mirror of
https://github.com/typst/typst
synced 2025-05-14 04:56:26 +08:00
636 lines
20 KiB
Rust
636 lines
20 KiB
Rust
use std::ops::Range;
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use std::str::FromStr;
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use rustybuzz::{Feature, UnicodeBuffer};
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use super::*;
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use crate::font::{FaceId, FontStore, FontVariant};
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use crate::library::prelude::*;
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use crate::util::SliceExt;
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/// The result of shaping text.
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///
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/// This type contains owned or borrowed shaped text runs, which can be
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/// measured, used to reshape substrings more quickly and converted into a
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/// frame.
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pub struct ShapedText<'a> {
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/// The text that was shaped.
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pub text: &'a str,
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/// The text direction.
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pub dir: Dir,
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/// The text's style properties.
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pub styles: StyleChain<'a>,
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/// The font variant.
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pub variant: FontVariant,
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/// The font size.
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pub size: Length,
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/// The width of the text's bounding box.
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pub width: Length,
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/// The shaped glyphs.
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pub glyphs: Cow<'a, [ShapedGlyph]>,
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}
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/// A single glyph resulting from shaping.
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#[derive(Debug, Copy, Clone)]
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pub struct ShapedGlyph {
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/// The font face the glyph is contained in.
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pub face_id: FaceId,
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/// The glyph's index in the face.
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pub glyph_id: u16,
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/// The advance width of the glyph.
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pub x_advance: Em,
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/// The horizontal offset of the glyph.
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pub x_offset: Em,
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/// A value that is the same for all glyphs belong to one cluster.
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pub cluster: usize,
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/// Whether splitting the shaping result before this glyph would yield the
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/// same results as shaping the parts to both sides of `text_index`
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/// separately.
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pub safe_to_break: bool,
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/// The first char in this glyph's cluster.
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pub c: char,
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}
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impl ShapedGlyph {
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/// Whether the glyph is a space.
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pub fn is_space(&self) -> bool {
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self.c == ' '
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}
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/// Whether the glyph is justifiable.
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pub fn is_justifiable(&self) -> bool {
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matches!(self.c, ' ' | '，' | ' ' | '。' | '、')
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}
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}
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/// A side you can go toward.
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enum Side {
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/// Go toward the west.
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Left,
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/// Go toward the east.
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Right,
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}
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impl<'a> ShapedText<'a> {
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/// Build the shaped text's frame.
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///
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/// The `justification` defines how much extra advance width each
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/// [justifiable glyph](ShapedGlyph::is_justifiable) will get.
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pub fn build(&self, fonts: &mut FontStore, justification: Length) -> Frame {
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let (top, bottom) = self.measure(fonts);
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let size = Size::new(self.width, top + bottom);
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let mut offset = Length::zero();
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let mut frame = Frame::new(size);
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frame.baseline = Some(top);
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for (face_id, group) in self.glyphs.as_ref().group_by_key(|g| g.face_id) {
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let pos = Point::new(offset, top);
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let fill = self.styles.get(TextNode::FILL);
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let glyphs = group
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.iter()
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.map(|glyph| Glyph {
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id: glyph.glyph_id,
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x_advance: glyph.x_advance
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+ if glyph.is_justifiable() {
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frame.size.x += justification;
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Em::from_length(justification, self.size)
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} else {
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Em::zero()
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},
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x_offset: glyph.x_offset,
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c: glyph.c,
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})
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.collect();
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let text = Text {
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face_id,
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size: self.size,
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lang: self.styles.get(TextNode::LANG),
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fill,
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glyphs,
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};
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let text_layer = frame.layer();
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let width = text.width();
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// Apply line decorations.
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for deco in self.styles.get(TextNode::DECO) {
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decorate(&mut frame, &deco, fonts, &text, pos, width);
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}
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frame.insert(text_layer, pos, Element::Text(text));
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offset += width;
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}
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// Apply link if it exists.
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if let Some(url) = self.styles.get(TextNode::LINK) {
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frame.link(url.clone());
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}
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frame
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}
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/// Measure the top and bottom extent of a this text.
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fn measure(&self, fonts: &mut FontStore) -> (Length, Length) {
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let mut top = Length::zero();
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let mut bottom = Length::zero();
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let top_edge = self.styles.get(TextNode::TOP_EDGE);
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let bottom_edge = self.styles.get(TextNode::BOTTOM_EDGE);
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// Expand top and bottom by reading the face's vertical metrics.
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let mut expand = |face: &Face| {
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let metrics = face.metrics();
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top.set_max(top_edge.resolve(self.styles, metrics));
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bottom.set_max(-bottom_edge.resolve(self.styles, metrics));
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};
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if self.glyphs.is_empty() {
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// When there are no glyphs, we just use the vertical metrics of the
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// first available font.
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for family in families(self.styles) {
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if let Some(face_id) = fonts.select(family, self.variant) {
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expand(fonts.get(face_id));
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break;
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}
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}
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} else {
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for (face_id, _) in self.glyphs.group_by_key(|g| g.face_id) {
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let face = fonts.get(face_id);
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expand(face);
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}
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}
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(top, bottom)
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}
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/// How many justifiable glyphs the text contains.
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pub fn justifiables(&self) -> usize {
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self.glyphs.iter().filter(|g| g.is_justifiable()).count()
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}
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/// The width of the spaces in the text.
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pub fn stretch(&self) -> Length {
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self.glyphs
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.iter()
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.filter(|g| g.is_justifiable())
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.map(|g| g.x_advance)
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.sum::<Em>()
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.at(self.size)
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}
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/// Reshape a range of the shaped text, reusing information from this
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/// shaping process if possible.
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pub fn reshape(
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&'a self,
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fonts: &mut FontStore,
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text_range: Range<usize>,
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) -> ShapedText<'a> {
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if let Some(glyphs) = self.slice_safe_to_break(text_range.clone()) {
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Self {
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text: &self.text[text_range],
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dir: self.dir,
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styles: self.styles,
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size: self.size,
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variant: self.variant,
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width: glyphs.iter().map(|g| g.x_advance).sum::<Em>().at(self.size),
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glyphs: Cow::Borrowed(glyphs),
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}
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} else {
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shape(fonts, &self.text[text_range], self.styles, self.dir)
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}
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}
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/// Push a hyphen to end of the text.
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pub fn push_hyphen(&mut self, fonts: &mut FontStore) {
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families(self.styles).find_map(|family| {
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let face_id = fonts.select(family, self.variant)?;
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let face = fonts.get(face_id);
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let ttf = face.ttf();
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let glyph_id = ttf.glyph_index('-')?;
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let x_advance = face.to_em(ttf.glyph_hor_advance(glyph_id)?);
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let cluster = self.glyphs.last().map(|g| g.cluster).unwrap_or_default();
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self.width += x_advance.at(self.size);
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self.glyphs.to_mut().push(ShapedGlyph {
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face_id,
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glyph_id: glyph_id.0,
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x_advance,
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x_offset: Em::zero(),
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cluster,
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safe_to_break: true,
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c: '-',
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});
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Some(())
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});
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}
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/// Find the subslice of glyphs that represent the given text range if both
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/// sides are safe to break.
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fn slice_safe_to_break(&self, text_range: Range<usize>) -> Option<&[ShapedGlyph]> {
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let Range { mut start, mut end } = text_range;
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if !self.dir.is_positive() {
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std::mem::swap(&mut start, &mut end);
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}
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let left = self.find_safe_to_break(start, Side::Left)?;
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let right = self.find_safe_to_break(end, Side::Right)?;
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Some(&self.glyphs[left .. right])
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}
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/// Find the glyph offset matching the text index that is most towards the
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/// given side and safe-to-break.
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fn find_safe_to_break(&self, text_index: usize, towards: Side) -> Option<usize> {
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let ltr = self.dir.is_positive();
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// Handle edge cases.
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let len = self.glyphs.len();
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if text_index == 0 {
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return Some(if ltr { 0 } else { len });
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} else if text_index == self.text.len() {
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return Some(if ltr { len } else { 0 });
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}
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// Find any glyph with the text index.
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let mut idx = self
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.glyphs
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.binary_search_by(|g| {
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let ordering = g.cluster.cmp(&text_index);
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if ltr { ordering } else { ordering.reverse() }
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})
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.ok()?;
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let next = match towards {
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Side::Left => usize::checked_sub,
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Side::Right => usize::checked_add,
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};
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// Search for the outermost glyph with the text index.
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while let Some(next) = next(idx, 1) {
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if self.glyphs.get(next).map_or(true, |g| g.cluster != text_index) {
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break;
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}
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idx = next;
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}
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// RTL needs offset one because the left side of the range should be
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// exclusive and the right side inclusive, contrary to the normal
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// behaviour of ranges.
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self.glyphs[idx].safe_to_break.then(|| idx + (!ltr) as usize)
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}
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}
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impl Debug for ShapedText<'_> {
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fn fmt(&self, f: &mut Formatter) -> fmt::Result {
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self.text.fmt(f)
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}
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}
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/// Holds shaping results and metadata common to all shaped segments.
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struct ShapingContext<'a> {
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fonts: &'a mut FontStore,
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glyphs: Vec<ShapedGlyph>,
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used: Vec<FaceId>,
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styles: StyleChain<'a>,
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size: Length,
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variant: FontVariant,
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tags: Vec<rustybuzz::Feature>,
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fallback: bool,
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dir: Dir,
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}
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/// Shape text into [`ShapedText`].
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pub fn shape<'a>(
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fonts: &mut FontStore,
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text: &'a str,
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styles: StyleChain<'a>,
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dir: Dir,
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) -> ShapedText<'a> {
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let size = styles.get(TextNode::SIZE);
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let mut ctx = ShapingContext {
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fonts,
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size,
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glyphs: vec![],
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used: vec![],
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styles,
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variant: variant(styles),
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tags: tags(styles),
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fallback: styles.get(TextNode::FALLBACK),
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dir,
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};
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if !text.is_empty() {
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shape_segment(&mut ctx, 0, &text, families(styles));
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}
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track_and_space(&mut ctx);
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ShapedText {
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text,
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dir,
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styles,
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variant: ctx.variant,
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size,
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width: ctx.glyphs.iter().map(|g| g.x_advance).sum::<Em>().at(size),
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glyphs: Cow::Owned(ctx.glyphs),
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}
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}
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/// Shape text with font fallback using the `families` iterator.
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fn shape_segment<'a>(
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ctx: &mut ShapingContext,
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base: usize,
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text: &str,
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mut families: impl Iterator<Item = &'a str> + Clone,
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) {
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// Fonts dont have newlines and tabs.
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if text.chars().all(|c| c == '\n' || c == '\t') {
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return;
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}
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// Find the next available family.
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let mut selection = families.find_map(|family| {
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ctx.fonts
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.select(family, ctx.variant)
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.filter(|id| !ctx.used.contains(id))
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});
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// Do font fallback if the families are exhausted and fallback is enabled.
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if selection.is_none() && ctx.fallback {
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let first = ctx.used.first().copied();
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selection = ctx
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.fonts
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.select_fallback(first, ctx.variant, text)
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.filter(|id| !ctx.used.contains(id));
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}
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// Extract the face id or shape notdef glyphs if we couldn't find any face.
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let face_id = if let Some(id) = selection {
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id
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} else {
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if let Some(&face_id) = ctx.used.first() {
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shape_tofus(ctx, base, text, face_id);
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}
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return;
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};
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ctx.used.push(face_id);
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// Fill the buffer with our text.
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let mut buffer = UnicodeBuffer::new();
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buffer.push_str(text);
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buffer.set_language(language(ctx.styles));
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buffer.set_direction(match ctx.dir {
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Dir::LTR => rustybuzz::Direction::LeftToRight,
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Dir::RTL => rustybuzz::Direction::RightToLeft,
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_ => unimplemented!("vertical text layout"),
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});
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// Shape!
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let mut face = ctx.fonts.get(face_id);
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let buffer = rustybuzz::shape(face.ttf(), &ctx.tags, buffer);
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let infos = buffer.glyph_infos();
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let pos = buffer.glyph_positions();
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// Collect the shaped glyphs, doing fallback and shaping parts again with
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// the next font if necessary.
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let mut i = 0;
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while i < infos.len() {
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let info = &infos[i];
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let cluster = info.cluster as usize;
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if info.glyph_id != 0 {
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// Add the glyph to the shaped output.
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// TODO: Don't ignore y_advance and y_offset.
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ctx.glyphs.push(ShapedGlyph {
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face_id,
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glyph_id: info.glyph_id as u16,
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x_advance: face.to_em(pos[i].x_advance),
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x_offset: face.to_em(pos[i].x_offset),
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cluster: base + cluster,
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safe_to_break: !info.unsafe_to_break(),
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c: text[cluster ..].chars().next().unwrap(),
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});
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} else {
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// Determine the source text range for the tofu sequence.
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let range = {
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// First, search for the end of the tofu sequence.
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let k = i;
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while infos.get(i + 1).map_or(false, |info| info.glyph_id == 0) {
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i += 1;
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}
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// Then, determine the start and end text index.
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//
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// Examples:
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// Everything is shown in visual order. Tofus are written as "_".
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// We want to find out that the tofus span the text `2..6`.
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// Note that the clusters are longer than 1 char.
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//
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// Left-to-right:
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// Text: h a l i h a l l o
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// Glyphs: A _ _ C E
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// Clusters: 0 2 4 6 8
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// k=1 i=2
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//
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// Right-to-left:
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// Text: O L L A H I L A H
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// Glyphs: E C _ _ A
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// Clusters: 8 6 4 2 0
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// k=2 i=3
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let ltr = ctx.dir.is_positive();
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let first = if ltr { k } else { i };
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let start = infos[first].cluster as usize;
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let last = if ltr { i.checked_add(1) } else { k.checked_sub(1) };
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let end = last
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.and_then(|last| infos.get(last))
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.map_or(text.len(), |info| info.cluster as usize);
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start .. end
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};
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// Trim half-baked cluster.
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let remove = base + range.start .. base + range.end;
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while ctx.glyphs.last().map_or(false, |g| remove.contains(&g.cluster)) {
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ctx.glyphs.pop();
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}
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// Recursively shape the tofu sequence with the next family.
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shape_segment(ctx, base + range.start, &text[range], families.clone());
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face = ctx.fonts.get(face_id);
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}
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i += 1;
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}
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ctx.used.pop();
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}
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/// Shape the text with tofus from the given face.
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fn shape_tofus(ctx: &mut ShapingContext, base: usize, text: &str, face_id: FaceId) {
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let face = ctx.fonts.get(face_id);
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let x_advance = face.advance(0).unwrap_or_default();
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for (cluster, c) in text.char_indices() {
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ctx.glyphs.push(ShapedGlyph {
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face_id,
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glyph_id: 0,
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x_advance,
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x_offset: Em::zero(),
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cluster: base + cluster,
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safe_to_break: true,
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c,
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});
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}
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}
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/// Apply tracking and spacing to a slice of shaped glyphs.
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fn track_and_space(ctx: &mut ShapingContext) {
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let tracking = Em::from_length(ctx.styles.get(TextNode::TRACKING), ctx.size);
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let spacing = ctx
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.styles
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.get(TextNode::SPACING)
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.map(|abs| Em::from_length(abs, ctx.size));
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if tracking.is_zero() && spacing.is_one() {
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return;
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}
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let mut glyphs = ctx.glyphs.iter_mut().peekable();
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while let Some(glyph) = glyphs.next() {
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if glyph.is_space() {
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glyph.x_advance = spacing.relative_to(glyph.x_advance);
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}
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if glyphs.peek().map_or(false, |next| glyph.cluster != next.cluster) {
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glyph.x_advance += tracking;
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}
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}
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}
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/// Resolve the font variant with `STRONG` and `EMPH` factored in.
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fn variant(styles: StyleChain) -> FontVariant {
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let mut variant = FontVariant::new(
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styles.get(TextNode::STYLE),
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styles.get(TextNode::WEIGHT),
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styles.get(TextNode::STRETCH),
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);
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if styles.get(TextNode::STRONG) {
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variant.weight = variant.weight.thicken(300);
|
||
}
|
||
|
||
if styles.get(TextNode::EMPH) {
|
||
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.
|
||
fn families(styles: StyleChain) -> impl Iterator<Item = &str> + Clone {
|
||
const FALLBACKS: &[&str] = &[
|
||
"ibm plex sans",
|
||
"twitter color emoji",
|
||
"noto color emoji",
|
||
"apple color emoji",
|
||
"segoe ui emoji",
|
||
];
|
||
|
||
let tail = if styles.get(TextNode::FALLBACK) { FALLBACKS } else { &[] };
|
||
styles
|
||
.get(TextNode::FAMILY)
|
||
.iter()
|
||
.map(|family| family.as_str())
|
||
.chain(tail.iter().copied())
|
||
}
|
||
|
||
/// 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 !styles.get(TextNode::KERNING) {
|
||
feat(b"kern", 0);
|
||
}
|
||
|
||
// Features that are off by default in Harfbuzz are only added if enabled.
|
||
if styles.get(TextNode::SMALLCAPS) {
|
||
feat(b"smcp", 1);
|
||
}
|
||
|
||
if styles.get(TextNode::ALTERNATES) {
|
||
feat(b"salt", 1);
|
||
}
|
||
|
||
let storage;
|
||
if let Some(set) = styles.get(TextNode::STYLISTIC_SET) {
|
||
storage = [b's', b's', b'0' + set.get() / 10, b'0' + set.get() % 10];
|
||
feat(&storage, 1);
|
||
}
|
||
|
||
if !styles.get(TextNode::LIGATURES) {
|
||
feat(b"liga", 0);
|
||
feat(b"clig", 0);
|
||
}
|
||
|
||
if styles.get(TextNode::DISCRETIONARY_LIGATURES) {
|
||
feat(b"dlig", 1);
|
||
}
|
||
|
||
if styles.get(TextNode::HISTORICAL_LIGATURES) {
|
||
feat(b"hilg", 1);
|
||
}
|
||
|
||
match styles.get(TextNode::NUMBER_TYPE) {
|
||
Smart::Auto => {}
|
||
Smart::Custom(NumberType::Lining) => feat(b"lnum", 1),
|
||
Smart::Custom(NumberType::OldStyle) => feat(b"onum", 1),
|
||
}
|
||
|
||
match styles.get(TextNode::NUMBER_WIDTH) {
|
||
Smart::Auto => {}
|
||
Smart::Custom(NumberWidth::Proportional) => feat(b"pnum", 1),
|
||
Smart::Custom(NumberWidth::Tabular) => feat(b"tnum", 1),
|
||
}
|
||
|
||
match styles.get(TextNode::NUMBER_POSITION) {
|
||
NumberPosition::Normal => {}
|
||
NumberPosition::Subscript => feat(b"subs", 1),
|
||
NumberPosition::Superscript => feat(b"sups", 1),
|
||
}
|
||
|
||
if styles.get(TextNode::SLASHED_ZERO) {
|
||
feat(b"zero", 1);
|
||
}
|
||
|
||
if styles.get(TextNode::FRACTIONS) {
|
||
feat(b"frac", 1);
|
||
}
|
||
|
||
for (tag, value) in styles.get(TextNode::FEATURES) {
|
||
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 = styles.get(TextNode::LANG).as_str().into();
|
||
if let Some(region) = styles.get(TextNode::REGION) {
|
||
bcp.push('-');
|
||
bcp.push_str(region.as_str());
|
||
}
|
||
rustybuzz::Language::from_str(&bcp).unwrap()
|
||
}
|