tek/crates/tek_layout/src/inset.rs

use crate::*;

impl<E: Engine, W: Render<E>> LayoutInset<E> for W {}

pub trait LayoutInset<E: Engine>: Render<E> + Sized {
    fn inset_x (self, x: E::Unit) -> Inset<E, Self> {
        Inset::X(x, self)
    }
    fn inset_y (self, y: E::Unit) -> Inset<E, Self> {
        Inset::Y(y, self)
    }
    fn inset_xy (self, x: E::Unit, y: E::Unit) -> Inset<E, Self> {
        Inset::XY(x, y, self)
    }
}

/// Shrink from each side
pub enum Inset<E: Engine, T> {
    _Unused(PhantomData<E>),
    /// Decrease width
    X(E::Unit, T),
    /// Decrease height
    Y(E::Unit, T),
    /// Decrease width and height
    XY(E::Unit, E::Unit, T),
}

impl<E: Engine, T: Render<E>> Inset<E, T> {
    pub fn inner (&self) -> &T {
        match self {
            Self::X(_, i) => i,
            Self::Y(_, i) => i,
            Self::XY(_, _, i) => i,
            _ => unreachable!(),
        }
    }
}

impl<E: Engine, T: Render<E>> Render<E> for Inset<E, T> {
    fn render (&self, to: &mut E::Output) -> Usually<()> {
        match *self {
            Self::X(x, ref inner)     => (inner as &dyn Render<E>).shrink_x(x).push_x(x),
            Self::Y(y, ref inner)     => (inner as &dyn Render<E>).shrink_y(y).push_y(y),
            Self::XY(x, y, ref inner) => (inner as &dyn Render<E>).shrink_xy(x, y).push_xy(x, y),
            _ => unreachable!(),
        }.render(to)
    }
}