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|
use super::*;
/// A node that adds padding to its child.
#[derive(Debug, Hash)]
pub struct PadNode {
/// The amount of padding.
pub padding: Sides<Linear>,
/// The child node whose sides to pad.
pub child: BlockNode,
}
impl BlockLevel for PadNode {
fn layout(
&self,
ctx: &mut LayoutContext,
regions: &Regions,
) -> Vec<Constrained<Rc<Frame>>> {
// Layout child into padded regions.
let mut frames = self.child.layout(
ctx,
®ions.map(|size| size - self.padding.resolve(size).size()),
);
for (Constrained { item: frame, cts }, (current, base)) in
frames.iter_mut().zip(regions.iter())
{
fn solve_axis(length: Length, padding: Linear) -> Length {
(length + padding.abs)
.div_finite(1.0 - padding.rel.get())
.unwrap_or_default()
}
// Solve for the size `padded` that satisfies (approximately):
// `padded - padding.resolve(padded).size() == size`
let padded = Size::new(
solve_axis(frame.size.w, self.padding.left + self.padding.right),
solve_axis(frame.size.h, self.padding.top + self.padding.bottom),
);
let padding = self.padding.resolve(padded);
let origin = Point::new(padding.left, padding.top);
// Create a new larger frame and place the child's frame inside it.
let empty = Frame::new(padded, frame.baseline + origin.y);
let prev = std::mem::replace(frame, Rc::new(empty));
let new = Rc::make_mut(frame);
new.push_frame(origin, prev);
// Inflate min and max contraints by the padding.
for spec in [&mut cts.min, &mut cts.max] {
if let Some(x) = spec.x.as_mut() {
*x += padding.size().w;
}
if let Some(y) = spec.y.as_mut() {
*y += padding.size().h;
}
}
// Set exact and base constraints if the child had them.
cts.exact.x.and_set(Some(current.w));
cts.exact.y.and_set(Some(current.h));
cts.base.x.and_set(Some(base.w));
cts.base.y.and_set(Some(base.h));
// Also set base constraints if the padding is relative.
if self.padding.left.is_relative() || self.padding.right.is_relative() {
cts.base.x = Some(base.w);
}
if self.padding.top.is_relative() || self.padding.bottom.is_relative() {
cts.base.y = Some(base.h);
}
}
frames
}
}
|
