` is `false` or where using the
// OpenType feature would not work.
.flatten()
.unwrap_or_else(|| {
let script_metrics = settings.kind.read_metrics(font.metrics());
(
settings.shift.unwrap_or(script_metrics.vertical_offset),
script_metrics.horizontal_offset,
settings.size.unwrap_or(script_metrics.height),
None,
)
})
}
/// Create a shape plan.
#[comemo::memoize]
pub fn create_shape_plan(
@ -963,6 +1050,7 @@ fn shape_tofus(ctx: &mut ShapingContext, base: usize, text: &str, font: Font) {
x_advance,
x_offset: Em::zero(),
y_offset: Em::zero(),
size: ctx.size,
adjustability: Adjustability::default(),
range: start..end,
safe_to_break: true,
@ -985,9 +1073,8 @@ fn shape_tofus(ctx: &mut ShapingContext, base: usize, text: &str, font: Font) {
/// 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 tracking = Em::from_abs(TextElem::tracking_in(ctx.styles), ctx.size);
let spacing = TextElem::spacing_in(ctx.styles).map(|abs| Em::from_abs(abs, ctx.size));
let mut glyphs = ctx.glyphs.iter_mut().peekable();
while let Some(glyph) = glyphs.next() {

6
crates/typst-layout/src/math/fragment.rs
View File

@ -215,7 +215,7 @@ impl MathFragment {
&glyph.item.font,
GlyphId(glyph.item.glyphs[glyph_index].id),
corner,
Em::from_length(height, glyph.item.size),
Em::from_abs(height, glyph.item.size),
)
.unwrap_or_default()
.at(glyph.item.size)
@ -767,8 +767,8 @@ fn assemble(
advance += ratio * (max_overlap - min_overlap);
}
let (x, y) = match axis {
Axis::X => (Em::from_length(advance, base.item.size), Em::zero()),
Axis::Y => (Em::zero(), Em::from_length(advance, base.item.size)),
Axis::X => (Em::from_abs(advance, base.item.size), Em::zero()),
Axis::Y => (Em::zero(), Em::from_abs(advance, base.item.size)),
};
glyphs.push(Glyph {
id: part.glyph_id.0,

17
crates/typst-library/src/layout/em.rs
View File

@ -6,7 +6,7 @@ use ecow::EcoString;
use typst_utils::{Numeric, Scalar};
use crate::foundations::{cast, repr, Repr, Resolve, StyleChain, Value};
use crate::layout::Abs;
use crate::layout::{Abs, Length};
use crate::text::TextElem;
/// A length that is relative to the font size.
@ -26,18 +26,18 @@ impl Em {
Self(Scalar::ONE)
}
/// Create a font-relative length.
/// Creates a font-relative length.
pub const fn new(em: f64) -> Self {
Self(Scalar::new(em))
}
/// Create an em length from font units at the given units per em.
/// Creates an em length from font units at the given units per em.
pub fn from_units(units: impl Into<f64>, units_per_em: f64) -> Self {
Self(Scalar::new(units.into() / units_per_em))
}
/// Create an em length from a length at the given font size.
pub fn from_length(length: Abs, font_size: Abs) -> Self {
/// Creates an em length from an absolute length at the given font size.
pub fn from_abs(length: Abs, font_size: Abs) -> Self {
let result = length / font_size;
if result.is_finite() {
Self(Scalar::new(result))
@ -46,6 +46,11 @@ impl Em {
}
}
/// Creates an em length from a length at the given font size.
pub fn from_length(length: Length, font_size: Abs) -> Em {
length.em + Self::from_abs(length.abs, font_size)
}
/// The number of em units.
pub const fn get(self) -> f64 {
(self.0).get()
@ -56,7 +61,7 @@ impl Em {
Self::new(self.get().abs())
}
/// Convert to an absolute length at the given font size.
/// Converts to an absolute length at the given font size.
pub fn at(self, font_size: Abs) -> Abs {
let resolved = font_size * self.get();
if resolved.is_finite() {

39
crates/typst-library/src/text/font/mod.rs
View File

@ -228,6 +228,10 @@ pub struct FontMetrics {
pub underline: LineMetrics,
/// Recommended metrics for an overline.
pub overline: LineMetrics,
/// Metrics for subscripts, if provided by the font.
pub subscript: Option<ScriptMetrics>,
/// Metrics for superscripts, if provided by the font.
pub superscript: Option<ScriptMetrics>,
}
impl FontMetrics {
@ -240,6 +244,7 @@ impl FontMetrics {
let cap_height = ttf.capital_height().filter(|&h| h > 0).map_or(ascender, to_em);
let x_height = ttf.x_height().filter(|&h| h > 0).map_or(ascender, to_em);
let descender = to_em(ttf.typographic_descender().unwrap_or(ttf.descender()));
let strikeout = ttf.strikeout_metrics();
let underline = ttf.underline_metrics();
@ -262,6 +267,20 @@ impl FontMetrics {
thickness: underline.thickness,
};
let subscript = ttf.subscript_metrics().map(|metrics| ScriptMetrics {
width: to_em(metrics.x_size),
height: to_em(metrics.y_size),
horizontal_offset: to_em(metrics.x_offset),
vertical_offset: -to_em(metrics.y_offset),
});
let superscript = ttf.superscript_metrics().map(|metrics| ScriptMetrics {
width: to_em(metrics.x_size),
height: to_em(metrics.y_size),
horizontal_offset: to_em(metrics.x_offset),
vertical_offset: to_em(metrics.y_offset),
});
Self {
units_per_em,
ascender,
@ -271,6 +290,8 @@ impl FontMetrics {
strikethrough,
underline,
overline,
superscript,
subscript,
}
}
@ -296,6 +317,24 @@ pub struct LineMetrics {
pub thickness: Em,
}
/// Metrics for subscripts or superscripts.
#[derive(Debug, Copy, Clone)]
pub struct ScriptMetrics {
/// The width of those scripts, relative to the outer font size.
pub width: Em,
/// The height of those scripts, relative to the outer font size.
pub height: Em,
/// The horizontal (to the right) offset of those scripts, relative to the
/// outer font size.
///
/// This is used for italic correction.
pub horizontal_offset: Em,
/// The vertical (to the top) offset of those scripts, relative to the outer font size.
///
/// For superscripts, this is positive. For subscripts, this is negative.
pub vertical_offset: Em,
}
/// Identifies a vertical metric of a font.
#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash, Cast)]
pub enum VerticalFontMetric {

6
crates/typst-library/src/text/mod.rs
View File

@ -755,6 +755,12 @@ pub struct TextElem {
#[internal]
#[ghost]
pub smallcaps: Option<Smallcaps>,
/// The configuration for superscripts or subscripts, if one of them is
/// enabled.
#[internal]
#[ghost]
pub shift_settings: Option<ShiftSettings>,
}
impl TextElem {

298
crates/typst-library/src/text/shift.rs
View File

@ -1,14 +1,13 @@
use ecow::EcoString;
use crate::diag::SourceResult;
use crate::engine::Engine;
use crate::foundations::{
elem, Content, NativeElement, Packed, SequenceElem, Show, StyleChain, TargetElem,
elem, Content, NativeElement, Packed, Show, Smart, StyleChain, TargetElem,
};
use crate::html::{tag, HtmlElem};
use crate::layout::{Em, Length};
use crate::text::{variant, SpaceElem, TextElem, TextSize};
use crate::World;
use crate::text::{FontMetrics, TextElem, TextSize};
use ttf_parser::Tag;
use typst_library::text::ScriptMetrics;
/// Renders text in subscript.
///
@ -20,11 +19,16 @@ use crate::World;
/// ```
#[elem(title = "Subscript", Show)]
pub struct SubElem {
/// Whether to prefer the dedicated subscript characters of the font.
/// Whether to create artificial subscripts by lowering and scaling down
/// regular glyphs.
///
/// If this is enabled, Typst first tries to transform the text to subscript
/// codepoints. If that fails, it falls back to rendering lowered and shrunk
/// normal letters.
/// Ideally, subscripts glyphs are provided by the font (using the `subs`
/// OpenType feature). Otherwise, Typst is able to synthesize subscripts.
///
/// When this is set to `{false}`, synthesized glyphs will be used
/// regardless of whether the font provides dedicated subscript glyphs. When
/// `{true}`, synthesized glyphs may still be used in case the font does not
/// provide the necessary subscript glyphs.
///
/// ```example
/// N#sub(typographic: true)[1]
@ -33,17 +37,27 @@ pub struct SubElem {
#[default(true)]
pub typographic: bool,
/// The baseline shift for synthetic subscripts. Does not apply if
/// `typographic` is true and the font has subscript codepoints for the
/// given `body`.
#[default(Em::new(0.2).into())]
pub baseline: Length,
/// The downward baseline shift for synthesized subscripts.
///
/// This only applies to synthesized subscripts. In other words, this has no
/// effect if `typographic` is `{true}` and the font provides the necessary
/// subscript glyphs.
///
/// If set to `{auto}`, the baseline is shifted according to the metrics
/// provided by the font, with a fallback to `{0.2em}` in case the font does
/// not define the necessary metrics.
pub baseline: Smart<Length>,
/// The font size for synthetic subscripts. Does not apply if
/// `typographic` is true and the font has subscript codepoints for the
/// given `body`.
#[default(TextSize(Em::new(0.6).into()))]
pub size: TextSize,
/// The font size for synthesized subscripts.
///
/// This only applies to synthesized subscripts. In other words, this has no
/// effect if `typographic` is `{true}` and the font provides the necessary
/// subscript glyphs.
///
/// If set to `{auto}`, the size is scaled according to the metrics provided
/// by the font, with a fallback to `{0.6em}` in case the font does not
/// define the necessary metrics.
pub size: Smart<TextSize>,
/// The text to display in subscript.
#[required]
@ -52,7 +66,7 @@ pub struct SubElem {
impl Show for Packed<SubElem> {
#[typst_macros::time(name = "sub", span = self.span())]
fn show(&self, engine: &mut Engine, styles: StyleChain) -> SourceResult<Content> {
fn show(&self, _: &mut Engine, styles: StyleChain) -> SourceResult<Content> {
let body = self.body.clone();
if TargetElem::target_in(styles).is_html() {
@ -62,17 +76,14 @@ impl Show for Packed<SubElem> {
.spanned(self.span()));
}
if self.typographic(styles) {
if let Some(text) = convert_script(&body, true) {
if is_shapable(engine, &text, styles) {
return Ok(TextElem::packed(text));
}
}
};
Ok(body
.styled(TextElem::set_baseline(self.baseline(styles)))
.styled(TextElem::set_size(self.size(styles))))
show_script(
styles,
body,
self.typographic(styles),
self.baseline(styles),
self.size(styles),
ScriptKind::Sub,
)
}
}
@ -86,11 +97,16 @@ impl Show for Packed<SubElem> {
/// ```
#[elem(title = "Superscript", Show)]
pub struct SuperElem {
/// Whether to prefer the dedicated superscript characters of the font.
/// Whether to create artificial superscripts by raising and scaling down
/// regular glyphs.
///
/// If this is enabled, Typst first tries to transform the text to
/// superscript codepoints. If that fails, it falls back to rendering
/// raised and shrunk normal letters.
/// Ideally, superscripts glyphs are provided by the font (using the `sups`
/// OpenType feature). Otherwise, Typst is able to synthesize superscripts.
///
/// When this is set to `{false}`, synthesized glyphs will be used
/// regardless of whether the font provides dedicated superscript glyphs.
/// When `{true}`, synthesized glyphs may still be used in case the font
/// does not provide the necessary superscript glyphs.
///
/// ```example
/// N#super(typographic: true)[1]
@ -99,17 +115,31 @@ pub struct SuperElem {
#[default(true)]
pub typographic: bool,
/// The baseline shift for synthetic superscripts. Does not apply if
/// `typographic` is true and the font has superscript codepoints for the
/// given `body`.
#[default(Em::new(-0.5).into())]
pub baseline: Length,
/// The downward baseline shift for synthesized superscripts.
///
/// This only applies to synthesized superscripts. In other words, this has
/// no effect if `typographic` is `{true}` and the font provides the
/// necessary superscript glyphs.
///
/// If set to `{auto}`, the baseline is shifted according to the metrics
/// provided by the font, with a fallback to `{-0.5em}` in case the font
/// does not define the necessary metrics.
///
/// Note that, since the baseline shift is applied downward, you will need
/// to provide a negative value for the content to appear as raised above
/// the normal baseline.
pub baseline: Smart<Length>,
/// The font size for synthetic superscripts. Does not apply if
/// `typographic` is true and the font has superscript codepoints for the
/// given `body`.
#[default(TextSize(Em::new(0.6).into()))]
pub size: TextSize,
/// The font size for synthesized superscripts.
///
/// This only applies to synthesized superscripts. In other words, this has
/// no effect if `typographic` is `{true}` and the font provides the
/// necessary superscript glyphs.
///
/// If set to `{auto}`, the size is scaled according to the metrics provided
/// by the font, with a fallback to `{0.6em}` in case the font does not
/// define the necessary metrics.
pub size: Smart<TextSize>,
/// The text to display in superscript.
#[required]
@ -118,7 +148,7 @@ pub struct SuperElem {
impl Show for Packed<SuperElem> {
#[typst_macros::time(name = "super", span = self.span())]
fn show(&self, engine: &mut Engine, styles: StyleChain) -> SourceResult<Content> {
fn show(&self, _: &mut Engine, styles: StyleChain) -> SourceResult<Content> {
let body = self.body.clone();
if TargetElem::target_in(styles).is_html() {
@ -128,104 +158,102 @@ impl Show for Packed<SuperElem> {
.spanned(self.span()));
}
if self.typographic(styles) {
if let Some(text) = convert_script(&body, false) {
if is_shapable(engine, &text, styles) {
return Ok(TextElem::packed(text));
}
}
};
Ok(body
.styled(TextElem::set_baseline(self.baseline(styles)))
.styled(TextElem::set_size(self.size(styles))))
show_script(
styles,
body,
self.typographic(styles),
self.baseline(styles),
self.size(styles),
ScriptKind::Super,
)
}
}
/// Find and transform the text contained in `content` to the given script kind
/// if and only if it only consists of `Text`, `Space`, and `Empty` leaves.
fn convert_script(content: &Content, sub: bool) -> Option<EcoString> {
if content.is::<SpaceElem>() {
Some(' '.into())
} else if let Some(elem) = content.to_packed::<TextElem>() {
if sub {
elem.text.chars().map(to_subscript_codepoint).collect()
} else {
elem.text.chars().map(to_superscript_codepoint).collect()
}
} else if let Some(sequence) = content.to_packed::<SequenceElem>() {
sequence
.children
.iter()
.map(|item| convert_script(item, sub))
.collect()
} else {
None
}
fn show_script(
styles: StyleChain,
body: Content,
typographic: bool,
baseline: Smart<Length>,
size: Smart<TextSize>,
kind: ScriptKind,
) -> SourceResult<Content> {
let font_size = TextElem::size_in(styles);
Ok(body.styled(TextElem::set_shift_settings(Some(ShiftSettings {
typographic,
shift: baseline.map(|l| -Em::from_length(l, font_size)),
size: size.map(|t| Em::from_length(t.0, font_size)),
kind,
}))))
}
/// Checks whether the first retrievable family contains all code points of the
/// given string.
fn is_shapable(engine: &Engine, text: &str, styles: StyleChain) -> bool {
let world = engine.world;
for family in TextElem::font_in(styles) {
if let Some(font) = world
.book()
.select(family.as_str(), variant(styles))
.and_then(|id| world.font(id))
{
let covers = family.covers();
return text.chars().all(|c| {
covers.is_none_or(|cov| cov.is_match(c.encode_utf8(&mut [0; 4])))
&& font.ttf().glyph_index(c).is_some()
});
/// Configuration values for sub- or superscript text.
#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
pub struct ShiftSettings {
/// Whether the OpenType feature should be used if possible.
pub typographic: bool,
/// The baseline shift of the script, relative to the outer text size.
///
/// For superscripts, this is positive. For subscripts, this is negative. A
/// value of [`Smart::Auto`] indicates that the value should be obtained
/// from font metrics.
pub shift: Smart<Em>,
/// The size of the script, relative to the outer text size.
///
/// A value of [`Smart::Auto`] indicates that the value should be obtained
/// from font metrics.
pub size: Smart<Em>,
/// The kind of script (either a subscript, or a superscript).
///
/// This is used to know which OpenType table to use to resolve
/// [`Smart::Auto`] values.
pub kind: ScriptKind,
}
#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
pub enum ScriptKind {
Sub,
Super,
}
impl ScriptKind {
/// Returns the default metrics for this script kind.
///
/// This can be used as a last resort if neither the user nor the font
/// provided those metrics.
pub fn default_metrics(self) -> &'static ScriptMetrics {
match self {
Self::Sub => &DEFAULT_SUBSCRIPT_METRICS,
Self::Super => &DEFAULT_SUPERSCRIPT_METRICS,
}
}
false
}
/// Reads the script metrics from the font table for to this script kind.
pub fn read_metrics(self, font_metrics: &FontMetrics) -> &ScriptMetrics {
match self {
Self::Sub => font_metrics.subscript.as_ref(),
Self::Super => font_metrics.superscript.as_ref(),
}
.unwrap_or(self.default_metrics())
}
/// Convert a character to its corresponding Unicode superscript.
fn to_superscript_codepoint(c: char) -> Option<char> {
match c {
'1' => Some('¹'),
'2' => Some('²'),
'3' => Some('³'),
'0' | '4'..='9' => char::from_u32(c as u32 - '0' as u32 + '⁰' as u32),
'+' => Some('⁺'),
'−' => Some('⁻'),
'=' => Some('⁼'),
'(' => Some('⁽'),
')' => Some('⁾'),
'n' => Some('ⁿ'),
'i' => Some('ⁱ'),
' ' => Some(' '),
_ => None,
/// The corresponding OpenType feature.
pub const fn feature(self) -> Tag {
match self {
Self::Sub => Tag::from_bytes(b"subs"),
Self::Super => Tag::from_bytes(b"sups"),
}
}
}
static DEFAULT_SUBSCRIPT_METRICS: ScriptMetrics = ScriptMetrics {
width: Em::new(0.6),
height: Em::new(0.6),
horizontal_offset: Em::zero(),
vertical_offset: Em::new(-0.2),
};
/// Convert a character to its corresponding Unicode subscript.
fn to_subscript_codepoint(c: char) -> Option<char> {
match c {
'0'..='9' => char::from_u32(c as u32 - '0' as u32 + '₀' as u32),
'+' => Some('₊'),
'−' => Some('₋'),
'=' => Some('₌'),
'(' => Some('₍'),
')' => Some('₎'),
'a' => Some('ₐ'),
'e' => Some('ₑ'),
'o' => Some('ₒ'),
'x' => Some('ₓ'),
'h' => Some('ₕ'),
'k' => Some('ₖ'),
'l' => Some('ₗ'),
'm' => Some('ₘ'),
'n' => Some('ₙ'),
'p' => Some('ₚ'),
's' => Some('ₛ'),
't' => Some('ₜ'),
' ' => Some(' '),
_ => None,
}
}
static DEFAULT_SUPERSCRIPT_METRICS: ScriptMetrics = ScriptMetrics {
width: Em::new(0.6),
height: Em::new(0.6),
horizontal_offset: Em::zero(),
vertical_offset: Em::new(0.5),
};

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79
tests/suite/text/shift.typ
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@ -1,22 +1,89 @@
// Test sub- and superscript shifts.
--- sub-super ---
#let sq = box(square(size: 4pt))
#table(
columns: 3,
[Typo.], [Fallb.], [Synth],
[x#super[1]], [x#super[5n]], [x#super[2 #box(square(size: 6pt))]],
[x#sub[1]], [x#sub[5n]], [x#sub[2 #box(square(size: 6pt))]],
[Typo.], [Fallb.], [Synth.],
[x#super[1#sq]], [x#super[5: #sq]], [x#super(typographic: false)[2 #sq]],
[x#sub[1#sq]], [x#sub[5: #sq]], [x#sub(typographic: false)[2 #sq]],
)
--- sub-super-typographic ---
#set text(size: 20pt)
// Libertinus Serif supports "subs" and "sups" for `typo` and `sq`, but not for
// `synth`.
#let synth = [1,2,3]
#let typo = [123]
#let sq = [1#box(square(size: 4pt))2]
x#super(synth) x#super(typo) x#super(sq) \
x#sub(synth) x#sub(typo) x#sub(sq)
--- sub-super-italic-compensation ---
#set text(size: 20pt, style: "italic")
// Libertinus Serif supports "subs" and "sups" for `typo`, but not for `synth`.
#let synth = [1,2,3]
#let typo = [123]
#let sq = [1#box(square(size: 4pt))2]
x#super(synth) x#super(typo) x#super(sq) \
x#sub(synth) x#sub(typo) x#sub(sq)
--- sub-super-non-typographic ---
#set super(typographic: false, baseline: -0.25em, size: 0.7em)
n#super[1], n#sub[2], ... n#super[N]
--- super-underline ---
#set underline(stroke: 0.5pt, offset: 0.15em)
#underline[The claim#super[\[4\]]] has been disputed. \
The claim#super[#underline[\[4\]]] has been disputed. \
It really has been#super(box(text(baseline: 0pt, underline[\[4\]]))) \
#set super(typographic: false)
#underline[A#super[4]] B \
A#super[#underline[4]] B \
A #underline(super[4]) B \
#set super(typographic: true)
#underline[A#super[4]] B \
A#super[#underline[4]] B \
A #underline(super[4]) B
--- super-highlight ---
#set super(typographic: false)
#highlight[A#super[4]] B \
A#super[#highlight[4]] B \
A#super(highlight[4]) \
#set super(typographic: true)
#highlight[A#super[4]] B \
A#super[#highlight[4]] B \
A#super(highlight[4])
--- super-1em ---
#set text(size: 10pt)
#super(context test(1em.to-absolute(), 10pt))
--- long-scripts ---
|longscript| \
|#super(typographic: true)[longscript]| \
|#super(typographic: false)[longscript]| \
|#sub(typographic: true)[longscript]| \
|#sub(typographic: false)[longscript]|
--- script-metrics-bundeled-fonts ---
// Tests whether the script metrics are used properly by synthesizing
// superscripts and subscripts for all bundled fonts.
#set super(typographic: false)
#set sub(typographic: false)
#let test(font, weights, styles) = {
for weight in weights {
for style in styles {
text(font: font, weight: weight, style: style)[Xx#super[Xx]#sub[Xx]]
linebreak()
}
}
}
#test("DejaVu Sans Mono", ("regular", "bold"), ("normal", "oblique"))
#test("Libertinus Serif", ("regular", "semibold", "bold"), ("normal", "italic"))
#test("New Computer Modern", ("regular", "bold"), ("normal", "italic"))
#test("New Computer Modern Math", (400, 450, "bold"), ("normal",))
--- basic-sup-sub html ---
1#super[st], 2#super[nd], 3#super[rd].