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use crate::prelude::*;
/// A line from one point to another.
///
/// ## Example
/// ```example
/// #set page(height: 100pt)
/// #line(length: 100%)
/// #line(end: (50%, 50%))
/// ```
///
/// Display: Line
/// Category: visualize
#[element(Layout)]
pub struct LineElem {
/// The start point of the line.
///
/// Must be an array of exactly two relative lengths.
#[resolve]
pub start: Axes<Rel<Length>>,
/// The offset from `start` where the line ends.
#[resolve]
pub end: Option<Axes<Rel<Length>>>,
/// The line's length. This is only respected if `end` is `none`.
#[resolve]
#[default(Abs::pt(30.0).into())]
pub length: Rel<Length>,
/// The angle at which the line points away from the origin. This is only
/// respected if `end` is `none`.
pub angle: Angle,
/// How to stroke the line. This can be:
///
/// - A length specifying the stroke's thickness. The color is inherited,
/// defaulting to black.
/// - A color to use for the stroke. The thickness is inherited, defaulting
/// to `{1pt}`.
/// - A stroke combined from color and thickness using the `+` operator as
/// in `{2pt + red}`.
///
/// ```example
/// #line(length: 100%, stroke: 2pt + red)
/// ```
#[resolve]
#[fold]
pub stroke: PartialStroke,
}
impl Layout for LineElem {
fn layout(
&self,
_: &mut Vt,
styles: StyleChain,
regions: Regions,
) -> SourceResult<Fragment> {
let resolve = |axes: Axes<Rel<Abs>>| {
axes.zip(regions.base()).map(|(l, b)| l.relative_to(b))
};
let start = resolve(self.start(styles));
let delta =
self.end(styles).map(|end| resolve(end) - start).unwrap_or_else(|| {
let length = self.length(styles);
let angle = self.angle(styles);
let x = angle.cos() * length;
let y = angle.sin() * length;
resolve(Axes::new(x, y))
});
let stroke = self.stroke(styles).unwrap_or_default();
let size = start.max(start + delta).max(Size::zero());
let target = regions.expand.select(regions.size, size);
let mut frame = Frame::new(target);
let shape = Geometry::Line(delta.to_point()).stroked(stroke);
frame.push(start.to_point(), FrameItem::Shape(shape, self.span()));
Ok(Fragment::frame(frame))
}
}
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