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feat(no_std)!: option to disable layout cache for no_std compatibility (#1795)
Resolves #1780 BREAKING CHANGE: Disabling `default-features` will now disable layout cache, which can have a negative impact on performance. `Layout::init_cache` and `Layout::DEFAULT_CACHE_SIZE` are now only available if `layout-cache` feature is enabled.
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‎BREAKING-CHANGES.md‎

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@@ -20,6 +20,8 @@ This is a quick summary of the sections below:
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- `Backend` now uses `Self::Error` for error handling instead of `std::io::Error`
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- `Terminal<B>` now uses `B::Error` for error handling instead of `std::io::Error`
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- `TestBackend` now uses `core::convert::Infallible` for error handling instead of `std::io::Error`
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- Disabling `default-features` will now disable layout cache, which can have a negative impact on performance
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- `Layout::init_cache` and `Layout::DEFAULT_CACHE_SIZE` are now only available if `layout-cache` feature is enabled
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- [v0.29.0](#v0290)
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- `Sparkline::data` takes `IntoIterator<Item = SparklineBar>` instead of `&[u64]` and is no longer const
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- Removed public fields from `Rect` iterators
@@ -84,6 +86,26 @@ This is a quick summary of the sections below:
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## Unreleased (0.30.0)
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### `Layout::init_cache` and `Layout::DEFAULT_CACHE_SIZE` are now only available if `layout-cache` feature is enabled ([#1795])
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[#1795]: https://github.com/ratatui/ratatui/pull/1795
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Previously, `Layout::init_cache` and `Layout::DEFAULT_CACHE_SIZE` were available independently of
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enabled feature flags.
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### Disabling `default-features` will now disable layout cache, which can have a negative impact on performance ([#1795])
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[#1795]: https://github.com/ratatui/ratatui/pull/1795
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Layout cache is now opt-in in `ratatui-core` and enabled by default in `ratatui`. If app doesn't
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make use of `no_std`-compatibility, and disables `default-feature`, it is recommended to explicitly
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re-enable layout cache. Not doing so may impact performance.
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```diff
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- ratatui = { version = "0.29.0", default-features = false }
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+ ratatui = { version = "0.30.0", default-features = false, features = ["layout-cache"] }
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```
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### `TestBackend` now uses `core::convert::Infallible` for error handling instead of `std::io::Error` ([#1823])
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[#1823]: https://github.com/ratatui/ratatui/pull/1823

‎ratatui-core/Cargo.toml‎

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@@ -24,6 +24,12 @@ rustdoc-args = ["--cfg", "docsrs"]
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[features]
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default = []
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## enables std
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std = []
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## enables layout cache
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layout-cache = ["std"]
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## enables conversions to / from colors, modifiers, and styles in the ['anstyle'] crate
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anstyle = ["dep:anstyle"]
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‎ratatui-core/src/layout/layout.rs‎

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@@ -1,10 +1,9 @@
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use alloc::format;
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use alloc::rc::Rc;
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use alloc::vec::Vec;
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use core::cell::RefCell;
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use core::iter;
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use core::num::NonZeroUsize;
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use std::{dbg, thread_local};
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use std::dbg;
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use hashbrown::HashMap;
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use itertools::Itertools;
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// calculations.
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const FLOAT_PRECISION_MULTIPLIER: f64 = 100.0;
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thread_local! {
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static LAYOUT_CACHE: RefCell<Cache> = RefCell::new(Cache::new(
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#[cfg(feature = "layout-cache")]
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std::thread_local! {
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static LAYOUT_CACHE: core::cell::RefCell<Cache> = core::cell::RefCell::new(Cache::new(
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NonZeroUsize::new(Layout::DEFAULT_CACHE_SIZE).unwrap(),
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));
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}
@@ -188,6 +188,8 @@ impl Layout {
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/// bit more to make it a round number. This gives enough entries to store a layout for every
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/// row and every column, twice over, which should be enough for most apps. For those that need
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/// more, the cache size can be set with [`Layout::init_cache()`].
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/// This const is unused if layout cache is disabled.
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#[cfg(feature = "layout-cache")]
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pub const DEFAULT_CACHE_SIZE: usize = 500;
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/// Creates a new layout with default values.
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/// grows until `cache_size` is reached.
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///
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/// By default, the cache size is [`Self::DEFAULT_CACHE_SIZE`].
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#[cfg(feature = "layout-cache")]
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pub fn init_cache(cache_size: NonZeroUsize) {
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LAYOUT_CACHE.with_borrow_mut(|c| c.resize(cache_size));
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LAYOUT_CACHE.with_borrow_mut(|cache| cache.resize(cache_size));
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}
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/// Set the direction of the layout.
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/// );
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/// ```
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pub fn split_with_spacers(&self, area: Rect) -> (Segments, Spacers) {
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LAYOUT_CACHE.with_borrow_mut(|c| {
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let key = (area, self.clone());
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c.get_or_insert(key, || self.try_split(area).expect("failed to split"))
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.clone()
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})
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let split = || self.try_split(area).expect("failed to split");
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#[cfg(feature = "layout-cache")]
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{
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LAYOUT_CACHE.with_borrow_mut(|cache| {
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let key = (area, self.clone());
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cache.get_or_insert(key, split).clone()
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})
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}
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#[cfg(not(feature = "layout-cache"))]
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split()
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}
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fn try_split(&self, area: Rect) -> Result<(Segments, Spacers), AddConstraintError> {
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}
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#[test]
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#[cfg(feature = "layout-cache")]
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fn cache_size() {
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LAYOUT_CACHE.with_borrow(|c| {
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assert_eq!(c.cap().get(), Layout::DEFAULT_CACHE_SIZE);
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LAYOUT_CACHE.with_borrow(|cache| {
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assert_eq!(cache.cap().get(), Layout::DEFAULT_CACHE_SIZE);
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});
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Layout::init_cache(NonZeroUsize::new(10).unwrap());
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LAYOUT_CACHE.with_borrow(|c| {
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assert_eq!(c.cap().get(), 10);
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LAYOUT_CACHE.with_borrow(|cache| {
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assert_eq!(cache.cap().get(), 10);
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});
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}
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‎ratatui/Cargo.toml‎

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@@ -25,9 +25,10 @@ rustdoc-args = ["--cfg", "docsrs"]
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#!
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## By default, we enable the crossterm backend as this is a reasonable choice for most applications
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## as it is supported on Linux/Mac/Windows systems. We also enable the `underline-color` feature
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## which allows you to set the underline color of text and the `macros` feature which provides
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## some useful macros.
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default = ["crossterm", "underline-color", "all-widgets", "macros"]
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## which allows you to set the underline color of text, the `macros` feature which provides
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## some useful macros and `layout-cache` which speeds up layout cache calculations
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## in `std`-enabled environments.
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default = ["crossterm", "underline-color", "all-widgets", "macros", "layout-cache"]
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#! Generally an application will only use one backend, so you should only enable one of the following features:
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## enables the [`CrosstermBackend`](backend::CrosstermBackend) backend and adds a dependency on [`crossterm`].
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crossterm = ["dep:ratatui-crossterm"]
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"ratatui-termwiz?/serde",
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]
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## enables layout cache
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layout-cache = ["ratatui-core/layout-cache"]
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## enables conversions from colors in the [`palette`] crate to [`Color`](crate::style::Color).
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palette = ["ratatui-core/palette", "dep:palette"]
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‎xtask/src/commands/backend.rs‎

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@@ -54,6 +54,15 @@ impl Run for TestBackend {
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Backend::Termion => "termion",
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Backend::Termwiz => "termwiz",
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};
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// This is a temporary hack to run tests both with and without layout cache.
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// https://github.com/ratatui/ratatui/issues/1820
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run_cargo(vec![
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"test",
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"--all-targets",
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"--no-default-features",
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"--features",
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format!("{backend},layout-cache").as_str(),
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])?;
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run_cargo(vec![
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"test",
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"--all-targets",

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