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|
use crate::{
canvas::{Drawable, Frame, Geometry},
Primitive,
};
use iced_native::Size;
use std::{cell::RefCell, sync::Arc};
enum State {
Empty,
Filled {
bounds: Size,
primitive: Arc<Primitive>,
},
}
impl Default for State {
fn default() -> Self {
State::Empty
}
}
/// 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
/// [`Cache`]: struct.Cache.html
#[derive(Debug, Default)]
pub struct Cache {
state: RefCell<State>,
}
impl Cache {
/// Creates a new empty [`Cache`].
///
/// [`Cache`]: struct.Cache.html
pub fn new() -> Self {
Cache {
state: Default::default(),
}
}
/// 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;
}
pub fn draw<T>(&self, new_bounds: Size, input: T) -> Geometry
where
T: Drawable + std::fmt::Debug,
{
use std::ops::Deref;
if let State::Filled { bounds, primitive } = self.state.borrow().deref()
{
if *bounds == new_bounds {
return Geometry::from_primitive(Primitive::Cached {
cache: primitive.clone(),
});
}
}
let mut frame = Frame::new(new_bounds);
input.draw(&mut frame);
let primitive = {
let geometry = frame.into_geometry();
Arc::new(geometry.into_primitive())
};
*self.state.borrow_mut() = State::Filled {
bounds: new_bounds,
primitive: primitive.clone(),
};
Geometry::from_primitive(Primitive::Cached { cache: primitive })
}
pub fn with<'a, T, Message>(
&'a self,
input: T,
) -> impl crate::canvas::State<Message> + 'a
where
T: Drawable + std::fmt::Debug + 'a,
{
Bind { cache: self, input }
}
}
struct Bind<'a, T> {
cache: &'a Cache,
input: T,
}
impl<'a, T, Message> crate::canvas::State<Message> for Bind<'a, T>
where
T: Drawable + std::fmt::Debug + 'a,
{
fn draw(&self, bounds: Size) -> Vec<Geometry> {
vec![self.cache.draw(bounds, &self.input)]
}
}
impl std::fmt::Debug for State {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
State::Empty => write!(f, "Empty"),
State::Filled { primitive, bounds } => f
.debug_struct("Filled")
.field("primitive", primitive)
.field("bounds", bounds)
.finish(),
}
}
}
|
