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//! Absolute placement of nodes.
use super::prelude::*;
use super::AlignNode;
/// `place`: Place content at an absolute position.
pub fn place(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
let aligns = args.find().unwrap_or(Spec::new(Some(Align::Left), None));
let tx = args.named("dx")?.unwrap_or_default();
let ty = args.named("dy")?.unwrap_or_default();
let body: PackedNode = args.expect("body")?;
Ok(Value::block(PlacedNode(
body.moved(Point::new(tx, ty)).aligned(aligns),
)))
}
/// A node that places its child absolutely.
#[derive(Debug, Hash)]
pub struct PlacedNode(pub PackedNode);
impl PlacedNode {
/// Whether this node wants to be placed relative to its its parent's base
/// origin. instead of relative to the parent's current flow/cursor
/// position.
pub fn out_of_flow(&self) -> bool {
self.0
.downcast::<AlignNode>()
.map_or(false, |node| node.aligns.y.is_some())
}
}
impl Layout for PlacedNode {
fn layout(
&self,
ctx: &mut LayoutContext,
regions: &Regions,
styles: StyleChain,
) -> Vec<Constrained<Rc<Frame>>> {
let out_of_flow = self.out_of_flow();
// The pod is the base area of the region because for absolute
// placement we don't really care about the already used area (current).
let pod = {
let finite = regions.base.map(Length::is_finite);
let expand = finite & (regions.expand | out_of_flow);
Regions::one(regions.base, regions.base, expand)
};
let mut frames = self.0.layout(ctx, &pod, styles);
let Constrained { item: frame, cts } = &mut frames[0];
// If expansion is off, zero all sizes so that we don't take up any
// space in our parent. Otherwise, respect the expand settings.
let target = regions.expand.select(regions.current, Size::zero());
Rc::make_mut(frame).resize(target, Align::LEFT_TOP);
// Set base constraint because our pod size is base and exact
// constraints if we needed to expand or offset.
*cts = Constraints::new(regions.expand);
cts.base = regions.base.map(Some);
cts.exact = regions.current.filter(regions.expand | out_of_flow);
frames
}
}
|
