1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
|
use typst_library::diag::SourceResult;
use typst_library::foundations::{Packed, StyleChain};
use typst_library::layout::{Em, Frame, Point, Rel, Size};
use typst_library::math::{Accent, AccentElem};
use super::{
scaled_font_size, style_cramped, FrameFragment, GlyphFragment, MathContext,
MathFragment,
};
/// How much the accent can be shorter than the base.
const ACCENT_SHORT_FALL: Em = Em::new(0.5);
/// Lays out an [`AccentElem`].
#[typst_macros::time(name = "math.accent", span = elem.span())]
pub fn layout_accent(
elem: &Packed<AccentElem>,
ctx: &mut MathContext,
styles: StyleChain,
) -> SourceResult<()> {
let cramped = style_cramped();
let base = ctx.layout_into_fragment(elem.base(), styles.chain(&cramped))?;
// Preserve class to preserve automatic spacing.
let base_class = base.class();
let base_attach = base.accent_attach();
let width = elem
.size(styles)
.unwrap_or(Rel::one())
.at(scaled_font_size(ctx, styles))
.relative_to(base.width());
// Forcing the accent to be at least as large as the base makes it too
// wide in many case.
let Accent(c) = elem.accent();
let glyph = GlyphFragment::new(ctx, styles, *c, elem.span());
let short_fall = ACCENT_SHORT_FALL.at(glyph.font_size);
let variant = glyph.stretch_horizontal(ctx, width, short_fall);
let accent = variant.frame;
let accent_attach = variant.accent_attach;
// Descent is negative because the accent's ink bottom is above the
// baseline. Therefore, the default gap is the accent's negated descent
// minus the accent base height. Only if the base is very small, we need
// a larger gap so that the accent doesn't move too low.
let accent_base_height = scaled!(ctx, styles, accent_base_height);
let gap = -accent.descent() - base.height().min(accent_base_height);
let size = Size::new(base.width(), accent.height() + gap + base.height());
let accent_pos = Point::with_x(base_attach - accent_attach);
let base_pos = Point::with_y(accent.height() + gap);
let baseline = base_pos.y + base.ascent();
let base_italics_correction = base.italics_correction();
let base_text_like = base.is_text_like();
let base_ascent = match &base {
MathFragment::Frame(frame) => frame.base_ascent,
_ => base.ascent(),
};
let mut frame = Frame::soft(size);
frame.set_baseline(baseline);
frame.push_frame(accent_pos, accent);
frame.push_frame(base_pos, base.into_frame());
ctx.push(
FrameFragment::new(ctx, styles, frame)
.with_class(base_class)
.with_base_ascent(base_ascent)
.with_italics_correction(base_italics_correction)
.with_accent_attach(base_attach)
.with_text_like(base_text_like),
);
Ok(())
}
|
