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Load themes lazily for improved startup time
This is for sharkdp#951. Syntax lazy-loading will come later and have a much bigger impact, but lazy-loading of themes does not have negligible impact.
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Original file line number | Diff line number | Diff line change |
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use super::*; | ||
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use std::collections::BTreeMap; | ||
use std::convert::TryFrom; | ||
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use serde::Deserialize; | ||
use serde::Serialize; | ||
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use once_cell::unsync::OnceCell; | ||
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use syntect::highlighting::{Theme, ThemeSet}; | ||
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/// Same structure as a [`syntect::highlighting::ThemeSet`] but with themes | ||
/// stored in raw serialized form, and deserialized on demand. | ||
#[derive(Debug, Default, Serialize, Deserialize)] | ||
pub struct LazyThemeSet { | ||
/// This is a [`BTreeMap`] because that's what [`syntect::highlighting::ThemeSet`] uses | ||
themes: BTreeMap<String, LazyTheme>, | ||
} | ||
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/// Stores raw serialized data for a theme with methods to lazily deserialize | ||
/// (load) the theme. | ||
#[derive(Debug, Serialize, Deserialize)] | ||
struct LazyTheme { | ||
serialized: Vec<u8>, | ||
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#[serde(skip, default = "OnceCell::new")] | ||
deserialized: OnceCell<syntect::highlighting::Theme>, | ||
} | ||
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impl LazyThemeSet { | ||
/// Lazily load the given theme | ||
pub fn get(&self, name: &str) -> Option<&Theme> { | ||
self.themes.get(name).and_then(|lazy_theme| { | ||
lazy_theme | ||
.deserialized | ||
.get_or_try_init(|| lazy_theme.deserialize()) | ||
.ok() | ||
}) | ||
} | ||
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/// Returns the name of all themes. | ||
pub fn themes(&self) -> impl Iterator<Item = &str> { | ||
self.themes.keys().map(|name| name.as_ref()) | ||
} | ||
} | ||
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impl LazyTheme { | ||
fn deserialize(&self) -> Result<Theme> { | ||
asset_from_contents( | ||
&self.serialized[..], | ||
"lazy-loaded theme", | ||
COMPRESS_LAZY_THEMES, | ||
) | ||
} | ||
} | ||
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impl TryFrom<LazyThemeSet> for ThemeSet { | ||
type Error = Error; | ||
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/// Since the user might want to add custom themes to bat, we need a way to | ||
/// convert from a `LazyThemeSet` to a regular [`ThemeSet`] so that more | ||
/// themes can be added. This function does that pretty straight-forward | ||
/// conversion. | ||
fn try_from(lazy_theme_set: LazyThemeSet) -> Result<Self> { | ||
let mut theme_set = ThemeSet::default(); | ||
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for (name, lazy_theme) in lazy_theme_set.themes { | ||
theme_set.themes.insert(name, lazy_theme.deserialize()?); | ||
} | ||
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Ok(theme_set) | ||
} | ||
} | ||
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#[cfg(feature = "build-assets")] | ||
impl TryFrom<ThemeSet> for LazyThemeSet { | ||
type Error = Error; | ||
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/// To collect themes, a [`ThemeSet`] is needed. Once all desired themes | ||
/// have been added, we need a way to convert that into [`LazyThemeSet`] so | ||
/// that themes can be lazy-loaded later. This function does that | ||
/// conversion. | ||
fn try_from(theme_set: ThemeSet) -> Result<Self> { | ||
let mut lazy_theme_set = LazyThemeSet::default(); | ||
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for (name, theme) in theme_set.themes { | ||
// All we have to do is to serialize the theme | ||
let lazy_theme = LazyTheme { | ||
serialized: crate::assets::build_assets::asset_to_contents( | ||
&theme, | ||
&format!("theme {}", name), | ||
COMPRESS_LAZY_THEMES, | ||
)?, | ||
deserialized: OnceCell::new(), | ||
}; | ||
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// Ok done, now we can add it | ||
lazy_theme_set.themes.insert(name, lazy_theme); | ||
} | ||
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Ok(lazy_theme_set) | ||
} | ||
} |