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|
use super::*;
/// # Script
/// A mathematical sub- and/or superscript.
///
/// ## Syntax
/// This function also has dedicated syntax: Use the underscore (`_`) to
/// indicate a subscript and the circumflex (`^`) to indicate a superscript.
///
/// ## Example
/// ```
/// $ a_i = 2^(1+i) $
/// ```
///
/// ## Parameters
/// - base: Content (positional, required)
/// The base to which the applies the sub- and/or superscript.
///
/// - sub: Content (named)
/// The subscript.
///
/// - sup: Content (named)
/// The superscript.
///
/// ## Category
/// math
#[func]
#[capable(LayoutMath)]
#[derive(Debug, Hash)]
pub struct ScriptNode {
/// The base.
pub base: Content,
/// The subscript.
pub sub: Option<Content>,
/// The superscript.
pub sup: Option<Content>,
}
#[node]
impl ScriptNode {
fn construct(_: &Vm, args: &mut Args) -> SourceResult<Content> {
let base = args.expect("base")?;
let sub = args.named("sub")?;
let sup = args.named("sup")?;
Ok(Self { base, sub, sup }.pack())
}
}
impl LayoutMath for ScriptNode {
fn layout_math(&self, ctx: &mut MathContext) -> SourceResult<()> {
let base = ctx.layout_fragment(&self.base)?;
let mut sub = Frame::new(Size::zero());
if let Some(node) = &self.sub {
ctx.style(ctx.style.for_subscript());
sub = ctx.layout_frame(node)?;
ctx.unstyle();
}
let mut sup = Frame::new(Size::zero());
if let Some(node) = &self.sup {
ctx.style(ctx.style.for_superscript());
sup = ctx.layout_frame(node)?;
ctx.unstyle();
}
let render_limits = ctx.style.size == MathSize::Display
&& base.class() == Some(MathClass::Large)
&& match &base {
MathFragment::Variant(variant) => LIMITS.contains(&variant.c),
MathFragment::Frame(fragment) => fragment.limits,
_ => false,
};
if render_limits {
limits(ctx, base, sub, sup)
} else {
scripts(ctx, base, sub, sup, self.sub.is_some() && self.sup.is_some())
}
}
}
/// Layout normal sub- and superscripts.
fn scripts(
ctx: &mut MathContext,
base: MathFragment,
sub: Frame,
sup: Frame,
both: bool,
) -> SourceResult<()> {
let sup_shift_up = if ctx.style.cramped {
scaled!(ctx, superscript_shift_up_cramped)
} else {
scaled!(ctx, superscript_shift_up)
};
let sup_bottom_min = scaled!(ctx, superscript_bottom_min);
let sup_bottom_max_with_sub = scaled!(ctx, superscript_bottom_max_with_subscript);
let sup_drop_max = scaled!(ctx, superscript_baseline_drop_max);
let gap_min = scaled!(ctx, sub_superscript_gap_min);
let sub_shift_down = scaled!(ctx, subscript_shift_down);
let sub_top_max = scaled!(ctx, subscript_top_max);
let sub_drop_min = scaled!(ctx, subscript_baseline_drop_min);
let space_after = scaled!(ctx, space_after_script);
let mut shift_up = sup_shift_up
.max(base.ascent() - sup_drop_max)
.max(sup_bottom_min + sup.descent());
let mut shift_down = sub_shift_down
.max(base.descent() + sub_drop_min)
.max(sub.ascent() - sub_top_max);
if both {
let sup_bottom = shift_up - sup.descent();
let sub_top = sub.ascent() - shift_down;
let gap = sup_bottom - sub_top;
if gap < gap_min {
let increase = gap_min - gap;
let sup_only =
(sup_bottom_max_with_sub - sup_bottom).clamp(Abs::zero(), increase);
let rest = (increase - sup_only) / 2.0;
shift_up += sup_only + rest;
shift_down += rest;
}
}
let delta = base.italics_correction();
let ascent = shift_up + sup.ascent();
let descent = shift_down + sub.descent();
let height = ascent + descent;
let width = base.width() + sup.width().max(sub.width() - delta) + space_after;
let base_pos = Point::with_y(ascent - base.ascent());
let sup_pos = Point::with_x(base.width());
let sub_pos = Point::new(base.width() - delta, height - sub.height());
let class = base.class().unwrap_or(MathClass::Normal);
let mut frame = Frame::new(Size::new(width, height));
frame.set_baseline(ascent);
frame.push_frame(base_pos, base.to_frame(ctx));
frame.push_frame(sub_pos, sub);
frame.push_frame(sup_pos, sup);
ctx.push(FrameFragment { frame, class, limits: false });
Ok(())
}
/// Layout limits.
fn limits(
ctx: &mut MathContext,
base: MathFragment,
sub: Frame,
sup: Frame,
) -> SourceResult<()> {
let upper_gap_min = scaled!(ctx, upper_limit_gap_min);
let upper_rise_min = scaled!(ctx, upper_limit_baseline_rise_min);
let lower_gap_min = scaled!(ctx, lower_limit_gap_min);
let lower_drop_min = scaled!(ctx, lower_limit_baseline_drop_min);
let sup_gap = upper_gap_min.max(upper_rise_min - sup.descent());
let sub_gap = lower_gap_min.max(lower_drop_min - sub.ascent());
let delta = base.italics_correction() / 2.0;
let width = base.width().max(sup.width()).max(sub.width());
let height = sup.height() + sup_gap + base.height() + sub_gap + sub.height();
let base_pos = Point::new((width - base.width()) / 2.0, sup.height() + sup_gap);
let sup_pos = Point::with_x((width - sup.width()) / 2.0 + delta);
let sub_pos = Point::new((width - sub.width()) / 2.0 - delta, height - sub.height());
let class = base.class().unwrap_or(MathClass::Normal);
let mut frame = Frame::new(Size::new(width, height));
frame.set_baseline(base_pos.y + base.ascent());
frame.push_frame(base_pos, base.to_frame(ctx));
frame.push_frame(sub_pos, sub);
frame.push_frame(sup_pos, sup);
ctx.push(FrameFragment { frame, class, limits: false });
Ok(())
}
/// Codepoints that should have sub- and superscripts attached as limits.
const LIMITS: &[char] = &[
'\u{2210}', '\u{22C1}', '\u{22C0}', '\u{2A04}', '\u{22C2}', '\u{22C3}', '\u{220F}',
'\u{2211}', '\u{2A02}', '\u{2A01}', '\u{2A00}', '\u{2A06}',
];
|
