syntax_theme_file: preview code with a syntect .tmTheme file

src/app/app_context.rs

@@ -30,6 +30,10 @@ use {
         verb::*,
     },
     crokey::crossterm::tty::IsTty,
+    syntect::highlighting::{
+        Theme,
+        ThemeSet,
+    },
     std::{
         convert::{
             TryFrom,
@@ -91,6 +95,10 @@ pub struct AppContext {
     /// the syntect theme to use for text files previewing
     pub syntax_theme: Option<SyntaxTheme>,
 
+    /// a theme loaded from a .tmTheme file, used when syntax_theme is None,
+    /// which it is until a theme is chosen with :set_syntax_theme
+    pub custom_syntax_theme: Option<Theme>,
+
     /// precomputed status to display in standard cases
     /// (ie when no verb is involved)
     pub standard_status: StandardStatus,
@@ -261,6 +269,16 @@ impl AppContext {
         }
         let reset_terminal_title_on_exit = config.reset_terminal_title_on_exit.unwrap_or(false);
         let preview_transformers = PreviewTransformers::new(&config.preview_transformers)?;
+        let custom_syntax_theme = config
+            .syntax_theme_file
+            .as_ref()
+            .map(|path| {
+                ThemeSet::get_theme(path).map_err(|e| ConfError::InvalidSyntaxThemeFile {
+                    path: path.display().to_string(),
+                    details: e.to_string(),
+                })
+            })
+            .transpose()?;
         let layout_instructions = config.layout_instructions.clone().unwrap_or_default();
         let kept_kitty_temp_files = config.kept_kitty_temp_files.unwrap_or(
             #[expect(clippy::missing_panics_doc, reason = "infallible")]
@@ -284,6 +302,7 @@ impl AppContext {
             preview_overflow: config.wrap_previews.map(Overflow::from_wrap_bool).unwrap_or_default(),
             ext_colors,
             syntax_theme: config.syntax_theme,
+            custom_syntax_theme,
             standard_status,
             true_colors,
             icons,

src/conf/conf.rs

@@ -157,6 +157,11 @@ pub struct Conf {
     #[serde(alias = "syntax-theme")]
     pub syntax_theme: Option<SyntaxTheme>,
 
+    /// path to a syntect compatible .tmTheme file, used for previews
+    /// instead of syntax_theme. An empty path unsets it.
+    #[serde(alias = "syntax-theme-file")]
+    pub syntax_theme_file: Option<PathBuf>,
+
     #[serde(alias = "terminal-title")]
     pub terminal_title: Option<ExecPattern>,
 
@@ -248,7 +253,21 @@ impl Conf {
         overwrite!(self, default_flags, conf);
         overwrite!(self, date_time_format, conf);
         overwrite!(self, icon_theme, conf);
-        overwrite!(self, syntax_theme, conf);
+        // syntax_theme and syntax_theme_file replace each other, so that the
+        // last one read wins; when a file sets both, syntax_theme_file wins
+        if conf.syntax_theme.is_some() {
+            self.syntax_theme = conf.syntax_theme.take();
+            self.syntax_theme_file = None;
+        }
+        if let Some(file) = conf.syntax_theme_file.take() {
+            let file = file.to_string_lossy();
+            // an empty path unsets it
+            self.syntax_theme_file = (!file.is_empty()).then(|| {
+                // relative to the conf file declaring it
+                path_from(&path, PathAnchor::Parent, &file)
+            });
+            self.syntax_theme = None;
+        }
         overwrite!(self, disable_mouse_capture, conf);
         overwrite!(self, capture_mouse, conf);
         overwrite!(self, true_colors, conf);

src/conf/conf_error.rs

@@ -67,6 +67,8 @@ pub enum ConfError {
     InvalidDefaultFlags { flags: String },
     #[error("invalid syntax theme: `{name}`")]
     InvalidSyntaxTheme { name: String },
+    #[error("invalid syntax theme file `{path}`: {details}")]
+    InvalidSyntaxThemeFile { path: String, details: String },
     #[error("invalid glob pattern: `{pattern}`")]
     InvalidGlobPattern { pattern: String },
     #[error(

src/syntactic/syntaxer.rs

@@ -41,21 +41,23 @@ impl Syntaxer {
         self.theme_set.themes.keys()
     }
 
-    pub fn highlighter_for(
-        &self,
+    pub fn highlighter_for<'s>(
+        &'s self,
         path: &Path,
-        con: &AppContext,
-    ) -> Option<HighlightLines<'_>> {
+        con: &'s AppContext,
+    ) -> Option<HighlightLines<'s>> {
         path.extension()
             .and_then(|e| e.to_str())
             .and_then(|ext| self.syntax_set.find_syntax_by_extension(ext))
             .map(|syntax| {
-                let theme = con.syntax_theme.unwrap_or_default();
-                let theme = self
-                    .theme_set
-                    .themes
-                    .get(theme.syntect_name())
-                    .unwrap_or_else(|| self.theme_set.themes.iter().next().unwrap().1);
+                let theme = match (con.syntax_theme, &con.custom_syntax_theme) {
+                    (None, Some(theme)) => theme,
+                    (theme, _) => self
+                        .theme_set
+                        .themes
+                        .get(theme.unwrap_or_default().syntect_name())
+                        .unwrap_or_else(|| self.theme_set.themes.iter().next().unwrap().1),
+                };
                 let options = HighlightOptions {
                     ignore_errors: true,
                 };

src/syntactic/text_view.rs

@@ -63,7 +63,8 @@ pub static SEPARATOR_FILLING: Lazy<Filling> = Lazy::new(|| Filling::from_char('
 /// Homogeneously colored piece of a line
 #[derive(Debug, Clone)]
 pub struct Region {
-    pub fg: Color,
+    /// None when the preview's normal foreground is to be used
+    pub fg: Option<Color>,
     pub string: String,
 }
 
@@ -77,10 +78,18 @@ const INITIAL_LOAD: usize = 4_000_000;
 
 impl Region {
     pub fn from_syntect(region: &(Style, &str)) -> Self {
-        let fg = Color::Rgb {
-            r: region.0.foreground.r,
-            g: region.0.foreground.g,
-            b: region.0.foreground.b,
+        // As in bat's ansi and base16 themes, an alpha of 0 makes the red
+        // channel a terminal palette index, and an alpha of 1 means the
+        // default foreground
+        let c = region.0.foreground;
+        let fg = match c.a {
+            0 => Some(Color::AnsiValue(c.r)),
+            1 => None,
+            _ => Some(Color::Rgb {
+                r: c.r,
+                g: c.g,
+                b: c.b,
+            }),
         };
         let string = region.1.to_string();
         Self { fg, string }
@@ -572,7 +581,7 @@ impl TextView {
                         let regions = if line.regions.is_empty() && line.len > 0 {
                             match rows.read(line) {
                                 Some(string) => Cow::Owned(vec![Region {
-                                    fg: normal_fg,
+                                    fg: None,
                                     string,
                                 }]),
                                 None => {
@@ -618,7 +627,7 @@ impl TextView {
                     let pos_list = line.name_match.as_ref().map(|nm| &nm.pos);
                     if overflow == Overflow::NoWrap && pos_list.is_none() {
                         for region in regions {
-                            cw.w.queue(SetForegroundColor(region.fg))?;
+                            cw.w.queue(SetForegroundColor(region.fg.unwrap_or(normal_fg)))?;
                             let s = region.string.trim_end_matches(is_char_end_of_line);
                             if s.contains('\t') {
                                 cw.queue_unstyled_str(&s.replace('\t', &" ".repeat(TAB_WIDTH)))?;
@@ -634,7 +643,7 @@ impl TextView {
                         let mut run = String::new();
                         'regions: for region in regions {
                             flush(&mut cw, &mut run)?;
-                            cw.w.queue(SetForegroundColor(region.fg))?;
+                            cw.w.queue(SetForegroundColor(region.fg.unwrap_or(normal_fg)))?;
                             for c in region.string.chars() {
                                 if ci >= to {
                                     break 'regions;

website/src/conf_file.md

@@ -266,6 +266,24 @@ syntax_theme = "OceanLight"
 
 Those themes come from [syntect](https://github.com/trishume/syntect) and are bundled in broot.
 
+You may also use your own theme, in the `.tmTheme` format read by syntect (and by [bat](https://github.com/sharkdp/bat)), by giving its path:
+
+```Hjson
+syntax_theme_file: ~/.config/bat/themes/my-theme.tmTheme
+```
+```TOML
+syntax_theme_file = "~/.config/bat/themes/my-theme.tmTheme"
+```
+
+A relative path is resolved from the configuration file declaring it.
+
+`syntax_theme` and `syntax_theme_file` replace each other: the one read last wins.
+As imported files are read after the file importing them, a `syntax_theme` set in your skin replaces a `syntax_theme_file` set in `conf.hjson`, so it's usually best to set `syntax_theme_file` in the skin file your `conf.hjson` imports (for example `skins/dark-blue.hjson`), in place of its `syntax_theme`.
+An empty `syntax_theme_file` unsets it.
+A theme chosen with `:set_syntax_theme` replaces the theme file until broot is closed.
+
+Themes made for the terminal's palette, like bat's `ansi` and `base16` themes, are supported.
+
 
 # Terminal title