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|
use super::*;
const FRAC_AROUND: Em = Em::new(0.1);
/// A mathematical fraction.
///
/// ## Example { #example }
/// ```example
/// $ 1/2 < (x+1)/2 $
/// $ ((x+1)) / 2 = frac(a, b) $
/// ```
///
/// ## Syntax { #syntax }
/// This function also has dedicated syntax: Use a slash to turn neighbouring
/// expressions into a fraction. Multiple atoms can be grouped into a single
/// expression using round grouping parenthesis. Such parentheses are removed
/// from the output, but you can nest multiple to force them.
///
/// Display: Fraction
/// Category: math
#[element(LayoutMath)]
pub struct FracElem {
/// The fraction's numerator.
#[required]
pub num: Content,
/// The fraction's denominator.
#[required]
pub denom: Content,
}
impl LayoutMath for FracElem {
#[tracing::instrument(skip(ctx))]
fn layout_math(&self, ctx: &mut MathContext) -> SourceResult<()> {
layout(ctx, &self.num(), &self.denom(), false, self.span())
}
}
/// A binomial expression.
///
/// ## Example { #example }
/// ```example
/// $ binom(n, k) $
/// ```
///
/// Display: Binomial
/// Category: math
#[element(LayoutMath)]
pub struct BinomElem {
/// The binomial's upper index.
#[required]
pub upper: Content,
/// The binomial's lower index.
#[required]
pub lower: Content,
}
impl LayoutMath for BinomElem {
fn layout_math(&self, ctx: &mut MathContext) -> SourceResult<()> {
layout(ctx, &self.upper(), &self.lower(), true, self.span())
}
}
/// Layout a fraction or binomial.
fn layout(
ctx: &mut MathContext,
num: &Content,
denom: &Content,
binom: bool,
span: Span,
) -> SourceResult<()> {
let short_fall = DELIM_SHORT_FALL.scaled(ctx);
let axis = scaled!(ctx, axis_height);
let thickness = scaled!(ctx, fraction_rule_thickness);
let shift_up = scaled!(
ctx,
text: fraction_numerator_shift_up,
display: fraction_numerator_display_style_shift_up,
);
let shift_down = scaled!(
ctx,
text: fraction_denominator_shift_down,
display: fraction_denominator_display_style_shift_down,
);
let num_min = scaled!(
ctx,
text: fraction_numerator_gap_min,
display: fraction_num_display_style_gap_min,
);
let denom_min = scaled!(
ctx,
text: fraction_denominator_gap_min,
display: fraction_denom_display_style_gap_min,
);
ctx.style(ctx.style.for_numerator());
let num = ctx.layout_frame(num)?;
ctx.unstyle();
ctx.style(ctx.style.for_denominator());
let denom = ctx.layout_frame(denom)?;
ctx.unstyle();
let around = FRAC_AROUND.scaled(ctx);
let num_gap = (shift_up - axis - num.descent()).max(num_min + thickness / 2.0);
let denom_gap = (shift_down + axis - denom.ascent()).max(denom_min + thickness / 2.0);
let line_width = num.width().max(denom.width());
let width = line_width + 2.0 * around;
let height = num.height() + num_gap + thickness + denom_gap + denom.height();
let size = Size::new(width, height);
let num_pos = Point::with_x((width - num.width()) / 2.0);
let line_pos =
Point::new((width - line_width) / 2.0, num.height() + num_gap + thickness / 2.0);
let denom_pos = Point::new((width - denom.width()) / 2.0, height - denom.height());
let baseline = line_pos.y + axis;
let mut frame = Frame::new(size);
frame.set_baseline(baseline);
frame.push_frame(num_pos, num);
frame.push_frame(denom_pos, denom);
if binom {
ctx.push(
GlyphFragment::new(ctx, '(', span).stretch_vertical(ctx, height, short_fall),
);
ctx.push(FrameFragment::new(ctx, frame));
ctx.push(
GlyphFragment::new(ctx, ')', span).stretch_vertical(ctx, height, short_fall),
);
} else {
frame.push(
line_pos,
FrameItem::Shape(
Geometry::Line(Point::with_x(line_width)).stroked(Stroke {
paint: TextElem::fill_in(ctx.styles()),
thickness,
..Stroke::default()
}),
span,
),
);
ctx.push(FrameFragment::new(ctx, frame));
}
Ok(())
}
|
