386 lines
15 KiB
Rust
386 lines
15 KiB
Rust
//! Shaping: text runs -> positioned glyphs in points (before line breaking).
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use std::ops::Range;
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use std::sync::Arc;
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use unicode_bidi::Level;
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use unicode_script::{Script, UnicodeScript};
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use harfrust::{Direction, Feature, ShapeOptions, UnicodeBuffer};
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use skrifa::MetadataProvider;
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use skrifa::instance::Size;
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use vectorcraft_doc::CharStyle;
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use crate::features::OtFeatures;
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use crate::fontdb::{FontDb, FontFace};
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/// A shaped glyph with all character-style effects resolved, in points (y down).
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#[derive(Clone, Debug)]
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pub(crate) struct SGlyph {
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pub face: Arc<FontFace>,
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pub gid: u32,
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/// Byte offset of the cluster in the plain text, and its length in bytes.
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pub byte: usize,
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pub len: usize,
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pub run: usize,
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/// Advance in points (tracking, manual kerning and horizontal scale applied).
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pub adv: f64,
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/// Offset from the pen position, y down.
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pub dx: f64,
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pub dy: f64,
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/// Outline scale (font units -> points).
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pub sx: f64,
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pub sy: f64,
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/// Baseline shift in points (positive = up).
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pub bshift: f64,
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/// Character rotation in degrees (counter-clockwise).
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pub rotation: f64,
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pub ascent: f64,
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pub descent: f64,
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pub leading: f64,
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/// Cap height and x height in points.
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pub cap: f64,
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pub xh: f64,
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/// First source character of the cluster.
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pub ch: char,
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/// Vertical type: part of a tate-chu-yoko block (set across the column, upright).
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pub tcy: Option<Tcy>,
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/// Japanese composition: the space taken off before the glyph (an opening bracket after
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/// another, see [`crate::layout`]); the glyph is drawn that much earlier on the line.
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pub lead: f64,
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/// Resolved Unicode bidi embedding level (logical source order).
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pub level: Level,
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}
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/// A glyph's place in a tate-chu-yoko block: the block takes one em of the column, its glyphs side
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/// by side across it.
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#[derive(Clone, Copy, Debug, PartialEq)]
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pub(crate) struct Tcy {
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/// Laid-out distance from the block's start to this glyph's pen position.
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pub pen: f64,
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/// Distance from the block's start to the glyph in the block's own (horizontal) setting.
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pub ink: f64,
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/// Width of the block's own setting.
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pub width: f64,
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/// Horizontal scale that fits the block into one em (1 when it fits as it is).
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pub squeeze: f64,
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}
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impl SGlyph {
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pub fn is_space(&self) -> bool {
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matches!(self.ch, ' ' | '\t' | '\u{3000}' | '\u{2002}'..='\u{200B}')
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}
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/// A line may break after this glyph.
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pub fn break_after(&self) -> bool {
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self.is_space() || matches!(self.ch, '-' | '\u{2010}' | '\u{2013}' | '\u{2014}' | '/' | SOFT_HYPHEN) || is_cjk(self.ch)
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}
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/// A soft (discretionary) hyphen: invisible unless a line breaks after it.
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pub fn is_soft_hyphen(&self) -> bool {
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self.ch == SOFT_HYPHEN
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}
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/// Part of a word that may be hyphenated (letters and apostrophes).
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pub fn is_letter(&self) -> bool {
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self.ch.is_alphabetic() || matches!(self.ch, '\'' | '’')
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}
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/// Vertical type: a tate-chu-yoko glyph after its block's first, sharing that glyph's cell.
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pub fn continues_tcy(&self) -> bool {
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self.tcy.is_some_and(|t| t.pen > 0.0)
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}
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}
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pub(crate) const SOFT_HYPHEN: char = '\u{00AD}';
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/// A visible hyphen in the face and size of `g`, placed at the end of `g`'s cluster (zero source
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/// length) for a line broken inside a word.
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pub(crate) fn hyphen_glyph(g: &SGlyph) -> SGlyph {
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let gid = ['-', '\u{2010}', SOFT_HYPHEN].into_iter().map(|c| g.face.glyph_for(c)).find(|&id| id != 0).unwrap_or(0);
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let mut h = g.clone();
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h.gid = gid;
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h.adv = g.face.advance(gid) * g.sx;
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h.dx = 0.0;
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h.dy = 0.0;
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h.byte = g.byte + g.len;
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h.len = 0;
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h.ch = '-';
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h
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}
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/// Kinsoku (Japanese line breaking, the strict set): a character that can't start a line —
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/// closing brackets, the Japanese comma and full stop, middle dots, colons, ! and ?, the long
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/// vowel mark, iteration marks and small kana.
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pub(crate) fn no_line_start(c: char) -> bool {
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matches!(c,
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')' | ']' | '}' | ',' | '.' | ':' | ';' | '!' | '?' | '»' | '’' | '”' | '‐' | '–' | '‼' | '⁇' | '⁈' | '⁉'
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| '、' | '。' | '〉' | '》' | '」' | '』' | '】' | '〕' | '〗' | '〙' | '〛' | '〟' | '〜' | '゠' | '・' | '｠'
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| 'ー' | 'ゝ' | 'ゞ' | 'ヽ' | 'ヾ' | '々' | '〻'
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| 'ぁ' | 'ぃ' | 'ぅ' | 'ぇ' | 'ぉ' | 'っ' | 'ゃ' | 'ゅ' | 'ょ' | 'ゎ' | 'ゕ' | 'ゖ'
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| 'ァ' | 'ィ' | 'ゥ' | 'ェ' | 'ォ' | 'ッ' | 'ャ' | 'ュ' | 'ョ' | 'ヮ' | 'ヵ' | 'ヶ' | 'ㇰ'..='ㇿ'
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| '！' | '）' | '，' | '．' | '：' | '；' | '？' | '］' | '｝' | '～' | '｡' | '｣' | '､' | '･' | 'ｰ' | 'ｧ'..='ｯ')
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}
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/// Kinsoku: a character that can't end a line (opening brackets).
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pub(crate) fn no_line_end(c: char) -> bool {
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matches!(
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c,
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'(' | '['
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| '{'
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| '«'
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| '‘'
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| '“'
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| '〈'
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| '《'
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| '「'
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| '『'
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| '【'
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| '〔'
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| '〖'
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| '〘'
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| '〚'
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| '〝'
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| '（'
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| '［'
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| '｛'
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| '｟'
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| '｢'
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)
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}
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/// Full-width punctuation for Japanese composition (JLREQ cl-01, cl-02, cl-06, cl-07).
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#[derive(Clone, Copy, Debug, PartialEq, Eq)]
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pub(crate) enum Punct {
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/// An opening bracket: its half-em space is before the mark.
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Opening,
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/// A closing bracket, comma or full stop: its half-em space is after the mark.
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Closing,
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}
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pub(crate) fn punct(c: char) -> Option<Punct> {
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match c {
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'（' | '「' | '『' | '【' | '〔' | '〈' | '《' | '［' | '｛' | '〘' | '〖' | '｟' | '〝' => Some(Punct::Opening),
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'）' | '」' | '』' | '】' | '〕' | '〉' | '》' | '］' | '｝' | '〙' | '〗' | '｠' | '〟' | '、' | '。' | '，' | '．' => {
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Some(Punct::Closing)
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}
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_ => None,
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}
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}
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pub(crate) fn is_cjk(c: char) -> bool {
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matches!(c as u32, 0x2E80..=0x9FFF | 0xAC00..=0xD7AF | 0xF900..=0xFAFF | 0xFF00..=0xFFEF | 0x20000..=0x2FFFF)
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}
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/// Vertical metrics (points) of a style's resolved face: (ascent, descent, leading).
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pub(crate) fn style_metrics(db: &FontDb, st: &CharStyle) -> (f64, f64, f64) {
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let vs = st.v_scale / 100.0;
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let Some(face) = db.face(&st.font_family, &st.font_style) else { return (st.size * 0.8 * vs, st.size * 0.2 * vs, st.effective_leading()) };
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let k = st.size / face.upem;
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(face.ascent * k * vs, face.descent * k * vs, st.effective_leading())
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}
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/// Cap height and x height (points) of a style's resolved face.
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pub(crate) fn cap_x_heights(db: &FontDb, st: &CharStyle) -> (f64, f64) {
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let vs = st.v_scale / 100.0;
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let Some(face) = db.face(&st.font_family, &st.font_style) else { return (st.size * 0.7 * vs, st.size * 0.5 * vs) };
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let k = st.size / face.upem * vs;
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(face.cap_height * k, face.x_height * k)
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}
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/// Shape `text[range]`, where `runs` gives each run's byte range in `text` and style, and `levels`
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/// each byte's bidi embedding level from `range.start` (empty: all left to right). Glyphs come out
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/// in logical order, right-to-left ones shaped right to left.
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pub(crate) fn shape_range(
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db: &FontDb,
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text: &str,
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range: Range<usize>,
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runs: &[(Range<usize>, &CharStyle)],
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feats: &OtFeatures,
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levels: &[Level],
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out: &mut Vec<SGlyph>,
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) {
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let level_at = |i: usize| levels.get(i - range.start).copied().unwrap_or_else(Level::ltr);
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let output_start = out.len();
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for (ri, (rr, st)) in runs.iter().enumerate() {
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let a = rr.start.max(range.start);
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let b = rr.end.min(range.end);
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if a >= b {
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continue;
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}
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let Some(primary) = db.face(&st.font_family, &st.font_style) else { continue };
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let pmap = primary.skrifa().map(|f| f.charmap());
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// Synthesized Small Caps shape lowercase letters separately (as smaller capitals).
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let small_caps = st.small_caps.is_some() && !st.all_caps;
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// Split into segments by font coverage (and case, for Small Caps).
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let mut seg = Segment { range: a..a, run: ri, st, face: primary.clone(), small: false, level: level_at(a) };
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let mut cache: Vec<(char, Arc<FontFace>)> = Vec::new();
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let mut script = Script::Common;
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for (i, c) in text[a..b].char_indices() {
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let i = a + i;
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let level = level_at(i);
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let covered = c.is_whitespace() || c.is_control() || pmap.as_ref().is_none_or(|m| m.map(c).is_some());
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let face = if covered {
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primary.clone()
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} else if let Some((_, f)) = cache.iter().find(|(k, _)| *k == c) {
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f.clone()
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} else {
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let f = db.fallback_for(c, primary.id()).unwrap_or_else(|| primary.clone());
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cache.push((c, f.clone()));
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f
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};
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let small = small_caps && c.is_lowercase();
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let next_script = shaping_script(c);
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let strong_script = !matches!(next_script, Script::Common | Script::Inherited);
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let script_change = strong_script && script != Script::Common && script != next_script;
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// Combining marks stay with their base.
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if (face.id() != seg.face.id() || small != seg.small || level != seg.level || script_change) && !is_mark(c) {
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if i > seg.range.start {
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seg.range.end = i;
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shape_segment(text, &seg, feats, out);
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}
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seg = Segment { range: i..i, face, small, level, ..seg };
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}
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if strong_script {
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script = next_script;
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}
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}
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if b > seg.range.start {
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seg.range.end = b;
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shape_segment(text, &seg, feats, out);
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}
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}
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// Right-to-left segments come out of the shaper in visual order: back to logical order for
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// line breaking (the lines are put in visual order once broken).
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if levels.iter().any(|l| l.is_rtl())
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&& let Some(o) = out.get_mut(output_start..)
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{
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o.sort_by_key(|g| g.byte);
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}
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}
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/// The script `c` is shaped in: Japanese and Chinese text mixes Han, Hiragana, Katakana and
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/// Bopomofo, shaped together (splitting them would cost a shaper call per change of script).
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fn shaping_script(c: char) -> Script {
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match c.script() {
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Script::Hiragana | Script::Katakana | Script::Bopomofo => Script::Han,
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s => s,
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}
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}
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/// A piece of one run shaped in one go: one face and, for Small Caps, one case.
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struct Segment<'a> {
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range: Range<usize>,
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run: usize,
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st: &'a CharStyle,
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face: Arc<FontFace>,
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/// Lowercase letters drawn as synthesized small capitals.
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small: bool,
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level: Level,
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}
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fn is_mark(c: char) -> bool {
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use unicode_general_category::{GeneralCategory, get_general_category};
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matches!(get_general_category(c), GeneralCategory::NonspacingMark | GeneralCategory::SpacingMark | GeneralCategory::EnclosingMark)
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|| matches!(c, '\u{200D}' | '\u{FE00}'..='\u{FE0F}')
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}
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fn shape_segment(text: &str, seg: &Segment, feats: &OtFeatures, out: &mut Vec<SGlyph>) {
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let Segment { range, run, st, face, small, level } = seg;
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let (range, run, small) = (range.clone(), *run, *small);
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let text_seg = &text[range.clone()];
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let full = st.size.max(0.0);
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// Superscript/subscript and small capitals shrink the glyphs; line metrics keep the full size.
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let (pos_scale, pos_shift) = st.position.scale_shift(full);
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let small_scale = if small { st.small_caps.unwrap_or(100.0) / 100.0 } else { 1.0 };
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let size = full * pos_scale * small_scale;
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let k = size / face.upem;
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let km = full / face.upem;
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let hs = st.h_scale / 100.0;
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let vs = st.v_scale / 100.0;
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let tracking = st.tracking / 1000.0 * size;
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let manual_kern = st.kerning.map(|v| v / 1000.0 * size).unwrap_or(0.0);
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let ascent = face.ascent * km * vs;
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let descent = face.descent * km * vs;
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let leading = st.effective_leading();
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let cap = face.cap_height * km * vs;
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let xh = face.x_height * km * vs;
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let upper = st.all_caps || small;
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let first_char = |byte: usize| text[byte..].chars().next().unwrap_or(' ');
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let mut raw: Vec<(u32, u32, i32, i32, i32)> = Vec::with_capacity(text_seg.len()); // gid, cluster, xadv, xoff, yoff
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let shaped = face.hb().map(|hb| {
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let shaper = face.shaper.shaper(&hb).instance(face.instance.as_ref()).build();
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let mut buf = UnicodeBuffer::new();
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for (i, c) in text_seg.char_indices() {
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let cl = (range.start + i) as u32;
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if upper {
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for u in c.to_uppercase() {
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buf.add(u, cl);
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}
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} else {
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buf.add(c, cl);
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}
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}
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buf.set_direction(if level.is_rtl() { Direction::RightToLeft } else { Direction::LeftToRight });
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buf.guess_segment_properties();
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let feats: Vec<Feature> = feats.resolve(st);
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let gb = shaper.shape(buf, ShapeOptions::new().features(&feats));
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for (info, pos) in gb.glyph_infos().iter().zip(gb.glyph_positions()) {
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raw.push((info.glyph_id, info.cluster, pos.x_advance, pos.x_offset, pos.y_offset));
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}
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});
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if shaped.is_none() {
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// Fallback: nominal glyphs and hmtx advances, no shaping.
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if let Some(f) = face.skrifa() {
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let cmap = f.charmap();
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let gm = f.glyph_metrics(Size::unscaled(), face.location());
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for (i, c) in text_seg.char_indices() {
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let cl = (range.start + i) as u32;
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let chars: Vec<char> = if upper { c.to_uppercase().collect() } else { vec![c] };
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for u in chars {
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let g = cmap.map(u).unwrap_or_default();
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let adv = gm.advance_width(g).unwrap_or(face.upem as f32 * 0.5);
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raw.push((g.to_u32(), cl, adv.round() as i32, 0, 0));
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}
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}
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}
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}
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let mut cluster_starts: Vec<usize> = raw.iter().map(|r| r.1 as usize).collect();
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cluster_starts.sort_unstable();
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cluster_starts.dedup();
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let n = raw.len();
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for (gi, &(gid, cl, xa, xo, yo)) in raw.iter().enumerate() {
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let cl = cl as usize;
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// Cluster end: the next larger cluster value in the segment, else the segment end.
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let end = cluster_starts.get(cluster_starts.partition_point(|&c| c <= cl)).copied().unwrap_or(range.end);
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let last_in_cluster = gi + 1 == n || raw[gi + 1].1 as usize != cl;
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let ch = first_char(cl);
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let mut adv = xa as f64 * k * hs;
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if ch == SOFT_HYPHEN {
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adv = 0.0;
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} else if last_in_cluster {
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adv += tracking + manual_kern;
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}
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out.push(SGlyph {
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face: face.clone(),
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gid,
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byte: cl,
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len: end.saturating_sub(cl).max(1),
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run,
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adv,
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dx: xo as f64 * k * hs,
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dy: -(yo as f64) * k * vs,
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sx: k * hs,
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sy: k * vs,
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bshift: st.baseline_shift + pos_shift,
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rotation: st.rotation,
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ascent,
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descent,
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leading,
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cap,
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xh,
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ch,
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tcy: None,
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lead: 0.0,
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level: *level,
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});
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}
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}
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