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use crate::Vec2;
use crate::XY;
/// Cache around a one-dimensional layout result.
///
/// This is not a View, but something to help you if you create your own Views.
#[derive(PartialEq, Debug, Clone, Copy)]
pub struct SizeCache {
/// Cached value
pub value: usize,
/// `true` if the last size was constrained.
///
/// If unconstrained, any request larger than this value
/// would return the same size.
pub constrained: bool,
}
impl SizeCache {
/// Creates a new sized cache
pub fn new(value: usize, constrained: bool) -> Self {
SizeCache { value, constrained }
}
/// Returns `true` if `self` is still valid for the given `request`.
pub fn accept(self, request: usize) -> bool {
match (request, self.value) {
// Request a smaller size than last time? Hell no!
(r, v) if r < v => false,
// Request exactly what we had last time? Sure!
(r, v) if r == v => true,
// Request more than we had last time? Maybe?
_ => !self.constrained,
}
}
/// Returns the value in the cache.
pub fn value(self) -> usize {
self.value
}
/// Creates a new bi-dimensional cache.
///
/// It will stay valid for the same request, and compatible ones.
///
/// A compatible request is one where, for each axis, either:
///
/// * the request is equal to the cached size, or
/// * the request is larger than the cached size and the cache is
/// unconstrained
///
/// Notes:
///
/// * `size` must fit inside `req`.
/// * for each dimension, `constrained = (size == req)`
pub fn build(size: Vec2, req: Vec2) -> XY<Self> {
size.zip_map(req, |size, req| SizeCache::new(size, size >= req))
}
}