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use std::rc::Rc;
use super::Regions;
use crate::frame::Frame;
use crate::geom::{Length, Size, Spec};
/// Constrain a frame with constraints.
pub trait Constrain {
/// Reference-count the frame and wrap it with constraints.
fn constrain(self, cts: Constraints) -> Constrained<Rc<Frame>>;
}
impl Constrain for Frame {
fn constrain(self, cts: Constraints) -> Constrained<Rc<Frame>> {
Constrained::new(Rc::new(self), cts)
}
}
/// Carries an item that is only valid in certain regions and the constraints
/// that describe these regions.
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
pub struct Constrained<T> {
/// The item that is only valid if the constraints are fullfilled.
pub item: T,
/// Constraints on regions in which the item is valid.
pub cts: Constraints,
}
impl<T> Constrained<T> {
/// Constrain an item with constraints.
pub fn new(item: T, cts: Constraints) -> Self {
Self { item, cts }
}
}
/// Describe regions that match them.
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
pub struct Constraints {
/// The minimum available length in the region.
pub min: Spec<Option<Length>>,
/// The maximum available length in the region.
pub max: Spec<Option<Length>>,
/// The available length in the region.
pub exact: Spec<Option<Length>>,
/// The base length of the region used for relative length resolution.
pub base: Spec<Option<Length>>,
/// The expand settings of the region.
pub expand: Spec<bool>,
}
impl Constraints {
/// Create a new region constraint.
pub fn new(expand: Spec<bool>) -> Self {
Self {
min: Spec::default(),
max: Spec::default(),
exact: Spec::default(),
base: Spec::default(),
expand,
}
}
/// Create tight constraints for a region.
pub fn tight(regions: &Regions) -> Self {
Self {
min: Spec::default(),
max: Spec::default(),
exact: regions.current.map(Some),
base: regions.base.map(Some),
expand: regions.expand,
}
}
/// Check whether the constraints are fullfilled in a region with the given
/// properties.
pub fn check(&self, current: Size, base: Size, expand: Spec<bool>) -> bool {
self.expand == expand
&& verify(self.min, current, |m, c| c.fits(m))
&& verify(self.max, current, |m, c| m.fits(c))
&& verify(self.exact, current, Length::approx_eq)
&& verify(self.base, base, Length::approx_eq)
}
}
/// Verify a single constraint.
fn verify(spec: Spec<Option<Length>>, size: Size, f: fn(Length, Length) -> bool) -> bool {
spec.zip(size).all(|&(opt, s)| opt.map_or(true, |m| f(m, s)))
}
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