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use super::*;
/// A node that adds padding to its child.
#[derive(Debug, Clone, PartialEq, Hash)]
pub struct PadNode {
/// The amount of padding.
pub padding: Sides<Linear>,
/// The child node whose sides to pad.
pub child: AnyNode,
}
impl Layout for PadNode {
fn layout(&self, ctx: &mut LayoutContext, regions: &Regions) -> Vec<Frame> {
let regions = regions.map(|size| size - self.padding.resolve(size).size());
let mut frames = self.child.layout(ctx, ®ions);
for frame in &mut frames {
let padded = solve(self.padding, frame.size);
let padding = self.padding.resolve(padded);
let origin = Point::new(padding.left, padding.top);
frame.size = padded;
frame.baseline += origin.y;
for (point, _) in &mut frame.elements {
*point += origin;
}
}
frames
}
}
/// Solve for the size `padded` that satisfies (approximately):
/// `padded - padding.resolve(padded).size() == size`
fn solve(padding: Sides<Linear>, size: Size) -> Size {
fn solve_axis(length: Length, padding: Linear) -> Length {
(length + padding.abs) / (1.0 - padding.rel.get())
}
Size::new(
solve_axis(size.width, padding.left + padding.right),
solve_axis(size.height, padding.top + padding.bottom),
)
}
impl From<PadNode> for AnyNode {
fn from(pad: PadNode) -> Self {
Self::new(pad)
}
}
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