Choose Theme Based on The Terminal's Color Scheme

.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

CHANGELOG.md

@@ -9,6 +9,7 @@
 - Syntax highlighting for JavaScript files that start with `#!/usr/bin/env bun` #2913 (@sharunkumar)
 - `bat --strip-ansi={never,always,auto}` to remove ANSI escape sequences from bat's input, see #2999 (@eth-p)
 - Add or remove individual style components without replacing all styles #2929 (@eth-p)
+- Automatically choose theme based on the terminal's color scheme, see #2896 (@bash)
 
 ## Bugfixes
 
@@ -69,6 +70,9 @@
   - [BREAKING] `SyntaxMapping::mappings` is replaced by `SyntaxMapping::{builtin,custom,all}_mappings`
 - Make `Controller::run_with_error_handler`'s error handler `FnMut`, see #2831 (@rhysd)
 - Improve compile time by 20%, see #2815 (@dtolnay)
+- 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.
 
 # v0.24.0
 

Cargo.toml

@@ -68,6 +68,7 @@ bytesize = { version = "1.3.0" }
 encoding_rs = "0.8.34"
 os_str_bytes = { version = "~7.0", optional = true }
 run_script = { version = "^0.10.1", optional = true}
+terminal-colorsaurus = "0.4"
 
 [dependencies.git2]
 version = "0.18"

README.md

@@ -482,8 +482,10 @@ 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).
 

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('--color-scheme', 'color-scheme', [CompletionResultType]::ParameterName, 'Whether to choose a dark or light syntax highlighting theme (*auto*, auto:always, dark, light, system).')
             [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.')

assets/completions/bat.bash.in

@@ -104,6 +104,8 @@ _bat() {
 		COMPREPLY=($(compgen -W "auto never always" -- "$cur"))
 		return 0
 		;;
+	--color-scheme)
+		COMPREPLY=($(compgen -W "auto auto:always dark light system" -- "$cur"))
 	--italic-text)
 		COMPREPLY=($(compgen -W "always never" -- "$cur"))
 		return 0
@@ -112,7 +114,9 @@ _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
@@ -170,6 +174,9 @@ _bat() {
 			--map-syntax
 			--ignored-suffix
 			--theme
+			--theme-dark
+			--theme-light
+			--color-scheme
 			--list-themes
 			--squeeze-blank
 			--squeeze-limit

assets/completions/bat.fish.in

@@ -99,6 +99,13 @@ set -l color_opts '
 '
 set -l decorations_opts $color_opts
 set -l paging_opts $color_opts
+set -l color_scheme_opts "
+    auto\t'Use the terminal\'s color scheme if the output is not redirected (default)'
+    auto:always\t'Always use the terminal\'s color scheme'
+    dark\t'Use a dark syntax highlighting theme'
+    light\t'Use a light syntax highlighting theme'
+    system\t'Query the OS for its color scheme (macOS only)'
+"
 
 # Include some examples so we can indicate the default.
 set -l pager_opts '
@@ -143,6 +150,8 @@ 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 $bat -l color-scheme -x -a "$color_scheme_opts" -d "Whether to choose a dark or light syntax highlighting theme" -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
@@ -205,6 +214,10 @@ 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

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)'
+        --color-scheme="[whether to choose a dark or light syntax highlighting theme]:scheme:(auto auto:always dark light system)"
         --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'

assets/manual/bat.1.in

@@ -117,6 +117,24 @@ 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 \
@@ -152,9 +170,23 @@ will use JSON syntax, and ignore '.dev'
 .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

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="...").
+
+      --color-scheme <scheme>
+          Specify whether to choose a dark or light 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 this choice.
+
+          Possible values:
+          * auto (default):
+              Query the terminals for its color scheme if the output is not redirected. This is to
+              prevent race conditions with pagers such as less.
+          * 'auto:always':
+              Always query the terminal for its color scheme, regardless of whether or not the
+              output is redirected.
+          * dark: Use a dark syntax highlighting theme.
+          * light: Use a light syntax highlighting theme.
+          * system: Query the OS for its color scheme. Only works on macOS.
+
+      --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.

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.
+      --color-scheme <scheme>
+          Specify whether to choose a dark or light theme.
+      --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