Introduce new `iced_highlighter` subcrate

2 files changed, 241 insertions, 0 deletions

diff --git a/highlighter/Cargo.toml b/highlighter/Cargo.toml
new file mode 100644
index 00000000..311d2998
--- /dev/null
+++ b/highlighter/Cargo.toml
@@ -0,0 +1,16 @@
+[package]
+name = "iced_highlighter"
+description = "A syntax higlighter for iced"
+version.workspace = true
+authors.workspace = true
+edition.workspace = true
+license.workspace = true
+repository.workspace = true
+homepage.workspace = true
+categories.workspace = true
+keywords.workspace = true
+
+[dependencies]
+iced_core.workspace = true
+
+syntect.workspace = true
diff --git a/highlighter/src/lib.rs b/highlighter/src/lib.rs
new file mode 100644
index 00000000..79cfafcd
--- /dev/null
+++ b/highlighter/src/lib.rs
@@ -0,0 +1,225 @@
+use iced_core as core;
+
+use crate::core::text::highlighter::{self, Format};
+use crate::core::{Color, Font};
+
+use std::ops::Range;
+use syntect::highlighting;
+use syntect::parsing;
+
+pub struct Highlighter {
+    syntaxes: parsing::SyntaxSet,
+    syntax: parsing::SyntaxReference,
+    theme: highlighting::Theme,
+    caches: Vec<(parsing::ParseState, parsing::ScopeStack)>,
+    current_line: usize,
+}
+
+const LINES_PER_SNAPSHOT: usize = 50;
+
+impl highlighter::Highlighter for Highlighter {
+    type Settings = Settings;
+    type Highlight = Highlight;
+
+    type Iterator<'a> =
+        Box<dyn Iterator<Item = (Range<usize>, Self::Highlight)> + 'a>;
+
+    fn new(settings: &Self::Settings) -> Self {
+        let syntaxes = parsing::SyntaxSet::load_defaults_nonewlines();
+
+        let syntax = syntaxes
+            .find_syntax_by_token(&settings.extension)
+            .unwrap_or_else(|| syntaxes.find_syntax_plain_text());
+
+        let theme = highlighting::ThemeSet::load_defaults()
+            .themes
+            .remove(settings.theme.key())
+            .unwrap();
+
+        let parser = parsing::ParseState::new(syntax);
+        let stack = parsing::ScopeStack::new();
+
+        Highlighter {
+            syntax: syntax.clone(),
+            syntaxes,
+            theme,
+            caches: vec![(parser, stack)],
+            current_line: 0,
+        }
+    }
+
+    fn update(&mut self, new_settings: &Self::Settings) {
+        self.syntax = self
+            .syntaxes
+            .find_syntax_by_token(&new_settings.extension)
+            .unwrap_or_else(|| self.syntaxes.find_syntax_plain_text())
+            .clone();
+
+        self.theme = highlighting::ThemeSet::load_defaults()
+            .themes
+            .remove(new_settings.theme.key())
+            .unwrap();
+
+        // Restart the highlighter
+        self.change_line(0);
+    }
+
+    fn change_line(&mut self, line: usize) {
+        let snapshot = line / LINES_PER_SNAPSHOT;
+
+        if snapshot <= self.caches.len() {
+            self.caches.truncate(snapshot);
+            self.current_line = snapshot * LINES_PER_SNAPSHOT;
+        } else {
+            self.caches.truncate(1);
+            self.current_line = 0;
+        }
+
+        let (parser, stack) =
+            self.caches.last().cloned().unwrap_or_else(|| {
+                (
+                    parsing::ParseState::new(&self.syntax),
+                    parsing::ScopeStack::new(),
+                )
+            });
+
+        self.caches.push((parser, stack));
+    }
+
+    fn highlight_line(&mut self, line: &str) -> Self::Iterator<'_> {
+        if self.current_line / LINES_PER_SNAPSHOT >= self.caches.len() {
+            let (parser, stack) =
+                self.caches.last().expect("Caches must not be empty");
+
+            self.caches.push((parser.clone(), stack.clone()));
+        }
+
+        self.current_line += 1;
+
+        let (parser, stack) =
+            self.caches.last_mut().expect("Caches must not be empty");
+
+        let ops = parser.parse_line(line, &self.syntaxes).unwrap_or_default();
+
+        let highlighter = highlighting::Highlighter::new(&self.theme);
+
+        Box::new(
+            ScopeRangeIterator {
+                ops,
+                line_length: line.len(),
+                index: 0,
+                last_str_index: 0,
+            }
+            .filter_map(move |(range, scope)| {
+                let _ = stack.apply(&scope);
+
+                if range.is_empty() {
+                    None
+                } else {
+                    Some((
+                        range,
+                        Highlight(
+                            highlighter.style_mod_for_stack(&stack.scopes),
+                        ),
+                    ))
+                }
+            }),
+        )
+    }
+
+    fn current_line(&self) -> usize {
+        self.current_line
+    }
+}
+
+#[derive(Debug, Clone, PartialEq)]
+pub struct Settings {
+    pub theme: Theme,
+    pub extension: String,
+}
+
+pub struct Highlight(highlighting::StyleModifier);
+
+impl Highlight {
+    pub fn color(&self) -> Option<Color> {
+        self.0.foreground.map(|color| {
+            Color::from_rgba8(color.r, color.g, color.b, color.a as f32 / 255.0)
+        })
+    }
+
+    pub fn font(&self) -> Option<Font> {
+        None
+    }
+
+    pub fn to_format(&self) -> Format<Font> {
+        Format {
+            color: self.color(),
+            font: self.font(),
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Theme {
+    SolarizedDark,
+    InspiredGitHub,
+    Base16Mocha,
+}
+
+impl Theme {
+    pub const ALL: &[Self] =
+        &[Self::SolarizedDark, Self::InspiredGitHub, Self::Base16Mocha];
+
+    fn key(&self) -> &'static str {
+        match self {
+            Theme::InspiredGitHub => "InspiredGitHub",
+            Theme::Base16Mocha => "base16-mocha.dark",
+            Theme::SolarizedDark => "Solarized (dark)",
+        }
+    }
+}
+
+impl std::fmt::Display for Theme {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Theme::InspiredGitHub => write!(f, "Inspired GitHub"),
+            Theme::Base16Mocha => write!(f, "Mocha"),
+            Theme::SolarizedDark => write!(f, "Solarized Dark"),
+        }
+    }
+}
+
+pub struct ScopeRangeIterator {
+    ops: Vec<(usize, parsing::ScopeStackOp)>,
+    line_length: usize,
+    index: usize,
+    last_str_index: usize,
+}
+
+impl Iterator for ScopeRangeIterator {
+    type Item = (std::ops::Range<usize>, parsing::ScopeStackOp);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.index > self.ops.len() {
+            return None;
+        }
+
+        let next_str_i = if self.index == self.ops.len() {
+            self.line_length
+        } else {
+            self.ops[self.index].0
+        };
+
+        let range = self.last_str_index..next_str_i;
+        self.last_str_index = next_str_i;
+
+        let op = if self.index == 0 {
+            parsing::ScopeStackOp::Noop
+        } else {
+            self.ops[self.index - 1].1.clone()
+        };
+
+        self.index += 1;
+        Some((range, op))
+    }
+}