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use std::f64::consts::SQRT_2;
use codex::styling::{to_style, MathStyle};
use ecow::EcoString;
use typst_library::diag::SourceResult;
use typst_library::foundations::{Packed, StyleChain, SymbolElem};
use typst_library::layout::{Abs, Size};
use typst_library::math::{EquationElem, MathSize};
use typst_library::text::{
BottomEdge, BottomEdgeMetric, TextElem, TopEdge, TopEdgeMetric,
};
use typst_syntax::{is_newline, Span};
use unicode_math_class::MathClass;
use unicode_segmentation::UnicodeSegmentation;
use super::{
has_dtls_feat, style_dtls, FrameFragment, GlyphFragment, MathContext, MathFragment,
MathRun,
};
/// Lays out a [`TextElem`].
pub fn layout_text(
elem: &Packed<TextElem>,
ctx: &mut MathContext,
styles: StyleChain,
) -> SourceResult<()> {
let text = &elem.text;
let span = elem.span();
let fragment = if text.contains(is_newline) {
layout_text_lines(text.split(is_newline), span, ctx, styles)?
} else {
layout_inline_text(text, span, ctx, styles)?
};
ctx.push(fragment);
Ok(())
}
/// Layout multiple lines of text.
fn layout_text_lines<'a>(
lines: impl Iterator<Item = &'a str>,
span: Span,
ctx: &mut MathContext,
styles: StyleChain,
) -> SourceResult<FrameFragment> {
let mut fragments = vec![];
for (i, line) in lines.enumerate() {
if i != 0 {
fragments.push(MathFragment::Linebreak);
}
if !line.is_empty() {
fragments.push(layout_inline_text(line, span, ctx, styles)?.into());
}
}
let mut frame = MathRun::new(fragments).into_frame(styles);
let axis = scaled!(ctx, styles, axis_height);
frame.set_baseline(frame.height() / 2.0 + axis);
Ok(FrameFragment::new(styles, frame))
}
/// Layout the given text string into a [`FrameFragment`] after styling all
/// characters for the math font (without auto-italics).
fn layout_inline_text(
text: &str,
span: Span,
ctx: &mut MathContext,
styles: StyleChain,
) -> SourceResult<FrameFragment> {
let variant = styles.get(EquationElem::variant);
let bold = styles.get(EquationElem::bold);
// Disable auto-italic.
let italic = styles.get(EquationElem::italic).or(Some(false));
if text.chars().all(|c| c.is_ascii_digit() || c == '.') {
// Small optimization for numbers. Note that this lays out slightly
// differently to normal text and is worth re-evaluating in the future.
let mut fragments = vec![];
for unstyled_c in text.chars() {
// This is fine as ascii digits and '.' can never end up as more
// than a single char after styling.
let style = MathStyle::select(unstyled_c, variant, bold, italic);
let c = to_style(unstyled_c, style).next().unwrap();
let glyph = GlyphFragment::new_char(ctx.font, styles, c, span)?;
fragments.push(glyph.into());
}
let frame = MathRun::new(fragments).into_frame(styles);
Ok(FrameFragment::new(styles, frame).with_text_like(true))
} else {
let local = [
TextElem::top_edge.set(TopEdge::Metric(TopEdgeMetric::Bounds)),
TextElem::bottom_edge.set(BottomEdge::Metric(BottomEdgeMetric::Bounds)),
]
.map(|p| p.wrap());
let styles = styles.chain(&local);
let styled_text: EcoString = text
.chars()
.flat_map(|c| to_style(c, MathStyle::select(c, variant, bold, italic)))
.collect();
let spaced = styled_text.graphemes(true).nth(1).is_some();
let elem = TextElem::packed(styled_text).spanned(span);
// There isn't a natural width for a paragraph in a math environment;
// because it will be placed somewhere probably not at the left margin
// it will overflow. So emulate an `hbox` instead and allow the
// paragraph to extend as far as needed.
let frame = crate::inline::layout_inline(
ctx.engine,
&[(&elem, styles)],
&mut ctx.locator.next(&span).split(),
styles,
Size::splat(Abs::inf()),
false,
)?
.into_frame();
Ok(FrameFragment::new(styles, frame)
.with_class(MathClass::Alphabetic)
.with_text_like(true)
.with_spaced(spaced))
}
}
/// Layout a single character in the math font with the correct styling applied
/// (includes auto-italics).
pub fn layout_symbol(
elem: &Packed<SymbolElem>,
ctx: &mut MathContext,
styles: StyleChain,
) -> SourceResult<()> {
// Switch dotless char to normal when we have the dtls OpenType feature.
// This should happen before the main styling pass.
let dtls = style_dtls();
let (unstyled_c, symbol_styles) = match try_dotless(elem.text) {
Some(c) if has_dtls_feat(ctx.font) => (c, styles.chain(&dtls)),
_ => (elem.text, styles),
};
let variant = styles.get(EquationElem::variant);
let bold = styles.get(EquationElem::bold);
let italic = styles.get(EquationElem::italic);
let style = MathStyle::select(unstyled_c, variant, bold, italic);
let text: EcoString = to_style(unstyled_c, style).collect();
let fragment: MathFragment =
match GlyphFragment::new(ctx.font, symbol_styles, &text, elem.span()) {
Ok(mut glyph) => {
adjust_glyph_layout(&mut glyph, ctx, styles);
glyph.into()
}
Err(_) => {
// Not in the math font, fallback to normal inline text layout.
// TODO: Should replace this with proper fallback in [`GlyphFragment::new`].
layout_inline_text(&text, elem.span(), ctx, styles)?.into()
}
};
ctx.push(fragment);
Ok(())
}
/// Centers large glyphs vertically on the axis, scaling them if in display
/// style.
fn adjust_glyph_layout(
glyph: &mut GlyphFragment,
ctx: &mut MathContext,
styles: StyleChain,
) {
if glyph.class == MathClass::Large {
if styles.get(EquationElem::size) == MathSize::Display {
let height = scaled!(ctx, styles, display_operator_min_height)
.max(SQRT_2 * glyph.size.y);
glyph.stretch_vertical(ctx, height);
};
// TeXbook p 155. Large operators are always vertically centered on the
// axis.
glyph.center_on_axis();
}
}
/// The non-dotless version of a dotless character that can be used with the
/// `dtls` OpenType feature.
pub fn try_dotless(c: char) -> Option<char> {
match c {
'ı' => Some('i'),
'ȷ' => Some('j'),
_ => None,
}
}
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