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|
use typst_library::diag::SourceResult;
use typst_library::foundations::{Packed, StyleChain};
use typst_library::layout::{Abs, Axis, Rel};
use typst_library::math::{EquationElem, LrElem, MidElem};
use typst_utils::SliceExt;
use unicode_math_class::MathClass;
use super::{stretch_fragment, MathContext, MathFragment, DELIM_SHORT_FALL};
/// Lays out an [`LrElem`].
#[typst_macros::time(name = "math.lr", span = elem.span())]
pub fn layout_lr(
elem: &Packed<LrElem>,
ctx: &mut MathContext,
styles: StyleChain,
) -> SourceResult<()> {
// Extract from an EquationElem.
let mut body = &elem.body;
if let Some(equation) = body.to_packed::<EquationElem>() {
body = &equation.body;
}
// Extract implicit LrElem.
if let Some(lr) = body.to_packed::<LrElem>() {
if lr.size(styles).is_one() {
body = &lr.body;
}
}
let mut fragments = ctx.layout_into_fragments(body, styles)?;
// Ignore leading and trailing ignorant fragments.
let (start_idx, end_idx) = fragments.split_prefix_suffix(|f| f.is_ignorant());
let inner_fragments = &mut fragments[start_idx..end_idx];
let axis = scaled!(ctx, styles, axis_height);
let max_extent = inner_fragments
.iter()
.map(|fragment| (fragment.ascent() - axis).max(fragment.descent() + axis))
.max()
.unwrap_or_default();
let relative_to = 2.0 * max_extent;
let height = elem.size(styles);
// Scale up fragments at both ends.
match inner_fragments {
[one] => scale(ctx, styles, one, relative_to, height, None),
[first, .., last] => {
scale(ctx, styles, first, relative_to, height, Some(MathClass::Opening));
scale(ctx, styles, last, relative_to, height, Some(MathClass::Closing));
}
_ => {}
}
// Handle MathFragment::Variant fragments that should be scaled up.
for fragment in inner_fragments.iter_mut() {
if let MathFragment::Variant(ref mut variant) = fragment {
if variant.mid_stretched == Some(false) {
variant.mid_stretched = Some(true);
scale(ctx, styles, fragment, relative_to, height, Some(MathClass::Large));
}
}
}
// Remove weak SpacingFragment immediately after the opening or immediately
// before the closing.
let mut index = 0;
let opening_exists = inner_fragments
.first()
.is_some_and(|f| f.class() == MathClass::Opening);
let closing_exists = inner_fragments
.last()
.is_some_and(|f| f.class() == MathClass::Closing);
fragments.retain(|fragment| {
let discard = (index == start_idx + 1 && opening_exists
|| index + 2 == end_idx && closing_exists)
&& matches!(fragment, MathFragment::Spacing(_, true));
index += 1;
!discard
});
ctx.extend(fragments);
Ok(())
}
/// Lays out a [`MidElem`].
#[typst_macros::time(name = "math.mid", span = elem.span())]
pub fn layout_mid(
elem: &Packed<MidElem>,
ctx: &mut MathContext,
styles: StyleChain,
) -> SourceResult<()> {
let mut fragments = ctx.layout_into_fragments(&elem.body, styles)?;
for fragment in &mut fragments {
match fragment {
MathFragment::Glyph(glyph) => {
let mut new = glyph.clone().into_variant();
new.mid_stretched = Some(false);
new.class = MathClass::Fence;
*fragment = MathFragment::Variant(new);
}
MathFragment::Variant(variant) => {
variant.mid_stretched = Some(false);
variant.class = MathClass::Fence;
}
_ => {}
}
}
ctx.extend(fragments);
Ok(())
}
/// Scale a math fragment to a height.
fn scale(
ctx: &mut MathContext,
styles: StyleChain,
fragment: &mut MathFragment,
relative_to: Abs,
height: Rel<Abs>,
apply: Option<MathClass>,
) {
if matches!(
fragment.class(),
MathClass::Opening | MathClass::Closing | MathClass::Fence
) {
// This unwrap doesn't really matter. If it is None, then the fragment
// won't be stretchable anyways.
let short_fall = DELIM_SHORT_FALL.at(fragment.font_size().unwrap_or_default());
stretch_fragment(
ctx,
styles,
fragment,
Some(Axis::Y),
Some(relative_to),
height,
short_fall,
);
if let Some(class) = apply {
fragment.set_class(class);
}
}
}
|
