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|
use crate::{
canvas::{Drawable, Frame, Layer},
Primitive,
};
use iced_native::Size;
use std::{cell::RefCell, marker::PhantomData, sync::Arc};
/// 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.
///
/// [`Layer`]: ../trait.Layer.html
/// [`Cached`]: struct.Cached.html
#[derive(Debug)]
pub struct Cache<T: Drawable> {
input: PhantomData<T>,
state: RefCell<State>,
}
#[derive(Debug)]
enum State {
Empty,
Filled {
bounds: Size,
primitive: Arc<Primitive>,
},
}
impl<T> Cache<T>
where
T: Drawable + std::fmt::Debug,
{
/// Creates a new empty [`Cache`].
///
/// [`Cache`]: struct.Cache.html
pub fn new() -> Self {
Cache {
input: PhantomData,
state: RefCell::new(State::Empty),
}
}
/// Clears the cache, forcing a redraw the next time it is used.
///
/// [`Cached`]: struct.Cached.html
pub fn clear(&mut self) {
*self.state.borrow_mut() = State::Empty;
}
/// Binds the [`Cache`] with some data, producing a [`Layer`] that can be
/// added to a [`Canvas`].
///
/// [`Cache`]: struct.Cache.html
/// [`Layer`]: ../trait.Layer.html
/// [`Canvas`]: ../../struct.Canvas.html
pub fn with<'a>(&'a self, input: &'a T) -> impl Layer + 'a {
Bind {
cache: self,
input: input,
}
}
}
#[derive(Debug)]
struct Bind<'a, T: Drawable> {
cache: &'a Cache<T>,
input: &'a T,
}
impl<'a, T> Layer for Bind<'a, T>
where
T: Drawable + std::fmt::Debug,
{
fn draw(&self, current_bounds: Size) -> Arc<Primitive> {
use std::ops::Deref;
if let State::Filled { bounds, primitive } =
self.cache.state.borrow().deref()
{
if *bounds == current_bounds {
return primitive.clone();
}
}
let mut frame = Frame::new(current_bounds.width, current_bounds.height);
self.input.draw(&mut frame);
let primitive = Arc::new(frame.into_primitive());
*self.cache.state.borrow_mut() = State::Filled {
bounds: current_bounds,
primitive: primitive.clone(),
};
primitive
}
}
|
