Use light variant of theme automatically when terminal background is light

CHANGELOG.md

@@ -34,6 +34,7 @@ That said, these are more guidelines rather than hardset rules, though the proje
 
 ### Features
 
+- [#1843](https://github.com/ClementTsang/bottom/pull/1843): Use light variant of theme automatically when terminal background is light.
 - [#1812](https://github.com/ClementTsang/bottom/pull/1812): Add `free_arc` option to subtract ARC from total memory usage.
 
 ### Bug Fixes

Cargo.toml

@@ -105,6 +105,7 @@ time = { version = "0.3.44", features = ["local-offset", "formatting", "macros"]
 schemars = { version = "1.0.4", optional = true }
 serde_json = { version = "1.0.145", optional = true }
 strum = { version = "0.27.2", features = ["derive"], optional = true }
+terminal-colorsaurus = "1.0.1"
 
 [target.'cfg(unix)'.dependencies]
 libc = "0.2.176"

docs/content/configuration/config-file/styling.md

@@ -21,7 +21,8 @@ bottom has a few built-in themes:
 - [Nord](https://www.nordtheme.com/)
 - [Gruvbox](https://github.com/morhetz/gruvbox)
 
-These themes all also have light variants to support terminals using lighter colours.
+These themes all also have light variants to support terminals using lighter colours. The light variants will be used
+automatically if your terminal is using a light background.
 
 To set the theme from the command line:
 

sample_configs/default_config.toml

@@ -231,11 +231,8 @@
 #[styles] # Uncomment if you want to use custom styling
 # Built-in themes. Valid values are:
 # - "default"
-# - "default-light"
 # - "gruvbox"
-# - "gruvbox-light"
 # - "nord"
-# - "nord-light".
 #
 # This will have the lowest precedence if a custom colour palette is set,
 # or overridden if the command-line flag for a built-in theme is set.

schema/v0.9/bottom.json

@@ -175,11 +175,8 @@
           "default": "default",
           "enum": [
             "default",
-            "default-light",
             "gruvbox",
-            "gruvbox-light",
-            "nord",
-            "nord-light"
+            "nord"
           ],
           "description": "Built-in themes",
           "type": "string"

src/constants.rs

@@ -481,11 +481,8 @@ pub(crate) const CONFIG_TEXT: &str = r#"# This is a default config file for bott
 #[styles] # Uncomment if you want to use custom styling
 # Built-in themes. Valid values are:
 # - "default"
-# - "default-light"
 # - "gruvbox"
-# - "gruvbox-light"
 # - "nord"
-# - "nord-light".
 #
 # This will have the lowest precedence if a custom colour palette is set,
 # or overridden if the command-line flag for a built-in theme is set.

src/options/args.rs

@@ -616,24 +616,18 @@ pub struct StyleArgs {
         value_name = "SCHEME",
         value_parser = [
             "default",
-            "default-light",
             "gruvbox",
-            "gruvbox-light",
             "nord",
-            "nord-light",
         ],
         hide_possible_values = true,
         help = indoc! {
-            "Use a built-in color theme, use '--help' for info on the colors. [possible values: default, default-light, gruvbox, gruvbox-light, nord, nord-light]",
+            "Use a built-in color theme, use '--help' for info on the colors. [possible values: default, gruvbox, nord]",
         },
         long_help = indoc! {
             "Use a pre-defined color theme. Currently supported themes are:
             - default
-            - default-light (default but adjusted for lighter backgrounds)
             - gruvbox       (a bright theme with 'retro groove' colors)
-            - gruvbox-light (gruvbox but adjusted for lighter backgrounds)
-            - nord          (an arctic, north-bluish color palette)
-            - nord-light    (nord but adjusted for lighter backgrounds)"
+            - nord          (an arctic, north-bluish color palette)"
         }
     )]
     pub theme: Option<String>,

src/options/config/style.rs

@@ -20,6 +20,7 @@ use memory::MemoryStyle;
 use network::NetworkStyle;
 use serde::{Deserialize, Serialize};
 use tables::TableStyle;
+use terminal_colorsaurus::{QueryOptions, ThemeMode, theme_mode};
 use tui::{style::Style, widgets::BorderType};
 use utils::{opt, set_colour, set_colour_list, set_style};
 use widgets::WidgetStyle;
@@ -141,7 +142,7 @@ impl Styles {
             Some(theme) => Self::from_theme(theme)?,
             None => match config.styles.as_ref().and_then(|s| s.theme.as_ref()) {
                 Some(theme) => Self::from_theme(theme)?,
-                None => Self::default(),
+                None => Self::from_theme("default")?,
             },
         };
 
@@ -155,13 +156,29 @@ impl Styles {
 
     fn from_theme(theme: &str) -> anyhow::Result<Self> {
         let lower_case = theme.to_lowercase();
+
+        // Detect terminal theme mode.
+        // Prefer dark palette if detection fails.
+        let is_dark = theme_mode(QueryOptions::default())
+            .map(|mode| mode == ThemeMode::Dark)
+            .unwrap_or(true);
+
         match lower_case.as_str() {
-            "default" => Ok(Self::default_style()),
-            "default-light" => Ok(Self::default_light_mode()),
-            "gruvbox" => Ok(Self::gruvbox_palette()),
-            "gruvbox-light" => Ok(Self::gruvbox_light_palette()),
-            "nord" => Ok(Self::nord_palette()),
-            "nord-light" => Ok(Self::nord_light_palette()),
+            "default" => Ok(if is_dark {
+                Self::default_style()
+            } else {
+                Self::default_light_mode()
+            }),
+            "gruvbox" => Ok(if is_dark {
+                Self::gruvbox_palette()
+            } else {
+                Self::gruvbox_light_palette()
+            }),
+            "nord" => Ok(if is_dark {
+                Self::nord_palette()
+            } else {
+                Self::nord_light_palette()
+            }),
             _ => Err(
                 OptionError::other(format!("'{theme}' is an invalid built-in color scheme."))
                     .into(),
@@ -270,10 +287,41 @@ mod test {
     #[test]
     fn built_in_colour_schemes_work() {
         Styles::from_theme("default").unwrap();
-        Styles::from_theme("default-light").unwrap();
         Styles::from_theme("gruvbox").unwrap();
-        Styles::from_theme("gruvbox-light").unwrap();
         Styles::from_theme("nord").unwrap();
-        Styles::from_theme("nord-light").unwrap();
+    }
+
+    #[test]
+    fn invalid_theme_returns_error() {
+        let result = Styles::from_theme("nonexistent-theme");
+        assert!(result.is_err());
+        assert!(
+            result
+                .unwrap_err()
+                .to_string()
+                .contains("invalid built-in color scheme")
+        );
+    }
+
+    #[test]
+    fn theme_case_insensitive() {
+        // Theme names should work regardless of case
+        Styles::from_theme("DEFAULT").unwrap();
+        Styles::from_theme("GruvBox").unwrap();
+        Styles::from_theme("NORD").unwrap();
+    }
+
+    #[test]
+    fn theme_detection_does_not_panic() {
+        // Ensure theme detection doesn't panic in non-interactive environments (CI)
+        // This verifies the .unwrap_or(true) fallback works correctly
+        let default_style = Styles::from_theme("default").unwrap();
+        let gruvbox_style = Styles::from_theme("gruvbox").unwrap();
+        let nord_style = Styles::from_theme("nord").unwrap();
+
+        // Verify styles have expected color properties set (not all default)
+        assert_ne!(default_style.ram_style, Style::default());
+        assert_ne!(gruvbox_style.ram_style, Style::default());
+        assert_ne!(nord_style.ram_style, Style::default());
     }
 }

tests/valid_configs/styling_2.toml

@@ -4,11 +4,8 @@
 
 # Built-in themes. Valid values are:
 # - "default"
-# - "default-light"
 # - "gruvbox"
-# - "gruvbox-light"
 # - "nord"
-# - "nord-light".
 
 # This will have the lowest precedence if a custom colour palette is set,
 # or overriden if the command-line flag for a built-in theme is set.