mirror of
https://github.com/typst/typst
synced 2025-05-14 04:56:26 +08:00
1167 lines
37 KiB
Rust
1167 lines
37 KiB
Rust
use std::sync::Arc;
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use unicode_bidi::{BidiInfo, Level};
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use unicode_script::{Script, UnicodeScript};
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use xi_unicode::LineBreakIterator;
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use super::{shape, Lang, Quoter, Quotes, ShapedText, TextNode};
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use crate::font::FontStore;
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use crate::library::layout::Spacing;
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use crate::library::prelude::*;
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use crate::util::{ArcExt, EcoString};
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/// Arrange text, spacing and inline-level nodes into a paragraph.
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#[derive(Hash)]
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pub struct ParNode(pub StyleVec<ParChild>);
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/// A uniformly styled atomic piece of a paragraph.
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#[derive(Hash)]
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pub enum ParChild {
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/// A chunk of text.
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Text(EcoString),
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/// A smart quote, may be single (`false`) or double (`true`).
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Quote(bool),
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/// Horizontal spacing between other children.
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Spacing(Spacing),
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/// An arbitrary inline-level node.
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Node(LayoutNode),
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}
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#[node]
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impl ParNode {
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/// The spacing between lines.
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#[property(resolve)]
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pub const LEADING: RawLength = Em::new(0.65).into();
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/// The extra spacing between paragraphs.
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#[property(resolve)]
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pub const SPACING: RawLength = Em::new(0.55).into();
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/// The indent the first line of a consecutive paragraph should have.
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#[property(resolve)]
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pub const INDENT: RawLength = RawLength::zero();
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/// How to align text and inline objects in their line.
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#[property(resolve)]
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pub const ALIGN: HorizontalAlign = HorizontalAlign(RawAlign::Start);
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/// Whether to justify text in its line.
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pub const JUSTIFY: bool = false;
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/// How to determine line breaks.
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#[property(resolve)]
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pub const LINEBREAKS: Smart<Linebreaks> = Smart::Auto;
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fn construct(_: &mut Context, args: &mut Args) -> TypResult<Content> {
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// The paragraph constructor is special: It doesn't create a paragraph
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// since that happens automatically through markup. Instead, it just
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// lifts the passed body to the block level so that it won't merge with
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// adjacent stuff and it styles the contained paragraphs.
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Ok(Content::Block(args.expect("body")?))
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}
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}
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impl Layout for ParNode {
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fn layout(
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&self,
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ctx: &mut Context,
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regions: &Regions,
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styles: StyleChain,
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) -> TypResult<Vec<Arc<Frame>>> {
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// Collect all text into one string for BiDi analysis.
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let (text, segments) = collect(self, &styles);
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// Perform BiDi analysis and then prepare paragraph layout by building a
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// representation on which we can do line breaking without layouting
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// each and every line from scratch.
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let p = prepare(ctx, self, &text, segments, regions, styles)?;
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// Break the paragraph into lines.
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let lines = linebreak(&p, &mut ctx.fonts, regions.first.x);
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// Stack the lines into one frame per region.
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Ok(stack(&lines, &mut ctx.fonts, regions, styles))
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}
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}
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impl Debug for ParNode {
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fn fmt(&self, f: &mut Formatter) -> fmt::Result {
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f.write_str("Par ")?;
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self.0.fmt(f)
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}
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}
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impl Debug for ParChild {
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fn fmt(&self, f: &mut Formatter) -> fmt::Result {
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match self {
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Self::Text(text) => write!(f, "Text({:?})", text),
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Self::Quote(double) => write!(f, "Quote({})", double),
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Self::Spacing(kind) => write!(f, "{:?}", kind),
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Self::Node(node) => node.fmt(f),
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}
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}
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}
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/// A horizontal alignment.
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#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
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pub struct HorizontalAlign(pub RawAlign);
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castable! {
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HorizontalAlign,
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Expected: "alignment",
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@align: RawAlign => match align.axis() {
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SpecAxis::Horizontal => Self(*align),
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SpecAxis::Vertical => Err("must be horizontal")?,
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},
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}
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impl Resolve for HorizontalAlign {
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type Output = Align;
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fn resolve(self, styles: StyleChain) -> Self::Output {
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self.0.resolve(styles)
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}
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}
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/// How to determine line breaks in a paragraph.
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#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
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pub enum Linebreaks {
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/// Determine the linebreaks in a simple first-fit style.
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Simple,
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/// Optimize the linebreaks for the whole paragraph.
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Optimized,
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}
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castable! {
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Linebreaks,
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Expected: "string",
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Value::Str(string) => match string.as_str() {
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"simple" => Self::Simple,
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"optimized" => Self::Optimized,
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_ => Err(r#"expected "simple" or "optimized""#)?,
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},
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}
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impl Resolve for Smart<Linebreaks> {
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type Output = Linebreaks;
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fn resolve(self, styles: StyleChain) -> Self::Output {
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self.unwrap_or_else(|| {
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if styles.get(ParNode::JUSTIFY) {
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Linebreaks::Optimized
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} else {
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Linebreaks::Simple
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}
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})
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}
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}
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/// A paragraph break.
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pub struct ParbreakNode;
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#[node]
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impl ParbreakNode {
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fn construct(_: &mut Context, _: &mut Args) -> TypResult<Content> {
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Ok(Content::Parbreak)
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}
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}
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/// A line break.
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pub struct LinebreakNode;
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#[node]
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impl LinebreakNode {
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fn construct(_: &mut Context, args: &mut Args) -> TypResult<Content> {
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let soft = args.named("soft")?.unwrap_or(false);
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Ok(Content::Linebreak(soft))
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}
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}
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/// Range of a substring of text.
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type Range = std::ops::Range<usize>;
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// The characters by which spacing and nodes are replaced in the paragraph's
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// full text.
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const SPACING_REPLACE: char = ' ';
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const NODE_REPLACE: char = '\u{FFFC}';
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/// A paragraph representation in which children are already layouted and text
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/// is already preshaped.
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///
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/// In many cases, we can directly reuse these results when constructing a line.
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/// Only when a line break falls onto a text index that is not safe-to-break per
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/// rustybuzz, we have to reshape that portion.
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struct Preparation<'a> {
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/// Bidirectional text embedding levels for the paragraph.
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bidi: BidiInfo<'a>,
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/// Text runs, spacing and layouted nodes.
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items: Vec<Item<'a>>,
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/// The styles shared by all children.
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styles: StyleChain<'a>,
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/// The paragraph's children.
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children: &'a StyleVec<ParChild>,
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}
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impl<'a> Preparation<'a> {
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/// Find the item which is at the `text_offset`.
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fn find(&self, text_offset: usize) -> Option<&Item<'a>> {
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self.find_idx_and_offset(text_offset).map(|(idx, _)| &self.items[idx])
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}
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/// Find the index and text offset of the item which is at the
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/// `text_offset`.
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fn find_idx_and_offset(&self, text_offset: usize) -> Option<(usize, usize)> {
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let mut cursor = 0;
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for (idx, item) in self.items.iter().enumerate() {
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let end = cursor + item.len();
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if (cursor .. end).contains(&text_offset) {
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return Some((idx, cursor));
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}
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cursor = end;
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}
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None
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}
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/// Get a style property, but only if it is the same for all children of the
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/// paragraph.
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fn get_shared<K: Key<'a>>(&self, key: K) -> Option<K::Output> {
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self.children
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.maps()
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.all(|map| !map.contains(key))
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.then(|| self.styles.get(key))
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}
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}
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/// A segment of one or multiple collapsed children.
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#[derive(Debug, Copy, Clone)]
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enum Segment<'a> {
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/// One or multiple collapsed text or text-equivalent children. Stores how
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/// long the segment is (in bytes of the full text string).
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Text(usize),
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/// Horizontal spacing between other segments.
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Spacing(Spacing),
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/// An arbitrary inline-level layout node.
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Node(&'a LayoutNode),
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}
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impl Segment<'_> {
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/// The text length of the item.
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fn len(&self) -> usize {
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match *self {
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Self::Text(len) => len,
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Self::Spacing(_) => SPACING_REPLACE.len_utf8(),
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Self::Node(_) => NODE_REPLACE.len_utf8(),
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}
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}
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}
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/// A prepared item in a paragraph layout.
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#[derive(Debug)]
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enum Item<'a> {
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/// A shaped text run with consistent direction.
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Text(ShapedText<'a>),
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/// Absolute spacing between other items.
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Absolute(Length),
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/// Fractional spacing between other items.
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Fractional(Fraction),
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/// A layouted child node.
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Frame(Frame),
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}
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impl<'a> Item<'a> {
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/// If this a text item, return it.
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fn text(&self) -> Option<&ShapedText<'a>> {
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match self {
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Self::Text(shaped) => Some(shaped),
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_ => None,
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}
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}
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/// The text length of the item.
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fn len(&self) -> usize {
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match self {
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Self::Text(shaped) => shaped.text.len(),
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Self::Absolute(_) | Self::Fractional(_) => SPACING_REPLACE.len_utf8(),
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Self::Frame(_) => NODE_REPLACE.len_utf8(),
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}
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}
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/// The natural width of the item.
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fn width(&self) -> Length {
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match self {
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Item::Text(shaped) => shaped.width,
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Item::Absolute(v) => *v,
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Item::Fractional(_) => Length::zero(),
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Item::Frame(frame) => frame.size.x,
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}
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}
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}
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/// A layouted line, consisting of a sequence of layouted paragraph items that
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/// are mostly borrowed from the preparation phase. This type enables you to
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/// measure the size of a line in a range before comitting to building the
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/// line's frame.
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///
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/// At most two paragraph items must be created individually for this line: The
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/// first and last one since they may be broken apart by the start or end of the
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/// line, respectively. But even those can partially reuse previous results when
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/// the break index is safe-to-break per rustybuzz.
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struct Line<'a> {
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/// Bidi information about the paragraph.
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bidi: &'a BidiInfo<'a>,
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/// The (untrimmed) range the line spans in the paragraph.
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range: Range,
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/// A reshaped text item if the line sliced up a text item at the start.
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first: Option<Item<'a>>,
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/// Middle items which don't need to be reprocessed.
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items: &'a [Item<'a>],
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/// A reshaped text item if the line sliced up a text item at the end. If
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/// there is only one text item, this takes precedence over `first`.
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last: Option<Item<'a>>,
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/// The width of the line.
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width: Length,
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/// Whether the line is allowed to be justified.
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justify: bool,
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/// Whether the line ends with a hyphen or dash, either naturally or through
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/// hyphenation.
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dash: bool,
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}
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impl<'a> Line<'a> {
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/// Iterate over the line's items.
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fn items(&self) -> impl Iterator<Item = &Item<'a>> {
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self.first.iter().chain(self.items).chain(&self.last)
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}
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/// Get the item at the index.
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fn get(&self, index: usize) -> Option<&Item<'a>> {
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self.items().nth(index)
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}
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/// Find the index of the item whose range contains the `text_offset`.
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fn find(&self, text_offset: usize) -> usize {
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let mut idx = 0;
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let mut cursor = self.range.start;
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for item in self.items() {
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let end = cursor + item.len();
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if (cursor .. end).contains(&text_offset) {
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return idx;
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}
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cursor = end;
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idx += 1;
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}
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idx.saturating_sub(1)
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}
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// How many justifiable glyphs the line contains.
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fn justifiables(&self) -> usize {
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let mut count = 0;
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for shaped in self.items().filter_map(Item::text) {
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count += shaped.justifiables();
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}
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count
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}
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/// How much of the line is stretchable spaces.
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fn stretch(&self) -> Length {
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let mut stretch = Length::zero();
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for shaped in self.items().filter_map(Item::text) {
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stretch += shaped.stretch();
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}
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stretch
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}
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/// The sum of fractions in the line.
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fn fr(&self) -> Fraction {
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self.items()
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.filter_map(|item| match item {
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Item::Fractional(fr) => Some(*fr),
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_ => None,
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})
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.sum()
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}
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}
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/// Collect all text of the paragraph into one string. This also performs
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/// string-level preprocessing like case transformations.
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fn collect<'a>(
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par: &'a ParNode,
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styles: &'a StyleChain<'a>,
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) -> (String, Vec<(Segment<'a>, StyleChain<'a>)>) {
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let mut full = String::new();
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let mut quoter = Quoter::new();
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let mut segments = vec![];
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let mut iter = par.0.iter().peekable();
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while let Some((child, map)) = iter.next() {
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let styles = map.chain(&styles);
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let segment = match child {
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ParChild::Text(text) => {
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let prev = full.len();
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if let Some(case) = styles.get(TextNode::CASE) {
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full.push_str(&case.apply(text));
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} else {
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full.push_str(text);
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}
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Segment::Text(full.len() - prev)
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}
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ParChild::Quote(double) => {
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let prev = full.len();
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if styles.get(TextNode::SMART_QUOTES) {
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// TODO: Also get region.
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let lang = styles.get(TextNode::LANG);
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let quotes = lang
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.as_ref()
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.map(|lang| Quotes::from_lang(lang.as_str(), ""))
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.unwrap_or_default();
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let peeked = iter.peek().and_then(|(child, _)| match child {
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ParChild::Text(text) => text.chars().next(),
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ParChild::Quote(_) => Some('"'),
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ParChild::Spacing(_) => Some(SPACING_REPLACE),
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ParChild::Node(_) => Some(NODE_REPLACE),
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});
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full.push_str(quoter.quote("es, *double, peeked));
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} else {
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full.push(if *double { '"' } else { '\'' });
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}
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Segment::Text(full.len() - prev)
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}
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ParChild::Spacing(spacing) => {
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full.push(SPACING_REPLACE);
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Segment::Spacing(*spacing)
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}
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ParChild::Node(node) => {
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full.push(NODE_REPLACE);
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Segment::Node(node)
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}
|
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};
|
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if let Some(last) = full.chars().last() {
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quoter.last(last);
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}
|
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|
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if let (Some((Segment::Text(last_len), last_styles)), Segment::Text(len)) =
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(segments.last_mut(), segment)
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{
|
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if *last_styles == styles {
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*last_len += len;
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continue;
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}
|
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}
|
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|
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segments.push((segment, styles));
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}
|
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|
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(full, segments)
|
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}
|
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|
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/// Prepare paragraph layout by shaping the whole paragraph and layouting all
|
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/// contained inline-level nodes.
|
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fn prepare<'a>(
|
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ctx: &mut Context,
|
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par: &'a ParNode,
|
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text: &'a str,
|
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segments: Vec<(Segment<'a>, StyleChain<'a>)>,
|
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regions: &Regions,
|
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styles: StyleChain<'a>,
|
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) -> TypResult<Preparation<'a>> {
|
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let bidi = BidiInfo::new(&text, match styles.get(TextNode::DIR) {
|
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Dir::LTR => Some(Level::ltr()),
|
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Dir::RTL => Some(Level::rtl()),
|
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_ => None,
|
||
});
|
||
|
||
let mut cursor = 0;
|
||
let mut items = vec![];
|
||
|
||
// Layout the children and collect them into items.
|
||
for (segment, styles) in segments {
|
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let end = cursor + segment.len();
|
||
match segment {
|
||
Segment::Text(_) => {
|
||
let mut process = |text, level: Level| {
|
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let dir = if level.is_ltr() { Dir::LTR } else { Dir::RTL };
|
||
let shaped = shape(&mut ctx.fonts, text, styles, dir);
|
||
items.push(Item::Text(shaped));
|
||
};
|
||
|
||
let mut prev_level = Level::ltr();
|
||
let mut prev_script = Script::Unknown;
|
||
|
||
// Group by embedding level and script.
|
||
for i in cursor .. end {
|
||
if !text.is_char_boundary(i) {
|
||
continue;
|
||
}
|
||
|
||
let level = bidi.levels[i];
|
||
let script =
|
||
text[i ..].chars().next().map_or(Script::Unknown, |c| c.script());
|
||
|
||
if level != prev_level || !is_compatible(script, prev_script) {
|
||
if cursor < i {
|
||
process(&text[cursor .. i], prev_level);
|
||
}
|
||
cursor = i;
|
||
prev_level = level;
|
||
prev_script = script;
|
||
} else if is_generic_script(prev_script) {
|
||
prev_script = script;
|
||
}
|
||
}
|
||
|
||
process(&text[cursor .. end], prev_level);
|
||
}
|
||
Segment::Spacing(spacing) => match spacing {
|
||
Spacing::Relative(v) => {
|
||
let resolved = v.resolve(styles).relative_to(regions.base.x);
|
||
items.push(Item::Absolute(resolved));
|
||
}
|
||
Spacing::Fractional(v) => {
|
||
items.push(Item::Fractional(v));
|
||
}
|
||
},
|
||
Segment::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(Item::Frame(Arc::take(frame)));
|
||
}
|
||
}
|
||
|
||
cursor = end;
|
||
}
|
||
|
||
Ok(Preparation { bidi, items, styles, children: &par.0 })
|
||
}
|
||
|
||
/// Whether this is not a specific script.
|
||
fn is_generic_script(script: Script) -> bool {
|
||
matches!(script, Script::Unknown | Script::Common | Script::Inherited)
|
||
}
|
||
|
||
/// Whether these script can be part of the same shape run.
|
||
fn is_compatible(a: Script, b: Script) -> bool {
|
||
is_generic_script(a) || is_generic_script(b) || a == b
|
||
}
|
||
|
||
/// Find suitable linebreaks.
|
||
fn linebreak<'a>(
|
||
p: &'a Preparation<'a>,
|
||
fonts: &mut FontStore,
|
||
width: Length,
|
||
) -> Vec<Line<'a>> {
|
||
match p.styles.get(ParNode::LINEBREAKS) {
|
||
Linebreaks::Simple => linebreak_simple(p, fonts, width),
|
||
Linebreaks::Optimized => linebreak_optimized(p, fonts, width),
|
||
}
|
||
}
|
||
|
||
/// Perform line breaking in simple first-fit style. This means that we build
|
||
/// lines a greedily, always taking the longest possible line. This may lead to
|
||
/// very unbalanced line, but is fast and simple.
|
||
fn linebreak_simple<'a>(
|
||
p: &'a Preparation<'a>,
|
||
fonts: &mut FontStore,
|
||
width: Length,
|
||
) -> Vec<Line<'a>> {
|
||
let mut lines = vec![];
|
||
let mut start = 0;
|
||
let mut last = None;
|
||
|
||
for (end, mandatory, hyphen) in breakpoints(p) {
|
||
// Compute the line and its size.
|
||
let mut attempt = line(p, 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(attempt.width) {
|
||
if let Some((last_attempt, last_end)) = last.take() {
|
||
lines.push(last_attempt);
|
||
start = last_end;
|
||
attempt = line(p, 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(attempt.width) {
|
||
lines.push(attempt);
|
||
start = end;
|
||
last = None;
|
||
} else {
|
||
last = Some((attempt, end));
|
||
}
|
||
}
|
||
|
||
if let Some((line, _)) = last {
|
||
lines.push(line);
|
||
}
|
||
|
||
lines
|
||
}
|
||
|
||
/// Perform line breaking in optimized Knuth-Plass style. Here, we use more
|
||
/// context to determine the line breaks than in the simple first-fit style. For
|
||
/// example, we might choose to cut a line short even though there is still a
|
||
/// bit of space to improve the fit of one of the following lines. The
|
||
/// Knuth-Plass algorithm is based on the idea of "cost". A line which has a
|
||
/// very tight or very loose fit has a higher cost than one that is just right.
|
||
/// Ending a line with a hyphen incurs extra cost and endings two successive
|
||
/// lines with hyphens even more.
|
||
///
|
||
/// To find the layout with the minimal total cost the algorithm uses dynamic
|
||
/// programming: For each possible breakpoint it determines the optimal
|
||
/// paragraph layout _up to that point_. It walks over all possible start points
|
||
/// for a line ending at that point and finds the one for which the cost of the
|
||
/// line plus the cost of the optimal paragraph up to the start point (already
|
||
/// computed and stored in dynamic programming table) is minimal. The final
|
||
/// result is simply the layout determined for the last breakpoint at the end of
|
||
/// text.
|
||
fn linebreak_optimized<'a>(
|
||
p: &'a Preparation<'a>,
|
||
fonts: &mut FontStore,
|
||
width: Length,
|
||
) -> Vec<Line<'a>> {
|
||
/// The cost of a line or paragraph layout.
|
||
type Cost = f64;
|
||
|
||
/// An entry in the dynamic programming table.
|
||
struct Entry<'a> {
|
||
pred: usize,
|
||
total: Cost,
|
||
line: Line<'a>,
|
||
}
|
||
|
||
// Cost parameters.
|
||
const HYPH_COST: Cost = 0.5;
|
||
const CONSECUTIVE_DASH_COST: Cost = 30.0;
|
||
const MAX_COST: Cost = 1_000_000.0;
|
||
const MIN_COST: Cost = -MAX_COST;
|
||
const MIN_RATIO: f64 = -0.15;
|
||
|
||
let em = p.styles.get(TextNode::SIZE);
|
||
let justify = p.styles.get(ParNode::JUSTIFY);
|
||
|
||
// Dynamic programming table.
|
||
let mut active = 0;
|
||
let mut table = vec![Entry {
|
||
pred: 0,
|
||
total: 0.0,
|
||
line: line(p, fonts, 0 .. 0, false, false),
|
||
}];
|
||
|
||
for (end, mandatory, hyphen) in breakpoints(p) {
|
||
let k = table.len();
|
||
let eof = end == p.bidi.text.len();
|
||
let mut best: Option<Entry> = None;
|
||
|
||
// Find the optimal predecessor.
|
||
for (i, pred) in table.iter_mut().enumerate().skip(active) {
|
||
// Layout the line.
|
||
let start = pred.line.range.end;
|
||
let attempt = line(p, fonts, start .. end, mandatory, hyphen);
|
||
|
||
// Determine how much the line's spaces would need to be stretched
|
||
// to make it the desired width.
|
||
let delta = width - attempt.width;
|
||
let mut ratio = delta / attempt.stretch();
|
||
if ratio.is_infinite() {
|
||
ratio = delta / (em / 2.0);
|
||
}
|
||
|
||
// At some point, it doesn't matter any more.
|
||
ratio = ratio.min(10.0);
|
||
|
||
// Determine the cost of the line.
|
||
let mut cost = if ratio < if justify { MIN_RATIO } else { 0.0 } {
|
||
// The line is overfull. This is the case if
|
||
// - justification is on, but we'd need to shrink to much
|
||
// - justification is off and the line just doesn't fit
|
||
// Since any longer line will also be overfull, we can deactive
|
||
// this breakpoint.
|
||
active = i + 1;
|
||
MAX_COST
|
||
} else if eof {
|
||
// This is the final line and its not overfull since then
|
||
// we would have taken the above branch.
|
||
0.0
|
||
} else if mandatory {
|
||
// This is a mandatory break and the line is not overfull, so it
|
||
// has minimum cost. All breakpoints before this one become
|
||
// inactive since no line can span above the mandatory break.
|
||
active = k;
|
||
MIN_COST
|
||
} else {
|
||
// Normal line with cost of |ratio^3|.
|
||
ratio.powi(3).abs()
|
||
};
|
||
|
||
// Penalize hyphens.
|
||
if hyphen {
|
||
cost += HYPH_COST;
|
||
}
|
||
|
||
// Penalize two consecutive dashes (not necessarily hyphens) extra.
|
||
if attempt.dash && pred.line.dash {
|
||
cost += CONSECUTIVE_DASH_COST;
|
||
}
|
||
|
||
// The total cost of this line and its chain of predecessors.
|
||
let total = pred.total + cost;
|
||
|
||
// If this attempt is better than what we had before, take it!
|
||
if best.as_ref().map_or(true, |best| best.total >= total) {
|
||
best = Some(Entry { pred: i, total, line: attempt });
|
||
}
|
||
}
|
||
|
||
table.push(best.unwrap());
|
||
}
|
||
|
||
// Retrace the best path.
|
||
let mut lines = vec![];
|
||
let mut idx = table.len() - 1;
|
||
while idx != 0 {
|
||
table.truncate(idx + 1);
|
||
let entry = table.pop().unwrap();
|
||
lines.push(entry.line);
|
||
idx = entry.pred;
|
||
}
|
||
|
||
lines.reverse();
|
||
lines
|
||
}
|
||
|
||
/// Determine all possible points in the text where lines can broken.
|
||
///
|
||
/// Returns for each breakpoint the text index, whether the break is mandatory
|
||
/// (after `\n`) and whether a hyphen is required (when breaking inside of a
|
||
/// word).
|
||
fn breakpoints<'a>(p: &'a Preparation) -> Breakpoints<'a> {
|
||
Breakpoints {
|
||
p,
|
||
linebreaks: LineBreakIterator::new(p.bidi.text),
|
||
syllables: None,
|
||
offset: 0,
|
||
suffix: 0,
|
||
end: 0,
|
||
mandatory: false,
|
||
hyphenate: p.get_shared(TextNode::HYPHENATE),
|
||
lang: p.get_shared(TextNode::LANG).map(Option::as_ref),
|
||
}
|
||
}
|
||
|
||
/// An iterator over the line break opportunities in a text.
|
||
struct Breakpoints<'a> {
|
||
/// The paragraph's items.
|
||
p: &'a Preparation<'a>,
|
||
/// The inner iterator over the unicode line break opportunities.
|
||
linebreaks: LineBreakIterator<'a>,
|
||
/// Iterator over syllables of the current word.
|
||
syllables: Option<hypher::Syllables<'a>>,
|
||
/// The current text offset.
|
||
offset: usize,
|
||
/// The trimmed end of the current word.
|
||
suffix: usize,
|
||
/// The untrimmed end of the current word.
|
||
end: usize,
|
||
/// Whether the break after the current word is mandatory.
|
||
mandatory: bool,
|
||
/// Whether to hyphenate if it's the same for all children.
|
||
hyphenate: Option<bool>,
|
||
/// The text language if it's the same for all children.
|
||
lang: Option<Option<&'a Lang>>,
|
||
}
|
||
|
||
impl Iterator for Breakpoints<'_> {
|
||
type Item = (usize, bool, bool);
|
||
|
||
fn next(&mut self) -> Option<Self::Item> {
|
||
// If we're currently in a hyphenated "word", process the next syllable.
|
||
if let Some(syllable) = self.syllables.as_mut().and_then(Iterator::next) {
|
||
self.offset += syllable.len();
|
||
if self.offset == self.suffix {
|
||
self.offset = self.end;
|
||
}
|
||
|
||
// Filter out hyphenation opportunities where hyphenation was
|
||
// actually disabled.
|
||
let hyphen = self.offset < self.end;
|
||
if hyphen && !self.hyphenate_at(self.offset) {
|
||
return self.next();
|
||
}
|
||
|
||
return Some((self.offset, self.mandatory && !hyphen, hyphen));
|
||
}
|
||
|
||
// Get the next "word".
|
||
(self.end, self.mandatory) = self.linebreaks.next()?;
|
||
|
||
// Hyphenate the next word.
|
||
if self.hyphenate != Some(false) {
|
||
if let Some(lang) = self.lang_at(self.offset) {
|
||
let word = &self.p.bidi.text[self.offset .. self.end];
|
||
let trimmed = word.trim_end_matches(|c: char| !c.is_alphabetic());
|
||
if !trimmed.is_empty() {
|
||
self.suffix = self.offset + trimmed.len();
|
||
self.syllables = Some(hypher::hyphenate(trimmed, lang));
|
||
return self.next();
|
||
}
|
||
}
|
||
}
|
||
|
||
self.offset = self.end;
|
||
Some((self.end, self.mandatory, false))
|
||
}
|
||
}
|
||
|
||
impl Breakpoints<'_> {
|
||
/// Whether hyphenation is enabled at the given offset.
|
||
fn hyphenate_at(&self, offset: usize) -> bool {
|
||
self.hyphenate
|
||
.or_else(|| {
|
||
let shaped = self.p.find(offset)?.text()?;
|
||
Some(shaped.styles.get(TextNode::HYPHENATE))
|
||
})
|
||
.unwrap_or(false)
|
||
}
|
||
|
||
/// The text language at the given offset.
|
||
fn lang_at(&self, offset: usize) -> Option<hypher::Lang> {
|
||
let lang = self.lang.unwrap_or_else(|| {
|
||
let shaped = self.p.find(offset)?.text()?;
|
||
shaped.styles.get(TextNode::LANG).as_ref()
|
||
})?;
|
||
|
||
let bytes = lang.as_str().as_bytes().try_into().ok()?;
|
||
hypher::Lang::from_iso(bytes)
|
||
}
|
||
}
|
||
|
||
/// Create a line which spans the given range.
|
||
fn line<'a>(
|
||
p: &'a Preparation,
|
||
fonts: &mut FontStore,
|
||
range: Range,
|
||
mandatory: bool,
|
||
hyphen: bool,
|
||
) -> Line<'a> {
|
||
if range.is_empty() {
|
||
return Line {
|
||
bidi: &p.bidi,
|
||
range,
|
||
first: None,
|
||
items: &[],
|
||
last: None,
|
||
width: Length::zero(),
|
||
justify: !mandatory,
|
||
dash: false,
|
||
};
|
||
}
|
||
|
||
// Find the last item.
|
||
let (last_idx, last_offset) =
|
||
p.find_idx_and_offset(range.end.saturating_sub(1)).unwrap();
|
||
|
||
// Find the first item.
|
||
let (first_idx, first_offset) = if range.is_empty() {
|
||
(last_idx, last_offset)
|
||
} else {
|
||
p.find_idx_and_offset(range.start).unwrap()
|
||
};
|
||
|
||
// Slice out the relevant items.
|
||
let mut items = &p.items[first_idx ..= last_idx];
|
||
let mut width = Length::zero();
|
||
|
||
// Reshape the last item if it's split in half.
|
||
let mut last = None;
|
||
let mut dash = false;
|
||
let mut justify = !mandatory;
|
||
if let Some((Item::Text(shaped), before)) = items.split_last() {
|
||
// Compute the range we want to shape, trimming whitespace at the
|
||
// end of the line.
|
||
let base = last_offset;
|
||
let start = range.start.max(last_offset);
|
||
let end = range.end;
|
||
let text = &p.bidi.text[start .. end];
|
||
let trimmed = text.trim_end();
|
||
let shy = trimmed.ends_with('\u{ad}');
|
||
dash = hyphen || shy || trimmed.ends_with(['-', '–', '—']);
|
||
justify |= text.ends_with('\u{2028}');
|
||
|
||
// Usually, we don't want to shape an empty string because:
|
||
// - We don't want the height of trimmed whitespace in a different
|
||
// font to be considered for the line height.
|
||
// - Even if it's in the same font, its unnecessary.
|
||
//
|
||
// There is one exception though. When the whole line is empty, we
|
||
// need the shaped empty string to make the line the appropriate
|
||
// height. That is the case exactly if the string is empty and there
|
||
// are no other items in the line.
|
||
if hyphen || trimmed.len() < shaped.text.len() {
|
||
if hyphen || !trimmed.is_empty() || before.is_empty() {
|
||
let end = start + trimmed.len();
|
||
let shifted = start - base .. end - base;
|
||
let mut reshaped = shaped.reshape(fonts, shifted);
|
||
if hyphen || shy {
|
||
reshaped.push_hyphen(fonts);
|
||
}
|
||
width += reshaped.width;
|
||
last = Some(Item::Text(reshaped));
|
||
}
|
||
|
||
items = before;
|
||
}
|
||
}
|
||
|
||
// Reshape the start item if it's split in half.
|
||
let mut first = None;
|
||
if let Some((Item::Text(shaped), after)) = items.split_first() {
|
||
// Compute the range we want to shape.
|
||
let base = first_offset;
|
||
let start = range.start;
|
||
let end = range.end.min(first_offset + shaped.text.len());
|
||
|
||
// Reshape if necessary.
|
||
if end - start < shaped.text.len() {
|
||
if start < end {
|
||
let shifted = start - base .. end - base;
|
||
let reshaped = shaped.reshape(fonts, shifted);
|
||
width += reshaped.width;
|
||
first = Some(Item::Text(reshaped));
|
||
}
|
||
|
||
items = after;
|
||
}
|
||
}
|
||
|
||
// Measure the inner items.
|
||
for item in items {
|
||
width += item.width();
|
||
}
|
||
|
||
Line {
|
||
bidi: &p.bidi,
|
||
range,
|
||
first,
|
||
items,
|
||
last,
|
||
width,
|
||
justify,
|
||
dash,
|
||
}
|
||
}
|
||
|
||
/// Combine layouted lines into one frame per region.
|
||
fn stack(
|
||
lines: &[Line],
|
||
fonts: &mut FontStore,
|
||
regions: &Regions,
|
||
styles: StyleChain,
|
||
) -> Vec<Arc<Frame>> {
|
||
let leading = styles.get(ParNode::LEADING);
|
||
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.width).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 {
|
||
let frame = commit(line, fonts, width, align, justify);
|
||
let height = frame.size.y;
|
||
|
||
while !regions.first.y.fits(height) && !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 pos = Point::with_y(output.size.y);
|
||
output.size.y += height;
|
||
output.merge_frame(pos, frame);
|
||
|
||
regions.first.y -= height + leading;
|
||
first = false;
|
||
}
|
||
|
||
finished.push(Arc::new(output));
|
||
finished
|
||
}
|
||
|
||
/// Commit to a line and build its frame.
|
||
fn commit(
|
||
line: &Line,
|
||
fonts: &mut FontStore,
|
||
width: Length,
|
||
align: Align,
|
||
justify: bool,
|
||
) -> Frame {
|
||
let mut remaining = width - line.width;
|
||
let mut offset = Length::zero();
|
||
|
||
// Reorder the line from logical to visual order.
|
||
let reordered = reorder(line);
|
||
|
||
// Handle hanging punctuation to the left.
|
||
if let Some(Item::Text(text)) = reordered.first() {
|
||
if let Some(glyph) = text.glyphs.first() {
|
||
if !text.dir.is_positive()
|
||
&& text.styles.get(TextNode::OVERHANG)
|
||
&& (reordered.len() > 1 || text.glyphs.len() > 1)
|
||
{
|
||
let amount = overhang(glyph.c) * glyph.x_advance.at(text.size);
|
||
offset -= amount;
|
||
remaining += amount;
|
||
}
|
||
}
|
||
}
|
||
|
||
// Handle hanging punctuation to the right.
|
||
if let Some(Item::Text(text)) = reordered.last() {
|
||
if let Some(glyph) = text.glyphs.last() {
|
||
if text.dir.is_positive()
|
||
&& text.styles.get(TextNode::OVERHANG)
|
||
&& (reordered.len() > 1 || text.glyphs.len() > 1)
|
||
{
|
||
let amount = overhang(glyph.c) * glyph.x_advance.at(text.size);
|
||
remaining += amount;
|
||
}
|
||
}
|
||
}
|
||
|
||
// Determine how much to justify each space.
|
||
let fr = line.fr();
|
||
let mut justification = Length::zero();
|
||
if remaining < Length::zero()
|
||
|| (justify
|
||
&& line.justify
|
||
&& line.range.end < line.bidi.text.len()
|
||
&& fr.is_zero())
|
||
{
|
||
let justifiables = line.justifiables();
|
||
if justifiables > 0 {
|
||
justification = remaining / justifiables as f64;
|
||
remaining = Length::zero();
|
||
}
|
||
}
|
||
|
||
let mut top = Length::zero();
|
||
let mut bottom = Length::zero();
|
||
|
||
// Build the frames and determine the height and baseline.
|
||
let mut frames = vec![];
|
||
for item in reordered {
|
||
let frame = match item {
|
||
Item::Absolute(v) => {
|
||
offset += *v;
|
||
continue;
|
||
}
|
||
Item::Fractional(v) => {
|
||
offset += v.share(fr, remaining);
|
||
continue;
|
||
}
|
||
Item::Text(shaped) => shaped.build(fonts, justification),
|
||
Item::Frame(frame) => frame.clone(),
|
||
};
|
||
|
||
let width = frame.size.x;
|
||
top.set_max(frame.baseline());
|
||
bottom.set_max(frame.size.y - frame.baseline());
|
||
frames.push((offset, frame));
|
||
offset += width;
|
||
}
|
||
|
||
let size = Size::new(width, top + bottom);
|
||
let mut output = Frame::new(size);
|
||
output.baseline = Some(top);
|
||
|
||
// Construct the line's frame.
|
||
for (offset, frame) in frames {
|
||
let x = offset + align.position(remaining);
|
||
let y = top - frame.baseline();
|
||
output.merge_frame(Point::new(x, y), frame);
|
||
}
|
||
|
||
output
|
||
}
|
||
|
||
/// Return a line's items in visual order.
|
||
fn reorder<'a>(line: &'a Line<'a>) -> Vec<&'a Item<'a>> {
|
||
let mut reordered = vec![];
|
||
|
||
// The bidi crate doesn't like empty lines.
|
||
if line.range.is_empty() {
|
||
return reordered;
|
||
}
|
||
|
||
// Find the paragraph that contains the line.
|
||
let para = line
|
||
.bidi
|
||
.paragraphs
|
||
.iter()
|
||
.find(|para| para.range.contains(&line.range.start))
|
||
.unwrap();
|
||
|
||
// Compute the reordered ranges in visual order (left to right).
|
||
let (levels, runs) = line.bidi.visual_runs(para, line.range.clone());
|
||
|
||
// Collect the reordered items.
|
||
for run in runs {
|
||
let first_idx = line.find(run.start);
|
||
let last_idx = line.find(run.end - 1);
|
||
let range = first_idx ..= last_idx;
|
||
|
||
// Provide the items forwards or backwards depending on the run's
|
||
// direction.
|
||
if levels[run.start].is_ltr() {
|
||
reordered.extend(range.filter_map(|i| line.get(i)));
|
||
} else {
|
||
reordered.extend(range.rev().filter_map(|i| line.get(i)));
|
||
}
|
||
}
|
||
|
||
reordered
|
||
}
|
||
|
||
/// How much a character should hang into the end margin.
|
||
///
|
||
/// For more discussion, see:
|
||
/// https://recoveringphysicist.com/21/
|
||
fn overhang(c: char) -> f64 {
|
||
match c {
|
||
// Dashes.
|
||
'–' | '—' => 0.2,
|
||
'-' => 0.55,
|
||
|
||
// Punctuation.
|
||
'.' | ',' => 0.8,
|
||
':' | ';' => 0.3,
|
||
|
||
// Arabic and Ideographic
|
||
'\u{60C}' | '\u{6D4}' => 0.4,
|
||
'\u{3001}' | '\u{3002}' => 1.0,
|
||
|
||
_ => 0.0,
|
||
}
|
||
}
|