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use kurbo::{BezPath, Line, ParamCurve};
use ttf_parser::{GlyphId, OutlineBuilder};
use typst_library::layout::{Abs, Em, Frame, FrameItem, Point, Size};
use typst_library::text::{
BottomEdge, DecoLine, Decoration, TextEdgeBounds, TextItem, TopEdge,
};
use typst_library::visualize::{FixedStroke, Geometry};
use typst_syntax::Span;
use crate::shapes::styled_rect;
/// Add line decorations to a single run of shaped text.
pub fn decorate(
frame: &mut Frame,
deco: &Decoration,
text: &TextItem,
width: Abs,
shift: Abs,
pos: Point,
) {
let font_metrics = text.font.metrics();
if let DecoLine::Highlight { fill, stroke, top_edge, bottom_edge, radius } =
&deco.line
{
let (top, bottom) = determine_edges(text, *top_edge, *bottom_edge);
let size = Size::new(width + 2.0 * deco.extent, top + bottom);
let rects = styled_rect(size, radius, fill.clone(), stroke);
let origin = Point::new(pos.x - deco.extent, pos.y - top - shift);
frame.prepend_multiple(
rects
.into_iter()
.map(|shape| (origin, FrameItem::Shape(shape, Span::detached()))),
);
return;
}
let (stroke, metrics, offset, evade, background) = match &deco.line {
DecoLine::Strikethrough { stroke, offset, background } => {
(stroke, font_metrics.strikethrough, offset, false, *background)
}
DecoLine::Overline { stroke, offset, evade, background } => {
(stroke, font_metrics.overline, offset, *evade, *background)
}
DecoLine::Underline { stroke, offset, evade, background } => {
(stroke, font_metrics.underline, offset, *evade, *background)
}
_ => return,
};
let offset = offset.unwrap_or(-metrics.position.at(text.size)) - shift;
let stroke = stroke.clone().unwrap_or(FixedStroke::from_pair(
text.fill.as_decoration(),
metrics.thickness.at(text.size),
));
let gap_padding = 0.08 * text.size;
let min_width = 0.162 * text.size;
let start = pos.x - deco.extent;
let end = pos.x + width + deco.extent;
let mut push_segment = |from: Abs, to: Abs, prepend: bool| {
let origin = Point::new(from, pos.y + offset);
let target = Point::new(to - from, Abs::zero());
if target.x >= min_width || !evade {
let shape = Geometry::Line(target).stroked(stroke.clone());
if prepend {
frame.prepend(origin, FrameItem::Shape(shape, Span::detached()));
} else {
frame.push(origin, FrameItem::Shape(shape, Span::detached()));
}
}
};
if !evade {
push_segment(start, end, background);
return;
}
let line = Line::new(
kurbo::Point::new(pos.x.to_raw(), offset.to_raw()),
kurbo::Point::new((pos.x + width).to_raw(), offset.to_raw()),
);
let mut x = pos.x;
let mut intersections = vec![];
for glyph in text.glyphs.iter() {
let dx = glyph.x_offset.at(text.size) + x;
let mut builder =
BezPathBuilder::new(font_metrics.units_per_em, text.size, dx.to_raw());
let bbox = text.font.ttf().outline_glyph(GlyphId(glyph.id), &mut builder);
let path = builder.finish();
x += glyph.x_advance.at(text.size);
// Only do the costly segments intersection test if the line
// intersects the bounding box.
let intersect = bbox.is_some_and(|bbox| {
let y_min = -text.font.to_em(bbox.y_max).at(text.size);
let y_max = -text.font.to_em(bbox.y_min).at(text.size);
offset >= y_min && offset <= y_max
});
if intersect {
// Find all intersections of segments with the line.
intersections.extend(
path.segments()
.flat_map(|seg| seg.intersect_line(line))
.map(|is| Abs::raw(line.eval(is.line_t).x)),
);
}
}
// Add start and end points, taking padding into account.
intersections.push(start - gap_padding);
intersections.push(end + gap_padding);
// When emitting the decorative line segments, we move from left to
// right. The intersections are not necessarily in this order, yet.
intersections.sort();
for edge in intersections.windows(2) {
let l = edge[0];
let r = edge[1];
// If we are too close, don't draw the segment
if r - l < gap_padding {
continue;
} else {
push_segment(l + gap_padding, r - gap_padding, background);
}
}
}
// Return the top/bottom edge of the text given the metric of the font.
fn determine_edges(
text: &TextItem,
top_edge: TopEdge,
bottom_edge: BottomEdge,
) -> (Abs, Abs) {
let mut top = Abs::zero();
let mut bottom = Abs::zero();
for g in text.glyphs.iter() {
let (t, b) = text.font.edges(
top_edge,
bottom_edge,
text.size,
TextEdgeBounds::Glyph(g.id),
);
top.set_max(t);
bottom.set_max(b);
}
(top, bottom)
}
/// Builds a kurbo [`BezPath`] for a glyph.
struct BezPathBuilder {
path: BezPath,
units_per_em: f64,
font_size: Abs,
x_offset: f64,
}
impl BezPathBuilder {
fn new(units_per_em: f64, font_size: Abs, x_offset: f64) -> Self {
Self {
path: BezPath::new(),
units_per_em,
font_size,
x_offset,
}
}
fn finish(self) -> BezPath {
self.path
}
fn p(&self, x: f32, y: f32) -> kurbo::Point {
kurbo::Point::new(self.s(x) + self.x_offset, -self.s(y))
}
fn s(&self, v: f32) -> f64 {
Em::from_units(v, self.units_per_em).at(self.font_size).to_raw()
}
}
impl OutlineBuilder for BezPathBuilder {
fn move_to(&mut self, x: f32, y: f32) {
self.path.move_to(self.p(x, y));
}
fn line_to(&mut self, x: f32, y: f32) {
self.path.line_to(self.p(x, y));
}
fn quad_to(&mut self, x1: f32, y1: f32, x: f32, y: f32) {
self.path.quad_to(self.p(x1, y1), self.p(x, y));
}
fn curve_to(&mut self, x1: f32, y1: f32, x2: f32, y2: f32, x: f32, y: f32) {
self.path.curve_to(self.p(x1, y1), self.p(x2, y2), self.p(x, y));
}
fn close(&mut self) {
self.path.close_path();
}
}
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