Support x:<name> syntax to fetch color from .Xresources

cspell.yaml

@@ -31,9 +31,11 @@ words:
   - bugz
   - busctl
   - caldav
+  - ccache
   - chrono
   - clippy
   - CLOEXEC
+  - cmap
   - conn
   - consts
   - conv
@@ -182,15 +184,16 @@ words:
   - wofi
   - wttr
   - xclip
+  - xcolors
   - xesam
   - xkbswitch
   - XKCD
   - xrandr
+  - xresources
   - xtask
   - zbus
-  - zvariant
-  - zwlr
-  - zswap
   - zram
+  - zswap
   - Zswapped
-  - ccache
+  - zvariant
+  - zwlr

doc/themes.md

@@ -124,7 +124,11 @@ cpu_boost_off = "OFF"
 
 # Available theme overrides
 
-All `bg` and `fg` overrides are html hex color codes like `#000000` or `#789ABC`. A fourth byte for alpha (like `#acbdef42`) works on some systems. `00` is transparent, `FF` is opaque.
+All `bg` and `fg` overrides are either
+
+* html hex color codes like `#000000` or `#789ABC`; a fourth byte for alpha (like `#acbdef42`) works on some systems. `00` is transparent, `FF` is opaque, or
+* a reference to another override, e.g., `{ link = "idle-bg" }`, or
+* a reference to a color name defined in `~/.Xresources`, e.g., `x:background` looks for a line like `*background: #aabbcc` in `~/.Xresources` (see also [.Xresources](https://wiki.debian.org/Xresources)).
 
 The tints are added to every second block counting from the right. They will therefore always brighten the block and never darken it. The alpha channel, if it works, can also be alternated in the same way.
 

src/themes.rs

@@ -1,5 +1,6 @@
 pub mod color;
 pub mod separator;
+pub mod xresources;
 
 use std::fmt;
 use std::ops::{Deref, DerefMut};

src/themes/color.rs

@@ -216,6 +216,12 @@ impl FromStr for Color {
             let v = components.next().or_error(err_msg)??;
             let a = components.next().unwrap_or(Ok(100.))?;
             Color::Hsva(Hsva::new(h, s / 100., v / 100., (a / 100. * 255.) as u8))
+        } else if color.starts_with("x:") {
+            let name = color.split_at(2).1;
+            super::xresources::get_color(name)?
+                .or_error(|| format!("color '{name}' not defined in ~/.Xresources"))?
+                .parse()
+                .or_error(|| format!("invalid color definition '{name}'"))?
         } else {
             let err_msg = || format!("'{color}' is not a valid RGBA color");
             let rgb = color.get(1..7).or_error(err_msg)?;

src/themes/xresources.rs

@@ -0,0 +1,95 @@
+use log::debug;
+use regex::Regex;
+
+use std::collections::HashMap;
+use std::sync::LazyLock;
+
+use crate::errors::*;
+
+#[cfg(not(test))]
+use std::{env, path::PathBuf};
+
+#[cfg(not(test))]
+fn read_xresources() -> std::io::Result<String> {
+    use std::io::{Error, ErrorKind};
+    let home =
+        env::var("HOME").map_err(|_| Error::new(ErrorKind::Other, "HOME env var was not set"))?;
+    let xresources = PathBuf::from(home + "/.Xresources");
+    debug!(".Xresources @ {:?}", xresources);
+    std::fs::read_to_string(xresources)
+}
+
+#[cfg(test)]
+use tests::read_xresources;
+
+static COLOR_REGEX: LazyLock<Regex> = LazyLock::new(|| {
+    Regex::new(r"^\s*\*(?<name>[^: ]+)\s*:\s*(?<color>#[a-f0-9]{6,8}).*$").unwrap()
+});
+
+static COLORS: LazyLock<Result<HashMap<String, String>, Error>> = LazyLock::new(|| {
+    let content = read_xresources().error("could not read .Xresources")?;
+    debug!(".Xresources content:\n{}", content);
+    Ok(HashMap::from_iter(content.lines().filter_map(|line| {
+        COLOR_REGEX
+            .captures(line)
+            .map(|caps| (caps["name"].to_string(), caps["color"].to_string()))
+    })))
+});
+
+pub fn get_color(name: &str) -> Result<Option<&String>, Error> {
+    COLORS
+        .as_ref()
+        .map(|cmap| cmap.get(name))
+        .map_err(Clone::clone)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::io::Result;
+
+    #[allow(clippy::unnecessary_wraps)]
+    pub(crate) fn read_xresources() -> Result<String> {
+        static XRESOURCES: &str = "\
+        ! this is a comment\n\
+        \n\
+        *color4 : #feedda\n\
+    \n\
+        *background: #ee33aa99\n\
+        ";
+        Ok(XRESOURCES.to_string())
+    }
+
+    #[test]
+    fn test_reading_colors() {
+        let colors = COLORS.as_ref().unwrap();
+        assert_eq!(colors.get("color4"), Some(&"#feedda".to_string()));
+        assert_eq!(colors.get("background"), Some(&"#ee33aa99".to_string()));
+        assert_eq!(2, colors.len());
+    }
+
+    #[test]
+    fn test_deserializing_xcolors() {
+        use super::super::color::*;
+        let mut parsed_color = "x:color4".parse::<Color>().unwrap();
+        assert_eq!(
+            parsed_color,
+            Color::Rgba(Rgba {
+                r: 254,
+                g: 237,
+                b: 218,
+                a: 255
+            })
+        );
+        parsed_color = "x:background".parse::<Color>().unwrap();
+        assert_eq!(
+            parsed_color,
+            Color::Rgba(Rgba {
+                r: 238,
+                g: 51,
+                b: 170,
+                a: 153,
+            })
+        );
+    }
+}