typst/src/library/text/par.rs

672 lines
22 KiB
Rust

use std::sync::Arc;
use either::Either;
use unicode_bidi::{BidiInfo, Level};
use xi_unicode::LineBreakIterator;
use super::{shape, ShapedText, TextNode};
use crate::font::FontStore;
use crate::library::layout::SpacingKind;
use crate::library::prelude::*;
use crate::util::{ArcExt, EcoString, RangeExt, SliceExt};
/// Arrange text, spacing and inline-level nodes into a paragraph.
#[derive(Hash)]
pub struct ParNode(pub StyleVec<ParChild>);
/// A uniformly styled atomic piece of a paragraph.
#[derive(Hash)]
pub enum ParChild {
/// A chunk of text.
Text(EcoString),
/// Horizontal spacing between other children.
Spacing(SpacingKind),
/// An arbitrary inline-level node.
Node(LayoutNode),
}
#[class]
impl ParNode {
/// An ISO 639-1 language code.
pub const LANG: Option<EcoString> = None;
/// The direction for text and inline objects.
pub const DIR: Dir = Dir::LTR;
/// How to align text and inline objects in their line.
pub const ALIGN: Align = Align::Left;
/// Whether to justify text in its line.
pub const JUSTIFY: bool = false;
/// Whether to hyphenate text to improve line breaking. When `auto`, words
/// will will be hyphenated if and only if justification is enabled.
pub const HYPHENATE: Smart<bool> = Smart::Auto;
/// The spacing between lines (dependent on scaled font size).
pub const LEADING: Linear = Relative::new(0.65).into();
/// The extra spacing between paragraphs (dependent on scaled font size).
pub const SPACING: Linear = Relative::new(0.55).into();
/// The indent the first line of a consecutive paragraph should have.
pub const INDENT: Linear = Linear::zero();
fn construct(_: &mut Context, args: &mut Args) -> TypResult<Template> {
// The paragraph constructor is special: It doesn't create a paragraph
// since that happens automatically through markup. Instead, it just
// lifts the passed body to the block level so that it won't merge with
// adjacent stuff and it styles the contained paragraphs.
Ok(Template::Block(args.expect("body")?))
}
fn set(args: &mut Args, styles: &mut StyleMap) -> TypResult<()> {
let lang = args.named::<Option<EcoString>>("lang")?;
let mut dir =
lang.clone().flatten().map(|iso| match iso.to_lowercase().as_str() {
"ar" | "dv" | "fa" | "he" | "ks" | "pa" | "ps" | "sd" | "ug" | "ur"
| "yi" => Dir::RTL,
_ => Dir::LTR,
});
if let Some(Spanned { v, span }) = args.named::<Spanned<Dir>>("dir")? {
if v.axis() != SpecAxis::Horizontal {
bail!(span, "must be horizontal");
}
dir = Some(v);
}
let align =
if let Some(Spanned { v, span }) = args.named::<Spanned<Align>>("align")? {
if v.axis() != SpecAxis::Horizontal {
bail!(span, "must be horizontal");
}
Some(v)
} else {
dir.map(|dir| dir.start().into())
};
styles.set_opt(Self::LANG, lang);
styles.set_opt(Self::DIR, dir);
styles.set_opt(Self::ALIGN, align);
styles.set_opt(Self::JUSTIFY, args.named("justify")?);
styles.set_opt(Self::HYPHENATE, args.named("hyphenate")?);
styles.set_opt(Self::LEADING, args.named("leading")?);
styles.set_opt(Self::SPACING, args.named("spacing")?);
styles.set_opt(Self::INDENT, args.named("indent")?);
Ok(())
}
}
impl ParNode {
/// Concatenate all text in the paragraph into one string, replacing spacing
/// with a space character and other non-text nodes with the object
/// replacement character.
fn collect_text(&self) -> String {
let mut text = String::new();
for string in self.strings() {
text.push_str(string);
}
text
}
/// The range of each item in the collected text.
fn ranges(&self) -> impl Iterator<Item = Range> + '_ {
let mut cursor = 0;
self.strings().map(move |string| {
let start = cursor;
cursor += string.len();
start .. cursor
})
}
/// The string representation of each child.
fn strings(&self) -> impl Iterator<Item = &str> {
self.0.items().map(|child| match child {
ParChild::Text(text) => text,
ParChild::Spacing(_) => " ",
ParChild::Node(_) => "\u{FFFC}",
})
}
}
impl Layout for ParNode {
fn layout(
&self,
ctx: &mut Context,
regions: &Regions,
styles: StyleChain,
) -> TypResult<Vec<Arc<Frame>>> {
// Collect all text into one string and perform BiDi analysis.
let text = self.collect_text();
let bidi = BidiInfo::new(&text, match styles.get(Self::DIR) {
Dir::LTR => Some(Level::ltr()),
Dir::RTL => Some(Level::rtl()),
_ => None,
});
// Prepare paragraph layout by building a representation on which we can
// do line breaking without layouting each and every line from scratch.
let par = ParLayout::new(ctx, self, bidi, regions, &styles)?;
// Break the paragraph into lines.
let lines = break_into_lines(&mut ctx.fonts, &par, regions.first.x, styles);
// Stack the lines into one frame per region.
Ok(stack_lines(&ctx.fonts, lines, regions, styles))
}
}
impl Debug for ParNode {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
f.write_str("Par ")?;
self.0.fmt(f)
}
}
impl Debug for ParChild {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
match self {
Self::Text(text) => write!(f, "Text({:?})", text),
Self::Spacing(kind) => write!(f, "{:?}", kind),
Self::Node(node) => node.fmt(f),
}
}
}
impl Merge for ParChild {
fn merge(&mut self, next: &Self) -> bool {
if let (Self::Text(left), Self::Text(right)) = (self, next) {
left.push_str(right);
true
} else {
false
}
}
}
/// A paragraph break.
pub struct ParbreakNode;
#[class]
impl ParbreakNode {
fn construct(_: &mut Context, _: &mut Args) -> TypResult<Template> {
Ok(Template::Parbreak)
}
}
/// A line break.
pub struct LinebreakNode;
#[class]
impl LinebreakNode {
fn construct(_: &mut Context, _: &mut Args) -> TypResult<Template> {
Ok(Template::Linebreak)
}
}
/// A paragraph representation in which children are already layouted and text
/// is already preshaped.
struct ParLayout<'a> {
/// Bidirectional text embedding levels for the paragraph.
bidi: BidiInfo<'a>,
/// Spacing, separated text runs and layouted nodes.
items: Vec<ParItem<'a>>,
/// The ranges of the items in `bidi.text`.
ranges: Vec<Range>,
}
/// Range of a substring of text.
type Range = std::ops::Range<usize>;
/// A prepared item in a paragraph layout.
enum ParItem<'a> {
/// Absolute spacing between other items.
Absolute(Length),
/// Fractional spacing between other items.
Fractional(Fractional),
/// A shaped text run with consistent direction.
Text(ShapedText<'a>),
/// A layouted child node.
Frame(Frame),
}
impl<'a> ParLayout<'a> {
/// Prepare initial shaped text and layouted children.
fn new(
ctx: &mut Context,
par: &'a ParNode,
bidi: BidiInfo<'a>,
regions: &Regions,
styles: &'a StyleChain<'a>,
) -> TypResult<Self> {
let mut items = vec![];
let mut ranges = vec![];
// Layout the children and collect them into items.
for (range, (child, map)) in par.ranges().zip(par.0.iter()) {
let styles = map.chain(styles);
match child {
ParChild::Text(_) => {
// TODO: Also split by language and script.
let mut cursor = range.start;
for (level, count) in bidi.levels[range].group() {
let start = cursor;
cursor += count;
let subrange = start .. cursor;
let text = &bidi.text[subrange.clone()];
let dir = if level.is_ltr() { Dir::LTR } else { Dir::RTL };
let shaped = shape(&mut ctx.fonts, text, styles, dir);
items.push(ParItem::Text(shaped));
ranges.push(subrange);
}
}
ParChild::Spacing(kind) => match *kind {
SpacingKind::Linear(v) => {
let resolved = v.resolve(regions.first.x);
items.push(ParItem::Absolute(resolved));
ranges.push(range);
}
SpacingKind::Fractional(v) => {
items.push(ParItem::Fractional(v));
ranges.push(range);
}
},
ParChild::Node(node) => {
let size = Size::new(regions.first.x, regions.base.y);
let pod = Regions::one(size, regions.base, Spec::splat(false));
let frame = node.layout(ctx, &pod, styles)?.remove(0);
items.push(ParItem::Frame(Arc::take(frame)));
ranges.push(range);
}
}
}
Ok(Self { bidi, items, ranges })
}
/// Create a line which spans the given range.
fn line(
&'a self,
fonts: &mut FontStore,
mut range: Range,
mandatory: bool,
hyphen: bool,
) -> LineLayout<'a> {
// Find the items which bound the text range.
let last_idx = self.find(range.end.saturating_sub(1)).unwrap();
let first_idx = if range.is_empty() {
last_idx
} else {
self.find(range.start).unwrap()
};
// Slice out the relevant items and ranges.
let mut items = &self.items[first_idx ..= last_idx];
let ranges = &self.ranges[first_idx ..= last_idx];
// Reshape the last item if it's split in half.
let mut last = None;
if let Some((ParItem::Text(shaped), rest)) = items.split_last() {
// Compute the range we want to shape, trimming whitespace at the
// end of the line.
let base = self.ranges[last_idx].start;
let start = range.start.max(base);
let end = start + self.bidi.text[start .. range.end].trim_end().len();
let shifted = start - base .. end - base;
// Reshape if necessary.
if shifted.len() < shaped.text.len() {
// If start == end and the rest is empty, then we have an empty
// line. To make that line have the appropriate height, we shape the
// empty string.
if !shifted.is_empty() || rest.is_empty() {
// Reshape that part.
let mut reshaped = shaped.reshape(fonts, shifted);
if hyphen {
reshaped.push_hyphen(fonts);
}
last = Some(ParItem::Text(reshaped));
}
items = rest;
range.end = end;
}
}
// Reshape the start item if it's split in half.
let mut first = None;
if let Some((ParItem::Text(shaped), rest)) = items.split_first() {
// Compute the range we want to shape.
let Range { start: base, end: first_end } = self.ranges[first_idx];
let start = range.start;
let end = range.end.min(first_end);
let shifted = start - base .. end - base;
// Reshape if necessary.
if shifted.len() < shaped.text.len() {
if !shifted.is_empty() {
let reshaped = shaped.reshape(fonts, shifted);
first = Some(ParItem::Text(reshaped));
}
items = rest;
}
}
let mut width = Length::zero();
let mut top = Length::zero();
let mut bottom = Length::zero();
let mut fr = Fractional::zero();
// Measure the size of the line.
for item in first.iter().chain(items).chain(&last) {
match item {
ParItem::Absolute(v) => width += *v,
ParItem::Fractional(v) => fr += *v,
ParItem::Text(shaped) => {
width += shaped.size.x;
top.set_max(shaped.baseline);
bottom.set_max(shaped.size.y - shaped.baseline);
}
ParItem::Frame(frame) => {
width += frame.size.x;
top.set_max(frame.baseline());
bottom.set_max(frame.size.y - frame.baseline());
}
}
}
LineLayout {
bidi: &self.bidi,
range,
first,
items,
last,
ranges,
size: Size::new(width, top + bottom),
baseline: top,
fr,
mandatory,
}
}
/// Find the index of the item whose range contains the `text_offset`.
fn find(&self, text_offset: usize) -> Option<usize> {
self.ranges.binary_search_by(|r| r.locate(text_offset)).ok()
}
}
/// A lightweight representation of a line that spans a specific range in a
/// paragraph's text. This type enables you to cheaply measure the size of a
/// line in a range before comitting to building the line's frame.
struct LineLayout<'a> {
/// Bidi information about the paragraph.
bidi: &'a BidiInfo<'a>,
/// The range the line spans in the paragraph.
range: Range,
/// A reshaped text item if the line sliced up a text item at the start.
first: Option<ParItem<'a>>,
/// Middle items which don't need to be reprocessed.
items: &'a [ParItem<'a>],
/// A reshaped text item if the line sliced up a text item at the end. If
/// there is only one text item, this takes precedence over `first`.
last: Option<ParItem<'a>>,
/// The ranges, indexed as `[first, ..items, last]`. The ranges for `first`
/// and `last` aren't trimmed to the line, but it doesn't matter because
/// we're just checking which range an index falls into.
ranges: &'a [Range],
/// The size of the line.
size: Size,
/// The baseline of the line.
baseline: Length,
/// The sum of fractional ratios in the line.
fr: Fractional,
/// Whether the line ends at a mandatory break.
mandatory: bool,
}
impl<'a> LineLayout<'a> {
/// Build the line's frame.
fn build(
&self,
fonts: &FontStore,
width: Length,
align: Align,
justify: bool,
) -> Frame {
let size = Size::new(width, self.size.y);
let mut remaining = width - self.size.x;
let mut offset = Length::zero();
let mut output = Frame::new(size);
output.baseline = Some(self.baseline);
let mut justification = Length::zero();
if justify
&& !self.mandatory
&& self.range.end < self.bidi.text.len()
&& self.fr.is_zero()
{
justification = remaining / self.spaces() as f64;
remaining = Length::zero();
}
for item in self.reordered() {
let mut position = |frame: Frame| {
let x = offset + align.resolve(remaining);
let y = self.baseline - frame.baseline();
offset += frame.size.x;
output.merge_frame(Point::new(x, y), frame);
};
match item {
ParItem::Absolute(v) => offset += *v,
ParItem::Fractional(v) => offset += v.resolve(self.fr, remaining),
ParItem::Text(shaped) => position(shaped.build(fonts, justification)),
ParItem::Frame(frame) => position(frame.clone()),
}
}
output
}
/// The number of spaces in the line.
fn spaces(&self) -> usize {
self.shapeds().map(ShapedText::spaces).sum()
}
/// Iterate through the line's items in visual order.
fn reordered(&self) -> impl Iterator<Item = &ParItem<'a>> {
// The bidi crate doesn't like empty lines.
let (levels, runs) = if !self.range.is_empty() {
// Find the paragraph that contains the line.
let para = self
.bidi
.paragraphs
.iter()
.find(|para| para.range.contains(&self.range.start))
.unwrap();
// Compute the reordered ranges in visual order (left to right).
self.bidi.visual_runs(para, self.range.clone())
} else {
(vec![], vec![])
};
runs.into_iter()
.flat_map(move |run| {
let first_idx = self.find(run.start).unwrap();
let last_idx = self.find(run.end - 1).unwrap();
let range = first_idx ..= last_idx;
// Provide the items forwards or backwards depending on the run's
// direction.
if levels[run.start].is_ltr() {
Either::Left(range)
} else {
Either::Right(range.rev())
}
})
.map(move |idx| self.get(idx).unwrap())
}
/// Iterate over the line's items.
fn items(&self) -> impl Iterator<Item = &ParItem<'a>> {
self.first.iter().chain(self.items).chain(&self.last)
}
/// Iterate through the line's text items.
fn shapeds(&self) -> impl Iterator<Item = &ShapedText<'a>> {
self.items().filter_map(|item| match item {
ParItem::Text(shaped) => Some(shaped),
_ => None,
})
}
/// Find the index of the item whose range contains the `text_offset`.
fn find(&self, text_offset: usize) -> Option<usize> {
self.ranges.binary_search_by(|r| r.locate(text_offset)).ok()
}
/// Get the item at the index.
fn get(&self, index: usize) -> Option<&ParItem<'a>> {
self.items().nth(index)
}
}
/// Perform line breaking.
fn break_into_lines<'a>(
fonts: &mut FontStore,
par: &'a ParLayout<'a>,
width: Length,
styles: StyleChain,
) -> Vec<LineLayout<'a>> {
// The already determined lines and the current line attempt.
let mut lines = vec![];
let mut start = 0;
let mut last = None;
// Find suitable line breaks.
for (end, mandatory, hyphen) in breakpoints(&par.bidi.text, styles) {
// Compute the line and its size.
let mut line = par.line(fonts, start .. end, mandatory, hyphen);
// If the line doesn't fit anymore, we push the last fitting attempt
// into the stack and rebuild the line from its end. The resulting
// line cannot be broken up further.
if !width.fits(line.size.x) {
if let Some((last_line, last_end)) = last.take() {
lines.push(last_line);
start = last_end;
line = par.line(fonts, start .. end, mandatory, hyphen);
}
}
// Finish the current line if there is a mandatory line break (i.e.
// due to "\n") or if the line doesn't fit horizontally already
// since then no shorter line will be possible.
if mandatory || !width.fits(line.size.x) {
lines.push(line);
start = end;
last = None;
} else {
last = Some((line, end));
}
}
if let Some((line, _)) = last {
lines.push(line);
}
lines
}
/// Determine all possible points in the text where lines can broken.
fn breakpoints<'a>(
text: &'a str,
styles: StyleChain,
) -> impl Iterator<Item = (usize, bool, bool)> + 'a {
let mut lang = None;
if styles.get(ParNode::HYPHENATE).unwrap_or(styles.get(ParNode::JUSTIFY)) {
lang = styles
.get_ref(ParNode::LANG)
.as_ref()
.and_then(|iso| iso.as_bytes().try_into().ok())
.and_then(hypher::Lang::from_iso);
}
let breaks = LineBreakIterator::new(text);
let mut last = 0;
if let Some(lang) = lang {
Either::Left(breaks.flat_map(move |(end, mandatory)| {
let word = &text[last .. end];
let trimmed = word.trim_end_matches(|c: char| !c.is_alphabetic());
let suffix = last + trimmed.len();
let mut start = std::mem::replace(&mut last, end);
if trimmed.is_empty() {
Either::Left([(end, mandatory, false)].into_iter())
} else {
Either::Right(hypher::hyphenate(trimmed, lang).map(move |syllable| {
start += syllable.len();
if start == suffix {
start = end;
}
let hyphen = start < end;
(start, mandatory && !hyphen, hyphen)
}))
}
}))
} else {
Either::Right(breaks.map(|(e, m)| (e, m, false)))
}
}
/// Combine the lines into one frame per region.
fn stack_lines(
fonts: &FontStore,
lines: Vec<LineLayout>,
regions: &Regions,
styles: StyleChain,
) -> Vec<Arc<Frame>> {
let em = styles.get(TextNode::SIZE).abs;
let leading = styles.get(ParNode::LEADING).resolve(em);
let align = styles.get(ParNode::ALIGN);
let justify = styles.get(ParNode::JUSTIFY);
// Determine the paragraph's width: Full width of the region if we
// should expand or there's fractional spacing, fit-to-width otherwise.
let mut width = regions.first.x;
if !regions.expand.x && lines.iter().all(|line| line.fr.is_zero()) {
width = lines.iter().map(|line| line.size.x).max().unwrap_or_default();
}
// State for final frame building.
let mut regions = regions.clone();
let mut finished = vec![];
let mut first = true;
let mut output = Frame::new(Size::with_x(width));
// Stack the lines into one frame per region.
for line in lines {
while !regions.first.y.fits(line.size.y) && !regions.in_last() {
finished.push(Arc::new(output));
output = Frame::new(Size::with_x(width));
regions.next();
first = true;
}
if !first {
output.size.y += leading;
}
let frame = line.build(fonts, width, align, justify);
let pos = Point::with_y(output.size.y);
output.size.y += frame.size.y;
output.merge_frame(pos, frame);
regions.first.y -= line.size.y + leading;
first = false;
}
finished.push(Arc::new(output));
finished
}