85 lines
2.2 KiB
Rust
85 lines
2.2 KiB
Rust
use crate::widget::canvas::{Frame, Geometry};
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use crate::{Primitive, Renderer, Size};
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use std::cell::RefCell;
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use std::sync::Arc;
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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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#[derive(Debug, Default)]
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pub struct Cache {
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state: RefCell<State>,
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}
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#[derive(Debug, Default)]
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enum State {
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#[default]
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Empty,
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Filled {
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bounds: Size,
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primitive: Arc<Primitive>,
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},
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}
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impl Cache {
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/// Creates a new empty [`Cache`].
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pub fn new() -> Self {
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Cache {
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state: Default::default(),
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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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pub fn clear(&self) {
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*self.state.borrow_mut() = State::Empty;
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}
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/// Draws [`Geometry`] using the provided closure and stores it in the
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/// [`Cache`].
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///
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/// The closure will only be called when
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/// - the bounds have changed since the previous draw call.
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/// - the [`Cache`] is empty or has been explicitly cleared.
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///
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/// Otherwise, the previously stored [`Geometry`] will be returned. The
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/// [`Cache`] is not cleared in this case. In other words, it will keep
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/// returning the stored [`Geometry`] if needed.
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pub fn draw<Theme>(
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&self,
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renderer: &Renderer<Theme>,
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bounds: Size,
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draw_fn: impl FnOnce(&mut Frame),
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) -> Geometry {
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use std::ops::Deref;
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if let State::Filled {
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bounds: cached_bounds,
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primitive,
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} = self.state.borrow().deref()
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{
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if *cached_bounds == bounds {
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return Geometry(Primitive::Cache {
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content: primitive.clone(),
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});
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}
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}
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let mut frame = Frame::new(renderer, bounds);
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draw_fn(&mut frame);
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let primitive = {
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let geometry = frame.into_geometry();
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Arc::new(geometry.0)
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};
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*self.state.borrow_mut() = State::Filled {
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bounds,
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primitive: primitive.clone(),
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};
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Geometry(Primitive::Cache { content: primitive })
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}
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}
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