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use crate::cache::{self, Cached};
use crate::core::Size;
use crate::geometry::{self, Frame};
pub use cache::Group;
/// A simple cache that stores generated geometry to avoid recomputation.
///
/// A [`Cache`] will not redraw its geometry unless the dimensions of its layer
/// change or it is explicitly cleared.
pub struct Cache<Renderer>
where
Renderer: geometry::Renderer,
{
raw: crate::Cache<Data<<Renderer::Geometry as Cached>::Cache>>,
}
#[derive(Debug, Clone)]
struct Data<T> {
bounds: Size,
geometry: T,
}
impl<Renderer> Cache<Renderer>
where
Renderer: geometry::Renderer,
{
/// Creates a new empty [`Cache`].
pub fn new() -> Self {
Cache {
raw: cache::Cache::new(),
}
}
/// Creates a new empty [`Cache`] with the given [`Group`].
///
/// Caches within the same group may reuse internal rendering storage.
///
/// You should generally group caches that are likely to change
/// together.
pub fn with_group(group: Group) -> Self {
Cache {
raw: crate::Cache::with_group(group),
}
}
/// Clears the [`Cache`], forcing a redraw the next time it is used.
pub fn clear(&self) {
self.raw.clear();
}
/// Draws geometry using the provided closure and stores it in the
/// [`Cache`].
///
/// The closure will only be called when
/// - the bounds have changed since the previous draw call.
/// - the [`Cache`] is empty or has been explicitly cleared.
///
/// Otherwise, the previously stored geometry will be returned. The
/// [`Cache`] is not cleared in this case. In other words, it will keep
/// returning the stored geometry if needed.
pub fn draw(
&self,
renderer: &Renderer,
bounds: Size,
draw_fn: impl FnOnce(&mut Frame<Renderer>),
) -> Renderer::Geometry {
use std::ops::Deref;
let state = self.raw.state();
let previous = match state.borrow().deref() {
cache::State::Empty { previous } => {
previous.as_ref().map(|data| data.geometry.clone())
}
cache::State::Filled { current } => {
if current.bounds == bounds {
return Cached::load(¤t.geometry);
}
Some(current.geometry.clone())
}
};
let mut frame = Frame::new(renderer, bounds);
draw_fn(&mut frame);
let geometry = frame.into_geometry().cache(self.raw.group(), previous);
let result = Cached::load(&geometry);
*state.borrow_mut() = cache::State::Filled {
current: Data { bounds, geometry },
};
result
}
}
impl<Renderer> std::fmt::Debug for Cache<Renderer>
where
Renderer: geometry::Renderer,
<Renderer::Geometry as Cached>::Cache: std::fmt::Debug,
{
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "{:?}", &self.raw)
}
}
impl<Renderer> Default for Cache<Renderer>
where
Renderer: geometry::Renderer,
{
fn default() -> Self {
Self::new()
}
}
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