mirror of
https://github.com/typst/typst
synced 2025-05-14 04:56:26 +08:00
1516 lines
52 KiB
Rust
1516 lines
52 KiB
Rust
use comemo::Prehashed;
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use typst::eval::Tracer;
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use typst::model::DelayedErrors;
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use unicode_bidi::{BidiInfo, Level as BidiLevel};
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use unicode_script::{Script, UnicodeScript};
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use crate::layout::{AlignElem, BoxElem, HElem, Sizing, Spacing};
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use crate::math::EquationElem;
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use crate::prelude::*;
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use crate::text::{
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breakpoints, char_is_cjk_script, is_gb_style, shape, Breakpoint, LinebreakElem,
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Quoter, Quotes, ShapedGlyph, ShapedText, SmartquoteElem, SpaceElem, TextElem,
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BEGIN_PUNCT_PAT, END_PUNCT_PAT,
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};
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/// Arranges text, spacing and inline-level elements into a paragraph.
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///
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/// Although this function is primarily used in set rules to affect paragraph
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/// properties, it can also be used to explicitly render its argument onto a
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/// paragraph of its own.
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///
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/// # Example
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/// ```example
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/// #show par: set block(spacing: 0.65em)
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/// #set par(
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/// first-line-indent: 1em,
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/// justify: true,
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/// )
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///
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/// We proceed by contradiction.
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/// Suppose that there exists a set
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/// of positive integers $a$, $b$, and
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/// $c$ that satisfies the equation
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/// $a^n + b^n = c^n$ for some
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/// integer value of $n > 2$.
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///
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/// Without loss of generality,
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/// let $a$ be the smallest of the
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/// three integers. Then, we ...
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/// ```
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#[elem(title = "Paragraph", Construct)]
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pub struct ParElem {
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/// The spacing between lines.
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#[resolve]
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#[default(Em::new(0.65).into())]
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pub leading: Length,
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/// Whether to justify text in its line.
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///
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/// Hyphenation will be enabled for justified paragraphs if the
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/// [text function's `hyphenate` property]($text.hyphenate) is set to
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/// `{auto}` and the current language is known.
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///
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/// Note that the current [alignment]($align) still has an effect on the
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/// placement of the last line except if it ends with a
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/// [justified line break]($linebreak.justify).
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#[default(false)]
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pub justify: bool,
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/// How to determine line breaks.
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///
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/// When this property is set to `{auto}`, its default value, optimized line
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/// breaks will be used for justified paragraphs. Enabling optimized line
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/// breaks for ragged paragraphs may also be worthwhile to improve the
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/// appearance of the text.
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///
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/// ```example
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/// #set page(width: 207pt)
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/// #set par(linebreaks: "simple")
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/// Some texts feature many longer
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/// words. Those are often exceedingly
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/// challenging to break in a visually
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/// pleasing way.
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///
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/// #set par(linebreaks: "optimized")
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/// Some texts feature many longer
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/// words. Those are often exceedingly
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/// challenging to break in a visually
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/// pleasing way.
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/// ```
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pub linebreaks: Smart<Linebreaks>,
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/// The indent the first line of a paragraph should have.
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///
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/// Only the first line of a consecutive paragraph will be indented (not
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/// the first one in a block or on the page).
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///
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/// By typographic convention, paragraph breaks are indicated either by some
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/// space between paragraphs or by indented first lines. Consider reducing
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/// the [paragraph spacing]($block.spacing) to the [`leading`] when
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/// using this property (e.g. using
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/// `[#show par: set block(spacing: 0.65em)]`).
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pub first_line_indent: Length,
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/// The indent all but the first line of a paragraph should have.
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#[resolve]
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pub hanging_indent: Length,
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/// The contents of the paragraph.
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#[external]
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#[required]
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pub body: Content,
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/// The paragraph's children.
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#[internal]
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#[variadic]
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pub children: Vec<Prehashed<Content>>,
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}
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impl Construct for ParElem {
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fn construct(vm: &mut Vm, args: &mut Args) -> SourceResult<Content> {
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// The paragraph constructor is special: It doesn't create a paragraph
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// element. Instead, it just ensures that the passed content lives in a
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// separate paragraph and styles it.
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let styles = Self::set(vm, args)?;
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let body = args.expect::<Content>("body")?;
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Ok(Content::sequence([
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ParbreakElem::new().pack(),
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body.styled_with_map(styles),
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ParbreakElem::new().pack(),
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]))
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}
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}
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impl ParElem {
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/// Layout the paragraph into a collection of lines.
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#[tracing::instrument(name = "ParElement::layout", skip_all)]
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pub fn layout(
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&self,
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vt: &mut Vt,
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styles: StyleChain,
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consecutive: bool,
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region: Size,
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expand: bool,
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) -> SourceResult<Fragment> {
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#[comemo::memoize]
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#[allow(clippy::too_many_arguments)]
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fn cached(
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par: &ParElem,
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world: Tracked<dyn World + '_>,
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introspector: Tracked<Introspector>,
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locator: Tracked<Locator>,
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delayed: TrackedMut<DelayedErrors>,
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tracer: TrackedMut<Tracer>,
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styles: StyleChain,
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consecutive: bool,
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region: Size,
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expand: bool,
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) -> SourceResult<Fragment> {
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let mut locator = Locator::chained(locator);
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let mut vt = Vt {
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world,
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introspector,
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locator: &mut locator,
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delayed,
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tracer,
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};
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let children = par.children();
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// Collect all text into one string for BiDi analysis.
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let (text, segments, spans) = collect(children, &styles, consecutive)?;
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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(&mut vt, children, &text, segments, spans, styles, region)?;
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// Break the paragraph into lines.
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let lines = linebreak(&vt, &p, region.x - p.hang);
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// Stack the lines into one frame per region.
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finalize(&mut vt, &p, &lines, region, expand)
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}
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let fragment = cached(
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self,
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vt.world,
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vt.introspector,
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vt.locator.track(),
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TrackedMut::reborrow_mut(&mut vt.delayed),
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TrackedMut::reborrow_mut(&mut vt.tracer),
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styles,
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consecutive,
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region,
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expand,
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)?;
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vt.locator.visit_frames(&fragment);
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Ok(fragment)
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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, Cast)]
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pub enum Linebreaks {
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/// Determine the line breaks in a simple first-fit style.
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Simple,
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/// Optimize the line breaks for the whole paragraph.
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///
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/// Typst will try to produce more evenly filled lines of text by
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/// considering the whole paragraph when calculating line breaks.
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Optimized,
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}
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/// A paragraph break.
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///
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/// This starts a new paragraph. Especially useful when used within code like
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/// [for loops]($scripting/#loops). Multiple consecutive
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/// paragraph breaks collapse into a single one.
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///
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/// # Example
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/// ```example
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/// #for i in range(3) {
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/// [Blind text #i: ]
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/// lorem(5)
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/// parbreak()
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/// }
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/// ```
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///
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/// # Syntax
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/// Instead of calling this function, you can insert a blank line into your
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/// markup to create a paragraph break.
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#[elem(title = "Paragraph Break", Unlabellable)]
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pub struct ParbreakElem {}
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impl Unlabellable for ParbreakElem {}
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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, inline content and pins are replaced in the
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// paragraph's full text.
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const SPACING_REPLACE: char = ' '; // Space
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const OBJ_REPLACE: char = '\u{FFFC}'; // Object Replacement Character
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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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pub(crate) struct Preparation<'a> {
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/// Bidirectional text embedding levels for the paragraph.
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pub bidi: BidiInfo<'a>,
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/// Text runs, spacing and layouted elements.
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pub items: Vec<Item<'a>>,
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/// The span mapper.
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pub spans: SpanMapper,
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/// Whether to hyphenate if it's the same for all children.
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pub hyphenate: Option<bool>,
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/// The text language if it's the same for all children.
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pub lang: Option<Lang>,
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/// The paragraph's resolved horizontal alignment.
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pub align: FixedAlign,
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/// Whether to justify the paragraph.
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pub justify: bool,
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/// The paragraph's hanging indent.
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pub hang: Abs,
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/// Whether to add spacing between CJK and Latin characters.
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pub cjk_latin_spacing: bool,
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/// Whether font fallback is enabled for this paragraph.
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pub fallback: bool,
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/// The leading of the paragraph.
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pub leading: Abs,
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/// How to determine line breaks.
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pub linebreaks: Smart<Linebreaks>,
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/// The text size.
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pub size: Abs,
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}
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impl<'a> Preparation<'a> {
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/// Find the item that contains the given `text_offset`.
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pub fn find(&self, text_offset: usize) -> Option<&Item<'a>> {
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let mut cursor = 0;
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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 Some(item);
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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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/// Return the items that intersect the given `text_range`.
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///
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/// Returns the expanded range around the items and the items.
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pub fn slice(&self, text_range: Range) -> (Range, &[Item<'a>]) {
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let mut cursor = 0;
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let mut start = 0;
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let mut end = 0;
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let mut expanded = text_range.clone();
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for (i, item) in self.items.iter().enumerate() {
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if cursor <= text_range.start {
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start = i;
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expanded.start = cursor;
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}
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let len = item.len();
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if cursor < text_range.end || cursor + len <= text_range.end {
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end = i + 1;
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expanded.end = cursor + len;
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} else {
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break;
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}
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cursor += len;
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}
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(expanded, &self.items[start..end])
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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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/// A mathematical equation.
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Equation(&'a EquationElem),
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/// A box with arbitrary content.
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Box(&'a BoxElem, bool),
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/// Metadata.
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Meta,
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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::Box(_, true) => SPACING_REPLACE.len_utf8(),
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Self::Equation(_) | Self::Box(_, _) => OBJ_REPLACE.len_utf8(),
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Self::Meta => 0,
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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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pub(crate) enum Item<'a> {
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/// A shaped text run with consistent style and direction.
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Text(ShapedText<'a>),
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/// Absolute spacing between other items.
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Absolute(Abs),
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/// Fractional spacing between other items.
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Fractional(Fr, Option<(&'a BoxElem, StyleChain<'a>)>),
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/// Layouted inline-level content.
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Frame(Frame),
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/// Metadata.
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Meta(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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pub 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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pub fn text_mut(&mut self) -> Option<&mut 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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pub 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(_) => OBJ_REPLACE.len_utf8(),
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Self::Meta(_) => 0,
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}
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}
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/// The natural layouted width of the item.
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pub fn width(&self) -> Abs {
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match self {
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Self::Text(shaped) => shaped.width,
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Self::Absolute(v) => *v,
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Self::Frame(frame) => frame.width(),
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Self::Fractional(_, _) | Self::Meta(_) => Abs::zero(),
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}
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}
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}
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/// Maps byte offsets back to spans.
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#[derive(Default)]
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pub struct SpanMapper(Vec<(usize, Span)>);
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impl SpanMapper {
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/// Create a new span mapper.
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pub fn new() -> Self {
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Self::default()
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}
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/// Push a span for a segment with the given length.
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pub fn push(&mut self, len: usize, span: Span) {
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self.0.push((len, span));
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}
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/// Determine the span at the given byte offset.
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///
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/// May return a detached span.
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pub fn span_at(&self, offset: usize) -> (Span, u16) {
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let mut cursor = 0;
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for &(len, span) in &self.0 {
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if (cursor..=cursor + len).contains(&offset) {
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return (span, u16::try_from(offset - cursor).unwrap_or(0));
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}
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cursor += len;
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}
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(Span::detached(), 0)
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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 committing 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 trimmed range the line spans in the paragraph.
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trimmed: Range,
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/// The untrimmed end where the line ends.
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end: usize,
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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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/// Inner items which don't need to be reprocessed.
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inner: &'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.
|
||
width: Abs,
|
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/// Whether the line should be justified.
|
||
justify: bool,
|
||
/// Whether the line ends with a hyphen or dash, either naturally or through
|
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/// hyphenation.
|
||
dash: bool,
|
||
}
|
||
|
||
impl<'a> Line<'a> {
|
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/// Iterate over the line's items.
|
||
fn items(&self) -> impl Iterator<Item = &Item<'a>> {
|
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self.first.iter().chain(self.inner).chain(&self.last)
|
||
}
|
||
|
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/// Return items that intersect the given `text_range`.
|
||
fn slice(&self, text_range: Range) -> impl Iterator<Item = &Item<'a>> {
|
||
let mut cursor = self.trimmed.start;
|
||
let mut start = 0;
|
||
let mut end = 0;
|
||
|
||
for (i, item) in self.items().enumerate() {
|
||
if cursor <= text_range.start {
|
||
start = i;
|
||
}
|
||
|
||
let len = item.len();
|
||
if cursor < text_range.end || cursor + len <= text_range.end {
|
||
end = i + 1;
|
||
} else {
|
||
break;
|
||
}
|
||
|
||
cursor += len;
|
||
}
|
||
|
||
self.items().skip(start).take(end - start)
|
||
}
|
||
|
||
/// How many glyphs are in the text where we can insert additional
|
||
/// space when encountering underfull lines.
|
||
fn justifiables(&self) -> usize {
|
||
let mut count = 0;
|
||
for shaped in self.items().filter_map(Item::text) {
|
||
count += shaped.justifiables();
|
||
}
|
||
// CJK character at line end should not be adjusted.
|
||
if self
|
||
.items()
|
||
.last()
|
||
.and_then(Item::text)
|
||
.map(|s| s.cjk_justifiable_at_last())
|
||
.unwrap_or(false)
|
||
{
|
||
count -= 1;
|
||
}
|
||
|
||
count
|
||
}
|
||
|
||
/// How much can the line stretch
|
||
fn stretchability(&self) -> Abs {
|
||
self.items().filter_map(Item::text).map(|s| s.stretchability()).sum()
|
||
}
|
||
|
||
/// How much can the line shrink
|
||
fn shrinkability(&self) -> Abs {
|
||
self.items().filter_map(Item::text).map(|s| s.shrinkability()).sum()
|
||
}
|
||
|
||
/// The sum of fractions in the line.
|
||
fn fr(&self) -> Fr {
|
||
self.items()
|
||
.filter_map(|item| match item {
|
||
Item::Fractional(fr, _) => Some(*fr),
|
||
_ => None,
|
||
})
|
||
.sum()
|
||
}
|
||
}
|
||
|
||
/// Collect all text of the paragraph into one string. This also performs
|
||
/// string-level preprocessing like case transformations.
|
||
#[allow(clippy::type_complexity)]
|
||
fn collect<'a>(
|
||
children: &'a [Prehashed<Content>],
|
||
styles: &'a StyleChain<'a>,
|
||
consecutive: bool,
|
||
) -> SourceResult<(String, Vec<(Segment<'a>, StyleChain<'a>)>, SpanMapper)> {
|
||
let mut full = String::new();
|
||
let mut quoter = Quoter::new();
|
||
let mut segments = Vec::with_capacity(2 + children.len());
|
||
let mut spans = SpanMapper::new();
|
||
let mut iter = children.iter().map(|c| &**c).peekable();
|
||
|
||
let first_line_indent = ParElem::first_line_indent_in(*styles);
|
||
if !first_line_indent.is_zero()
|
||
&& consecutive
|
||
&& AlignElem::alignment_in(*styles).resolve(*styles).x
|
||
== TextElem::dir_in(*styles).start().into()
|
||
{
|
||
full.push(SPACING_REPLACE);
|
||
segments.push((Segment::Spacing(first_line_indent.into()), *styles));
|
||
}
|
||
|
||
let hang = ParElem::hanging_indent_in(*styles);
|
||
if !hang.is_zero() {
|
||
full.push(SPACING_REPLACE);
|
||
segments.push((Segment::Spacing((-hang).into()), *styles));
|
||
}
|
||
|
||
while let Some(mut child) = iter.next() {
|
||
let outer = styles;
|
||
let mut styles = *styles;
|
||
if let Some((elem, local)) = child.to_styled() {
|
||
child = elem;
|
||
styles = outer.chain(local);
|
||
}
|
||
|
||
let segment = if child.is::<SpaceElem>() {
|
||
full.push(' ');
|
||
Segment::Text(1)
|
||
} else if let Some(elem) = child.to::<TextElem>() {
|
||
let prev = full.len();
|
||
if let Some(case) = TextElem::case_in(styles) {
|
||
full.push_str(&case.apply(elem.text()));
|
||
} else {
|
||
full.push_str(elem.text());
|
||
}
|
||
Segment::Text(full.len() - prev)
|
||
} else if let Some(elem) = child.to::<HElem>() {
|
||
if elem.amount().is_zero() {
|
||
continue;
|
||
}
|
||
|
||
full.push(SPACING_REPLACE);
|
||
Segment::Spacing(*elem.amount())
|
||
} else if let Some(elem) = child.to::<LinebreakElem>() {
|
||
let c = if elem.justify(styles) { '\u{2028}' } else { '\n' };
|
||
full.push(c);
|
||
Segment::Text(c.len_utf8())
|
||
} else if let Some(elem) = child.to::<SmartquoteElem>() {
|
||
let prev = full.len();
|
||
if SmartquoteElem::enabled_in(styles) {
|
||
let quotes = SmartquoteElem::quotes_in(styles);
|
||
let lang = TextElem::lang_in(styles);
|
||
let region = TextElem::region_in(styles);
|
||
let quotes = Quotes::new(
|
||
quotes,
|
||
lang,
|
||
region,
|
||
SmartquoteElem::alternative_in(styles),
|
||
);
|
||
let peeked = iter.peek().and_then(|child| {
|
||
let child = if let Some((child, _)) = child.to_styled() {
|
||
child
|
||
} else {
|
||
child
|
||
};
|
||
if let Some(elem) = child.to::<TextElem>() {
|
||
elem.text().chars().next()
|
||
} else if child.is::<SmartquoteElem>() {
|
||
Some('"')
|
||
} else if child.is::<SpaceElem>()
|
||
|| child.is::<HElem>()
|
||
|| child.is::<LinebreakElem>()
|
||
{
|
||
Some(SPACING_REPLACE)
|
||
} else {
|
||
Some(OBJ_REPLACE)
|
||
}
|
||
});
|
||
|
||
full.push_str(quoter.quote("es, elem.double(styles), peeked));
|
||
} else {
|
||
full.push(if elem.double(styles) { '"' } else { '\'' });
|
||
}
|
||
Segment::Text(full.len() - prev)
|
||
} else if let Some(elem) = child.to::<EquationElem>() {
|
||
full.push(OBJ_REPLACE);
|
||
Segment::Equation(elem)
|
||
} else if let Some(elem) = child.to::<BoxElem>() {
|
||
let frac = elem.width(styles).is_fractional();
|
||
full.push(if frac { SPACING_REPLACE } else { OBJ_REPLACE });
|
||
Segment::Box(elem, frac)
|
||
} else if child.is::<MetaElem>() {
|
||
Segment::Meta
|
||
} else {
|
||
bail!(child.span(), "unexpected paragraph child");
|
||
};
|
||
|
||
if let Some(last) = full.chars().last() {
|
||
quoter.last(last, child.is::<SmartquoteElem>());
|
||
}
|
||
|
||
spans.push(segment.len(), child.span());
|
||
|
||
if let (Some((Segment::Text(last_len), last_styles)), Segment::Text(len)) =
|
||
(segments.last_mut(), segment)
|
||
{
|
||
if *last_styles == styles {
|
||
*last_len += len;
|
||
continue;
|
||
}
|
||
}
|
||
|
||
segments.push((segment, styles));
|
||
}
|
||
|
||
Ok((full, segments, spans))
|
||
}
|
||
|
||
/// Prepare paragraph layout by shaping the whole paragraph and layouting all
|
||
/// contained inline-level content.
|
||
fn prepare<'a>(
|
||
vt: &mut Vt,
|
||
children: &'a [Prehashed<Content>],
|
||
text: &'a str,
|
||
segments: Vec<(Segment<'a>, StyleChain<'a>)>,
|
||
spans: SpanMapper,
|
||
styles: StyleChain<'a>,
|
||
region: Size,
|
||
) -> SourceResult<Preparation<'a>> {
|
||
let dir = TextElem::dir_in(styles);
|
||
let bidi = BidiInfo::new(
|
||
text,
|
||
match dir {
|
||
Dir::LTR => Some(BidiLevel::ltr()),
|
||
Dir::RTL => Some(BidiLevel::rtl()),
|
||
_ => None,
|
||
},
|
||
);
|
||
|
||
let mut cursor = 0;
|
||
let mut items = Vec::with_capacity(segments.len());
|
||
|
||
// Shape / layout the children and collect them into items.
|
||
for (segment, styles) in segments {
|
||
let end = cursor + segment.len();
|
||
match segment {
|
||
Segment::Text(_) => {
|
||
shape_range(&mut items, vt, &bidi, cursor..end, &spans, styles);
|
||
}
|
||
Segment::Spacing(spacing) => match spacing {
|
||
Spacing::Rel(v) => {
|
||
let resolved = v.resolve(styles).relative_to(region.x);
|
||
items.push(Item::Absolute(resolved));
|
||
}
|
||
Spacing::Fr(v) => {
|
||
items.push(Item::Fractional(v, None));
|
||
}
|
||
},
|
||
Segment::Equation(equation) => {
|
||
let pod = Regions::one(region, Axes::splat(false));
|
||
let mut frame = equation.layout(vt, styles, pod)?.into_frame();
|
||
frame.translate(Point::with_y(TextElem::baseline_in(styles)));
|
||
items.push(Item::Frame(frame));
|
||
}
|
||
Segment::Box(elem, _) => {
|
||
if let Sizing::Fr(v) = elem.width(styles) {
|
||
items.push(Item::Fractional(v, Some((elem, styles))));
|
||
} else {
|
||
let pod = Regions::one(region, Axes::splat(false));
|
||
let mut frame = elem.layout(vt, styles, pod)?.into_frame();
|
||
frame.translate(Point::with_y(TextElem::baseline_in(styles)));
|
||
items.push(Item::Frame(frame));
|
||
}
|
||
}
|
||
Segment::Meta => {
|
||
let mut frame = Frame::soft(Size::zero());
|
||
frame.meta(styles, true);
|
||
items.push(Item::Meta(frame));
|
||
}
|
||
}
|
||
|
||
cursor = end;
|
||
}
|
||
|
||
let cjk_latin_spacing = TextElem::cjk_latin_spacing_in(styles).is_auto();
|
||
if cjk_latin_spacing {
|
||
add_cjk_latin_spacing(&mut items);
|
||
}
|
||
|
||
Ok(Preparation {
|
||
bidi,
|
||
items,
|
||
spans,
|
||
hyphenate: shared_get(styles, children, TextElem::hyphenate_in),
|
||
lang: shared_get(styles, children, TextElem::lang_in),
|
||
align: AlignElem::alignment_in(styles).resolve(styles).x,
|
||
justify: ParElem::justify_in(styles),
|
||
hang: ParElem::hanging_indent_in(styles),
|
||
cjk_latin_spacing,
|
||
fallback: TextElem::fallback_in(styles),
|
||
leading: ParElem::leading_in(styles),
|
||
linebreaks: ParElem::linebreaks_in(styles),
|
||
size: TextElem::size_in(styles),
|
||
})
|
||
}
|
||
|
||
/// Add some spacing between Han characters and western characters.
|
||
/// See Requirements for Chinese Text Layout, Section 3.2.2 Mixed Text Composition in Horizontal
|
||
/// Written Mode
|
||
fn add_cjk_latin_spacing(items: &mut [Item]) {
|
||
let mut items = items.iter_mut().filter(|x| !matches!(x, Item::Meta(_))).peekable();
|
||
let mut prev: Option<&ShapedGlyph> = None;
|
||
while let Some(item) = items.next() {
|
||
let Some(text) = item.text_mut() else {
|
||
prev = None;
|
||
continue;
|
||
};
|
||
|
||
// Since we only call this function in [`prepare`], we can assume
|
||
// that the Cow is owned, and `to_mut` can be called without overhead.
|
||
debug_assert!(matches!(text.glyphs, std::borrow::Cow::Owned(_)));
|
||
let mut glyphs = text.glyphs.to_mut().iter_mut().peekable();
|
||
|
||
while let Some(glyph) = glyphs.next() {
|
||
let next = glyphs.peek().map(|n| n as _).or_else(|| {
|
||
items
|
||
.peek()
|
||
.and_then(|i| i.text())
|
||
.and_then(|shaped| shaped.glyphs.first())
|
||
});
|
||
|
||
// Case 1: CJK followed by a Latin character
|
||
if glyph.is_cjk_script() && next.map_or(false, |g| g.is_letter_or_number()) {
|
||
// The spacing is default to 1/4 em, and can be shrunk to 1/8 em.
|
||
glyph.x_advance += Em::new(0.25);
|
||
glyph.adjustability.shrinkability.1 += Em::new(0.125);
|
||
text.width += Em::new(0.25).at(text.size);
|
||
}
|
||
|
||
// Case 2: Latin followed by a CJK character
|
||
if glyph.is_cjk_script() && prev.map_or(false, |g| g.is_letter_or_number()) {
|
||
glyph.x_advance += Em::new(0.25);
|
||
glyph.x_offset += Em::new(0.25);
|
||
glyph.adjustability.shrinkability.0 += Em::new(0.125);
|
||
text.width += Em::new(0.25).at(text.size);
|
||
}
|
||
|
||
prev = Some(glyph);
|
||
}
|
||
}
|
||
}
|
||
|
||
/// Group a range of text by BiDi level and script, shape the runs and generate
|
||
/// items for them.
|
||
fn shape_range<'a>(
|
||
items: &mut Vec<Item<'a>>,
|
||
vt: &Vt,
|
||
bidi: &BidiInfo<'a>,
|
||
range: Range,
|
||
spans: &SpanMapper,
|
||
styles: StyleChain<'a>,
|
||
) {
|
||
let script = TextElem::script_in(styles);
|
||
let lang = TextElem::lang_in(styles);
|
||
let region = TextElem::region_in(styles);
|
||
let mut process = |range: Range, level: BidiLevel| {
|
||
let dir = if level.is_ltr() { Dir::LTR } else { Dir::RTL };
|
||
let shaped =
|
||
shape(vt, range.start, &bidi.text[range], spans, styles, dir, lang, region);
|
||
items.push(Item::Text(shaped));
|
||
};
|
||
|
||
let mut prev_level = BidiLevel::ltr();
|
||
let mut prev_script = Script::Unknown;
|
||
let mut cursor = range.start;
|
||
|
||
// Group by embedding level and script. If the text's script is explicitly
|
||
// set (rather than inferred from the glyphs), we keep the script at an
|
||
// unchanging `Script::Unknown` so that only level changes cause breaks.
|
||
for i in range.clone() {
|
||
if !bidi.text.is_char_boundary(i) {
|
||
continue;
|
||
}
|
||
|
||
let level = bidi.levels[i];
|
||
let curr_script = match script {
|
||
Smart::Auto => {
|
||
bidi.text[i..].chars().next().map_or(Script::Unknown, |c| c.script())
|
||
}
|
||
Smart::Custom(_) => Script::Unknown,
|
||
};
|
||
|
||
if level != prev_level || !is_compatible(curr_script, prev_script) {
|
||
if cursor < i {
|
||
process(cursor..i, prev_level);
|
||
}
|
||
cursor = i;
|
||
prev_level = level;
|
||
prev_script = curr_script;
|
||
} else if is_generic_script(prev_script) {
|
||
prev_script = curr_script;
|
||
}
|
||
}
|
||
|
||
process(cursor..range.end, prev_level);
|
||
}
|
||
|
||
/// 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
|
||
}
|
||
|
||
/// Get a style property, but only if it is the same for all children of the
|
||
/// paragraph.
|
||
fn shared_get<T: PartialEq>(
|
||
styles: StyleChain<'_>,
|
||
children: &[Prehashed<Content>],
|
||
getter: fn(StyleChain) -> T,
|
||
) -> Option<T> {
|
||
let value = getter(styles);
|
||
children
|
||
.iter()
|
||
.filter_map(|child| child.to_styled())
|
||
.all(|(_, local)| getter(styles.chain(local)) == value)
|
||
.then_some(value)
|
||
}
|
||
|
||
/// Find suitable linebreaks.
|
||
fn linebreak<'a>(vt: &Vt, p: &'a Preparation<'a>, width: Abs) -> Vec<Line<'a>> {
|
||
let linebreaks = p.linebreaks.unwrap_or_else(|| {
|
||
if p.justify {
|
||
Linebreaks::Optimized
|
||
} else {
|
||
Linebreaks::Simple
|
||
}
|
||
});
|
||
|
||
match linebreaks {
|
||
Linebreaks::Simple => linebreak_simple(vt, p, width),
|
||
Linebreaks::Optimized => linebreak_optimized(vt, p, width),
|
||
}
|
||
}
|
||
|
||
/// Perform line breaking in simple first-fit style. This means that we build
|
||
/// lines greedily, always taking the longest possible line. This may lead to
|
||
/// very unbalanced line, but is fast and simple.
|
||
fn linebreak_simple<'a>(vt: &Vt, p: &'a Preparation<'a>, width: Abs) -> Vec<Line<'a>> {
|
||
let mut lines = Vec::with_capacity(16);
|
||
let mut start = 0;
|
||
let mut last = None;
|
||
|
||
breakpoints(p, |end, breakpoint| {
|
||
// Compute the line and its size.
|
||
let mut attempt = line(vt, p, start..end, breakpoint);
|
||
|
||
// If the line doesn't fit anymore, we push the last fitting attempt
|
||
// into the stack and rebuild the line from the attempt's 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(vt, p, start..end, breakpoint);
|
||
}
|
||
}
|
||
|
||
// 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 breakpoint == Breakpoint::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>(vt: &Vt, p: &'a Preparation<'a>, width: Abs) -> 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 RUNT_COST: Cost = 0.5;
|
||
const CONSECUTIVE_DASH_COST: Cost = 0.3;
|
||
const MAX_COST: Cost = 1_000_000.0;
|
||
const MIN_RATIO: f64 = -1.0;
|
||
|
||
// Dynamic programming table.
|
||
let mut active = 0;
|
||
let mut table = vec![Entry {
|
||
pred: 0,
|
||
total: 0.0,
|
||
line: line(vt, p, 0..0, Breakpoint::Mandatory),
|
||
}];
|
||
|
||
let em = p.size;
|
||
let mut lines = Vec::with_capacity(16);
|
||
breakpoints(p, |end, breakpoint| {
|
||
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().enumerate().skip(active) {
|
||
// Layout the line.
|
||
let start = pred.line.end;
|
||
|
||
let attempt = line(vt, p, start..end, breakpoint);
|
||
|
||
// Determine how much the line's spaces would need to be stretched
|
||
// to make it the desired width.
|
||
let delta = width - attempt.width;
|
||
// Determine how much stretch are permitted.
|
||
let adjust = if delta >= Abs::zero() {
|
||
attempt.stretchability()
|
||
} else {
|
||
attempt.shrinkability()
|
||
};
|
||
// Ideally, the ratio should between -1.0 and 1.0, but sometimes a value above 1.0
|
||
// is possible, in which case the line is underfull.
|
||
let mut ratio = delta / adjust;
|
||
if ratio.is_nan() {
|
||
// The line is not stretchable, but it just fits.
|
||
// This often happens with monospace fonts and CJK texts.
|
||
ratio = 0.0;
|
||
}
|
||
if ratio > 1.0 {
|
||
// We should stretch the line above its stretchability. Now
|
||
// calculate the extra amount. Also, don't divide by zero.
|
||
let extra_stretch =
|
||
(delta - adjust) / attempt.justifiables().max(1) as f64;
|
||
// Normalize the amount by half Em size.
|
||
ratio = 1.0 + extra_stretch / (em / 2.0);
|
||
}
|
||
|
||
// Determine the cost of the line.
|
||
let min_ratio = if p.justify { MIN_RATIO } else { 0.0 };
|
||
let mut cost = if ratio < min_ratio {
|
||
// The line is overfull. This is the case if
|
||
// - justification is on, but we'd need to shrink too much
|
||
// - justification is off and the line just doesn't fit
|
||
//
|
||
// If this is the earliest breakpoint in the active set
|
||
// (active == i), remove it from the active set. If there is an
|
||
// earlier one (active < i), then the logically shorter line was
|
||
// in fact longer (can happen with negative spacing) and we
|
||
// can't trim the active set just yet.
|
||
if active == i {
|
||
active += 1;
|
||
}
|
||
MAX_COST
|
||
} else if breakpoint == Breakpoint::Mandatory || eof {
|
||
// This is a mandatory break and the line is not overfull, so
|
||
// all breakpoints before this one become inactive since no line
|
||
// can span above the mandatory break.
|
||
active = k;
|
||
// If ratio > 0, we need to stretch the line only when justify is needed.
|
||
// If ratio < 0, we always need to shrink the line.
|
||
if (ratio > 0.0 && attempt.justify) || ratio < 0.0 {
|
||
ratio.powi(3).abs()
|
||
} else {
|
||
0.0
|
||
}
|
||
} else {
|
||
// Normal line with cost of |ratio^3|.
|
||
ratio.powi(3).abs()
|
||
};
|
||
|
||
// Penalize runts.
|
||
if k == i + 1 && eof {
|
||
cost += RUNT_COST;
|
||
}
|
||
|
||
// Penalize hyphens.
|
||
if breakpoint == Breakpoint::Hyphen {
|
||
cost += HYPH_COST;
|
||
}
|
||
|
||
// In Knuth paper, cost = (1 + 100|r|^3 + p)^2 + a,
|
||
// where r is the ratio, p=50 is the penalty, and a=3000 is consecutive the penalty.
|
||
// We divide the whole formula by 10, resulting (0.01 + |r|^3 + p)^2 + a,
|
||
// where p=0.5 and a=0.3
|
||
cost = (0.01 + cost).powi(2);
|
||
|
||
// 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 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
|
||
}
|
||
|
||
/// Create a line which spans the given range.
|
||
fn line<'a>(
|
||
vt: &Vt,
|
||
p: &'a Preparation,
|
||
mut range: Range,
|
||
breakpoint: Breakpoint,
|
||
) -> Line<'a> {
|
||
let end = range.end;
|
||
let mut justify =
|
||
p.justify && end < p.bidi.text.len() && breakpoint != Breakpoint::Mandatory;
|
||
|
||
if range.is_empty() {
|
||
return Line {
|
||
bidi: &p.bidi,
|
||
end,
|
||
trimmed: range,
|
||
first: None,
|
||
inner: &[],
|
||
last: None,
|
||
width: Abs::zero(),
|
||
justify,
|
||
dash: false,
|
||
};
|
||
}
|
||
|
||
// Slice out the relevant items.
|
||
let (expanded, mut inner) = p.slice(range.clone());
|
||
let mut width = Abs::zero();
|
||
|
||
// Reshape the last item if it's split in half or hyphenated.
|
||
let mut last = None;
|
||
let mut dash = false;
|
||
if let Some((Item::Text(shaped), before)) = inner.split_last() {
|
||
// Compute the range we want to shape, trimming whitespace at the
|
||
// end of the line.
|
||
let base = expanded.end - shaped.text.len();
|
||
let start = range.start.max(base);
|
||
let text = &p.bidi.text[start..range.end];
|
||
// U+200B ZERO WIDTH SPACE is used to provide a line break opportunity,
|
||
// we want to trim it too.
|
||
let trimmed = text.trim_end().trim_end_matches('\u{200B}');
|
||
range.end = start + trimmed.len();
|
||
|
||
// Deal with hyphens, dashes and justification.
|
||
let shy = trimmed.ends_with('\u{ad}');
|
||
let hyphen = breakpoint == Breakpoint::Hyphen;
|
||
dash = hyphen || shy || trimmed.ends_with(['-', '–', '—']);
|
||
justify |= text.ends_with('\u{2028}');
|
||
|
||
// Deal with CJK punctuation at line ends.
|
||
let gb_style = is_gb_style(shaped.lang, shaped.region);
|
||
let maybe_adjust_last_glyph = trimmed.ends_with(END_PUNCT_PAT)
|
||
|| (p.cjk_latin_spacing && trimmed.ends_with(char_is_cjk_script));
|
||
|
||
// 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 || start + shaped.text.len() > range.end || maybe_adjust_last_glyph {
|
||
if hyphen || start < range.end || before.is_empty() {
|
||
let mut reshaped = shaped.reshape(vt, &p.spans, start..range.end);
|
||
if hyphen || shy {
|
||
reshaped.push_hyphen(vt, p.fallback);
|
||
}
|
||
|
||
if let Some(last_glyph) = reshaped.glyphs.last() {
|
||
if last_glyph.is_cjk_left_aligned_punctuation(gb_style) {
|
||
// If the last glyph is a CJK punctuation, we want to shrink it.
|
||
// See Requirements for Chinese Text Layout, Section 3.1.6.3
|
||
// Compression of punctuation marks at line start or line end
|
||
let shrink_amount = last_glyph.shrinkability().1;
|
||
let punct = reshaped.glyphs.to_mut().last_mut().unwrap();
|
||
punct.shrink_right(shrink_amount);
|
||
reshaped.width -= shrink_amount.at(reshaped.size);
|
||
} else if p.cjk_latin_spacing
|
||
&& last_glyph.is_cjk_script()
|
||
&& (last_glyph.x_advance - last_glyph.x_offset) > Em::one()
|
||
{
|
||
// If the last glyph is a CJK character adjusted by [`add_cjk_latin_spacing`],
|
||
// restore the original width.
|
||
let shrink_amount =
|
||
last_glyph.x_advance - last_glyph.x_offset - Em::one();
|
||
let glyph = reshaped.glyphs.to_mut().last_mut().unwrap();
|
||
glyph.x_advance -= shrink_amount;
|
||
glyph.adjustability.shrinkability.1 = Em::zero();
|
||
reshaped.width -= shrink_amount.at(reshaped.size);
|
||
}
|
||
}
|
||
|
||
width += reshaped.width;
|
||
last = Some(Item::Text(reshaped));
|
||
}
|
||
|
||
inner = before;
|
||
}
|
||
}
|
||
|
||
// Deal with CJK characters at line starts.
|
||
let text = &p.bidi.text[range.start..end];
|
||
let maybe_adjust_first_glyph = text.starts_with(BEGIN_PUNCT_PAT)
|
||
|| (p.cjk_latin_spacing && text.starts_with(char_is_cjk_script));
|
||
|
||
// Reshape the start item if it's split in half.
|
||
let mut first = None;
|
||
if let Some((Item::Text(shaped), after)) = inner.split_first() {
|
||
// Compute the range we want to shape.
|
||
let base = expanded.start;
|
||
let end = range.end.min(base + shaped.text.len());
|
||
|
||
// Reshape if necessary.
|
||
if range.start + shaped.text.len() > end || maybe_adjust_first_glyph {
|
||
// If the range is empty, we don't want to push an empty text item.
|
||
if range.start < end {
|
||
let reshaped = shaped.reshape(vt, &p.spans, range.start..end);
|
||
width += reshaped.width;
|
||
first = Some(Item::Text(reshaped));
|
||
}
|
||
|
||
inner = after;
|
||
}
|
||
}
|
||
|
||
if maybe_adjust_first_glyph {
|
||
let reshaped = first.as_mut().or(last.as_mut()).and_then(Item::text_mut);
|
||
if let Some(reshaped) = reshaped {
|
||
if let Some(first_glyph) = reshaped.glyphs.first() {
|
||
if first_glyph.is_cjk_right_aligned_punctuation() {
|
||
// If the first glyph is a CJK punctuation, we want to shrink it.
|
||
let shrink_amount = first_glyph.shrinkability().0;
|
||
let glyph = reshaped.glyphs.to_mut().first_mut().unwrap();
|
||
glyph.shrink_left(shrink_amount);
|
||
let amount_abs = shrink_amount.at(reshaped.size);
|
||
reshaped.width -= amount_abs;
|
||
width -= amount_abs;
|
||
} else if p.cjk_latin_spacing
|
||
&& first_glyph.is_cjk_script()
|
||
&& first_glyph.x_offset > Em::zero()
|
||
{
|
||
// If the first glyph is a CJK character adjusted by [`add_cjk_latin_spacing`],
|
||
// restore the original width.
|
||
let shrink_amount = first_glyph.x_offset;
|
||
let glyph = reshaped.glyphs.to_mut().first_mut().unwrap();
|
||
glyph.x_advance -= shrink_amount;
|
||
glyph.x_offset = Em::zero();
|
||
glyph.adjustability.shrinkability.0 = Em::zero();
|
||
let amount_abs = shrink_amount.at(reshaped.size);
|
||
reshaped.width -= amount_abs;
|
||
width -= amount_abs;
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
// Measure the inner items.
|
||
for item in inner {
|
||
width += item.width();
|
||
}
|
||
|
||
Line {
|
||
bidi: &p.bidi,
|
||
trimmed: range,
|
||
end,
|
||
first,
|
||
inner,
|
||
last,
|
||
width,
|
||
justify,
|
||
dash,
|
||
}
|
||
}
|
||
|
||
/// Combine layouted lines into one frame per region.
|
||
fn finalize(
|
||
vt: &mut Vt,
|
||
p: &Preparation,
|
||
lines: &[Line],
|
||
region: Size,
|
||
expand: bool,
|
||
) -> SourceResult<Fragment> {
|
||
// Determine the paragraph's width: Full width of the region if we
|
||
// should expand or there's fractional spacing, fit-to-width otherwise.
|
||
let width = if !region.x.is_finite()
|
||
|| (!expand && lines.iter().all(|line| line.fr().is_zero()))
|
||
{
|
||
region
|
||
.x
|
||
.min(p.hang + lines.iter().map(|line| line.width).max().unwrap_or_default())
|
||
} else {
|
||
region.x
|
||
};
|
||
|
||
// Stack the lines into one frame per region.
|
||
let mut frames: Vec<Frame> = lines
|
||
.iter()
|
||
.map(|line| commit(vt, p, line, width, region.y))
|
||
.collect::<SourceResult<_>>()?;
|
||
|
||
// Prevent orphans.
|
||
if frames.len() >= 2 && !frames[1].is_empty() {
|
||
let second = frames.remove(1);
|
||
let first = &mut frames[0];
|
||
merge(first, second, p.leading);
|
||
}
|
||
|
||
// Prevent widows.
|
||
let len = frames.len();
|
||
if len >= 2 && !frames[len - 2].is_empty() {
|
||
let second = frames.pop().unwrap();
|
||
let first = frames.last_mut().unwrap();
|
||
merge(first, second, p.leading);
|
||
}
|
||
|
||
Ok(Fragment::frames(frames))
|
||
}
|
||
|
||
/// Merge two line frames
|
||
fn merge(first: &mut Frame, second: Frame, leading: Abs) {
|
||
let offset = first.height() + leading;
|
||
let total = offset + second.height();
|
||
first.push_frame(Point::with_y(offset), second);
|
||
first.size_mut().y = total;
|
||
}
|
||
|
||
/// Commit to a line and build its frame.
|
||
fn commit(
|
||
vt: &mut Vt,
|
||
p: &Preparation,
|
||
line: &Line,
|
||
width: Abs,
|
||
full: Abs,
|
||
) -> SourceResult<Frame> {
|
||
let mut remaining = width - line.width - p.hang;
|
||
let mut offset = Abs::zero();
|
||
|
||
// Reorder the line from logical to visual order.
|
||
let (reordered, starts_rtl) = reorder(line);
|
||
if !starts_rtl {
|
||
offset += p.hang;
|
||
}
|
||
|
||
// 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()
|
||
&& TextElem::overhang_in(text.styles)
|
||
&& (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()
|
||
&& TextElem::overhang_in(text.styles)
|
||
&& (reordered.len() > 1 || text.glyphs.len() > 1)
|
||
{
|
||
let amount = overhang(glyph.c) * glyph.x_advance.at(text.size);
|
||
remaining += amount;
|
||
}
|
||
}
|
||
}
|
||
|
||
// Determine how much additional space is needed.
|
||
// The justicication_ratio is for the first step justification,
|
||
// extra_justification is for the last step.
|
||
// For more info on multi-step justification, see Procedures for Inter-
|
||
// Character Space Expansion in W3C document Chinese Layout Requirements.
|
||
let fr = line.fr();
|
||
let mut justification_ratio = 0.0;
|
||
let mut extra_justification = Abs::zero();
|
||
|
||
let shrink = line.shrinkability();
|
||
let stretch = line.stretchability();
|
||
if remaining < Abs::zero() && shrink > Abs::zero() {
|
||
// Attempt to reduce the length of the line, using shrinkability.
|
||
justification_ratio = (remaining / shrink).max(-1.0);
|
||
remaining = (remaining + shrink).min(Abs::zero());
|
||
} else if line.justify && fr.is_zero() {
|
||
// Attempt to increase the length of the line, using stretchability.
|
||
if stretch > Abs::zero() {
|
||
justification_ratio = (remaining / stretch).min(1.0);
|
||
remaining = (remaining - stretch).max(Abs::zero());
|
||
}
|
||
|
||
let justifiables = line.justifiables();
|
||
if justifiables > 0 && remaining > Abs::zero() {
|
||
// Underfull line, distribute the extra space.
|
||
extra_justification = remaining / justifiables as f64;
|
||
remaining = Abs::zero();
|
||
}
|
||
}
|
||
|
||
let mut top = Abs::zero();
|
||
let mut bottom = Abs::zero();
|
||
|
||
// Build the frames and determine the height and baseline.
|
||
let mut frames = vec![];
|
||
for item in reordered {
|
||
let mut push = |offset: &mut Abs, frame: Frame| {
|
||
let width = frame.width();
|
||
top.set_max(frame.baseline());
|
||
bottom.set_max(frame.size().y - frame.baseline());
|
||
frames.push((*offset, frame));
|
||
*offset += width;
|
||
};
|
||
|
||
match item {
|
||
Item::Absolute(v) => {
|
||
offset += *v;
|
||
}
|
||
Item::Fractional(v, elem) => {
|
||
let amount = v.share(fr, remaining);
|
||
if let Some((elem, styles)) = elem {
|
||
let region = Size::new(amount, full);
|
||
let pod = Regions::one(region, Axes::new(true, false));
|
||
let mut frame = elem.layout(vt, *styles, pod)?.into_frame();
|
||
frame.translate(Point::with_y(TextElem::baseline_in(*styles)));
|
||
push(&mut offset, frame);
|
||
} else {
|
||
offset += amount;
|
||
}
|
||
}
|
||
Item::Text(shaped) => {
|
||
let frame = shaped.build(vt, justification_ratio, extra_justification);
|
||
push(&mut offset, frame);
|
||
}
|
||
Item::Frame(frame) | Item::Meta(frame) => {
|
||
push(&mut offset, frame.clone());
|
||
}
|
||
}
|
||
}
|
||
|
||
// Remaining space is distributed now.
|
||
if !fr.is_zero() {
|
||
remaining = Abs::zero();
|
||
}
|
||
|
||
let size = Size::new(width, top + bottom);
|
||
let mut output = Frame::soft(size);
|
||
output.set_baseline(top);
|
||
|
||
// Construct the line's frame.
|
||
for (offset, frame) in frames {
|
||
let x = offset + p.align.position(remaining);
|
||
let y = top - frame.baseline();
|
||
output.push_frame(Point::new(x, y), frame);
|
||
}
|
||
|
||
Ok(output)
|
||
}
|
||
|
||
/// Return a line's items in visual order.
|
||
fn reorder<'a>(line: &'a Line<'a>) -> (Vec<&Item<'a>>, bool) {
|
||
let mut reordered = vec![];
|
||
|
||
// The bidi crate doesn't like empty lines.
|
||
if line.trimmed.is_empty() {
|
||
return (line.slice(line.trimmed.clone()).collect(), false);
|
||
}
|
||
|
||
// Find the paragraph that contains the line.
|
||
let para = line
|
||
.bidi
|
||
.paragraphs
|
||
.iter()
|
||
.find(|para| para.range.contains(&line.trimmed.start))
|
||
.unwrap();
|
||
|
||
// Compute the reordered ranges in visual order (left to right).
|
||
let (levels, runs) = line.bidi.visual_runs(para, line.trimmed.clone());
|
||
let starts_rtl = levels.first().map_or(false, |level| level.is_rtl());
|
||
|
||
// Collect the reordered items.
|
||
for run in runs {
|
||
// Skip reset L1 runs because handling them would require reshaping
|
||
// again in some cases.
|
||
if line.bidi.levels[run.start] != levels[run.start] {
|
||
continue;
|
||
}
|
||
|
||
let prev = reordered.len();
|
||
reordered.extend(line.slice(run.clone()));
|
||
|
||
if levels[run.start].is_rtl() {
|
||
reordered[prev..].reverse();
|
||
}
|
||
}
|
||
|
||
(reordered, starts_rtl)
|
||
}
|
||
|
||
/// 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
|
||
'\u{60C}' | '\u{6D4}' => 0.4,
|
||
|
||
_ => 0.0,
|
||
}
|
||
}
|