96 lines
2.3 KiB
Rust
96 lines
2.3 KiB
Rust
use crate::{
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canvas::{Drawable, Frame, Layer},
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Primitive,
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};
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use iced_native::{Point, Size};
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use std::{cell::RefCell, marker::PhantomData};
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/// A simple cache that stores generated geometry to avoid recomputation.
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///
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/// A [`Cache`] will not redraw its geometry unless the dimensions of its layer
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/// change or it is explicitly cleared.
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///
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/// [`Layer`]: ../trait.Layer.html
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/// [`Cached`]: struct.Cached.html
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#[derive(Debug)]
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pub struct Cache<T: Drawable> {
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input: PhantomData<T>,
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state: RefCell<State>,
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}
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#[derive(Debug)]
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enum State {
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Empty,
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Filled { bounds: Size, primitive: Primitive },
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}
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impl<T> Cache<T>
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where
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T: Drawable + std::fmt::Debug,
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{
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/// Creates a new empty [`Cache`].
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///
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/// [`Cache`]: struct.Cache.html
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pub fn new() -> Self {
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Cache {
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input: PhantomData,
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state: RefCell::new(State::Empty),
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}
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}
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/// Clears the cache, forcing a redraw the next time it is used.
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///
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/// [`Cached`]: struct.Cached.html
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pub fn clear(&mut self) {
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*self.state.borrow_mut() = State::Empty;
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}
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/// Binds the [`Cache`] with some data, producing a [`Layer`] that can be
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/// added to a [`Canvas`].
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///
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/// [`Cache`]: struct.Cache.html
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/// [`Layer`]: ../trait.Layer.html
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/// [`Canvas`]: ../../struct.Canvas.html
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pub fn with<'a>(&'a self, input: &'a T) -> impl Layer + 'a {
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Bind {
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cache: self,
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input: input,
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}
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}
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}
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#[derive(Debug)]
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struct Bind<'a, T: Drawable> {
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cache: &'a Cache<T>,
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input: &'a T,
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}
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impl<'a, T> Layer for Bind<'a, T>
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where
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T: Drawable + std::fmt::Debug,
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{
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fn draw(&self, origin: Point, current_bounds: Size) -> Primitive {
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use std::ops::Deref;
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if let State::Filled { bounds, primitive } =
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self.cache.state.borrow().deref()
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{
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if *bounds == current_bounds {
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return primitive.clone();
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}
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}
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let mut frame = Frame::new(current_bounds.width, current_bounds.height);
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self.input.draw(&mut frame);
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let primitive = frame.into_primitive(origin);
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*self.cache.state.borrow_mut() = State::Filled {
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bounds: current_bounds,
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primitive: primitive.clone(),
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};
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primitive
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}
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}
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