Merge 6213319adc into a1f85b9e06

Document breaking change in library
Update terminal-colorsaurus (again)
2024-03-31 22:56:13 -04:00 · 2024-03-19 10:20:01 +01:00 · 2024-03-19 10:20:00 +01:00 · 2024-03-19 10:19:59 +01:00 · 2024-03-19 10:19:58 +01:00 · 2024-03-19 10:19:57 +01:00
20 changed files with 636 additions and 111 deletions
--- a/.gitignore
+++ b/.gitignore
@ -2,6 +2,7 @@
 **/*.rs.bk

 # Generated files
+/assets/completions/_bat.ps1
 /assets/completions/bat.bash
 /assets/completions/bat.fish
 /assets/completions/bat.zsh
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@ -6,6 +6,7 @@
 - `bat --squeeze-blank`/`bat -s` will now squeeze consecutive empty lines, see #1441 (@eth-p) and #2665 (@einfachIrgendwer0815)
 - `bat --squeeze-limit` to set the maximum number of empty consecutive when using `--squeeze-blank`, see #1441 (@eth-p) and #2665 (@einfachIrgendwer0815)
 - `PrettyPrinter::squeeze_empty_lines` to support line squeezing for bat as a library, see #1441 (@eth-p) and #2665 (@einfachIrgendwer0815)
+- Automatically choose theme based on the terminal's color scheme, see #2896 (@bash)

 ## Bugfixes

@ -49,6 +50,9 @@

 ## `bat` as a library

+- Add `theme::theme` for choosing an appropriate theme based on the
+  terminal's color scheme, see #2896 (@bash)
+  - [BREAKING] Remove `HighlightingAssets::default_theme`. Use `theme::default_theme` instead.
 - Changes to `syntax_mapping::SyntaxMapping` #2755 (@cyqsimon)
  - `SyntaxMapping::get_syntax_for` is now correctly public
  - [BREAKING] `SyntaxMapping::{empty,builtin}` are removed; use `SyntaxMapping::new` instead
--- a/Cargo.lock
+++ b/Cargo.lock
@ -149,6 +149,7 @@ dependencies = [
 "shell-words",
 "syntect",
 "tempfile",
+ "terminal-colorsaurus",
 "thiserror",
 "toml",
 "unicode-width",
@ -697,9 +698,9 @@ checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"

 [[package]]
 name = "libc"
-version = "0.2.149"
+version = "0.2.153"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a08173bc88b7955d1b3145aa561539096c421ac8debde8cbc3612ec635fee29b"
+checksum = "9c198f91728a82281a64e1f4f9eeb25d82cb32a5de251c6bd1b5154d63a8e7bd"

 [[package]]
 name = "libgit2-sys"
@ -764,9 +765,9 @@ checksum = "b5e6163cb8c49088c2c36f57875e58ccd8c87c7427f7fbd50ea6710b2f3f2e8f"

 [[package]]
 name = "memchr"
-version = "2.6.4"
+version = "2.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f665ee40bc4a3c5590afb1e9677db74a508659dfd71e126420da8274909a0167"
+checksum = "523dc4f511e55ab87b694dc30d0f820d60906ef06413f93d4d7a1385599cc149"

 [[package]]
 name = "miniz_oxide"
@ -777,6 +778,17 @@ dependencies = [
 "adler",
 ]

+[[package]]
+name = "mio"
+version = "0.8.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a4a650543ca06a924e8b371db273b2756685faae30f8487da1b56505a8f78b0c"
+dependencies = [
+ "libc",
+ "wasi",
+ "windows-sys 0.48.0",
+]
+
 [[package]]
 name = "nix"
 version = "0.26.4"
@ -958,9 +970,9 @@ dependencies = [

 [[package]]
 name = "proc-macro2"
-version = "1.0.66"
+version = "1.0.78"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "18fb31db3f9bddb2ea821cde30a9f70117e3f119938b5ee630b7403aa6e2ead9"
+checksum = "e2422ad645d89c99f8f3e6b88a9fdeca7fabeac836b1002371c4367c8f984aae"
 dependencies = [
 "unicode-ident",
 ]
@ -976,9 +988,9 @@ dependencies = [

 [[package]]
 name = "quote"
-version = "1.0.33"
+version = "1.0.35"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5267fca4496028628a95160fc423a33e8b2e6af8a5302579e322e4b520293cae"
+checksum = "291ec9ab5efd934aaf503a6466c5d5251535d108ee747472c3977cc5acc868ef"
 dependencies = [
 "proc-macro2",
 ]
@ -1255,9 +1267,9 @@ checksum = "73473c0e59e6d5812c5dfe2a064a6444949f089e20eec9a2e5506596494e4623"

 [[package]]
 name = "syn"
-version = "2.0.32"
+version = "2.0.52"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "239814284fd6f1a4ffe4ca893952cdd93c224b6a1571c9a9eadd670295c0c9e2"
+checksum = "b699d15b36d1f02c3e7c69f8ffef53de37aefae075d8488d4ba1a7788d574a07"
 dependencies = [
 "proc-macro2",
 "quote",
@ -1319,6 +1331,29 @@ dependencies = [
 "winapi-util",
 ]

+[[package]]
+name = "terminal-colorsaurus"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a11d4fd698c3b697b6f712fa75f62f7b15119f41b0bb660741dd02297f534d78"
+dependencies = [
+ "libc",
+ "memchr",
+ "mio",
+ "terminal-trx",
+ "thiserror",
+]
+
+[[package]]
+name = "terminal-trx"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1a4af7c93f02d5bd5e120c812f7fb413003b7060e8a22d0ea90346f1be769210"
+dependencies = [
+ "libc",
+ "windows-sys 0.52.0",
+]
+
 [[package]]
 name = "terminal_size"
 version = "0.3.0"
@ -1337,18 +1372,18 @@ checksum = "507e9898683b6c43a9aa55b64259b721b52ba226e0f3779137e50ad114a4c90b"

 [[package]]
 name = "thiserror"
-version = "1.0.53"
+version = "1.0.57"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b2cd5904763bad08ad5513ddbb12cf2ae273ca53fa9f68e843e236ec6dfccc09"
+checksum = "1e45bcbe8ed29775f228095caf2cd67af7a4ccf756ebff23a306bf3e8b47b24b"
 dependencies = [
 "thiserror-impl",
 ]

 [[package]]
 name = "thiserror-impl"
-version = "1.0.53"
+version = "1.0.57"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3dcf4a824cce0aeacd6f38ae6f24234c8e80d68632338ebaa1443b5df9e29e19"
+checksum = "a953cb265bef375dae3de6663da4d3804eee9682ea80d8e2542529b73c531c81"
 dependencies = [
 "proc-macro2",
 "quote",
--- a/Cargo.toml
+++ b/Cargo.toml
@ -68,6 +68,7 @@ bytesize = { version = "1.3.0" }
 encoding_rs = "0.8.33"
 os_str_bytes = { version = "~6.6", optional = true }
 run_script = { version = "^0.10.1", optional = true}
+terminal-colorsaurus = { version = "0.3.3" }

 [dependencies.git2]
 version = "0.18"
--- a/README.md
+++ b/README.md
@ -474,8 +474,10 @@ the following command (you need [`fzf`](https://github.com/junegunn/fzf) for thi
 bat --list-themes | fzf --preview="bat --theme={} --color=always /path/to/file"
 ```

-`bat` looks good on a dark background by default. However, if your terminal uses a
-light background, some themes like `GitHub` or `OneHalfLight` will work better for you.
+`bat` automatically picks a fitting theme depending on your terminal's background color.
+You can use the `--theme-light` / `--theme-light` options or the `BAT_THEME_DARK` / `BAT_THEME_LIGHT` environment variables
+to customize the themes used. This is especially useful if you frequently switch between dark and light mode.
+
 You can also use a custom theme by following the
 ['Adding new themes' section below](https://github.com/sharkdp/bat#adding-new-themes).

--- a/assets/completions/_bat.ps1.in
+++ b/assets/completions/_bat.ps1.in
@ -32,11 +32,14 @@ Register-ArgumentCompleter -Native -CommandName '{{PROJECT_EXECUTABLE}}' -Script
            [CompletionResult]::new('--color', 'color', [CompletionResultType]::ParameterName, 'When to use colors (*auto*, never, always).')
            [CompletionResult]::new('--italic-text', 'italic-text', [CompletionResultType]::ParameterName, 'Use italics in output (always, *never*)')
            [CompletionResult]::new('--decorations', 'decorations', [CompletionResultType]::ParameterName, 'When to show the decorations (*auto*, never, always).')
+            [CompletionResult]::new('--detect-color-scheme', 'detect-color-scheme', [CompletionResultType]::ParameterName, 'When to detect the terminal''s color scheme (*auto*, never, always).')
            [CompletionResult]::new('--paging', 'paging', [CompletionResultType]::ParameterName, 'Specify when to use the pager, or use `-P` to disable (*auto*, never, always).')
            [CompletionResult]::new('--pager', 'pager', [CompletionResultType]::ParameterName, 'Determine which pager to use.')
            [CompletionResult]::new('-m', 'm', [CompletionResultType]::ParameterName, 'Use the specified syntax for files matching the glob pattern (''*.cpp:C++'').')
            [CompletionResult]::new('--map-syntax', 'map-syntax', [CompletionResultType]::ParameterName, 'Use the specified syntax for files matching the glob pattern (''*.cpp:C++'').')
            [CompletionResult]::new('--theme', 'theme', [CompletionResultType]::ParameterName, 'Set the color theme for syntax highlighting.')
+            [CompletionResult]::new('--theme-dark', 'theme', [CompletionResultType]::ParameterName, 'Set the color theme for syntax highlighting for dark backgrounds.')
+            [CompletionResult]::new('--theme-light', 'theme', [CompletionResultType]::ParameterName, 'Set the color theme for syntax highlighting for light backgrounds.')
            [CompletionResult]::new('--style', 'style', [CompletionResultType]::ParameterName, 'Comma-separated list of style elements to display (*default*, auto, full, plain, changes, header, header-filename, header-filesize, grid, rule, numbers, snip).')
            [CompletionResult]::new('-r', 'r', [CompletionResultType]::ParameterName, 'Only print the lines from N to M.')
            [CompletionResult]::new('--line-range', 'line-range', [CompletionResultType]::ParameterName, 'Only print the lines from N to M.')
--- a/assets/completions/bat.bash.in
+++ b/assets/completions/bat.bash.in
@ -99,7 +99,7 @@ _bat() {
 		COMPREPLY=($(compgen -W "auto never character" -- "$cur"))
 		return 0
 		;;
-	--color | --decorations | --paging)
+	--color | --decorations | --paging | --detect-color-scheme)
 		COMPREPLY=($(compgen -W "auto never always" -- "$cur"))
 		return 0
 		;;
@ -111,7 +111,9 @@ _bat() {
 		COMPREPLY=($(compgen -c -- "$cur"))
 		return 0
 		;;
-	--theme)
+	--theme | \
+	--theme-dark | \
+	--theme-light)
 		local IFS=$'\n'
 		COMPREPLY=($(compgen -W "$("$1" --list-themes)" -- "$cur"))
                __bat_escape_completions
@ -162,12 +164,15 @@ _bat() {
 			--color
 			--italic-text
 			--decorations
+			--detect-color-scheme
 			--force-colorization
 			--paging
 			--pager
 			--map-syntax
 			--ignored-suffix
 			--theme
+			--theme-dark
+			--theme-light
 			--list-themes
 			--style
 			--line-range
--- a/assets/completions/bat.fish.in
+++ b/assets/completions/bat.fish.in
@ -99,6 +99,7 @@ set -l color_opts '
 '
 set -l decorations_opts $color_opts
 set -l paging_opts $color_opts
+set -l detect_color_scheme_opts $color_opts

 # Include some examples so we can indicate the default.
 set -l pager_opts '
@ -141,6 +142,8 @@ complete -c $bat -l config-file -f -d "Display location of configuration file" -

 complete -c $bat -l decorations -x -a "$decorations_opts" -d "When to use --style decorations" -n __bat_no_excl_args

+complete -c $bat -l detect-color-scheme -x -a "$detect_color_scheme_opts" -d "When to detect the terminal's color scheme" -n __bat_no_excl_args
+
 complete -c $bat -l diagnostic -d "Print diagnostic info for bug reports" -n __fish_is_first_arg

 complete -c $bat -s d -l diff -d "Only show lines with Git changes" -n __bat_no_excl_args
@ -203,6 +206,10 @@ complete -c $bat -l terminal-width -x -d "Set terminal <width>, +<offset>, or -<

 complete -c $bat -l theme -x -a "(command $bat --list-themes | command cat)" -d "Set the syntax highlighting theme" -n __bat_no_excl_args

+complete -c $bat -l theme-dark -x -a "(command $bat --list-themes | command cat)" -d "Set the syntax highlighting theme for dark backgrounds" -n __bat_no_excl_args
+
+complete -c $bat -l theme-light -x -a "(command $bat --list-themes | command cat)" -d "Set the syntax highlighting theme for light backgrounds" -n __bat_no_excl_args
+
 complete -c $bat -s V -l version -f -d "Show version information" -n __fish_is_first_arg

 complete -c $bat -l wrap -x -a "$wrap_opts" -d "Text-wrapping mode" -n __bat_no_excl_args
--- a/assets/completions/bat.zsh.in
+++ b/assets/completions/bat.zsh.in
@ -40,9 +40,12 @@ _{{PROJECT_EXECUTABLE}}_main() {
        --color='[specify when to use colors]:when:(auto never always)'
        --italic-text='[use italics in output]:when:(always never)'
        --decorations='[specify when to show the decorations]:when:(auto never always)'
+        --detect-color-scheme="[specify when to detect the terminal's color scheme]:when:(auto never always)"
        --paging='[specify when to use the pager]:when:(auto never always)'
        '(-m --map-syntax)'{-m+,--map-syntax=}'[map a glob pattern to an existing syntax name]: :->syntax-maps'
        '(--theme)'--theme='[set the color theme for syntax highlighting]:theme:->themes'
+        '(--theme-dark)'--theme-dark='[set the color theme for syntax highlighting for dark backgrounds]:theme:->themes'
+        '(--theme-light)'--theme-light='[set the color theme for syntax highlighting for light backgrounds]:theme:->themes'
        '(: --list-themes --list-languages -L)'--list-themes'[show all supported highlighting themes]'
        --style='[comma-separated list of style elements to display]: : _values "style [default]"
            default auto full plain changes header header-filename header-filesize grid rule numbers snip'
--- a/assets/manual/bat.1.in
+++ b/assets/manual/bat.1.in
@ -113,6 +113,24 @@ Specify when to use the decorations that have been specified via '\-\-style'. Th
 automatic mode only enables decorations if an interactive terminal is detected. Possible
 values: *auto*, never, always.
 .HP
+\fB\-\-detect\-color\-scheme\fR <when>
+.IP
+Specify when to query the terminal for its colors in order to pick an appropriate syntax
+highlighting theme. Use \fB\-\-theme-light\fP and \fB\-\-theme-dark\fP (or the environment variables
+\fBBAT_THEME_LIGHT\fP and \fBBAT_THEME_DARK\fP) to configure which themes are picked. You can also use
+\fP\-\-theme\fP to set a theme that is used regardless of the terminal's colors.
+.IP
+\fI<when>\fP can be one of:
+.RS
+.IP "\fBauto\fP"
+Only query the terminals colors if the output is not redirected. This is to prevent
+race conditions with pagers such as less.
+.IP "never"
+Never query the terminal for its colors and assume that the terminal has a dark background.
+.IP "always"
+Always query the terminal for its colors, regardless of whether or not the output is redirected.
+.RE
+.HP
 \fB\-f\fR, \fB\-\-force\-colorization\fR
 .IP
 Alias for '--decorations=always --color=always'. This is useful \
@ -143,9 +161,23 @@ Note that the right-hand side is the *name* of the syntax, not a file extension.
 .HP
 \fB\-\-theme\fR <theme>
 .IP
-Set the theme for syntax highlighting. Use '\-\-list\-themes' to see all available themes.
-To set a default theme, add the '\-\-theme="..."' option to the configuration file or
-export the BAT_THEME environment variable (e.g.: export BAT_THEME="...").
+Set the theme for syntax highlighting. Use \fB\-\-list\-themes\fP to see all available themes.
+To set a default theme, add the \fB\-\-theme="..."\fP option to the configuration file or
+export the \fBBAT_THEME\fP environment variable (e.g.: \fBexport BAT_THEME="..."\fP).
+.HP
+\fB\-\-theme\-dark\fR <theme>
+.IP
+Sets the theme name for syntax highlighting used when the terminal uses a dark background.
+To set a default theme, add the \fB\-\-theme-dark="..."\fP option to the configuration file or 
+export the \fBBAT_THEME_DARK\fP environment variable (e.g. \fBexport BAT_THEME_DARK="..."\fP).
+This option is ignored if \fB\-\-theme\fP option is set.
+.HP
+\fB\-\-theme\-light\fR <theme>
+.IP
+Sets the theme name for syntax highlighting used when the terminal uses a dark background.
+To set a default theme, add the \fB\-\-theme-dark="..."\fP option to the configuration file or 
+export the \fBBAT_THEME_LIGHT\fP environment variable (e.g. \fBexport BAT_THEME_LIGHT="..."\fP).
+This option is ignored if \fB\-\-theme\fP option is set.
 .HP
 \fB\-\-list\-themes\fR
 .IP
--- a/doc/long-help.txt
+++ b/doc/long-help.txt
@ -109,9 +109,39 @@ Options:
            'bat --ignored-suffix ".dev" my_file.json.dev' will use JSON syntax, and ignore '.dev'

      --theme <theme>
-          Set the theme for syntax highlighting. Use '--list-themes' to see all available themes. To
-          set a default theme, add the '--theme="..."' option to the configuration file or export
-          the BAT_THEME environment variable (e.g.: export BAT_THEME="...").
+          Set the theme for syntax highlighting. Note that this option overrides '--theme-dark' and
+          '--theme-light'. Use '--list-themes' to see all available themes. To set a default theme,
+          add the '--theme="..."' option to the configuration file or export the BAT_THEME
+          environment variable (e.g.: export BAT_THEME="...").
+
+      --detect-color-scheme <when>
+          Specify when to query the terminal for its colors in order to pick an appropriate syntax
+          highlighting theme. Use '--theme-light' and '--theme-dark' (or the environment variables
+          BAT_THEME_LIGHT and BAT_THEME_DARK) to configure which themes are picked. You may also use
+          '--theme' to set a theme that is used regardless of the terminal's colors.
+          
+          Possible values:
+          * auto (default):
+               Only query the terminals colors if the output is not redirected. This is to prevent
+               race conditions with pagers such as less.
+          * never
+               Never query the terminal for its colors and assume that the terminal has a dark
+               background.
+          * always
+               Always query the terminal for its colors, regardless of whether or not the output is
+               redirected.
+
+      --theme-light <theme>
+          Sets the theme name for syntax highlighting used when the terminal uses a light
+          background. Use '--list-themes' to see all available themes. To set a default theme, add
+          the '--theme-light="..." option to the configuration file or export the BAT_THEME_LIGHT
+          environment variable (e.g. export BAT_THEME_LIGHT="...").
+
+      --theme-dark <theme>
+          Sets the theme name for syntax highlighting used when the terminal uses a dark background.
+          Use '--list-themes' to see all available themes. To set a default theme, add the
+          '--theme-dark="..." option to the configuration file or export the BAT_THEME_DARK
+          environment variable (e.g. export BAT_THEME_DARK="...").

      --list-themes
          Display a list of supported themes for syntax highlighting.
--- a/doc/short-help.txt
+++ b/doc/short-help.txt
@ -41,6 +41,12 @@ Options:
          Use the specified syntax for files matching the glob pattern ('*.cpp:C++').
      --theme <theme>
          Set the color theme for syntax highlighting.
+      --detect-color-scheme <when>
+          Specify when to query the terminal for its colors.
+      --theme-light <theme>
+          Sets the color theme for syntax highlighting used for light backgrounds.
+      --theme-dark <theme>
+          Sets the color theme for syntax highlighting used for dark backgrounds.
      --list-themes
          Display all supported highlighting themes.
  -s, --squeeze-blank
--- a/src/assets.rs
+++ b/src/assets.rs
@ -13,6 +13,7 @@ use crate::error::*;
 use crate::input::{InputReader, OpenedInput};
 use crate::syntax_mapping::ignored_suffixes::IgnoredSuffixes;
 use crate::syntax_mapping::MappingTarget;
+use crate::theme::{default_theme, ColorScheme};
 use crate::{bat_warning, SyntaxMapping};

 use lazy_theme_set::LazyThemeSet;
@ -69,57 +70,6 @@ impl HighlightingAssets {
        }
    }

-    /// The default theme.
-    ///
-    /// ### Windows and Linux
-    ///
-    /// Windows and most Linux distributions has a dark terminal theme by
-    /// default. On these platforms, this function always returns a theme that
-    /// looks good on a dark background.
-    ///
-    /// ### macOS
-    ///
-    /// On macOS the default terminal background is light, but it is common that
-    /// Dark Mode is active, which makes the terminal background dark. On this
-    /// platform, the default theme depends on
-    /// ```bash
-    /// defaults read -globalDomain AppleInterfaceStyle
-    /// ```
-    /// To avoid the overhead of the check on macOS, simply specify a theme
-    /// explicitly via `--theme`, `BAT_THEME`, or `~/.config/bat`.
-    ///
-    /// See <https://github.com/sharkdp/bat/issues/1746> and
-    /// <https://github.com/sharkdp/bat/issues/1928> for more context.
-    pub fn default_theme() -> &'static str {
-        #[cfg(not(target_os = "macos"))]
-        {
-            Self::default_dark_theme()
-        }
-        #[cfg(target_os = "macos")]
-        {
-            if macos_dark_mode_active() {
-                Self::default_dark_theme()
-            } else {
-                Self::default_light_theme()
-            }
-        }
-    }
-
-    /**
-     * The default theme that looks good on a dark background.
-     */
-    fn default_dark_theme() -> &'static str {
-        "Monokai Extended"
-    }
-
-    /**
-     * The default theme that looks good on a light background.
-     */
-    #[cfg(target_os = "macos")]
-    fn default_light_theme() -> &'static str {
-        "Monokai Extended Light"
-    }
-
    pub fn from_cache(cache_path: &Path) -> Result<Self> {
        Ok(HighlightingAssets::new(
            SerializedSyntaxSet::FromFile(cache_path.join("syntaxes.bin")),
@ -248,7 +198,10 @@ impl HighlightingAssets {
                    bat_warning!("Unknown theme '{}', using default.", theme)
                }
                self.get_theme_set()
-                    .get(self.fallback_theme.unwrap_or_else(Self::default_theme))
+                    .get(
+                        self.fallback_theme
+                            .unwrap_or_else(|| default_theme(ColorScheme::Dark)),
+                    )
                    .expect("something is very wrong if the default theme is missing")
            }
        }
@ -399,26 +352,6 @@ fn asset_from_cache<T: serde::de::DeserializeOwned>(
        .map_err(|_| format!("Could not parse cached {description}").into())
 }

-#[cfg(target_os = "macos")]
-fn macos_dark_mode_active() -> bool {
-    const PREFERENCES_FILE: &str = "Library/Preferences/.GlobalPreferences.plist";
-    const STYLE_KEY: &str = "AppleInterfaceStyle";
-
-    let preferences_file = home::home_dir()
-        .map(|home| home.join(PREFERENCES_FILE))
-        .expect("Could not get home directory");
-
-    match plist::Value::from_file(preferences_file).map(|file| file.into_dictionary()) {
-        Ok(Some(preferences)) => match preferences.get(STYLE_KEY).and_then(|val| val.as_string()) {
-            Some(value) => value == "Dark",
-            // If the key does not exist, then light theme is currently in use.
-            None => false,
-        },
-        // Unreachable, in theory. All macOS users have a home directory and preferences file setup.
-        Ok(None) | Err(_) => true,
-    }
-}
-
 #[cfg(test)]
 mod tests {
    use super::*;
--- a/src/bin/bat/app.rs
+++ b/src/bin/bat/app.rs
@ -2,18 +2,19 @@ use std::collections::HashSet;
 use std::env;
 use std::io::IsTerminal;
 use std::path::{Path, PathBuf};
+use std::str::FromStr as _;

 use crate::{
    clap_app,
    config::{get_args_from_config_file, get_args_from_env_opts_var, get_args_from_env_vars},
 };
+use bat::theme::{theme, DetectColorScheme, ThemeOptions, ThemeRequest};
 use clap::ArgMatches;

 use console::Term;

 use crate::input::{new_file_input, new_stdin_input};
 use bat::{
-    assets::HighlightingAssets,
    bat_warning,
    config::{Config, VisibleLines},
    error::*,
@ -242,18 +243,7 @@ impl App {
                        4
                    },
                ),
-            theme: self
-                .matches
-                .get_one::<String>("theme")
-                .map(String::from)
-                .map(|s| {
-                    if s == "default" {
-                        String::from(HighlightingAssets::default_theme())
-                    } else {
-                        s
-                    }
-                })
-                .unwrap_or_else(|| String::from(HighlightingAssets::default_theme())),
+            theme: theme(self.theme_options()),
            visible_lines: match self.matches.try_contains_id("diff").unwrap_or_default()
                && self.matches.get_flag("diff")
            {
@ -389,4 +379,35 @@ impl App {

        Ok(styled_components)
    }
+
+    fn theme_options(&self) -> ThemeOptions {
+        let theme = self
+            .matches
+            .get_one::<String>("theme")
+            .map(|t| ThemeRequest::from_str(t).unwrap());
+        let theme_dark = self
+            .matches
+            .get_one::<String>("theme-dark")
+            .map(|t| ThemeRequest::from_str(t).unwrap());
+        let theme_light = self
+            .matches
+            .get_one::<String>("theme-light")
+            .map(|t| ThemeRequest::from_str(t).unwrap());
+        let detect_color_scheme = match self
+            .matches
+            .get_one::<String>("detect-color-scheme")
+            .map(|s| s.as_str())
+        {
+            Some("auto") => DetectColorScheme::Auto,
+            Some("never") => DetectColorScheme::Never,
+            Some("always") => DetectColorScheme::Always,
+            _ => unreachable!("other values for --detect-color-scheme are not allowed"),
+        };
+        ThemeOptions {
+            theme,
+            theme_dark,
+            theme_light,
+            detect_color_scheme,
+        }
+    }
 }
--- a/src/bin/bat/clap_app.rs
+++ b/src/bin/bat/clap_app.rs
@ -373,13 +373,64 @@ pub fn build_app(interactive_output: bool) -> Command {
                .overrides_with("theme")
                .help("Set the color theme for syntax highlighting.")
                .long_help(
-                    "Set the theme for syntax highlighting. Use '--list-themes' to \
+                    "Set the theme for syntax highlighting. Note that this option overrides \
+                    '--theme-dark' and '--theme-light'. Use '--list-themes' to \
                     see all available themes. To set a default theme, add the \
                     '--theme=\"...\"' option to the configuration file or export the \
                     BAT_THEME environment variable (e.g.: export \
                     BAT_THEME=\"...\").",
                ),
        )
+        .arg(
+            Arg::new("detect-color-scheme")
+                .long("detect-color-scheme")
+                .overrides_with("detect-color-scheme")
+                .value_name("when")
+                .value_parser(["auto", "never", "always"])
+                .default_value("auto")
+                .hide_default_value(true)
+                .help("Specify when to query the terminal for its colors.")
+                .long_help(
+                    "Specify when to query the terminal for its colors \
+                     in order to pick an appropriate syntax highlighting theme. \
+                     Use '--theme-light' and '--theme-dark' (or the environment variables \
+                     BAT_THEME_LIGHT and BAT_THEME_DARK) to configure which themes are picked. \
+                     You may also use '--theme' to set a theme that is used regardless of the terminal's colors.\n\n\
+                     Possible values:\n\
+                     * auto (default):\n     \
+                            Only query the terminals colors if the output is not redirected. \
+                            This is to prevent race conditions with pagers such as less.\n\
+                     * never\n     \
+                           Never query the terminal for its colors \
+                           and assume that the terminal has a dark background.\n\
+                     * always\n     \
+                           Always query the terminal for its colors, \
+                           regardless of whether or not the output is redirected."),
+        )
+        .arg(
+            Arg::new("theme-light")
+                .long("theme-light")
+                .overrides_with("theme-light")
+                .value_name("theme")
+                .help("Sets the color theme for syntax highlighting used for light backgrounds.")
+                .long_help(
+                    "Sets the theme name for syntax highlighting used when the terminal uses a light background. \
+                    Use '--list-themes' to see all available themes. To set a default theme, add the \
+                    '--theme-light=\"...\" option to the configuration file or export the BAT_THEME_LIGHT \
+                    environment variable (e.g. export BAT_THEME_LIGHT=\"...\")."),
+        )
+        .arg(
+            Arg::new("theme-dark")
+                .long("theme-dark")
+                .overrides_with("theme-dark")
+                .value_name("theme")
+                .help("Sets the color theme for syntax highlighting used for dark backgrounds.")
+                .long_help(
+                    "Sets the theme name for syntax highlighting used when the terminal uses a dark background. \
+                    Use '--list-themes' to see all available themes. To set a default theme, add the \
+                    '--theme-dark=\"...\" option to the configuration file or export the BAT_THEME_DARK \
+                    environment variable (e.g. export BAT_THEME_DARK=\"...\")."),
+        )
        .arg(
            Arg::new("list-themes")
                .long("list-themes")
--- a/src/bin/bat/config.rs
+++ b/src/bin/bat/config.rs
@ -141,6 +141,8 @@ pub fn get_args_from_env_vars() -> Vec<OsString> {
    [
        ("--tabs", "BAT_TABS"),
        ("--theme", "BAT_THEME"),
+        ("--theme-dark", "BAT_THEME_DARK"),
+        ("--theme-light", "BAT_THEME_LIGHT"),
        ("--pager", "BAT_PAGER"),
        ("--paging", "BAT_PAGING"),
        ("--style", "BAT_STYLE"),
--- a/src/lib.rs
+++ b/src/lib.rs
@ -49,6 +49,7 @@ pub(crate) mod printer;
 pub mod style;
 pub(crate) mod syntax_mapping;
 mod terminal;
+pub mod theme;
 mod vscreen;
 pub(crate) mod wrapping;

--- a/src/pretty_printer.rs
+++ b/src/pretty_printer.rs
@ -236,7 +236,9 @@ impl<'a> PrettyPrinter<'a> {
        self
    }

-    /// Specify the highlighting theme
+    /// Specify the highlighting theme.
+    /// You can use [`crate::theme::theme`] to pick a theme based on user preferences
+    /// and the terminal's background color.
    pub fn theme(&mut self, theme: impl AsRef<str>) -> &mut Self {
        self.config.theme = theme.as_ref().to_owned();
        self
--- a/src/theme.rs
+++ b/src/theme.rs
@ -0,0 +1,384 @@
+//! Utilities for choosing an appropriate theme for syntax highlighting.
+
+use std::convert::Infallible;
+use std::io::IsTerminal as _;
+use std::str::FromStr;
+
+/// Chooses an appropriate theme or falls back to a default theme
+/// based on the user-provided options and the color scheme of the terminal.
+pub fn theme(options: ThemeOptions) -> String {
+    theme_from_detector(options, &TerminalColorSchemeDetector)
+}
+
+/// The default theme, suitable for the given color scheme.
+/// Use [`theme`] if you want to automatically detect the color scheme from the terminal.
+pub const fn default_theme(color_scheme: ColorScheme) -> &'static str {
+    match color_scheme {
+        ColorScheme::Dark => "Monokai Extended",
+        ColorScheme::Light => "Monokai Extended Light",
+    }
+}
+
+/// Options for configuring the theme used for syntax highlighting.
+/// Used together with [`theme`].
+#[derive(Debug, Default, PartialEq, Eq)]
+pub struct ThemeOptions {
+    /// Always use this theme regardless of the terminal's background color.
+    pub theme: Option<ThemeRequest>,
+    /// The theme to use in case the terminal uses a dark background with light text.
+    pub theme_dark: Option<ThemeRequest>,
+    /// The theme to use in case the terminal uses a light background with dark text.
+    pub theme_light: Option<ThemeRequest>,
+    /// Whether or not to test if the terminal is dark or light by querying for its colors.
+    pub detect_color_scheme: DetectColorScheme,
+}
+
+/// The name of a theme or the default theme.
+///
+/// ```
+/// # use bat::theme::ThemeRequest;
+/// # use std::str::FromStr as _;
+/// assert_eq!(ThemeRequest::Default, ThemeRequest::from_str("default").unwrap());
+/// assert_eq!(ThemeRequest::Named("example".to_string()), ThemeRequest::from_str("example").unwrap());
+/// ```
+#[derive(Debug, PartialEq, Eq, Hash)]
+pub enum ThemeRequest {
+    Named(String),
+    Default,
+}
+
+impl FromStr for ThemeRequest {
+    type Err = Infallible;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        if s == "default" {
+            Ok(ThemeRequest::Default)
+        } else {
+            Ok(ThemeRequest::Named(s.to_owned()))
+        }
+    }
+}
+
+impl ThemeRequest {
+    fn into_theme(self, color_scheme: ColorScheme) -> String {
+        match self {
+            ThemeRequest::Named(t) => t,
+            ThemeRequest::Default => default_theme(color_scheme).to_owned(),
+        }
+    }
+}
+
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum DetectColorScheme {
+    /// Only query the terminal for its colors when appropriate (i.e. when the the output is not redirected).
+    #[default]
+    Auto,
+    /// Always query the terminal for its colors.
+    Always,
+    /// Never query the terminal for its colors.
+    Never,
+}
+
+/// The color scheme used to pick a fitting theme. Defaults to [`ColorScheme::Dark`].
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum ColorScheme {
+    #[default]
+    Dark,
+    Light,
+}
+
+fn theme_from_detector(options: ThemeOptions, detector: &dyn ColorSchemeDetector) -> String {
+    // Implementation note: This function is mostly pure (i.e. it has no side effects) for the sake of testing.
+    // All the side effects (e.g. querying the terminal for its colors) are performed in the detector.
+    if let Some(theme) = options.theme {
+        theme.into_theme(ColorScheme::default())
+    } else {
+        let color_scheme = detect(options.detect_color_scheme, detector).unwrap_or_default();
+        choose_theme(options, color_scheme)
+            .map(|t| t.into_theme(color_scheme))
+            .unwrap_or_else(|| default_theme(color_scheme).to_owned())
+    }
+}
+
+fn choose_theme(options: ThemeOptions, color_scheme: ColorScheme) -> Option<ThemeRequest> {
+    match color_scheme {
+        ColorScheme::Dark => options.theme_dark,
+        ColorScheme::Light => options.theme_light,
+    }
+}
+
+fn detect(when: DetectColorScheme, detector: &dyn ColorSchemeDetector) -> Option<ColorScheme> {
+    let should_detect = match when {
+        DetectColorScheme::Auto => detector.should_detect(),
+        DetectColorScheme::Always => true,
+        DetectColorScheme::Never => false,
+    };
+    should_detect.then(|| detector.detect()).flatten()
+}
+
+trait ColorSchemeDetector {
+    fn should_detect(&self) -> bool;
+
+    fn detect(&self) -> Option<ColorScheme>;
+}
+
+struct TerminalColorSchemeDetector;
+
+impl ColorSchemeDetector for TerminalColorSchemeDetector {
+    fn should_detect(&self) -> bool {
+        // Querying the terminal for its colors via OSC 10 / OSC 11 requires "exclusive" access
+        // since we read/write from the terminal and enable/disable raw mode.
+        // This causes race conditions with pagers such as less when they are attached to the
+        // same terminal as us.
+        //
+        // This is usually only an issue when the output is manually piped to a pager.
+        // For example: `bat Cargo.toml | less`.
+        // Otherwise, if we start the pager ourselves, then there's no race condition
+        // since the pager is started *after* the color is detected.
+        std::io::stdout().is_terminal()
+    }
+
+    fn detect(&self) -> Option<ColorScheme> {
+        use terminal_colorsaurus::{color_scheme, QueryOptions};
+        let colors = color_scheme(QueryOptions::default()).ok()?;
+        if colors.is_light_on_dark() {
+            Some(ColorScheme::Dark)
+        } else {
+            Some(ColorScheme::Light)
+        }
+    }
+}
+
+#[cfg(test)]
+impl ColorSchemeDetector for Option<ColorScheme> {
+    fn should_detect(&self) -> bool {
+        true
+    }
+
+    fn detect(&self) -> Option<ColorScheme> {
+        *self
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::ColorScheme::*;
+    use super::DetectColorScheme::*;
+    use super::*;
+    use std::cell::Cell;
+    use std::iter;
+
+    mod color_scheme_detection {
+        use super::*;
+
+        #[test]
+        fn not_called_for_never() {
+            let detector = DetectorStub::should_detect(Some(Dark));
+            let options = ThemeOptions {
+                detect_color_scheme: Never,
+                ..Default::default()
+            };
+            _ = theme_from_detector(options, &detector);
+            assert!(!detector.was_called.get());
+        }
+
+        #[test]
+        fn called_for_always() {
+            let detectors = [
+                DetectorStub::should_detect(Some(Dark)),
+                DetectorStub::should_not_detect(),
+            ];
+            for detector in detectors {
+                let options = ThemeOptions {
+                    detect_color_scheme: Always,
+                    ..Default::default()
+                };
+                _ = theme_from_detector(options, &detector);
+                assert!(detector.was_called.get());
+            }
+        }
+
+        #[test]
+        fn called_for_auto_if_should_detect() {
+            let detector = DetectorStub::should_detect(Some(Dark));
+            _ = theme_from_detector(ThemeOptions::default(), &detector);
+            assert!(detector.was_called.get());
+        }
+
+        #[test]
+        fn not_called_for_auto_if_not_should_detect() {
+            let detector = DetectorStub::should_not_detect();
+            _ = theme_from_detector(ThemeOptions::default(), &detector);
+            assert!(!detector.was_called.get());
+        }
+    }
+
+    mod precedence {
+        use super::*;
+
+        #[test]
+        fn theme_is_preferred_over_light_or_dark_themes() {
+            for color_scheme in optional(color_schemes()) {
+                for options in [
+                    ThemeOptions {
+                        theme: Some(ThemeRequest::Named("Theme".to_string())),
+                        ..Default::default()
+                    },
+                    ThemeOptions {
+                        theme: Some(ThemeRequest::Named("Theme".to_string())),
+                        theme_dark: Some(ThemeRequest::Named("Dark Theme".to_string())),
+                        theme_light: Some(ThemeRequest::Named("Light Theme".to_string())),
+                        ..Default::default()
+                    },
+                ] {
+                    let detector = ConstantDetector(color_scheme);
+                    assert_eq!("Theme", theme_from_detector(options, &detector));
+                }
+            }
+        }
+
+        #[test]
+        fn detector_is_not_called_if_theme_is_present() {
+            let options = ThemeOptions {
+                theme: Some(ThemeRequest::Named("Theme".to_string())),
+                ..Default::default()
+            };
+            let detector = DetectorStub::should_detect(Some(Dark));
+            _ = theme_from_detector(options, &detector);
+            assert!(!detector.was_called.get());
+        }
+    }
+
+    mod default_theme {
+        use super::*;
+
+        #[test]
+        fn dark_if_unable_to_detect_color_scheme() {
+            let detector = ConstantDetector(None);
+            assert_eq!(
+                default_theme(ColorScheme::Dark),
+                theme_from_detector(ThemeOptions::default(), &detector)
+            );
+        }
+
+        // For backwards compatibility, if the default theme is requested
+        // explicitly through BAT_THEME, we always pick the default dark theme.
+        #[test]
+        fn dark_if_requested_explicitly_through_theme() {
+            for color_scheme in optional(color_schemes()) {
+                let options = ThemeOptions {
+                    theme: Some(ThemeRequest::Default),
+                    ..Default::default()
+                };
+                let detector = ConstantDetector(color_scheme);
+                assert_eq!(
+                    default_theme(ColorScheme::Dark),
+                    theme_from_detector(options, &detector)
+                );
+            }
+        }
+
+        #[test]
+        fn varies_depending_on_color_scheme() {
+            for color_scheme in color_schemes() {
+                for options in [
+                    ThemeOptions::default(),
+                    ThemeOptions {
+                        theme_dark: Some(ThemeRequest::Default),
+                        theme_light: Some(ThemeRequest::Default),
+                        ..Default::default()
+                    },
+                ] {
+                    let detector = ConstantDetector(Some(color_scheme));
+                    assert_eq!(
+                        default_theme(color_scheme),
+                        theme_from_detector(options, &detector)
+                    );
+                }
+            }
+        }
+    }
+
+    mod choosing {
+        use super::*;
+
+        #[test]
+        fn chooses_dark_theme_if_dark_or_unknown() {
+            for color_scheme in [Some(Dark), None] {
+                let options = ThemeOptions {
+                    theme_dark: Some(ThemeRequest::Named("Dark".to_string())),
+                    theme_light: Some(ThemeRequest::Named("Light".to_string())),
+                    ..Default::default()
+                };
+                let detector = ConstantDetector(color_scheme);
+                assert_eq!("Dark", theme_from_detector(options, &detector));
+            }
+        }
+
+        #[test]
+        fn chooses_light_theme_if_light() {
+            let options = ThemeOptions {
+                theme_dark: Some(ThemeRequest::Named("Dark".to_string())),
+                theme_light: Some(ThemeRequest::Named("Light".to_string())),
+                ..Default::default()
+            };
+            let detector = ConstantDetector(Some(ColorScheme::Light));
+            assert_eq!("Light", theme_from_detector(options, &detector));
+        }
+    }
+
+    struct DetectorStub {
+        should_detect: bool,
+        color_scheme: Option<ColorScheme>,
+        was_called: Cell<bool>,
+    }
+
+    impl DetectorStub {
+        fn should_detect(color_scheme: Option<ColorScheme>) -> Self {
+            DetectorStub {
+                should_detect: true,
+                color_scheme,
+                was_called: Cell::default(),
+            }
+        }
+
+        fn should_not_detect() -> Self {
+            DetectorStub {
+                should_detect: false,
+                color_scheme: None,
+                was_called: Cell::default(),
+            }
+        }
+    }
+
+    impl ColorSchemeDetector for DetectorStub {
+        fn should_detect(&self) -> bool {
+            self.should_detect
+        }
+
+        fn detect(&self) -> Option<ColorScheme> {
+            self.was_called.set(true);
+            self.color_scheme
+        }
+    }
+
+    struct ConstantDetector(Option<ColorScheme>);
+
+    impl ColorSchemeDetector for ConstantDetector {
+        fn should_detect(&self) -> bool {
+            true
+        }
+
+        fn detect(&self) -> Option<ColorScheme> {
+            self.0
+        }
+    }
+
+    fn optional<T>(value: impl Iterator<Item = T>) -> impl Iterator<Item = Option<T>> {
+        value.map(Some).chain(iter::once(None))
+    }
+
+    fn color_schemes() -> impl Iterator<Item = ColorScheme> {
+        [Dark, Light].into_iter()
+    }
+}
--- a/tests/integration_tests.rs
+++ b/tests/integration_tests.rs
@ -370,6 +370,7 @@ fn no_args_doesnt_break() {
    // as the slave end of a pseudo terminal. Although both point to the same "file", bat should
    // not exit, because in this case it is safe to read and write to the same fd, which is why
    // this test exists.
+
    let OpenptyResult { master, slave } = openpty(None, None).expect("Couldn't open pty.");
    let mut master = unsafe { File::from_raw_fd(master) };
    let stdin_file = unsafe { File::from_raw_fd(slave) };
@ -380,6 +381,7 @@ fn no_args_doesnt_break() {
    let mut child = bat_raw_command()
        .stdin(stdin)
        .stdout(stdout)
+        .env("TERM", "dumb") // Suppresses color detection
        .spawn()
        .expect("Failed to start.");
Author	SHA1	Message	Date
Tau	1099fc7bcf	Merge `6213319adc` into `a1f85b9e06`	2024-03-31 22:56:13 -04:00
Tau	6213319adc	Document breaking change in library	2024-03-19 10:20:01 +01:00
Tau	1a6353d576	Update terminal-colorsaurus (again)	2024-03-19 10:20:00 +01:00
Tau	4a7b65e2c2	Add changelog entry	2024-03-19 10:19:59 +01:00
Tau	02967933bc	Disable color detection in test	2024-03-19 10:19:58 +01:00
Tau	de358c1d65	Update readme	2024-03-19 10:19:57 +01:00
Tau	ffc95650fb	Update terminal-colorsaurus	2024-03-19 10:19:56 +01:00
Tau	b283a30091	Remove cargo feature	2024-03-19 10:19:55 +01:00
Tau	8f9a8f03d0	Improve upon the documentation	2024-03-19 10:19:54 +01:00
Tau	df89caeb85	Move actual detection into library	2024-03-19 10:19:53 +01:00
Tau	5fdc8066aa	Remove HighlightingAssets::default_theme()	2024-03-19 10:19:52 +01:00
Tau	22b23737a1	Add generated powershell completion to ignore list	2024-03-19 10:19:51 +01:00
Tau	725f3d0ac4	Update completions and man page	2024-03-19 10:19:50 +01:00
Tau	b6070cc3fb	Expose new theme selection in CLI	2024-03-19 10:19:49 +01:00
Tau	f106714673	Use `default_theme()` function from theme module	2024-03-19 10:19:48 +01:00
Tau	b4ef251af2	Deprecate old `default_theme` function	2024-03-19 10:19:47 +01:00
Tau	d22d864d7e	Choose theme based on the terminal's color scheme	2024-03-19 10:19:43 +01:00