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use super::*;

pub struct Shrink<T> {
    ratio: f64,
    child: T,
}

impl<T, R: AsRef<T>> AsRef<T> for Shrink<R> {
    fn as_ref(&self) -> &T {
        self.child.as_ref()
    }
}

impl<T, R: AsMut<T>> AsMut<T> for Shrink<R> {
    fn as_mut(&mut self) -> &mut T {
        self.child.as_mut()
    }
}

mod ext {
    use super::*;

    pub trait WidgetExt: Widget + Sized {
        fn shrink(self, ratio: f64) -> Shrink<Self> {
            Shrink { ratio, child: self }
        }
    }

    impl<T: Widget> WidgetExt for T {}
}

pub use ext::WidgetExt as _;

impl<T: Widget> Widget for Shrink<T> {
    fn calc_constraints(&mut self, children: &ConstraintsContext) -> Constraints {
        children.get_constraints(&self.child)
    }
    fn layout_children(&mut self, cx: &mut LayoutContext) {
        let ratio = self.ratio / 2.0;
        cx.set_position(
            &self.child,
            cx.position.extend_symmetric(-cx.position.size() * ratio),
        );
    }
    fn walk_children_mut<'a>(&mut self, f: &mut dyn FnMut(&mut dyn Widget)) {
        f(&mut self.child);
    }
}