Enable custom colors with environment variables (#248)

* Enable custom colors with environment variables

* Rename HEXYL_XYZ env vars to HEXYL_COLOR_XYZ

Cargo.toml

@@ -9,7 +9,7 @@ readme = "README.md"
 repository = "https://github.com/sharkdp/hexyl"
 version = "0.16.0"
 edition = "2021"
-rust-version = "1.74"
+rust-version = "1.80"
 
 [dependencies]
 anyhow = "1.0"

README.md

@@ -193,6 +193,22 @@ scoop install hexyl
 x env use hexyl
 ```
 
+## Configuration
+
+`hexyl` colors can be configured via environment variables. The variables used are as follows:
+
+ * `HEXYL_COLOR_ASCII_PRINTABLE`: Any non-whitespace printable ASCII character
+ * `HEXYL_COLOR_ASCII_WHITESPACE`: Whitespace such as space or newline (only visible in middle panel with byte values)
+ * `HEXYL_COLOR_ASCII_OTHER`: Any other ASCII character (< `0x80`) besides null
+ * `HEXYL_COLOR_NULL`: The null byte (`0x00`)
+ * `HEXYL_COLOR_NONASCII`: Any non-ASCII byte (> `0x7F`)
+ * `HEXYL_COLOR_OFFSET`: The lefthand file offset
+
+The colors can be any of the 8 standard terminal colors: `black`, `blue`, `cyan`, `green`, `magenta`, `red`,
+`yellow` and `white`. The "bright" variants are also supported (e.g., `bright blue`). Additionally, you can use
+the RGB hex format, `#abcdef`. For example, `HEXYL_COLOR_ASCII_PRINTABLE=blue HEXYL_COLOR_ASCII_WHITESPACE="bright green"
+HEXYL_COLOR_ASCII_OTHER="#ff7f99"`.
+
 ## License
 
 Licensed under either of

doc/hexyl.1.md

@@ -106,6 +106,22 @@ _FILE_
 **-V**, **\--version**
 :   Prints version information.
 
+# ENVIRONMENT VARIABLES
+
+**hexyl** colors can be configured via environment variables. The variables used are as follows:
+
+:   - **HEXYL_COLOR_ASCII_PRINTABLE**: Any non-whitespace printable ASCII character
+    - **HEXYL_COLOR_ASCII_WHITESPACE**: Whitespace such as space or newline (only visible in middle panel with byte values)
+    - **HEXYL_COLOR_ASCII_OTHER**: Any other ASCII character (< **0x80**) besides null
+    - **HEXYL_COLOR_NULL**: The null byte (**0x00**)
+    - **HEXYL_COLOR_NONASCII**: Any non-ASCII byte (> **0x7F**)
+    - **HEXYL_COLOR_OFFSET**: The lefthand file offset
+
+The colors can be any of the 8 standard terminal colors: **black**, **blue**, **cyan**, **green**, **magenta**, **red**,
+**yellow** and **white**. The "bright" variants are also supported (e.g., **bright blue**). Additionally, you can use
+the RGB hex format, **#abcdef**. For example, **HEXYL_COLOR_ASCII_PRINTABLE=blue HEXYL_COLOR_ASCII_WHITESPACE="bright green"
+HEXYL_COLOR_ASCII_OTHER="#ff7f99"**.
+
 # NOTES
 
 Source repository:

src/colors.rs

@@ -1,12 +1,39 @@
-use owo_colors::{colors, Color};
+use owo_colors::{colors, AnsiColors, Color, DynColors, OwoColorize};
+use std::str::FromStr;
+use std::sync::LazyLock;
 
-pub const COLOR_NULL: &[u8] = colors::BrightBlack::ANSI_FG.as_bytes();
-pub const COLOR_OFFSET: &[u8] = colors::BrightBlack::ANSI_FG.as_bytes();
-pub const COLOR_ASCII_PRINTABLE: &[u8] = colors::Cyan::ANSI_FG.as_bytes();
-pub const COLOR_ASCII_WHITESPACE: &[u8] = colors::Green::ANSI_FG.as_bytes();
-pub const COLOR_ASCII_OTHER: &[u8] = colors::Green::ANSI_FG.as_bytes();
-pub const COLOR_NONASCII: &[u8] = colors::Yellow::ANSI_FG.as_bytes();
-pub const COLOR_RESET: &[u8] = colors::Default::ANSI_FG.as_bytes();
+pub static COLOR_NULL: LazyLock<String> =
+    LazyLock::new(|| init_color("NULL", AnsiColors::BrightBlack));
+pub static COLOR_OFFSET: LazyLock<String> =
+    LazyLock::new(|| init_color("OFFSET", AnsiColors::BrightBlack));
+pub static COLOR_ASCII_PRINTABLE: LazyLock<String> =
+    LazyLock::new(|| init_color("ASCII_PRINTABLE", AnsiColors::Cyan));
+pub static COLOR_ASCII_WHITESPACE: LazyLock<String> =
+    LazyLock::new(|| init_color("ASCII_WHITESPACE", AnsiColors::Green));
+pub static COLOR_ASCII_OTHER: LazyLock<String> =
+    LazyLock::new(|| init_color("ASCII_OTHER", AnsiColors::Green));
+pub static COLOR_NONASCII: LazyLock<String> =
+    LazyLock::new(|| init_color("NONASCII", AnsiColors::Yellow));
+pub const COLOR_RESET: &str = colors::Default::ANSI_FG;
+
+fn init_color(name: &str, default_ansi: AnsiColors) -> String {
+    let default = DynColors::Ansi(default_ansi);
+    let env_var = format!("HEXYL_COLOR_{}", name);
+    let color = match std::env::var(env_var).as_deref() {
+        Ok(color) => match DynColors::from_str(color) {
+            Ok(color) => color,
+            _ => default,
+        },
+        _ => default,
+    };
+    // owo_colors' API isn't designed to get the terminal codes directly for
+    // dynamic colors, so we use this hack to get them from the LHS of some text.
+    format!("{}", "|".color(color))
+        .split_once("|")
+        .unwrap()
+        .0
+        .to_owned()
+}
 
 #[rustfmt::skip]
 pub const CP437: [char; 256] = [

src/lib.rs

@@ -84,11 +84,11 @@ impl Byte {
     fn color(self) -> &'static [u8] {
         use crate::ByteCategory::*;
         match self.category() {
-            Null => COLOR_NULL,
-            AsciiPrintable => COLOR_ASCII_PRINTABLE,
-            AsciiWhitespace => COLOR_ASCII_WHITESPACE,
-            AsciiOther => COLOR_ASCII_OTHER,
-            NonAscii => COLOR_NONASCII,
+            Null => COLOR_NULL.as_bytes(),
+            AsciiPrintable => COLOR_ASCII_PRINTABLE.as_bytes(),
+            AsciiWhitespace => COLOR_ASCII_WHITESPACE.as_bytes(),
+            AsciiOther => COLOR_ASCII_OTHER.as_bytes(),
+            NonAscii => COLOR_NONASCII.as_bytes(),
         }
     }
 
@@ -440,14 +440,14 @@ impl<'a, Writer: Write> Printer<'a, Writer> {
                 .as_bytes(),
         )?;
         if self.show_color {
-            self.writer.write_all(COLOR_OFFSET)?;
+            self.writer.write_all(COLOR_OFFSET.as_bytes())?;
         }
         if self.show_position_panel {
             match self.squeezer {
                 Squeezer::Print => {
                     self.writer.write_all(b"*")?;
                     if self.show_color {
-                        self.writer.write_all(COLOR_RESET)?;
+                        self.writer.write_all(COLOR_RESET.as_bytes())?;
                     }
                     self.writer.write_all(b"       ")?;
                 }
@@ -462,7 +462,7 @@ impl<'a, Writer: Write> Printer<'a, Writer> {
                             .write_all(self.byte_hex_panel_g[byte as usize].as_bytes())?;
                     }
                     if self.show_color {
-                        self.writer.write_all(COLOR_RESET)?;
+                        self.writer.write_all(COLOR_RESET.as_bytes())?;
                     }
                 }
             }
@@ -494,7 +494,7 @@ impl<'a, Writer: Write> Printer<'a, Writer> {
         }
         if i == 8 * self.panels - 1 {
             if self.show_color {
-                self.writer.write_all(COLOR_RESET)?;
+                self.writer.write_all(COLOR_RESET.as_bytes())?;
                 self.curr_color = None;
             }
             self.writer.write_all(
@@ -505,7 +505,7 @@ impl<'a, Writer: Write> Printer<'a, Writer> {
             )?;
         } else if i % 8 == 7 {
             if self.show_color {
-                self.writer.write_all(COLOR_RESET)?;
+                self.writer.write_all(COLOR_RESET.as_bytes())?;
                 self.curr_color = None;
             }
             self.writer.write_all(
@@ -531,12 +531,12 @@ impl<'a, Writer: Write> Printer<'a, Writer> {
             Squeezer::Print => {
                 if !self.show_position_panel && i == 0 {
                     if self.show_color {
-                        self.writer.write_all(COLOR_OFFSET)?;
+                        self.writer.write_all(COLOR_OFFSET.as_bytes())?;
                     }
                     self.writer
                         .write_all(self.byte_char_panel[b'*' as usize].as_bytes())?;
                     if self.show_color {
-                        self.writer.write_all(COLOR_RESET)?;
+                        self.writer.write_all(COLOR_RESET.as_bytes())?;
                     }
                 } else if i % (self.group_size as usize) == 0 {
                     self.writer.write_all(b" ")?;
@@ -562,7 +562,7 @@ impl<'a, Writer: Write> Printer<'a, Writer> {
         if i % 8 == 7 {
             if self.show_color {
                 self.curr_color = None;
-                self.writer.write_all(COLOR_RESET)?;
+                self.writer.write_all(COLOR_RESET.as_bytes())?;
             }
             self.writer.write_all(b" ")?;
             // byte is last in last panel

src/main.rs

@@ -493,32 +493,32 @@ fn print_color_table() -> io::Result<()> {
     writeln!(stdout, "hexyl color reference:\n")?;
 
     // NULL bytes
-    stdout.write_all(COLOR_NULL)?;
+    stdout.write_all(COLOR_NULL.as_bytes())?;
     writeln!(stdout, "⋄ NULL bytes (0x00)")?;
-    stdout.write_all(COLOR_RESET)?;
+    stdout.write_all(COLOR_RESET.as_bytes())?;
 
     // ASCII printable
-    stdout.write_all(COLOR_ASCII_PRINTABLE)?;
+    stdout.write_all(COLOR_ASCII_PRINTABLE.as_bytes())?;
     writeln!(stdout, "a ASCII printable characters (0x20 - 0x7E)")?;
-    stdout.write_all(COLOR_RESET)?;
+    stdout.write_all(COLOR_RESET.as_bytes())?;
 
     // ASCII whitespace
-    stdout.write_all(COLOR_ASCII_WHITESPACE)?;
+    stdout.write_all(COLOR_ASCII_WHITESPACE.as_bytes())?;
     writeln!(stdout, "_ ASCII whitespace (0x09 - 0x0D, 0x20)")?;
-    stdout.write_all(COLOR_RESET)?;
+    stdout.write_all(COLOR_RESET.as_bytes())?;
 
     // ASCII other
-    stdout.write_all(COLOR_ASCII_OTHER)?;
+    stdout.write_all(COLOR_ASCII_OTHER.as_bytes())?;
     writeln!(
         stdout,
         "• ASCII control characters (except NULL and whitespace)"
     )?;
-    stdout.write_all(COLOR_RESET)?;
+    stdout.write_all(COLOR_RESET.as_bytes())?;
 
     // Non-ASCII
-    stdout.write_all(COLOR_NONASCII)?;
+    stdout.write_all(COLOR_NONASCII.as_bytes())?;
     writeln!(stdout, "× Non-ASCII bytes (0x80 - 0xFF)")?;
-    stdout.write_all(COLOR_RESET)?;
+    stdout.write_all(COLOR_RESET.as_bytes())?;
 
     Ok(())
 }

tests/integration_tests.rs

@@ -785,3 +785,180 @@ mod character_table {
             );
     }
 }
+
+mod colors {
+    use super::hexyl;
+    use owo_colors::{colors, Color};
+    use std::collections::HashMap;
+
+    // This is a helper for testing color in output. Writing tests to expect
+    // raw color codes is ugly and hard to look at. Loading expected output
+    // from files works fine, but you end up with a lot of files for all the
+    // tests, and you have to cross-reference the file with the test that uses
+    // it. The files also suffer from the same problem of being hard to
+    // visually inspect. Just catting the file to see the colorized output
+    // loses the nuance of where exactly the color codes appear (before or
+    // after spaces, for example), or whether there are redundant codes.
+    //
+    // So this ColorMap solves the problem neatly by having two inputs:
+    // - the easy to read expected output in plain format without any colors
+    // - a mapping with identical structure except some characters replaced
+    //   with single character color codes.
+    // This makes it easy to reference the output and expected colors side by
+    // side, and provides fairly precise control over exactly where color codes
+    // are expected (the only caveat being you can't have two color codes back
+    // to back). ColorMap combines these into the actual expected output.
+    //
+    // The color mapping needs to be identical to the expected output, except
+    // it has some chars replaced by color code stand ins. These are replaced
+    // with the actual color codes by the colorize method. The '.' character
+    // is also ignored (it doesn't need to match the input). This makes the
+    // color map more readable and avoids input characters from conflicting
+    // with color chars.
+    struct ColorMap {
+        text_map: &'static str,
+        char_to_color: HashMap<char, &'static str>,
+    }
+
+    impl ColorMap {
+        fn from(text_map: &'static str) -> Self {
+            ColorMap {
+                text_map,
+                char_to_color: HashMap::new(),
+            }
+        }
+
+        fn with<C: Color>(&mut self, c: char) -> &mut Self {
+            self.char_to_color.insert(c, C::ANSI_FG);
+            self
+        }
+
+        fn colorize(&self, input: &str) -> String {
+            let mut output = String::new();
+            let mut input_chars = input.chars();
+            for c in self.text_map.chars() {
+                let next_input = input_chars.next().expect("input and color map don't match");
+                if let Some(color) = self.char_to_color.get(&c) {
+                    output.push_str(color);
+                } else if c != '.' {
+                    // ignore '.' in the mapping for readability
+                    assert_eq!(c, next_input, "input and color map don't match");
+                }
+                output.push(next_input);
+            }
+            output
+        }
+    }
+
+    #[test]
+    fn hex_colors() {
+        let input = b"He\x11\0 \xff\0\xdd";
+        let expected_text = "\
+            ┌────────┬─────────────────────────┬─────────────────────────┬────────┬────────┐\n\
+            │00000000│ 48 65 11 00 20 ff 00 dd ┊                         │He•⋄ ×⋄×┊        │\n\
+            └────────┴─────────────────────────┴─────────────────────────┴────────┴────────┘\n";
+        let expected = ColorMap::from(
+            "\
+            ┌────────┬─────────────────────────┬─────────────────────────┬────────┬────────┐\n\
+            │r.......d y. .. b. c. g. m. c. m.d┊                        d│y.bcgmcmd        d\n\
+            └────────┴─────────────────────────┴─────────────────────────┴────────┴────────┘\n",
+        )
+        .with::<colors::Red>('r')
+        .with::<colors::Default>('d')
+        .with::<colors::Yellow>('y')
+        .with::<colors::Blue>('b')
+        .with::<colors::Green>('g')
+        .with::<colors::BrightMagenta>('m')
+        .with::<colors::CustomColor<0xab, 0xcd, 0xef>>('c')
+        .colorize(expected_text);
+
+        hexyl()
+            .write_stdin(input)
+            .arg("--color=always")
+            .env("HEXYL_COLOR_OFFSET", "red")
+            .env("HEXYL_COLOR_ASCII_PRINTABLE", "yellow")
+            .env("HEXYL_COLOR_ASCII_WHITESPACE", "green")
+            .env("HEXYL_COLOR_ASCII_OTHER", "blue")
+            .env("HEXYL_COLOR_NONASCII", "bright magenta")
+            .env("HEXYL_COLOR_NULL", "#abcdef")
+            .assert()
+            .success()
+            .stdout(expected);
+    }
+
+    #[test]
+    fn binary_colors() {
+        let input = b"He\x11\0 \xff\0\xdd";
+        let expected_text = "\
+            ┌────────┬─────────────────────────────────────────────────────────────────────────┬────────┐\n\
+            │00000000│ 01001000 01100101 00010001 00000000 00100000 11111111 00000000 11011101 │He•⋄ ×⋄×│\n\
+            └────────┴─────────────────────────────────────────────────────────────────────────┴────────┘\n";
+        let expected = ColorMap::from(
+            "\
+            ┌────────┬─────────────────────────────────────────────────────────────────────────┬────────┐\n\
+            │r.......d y....... ........ b....... c....... g....... m....... c....... m.......d│y.bcgmcmd\n\
+            └────────┴─────────────────────────────────────────────────────────────────────────┴────────┘\n"
+        )
+        .with::<colors::Red>('r')
+        .with::<colors::Default>('d')
+        .with::<colors::Yellow>('y')
+        .with::<colors::Blue>('b')
+        .with::<colors::Green>('g')
+        .with::<colors::BrightMagenta>('m')
+        .with::<colors::CustomColor<0xab, 0xcd, 0xef>>('c')
+        .colorize(expected_text);
+
+        hexyl()
+            .write_stdin(input)
+            .arg("--color=always")
+            .arg("--panels=1")
+            .arg("--base=binary")
+            .env("HEXYL_COLOR_OFFSET", "red")
+            .env("HEXYL_COLOR_ASCII_PRINTABLE", "yellow")
+            .env("HEXYL_COLOR_ASCII_WHITESPACE", "green")
+            .env("HEXYL_COLOR_ASCII_OTHER", "blue")
+            .env("HEXYL_COLOR_NONASCII", "bright magenta")
+            .env("HEXYL_COLOR_NULL", "#abcdef")
+            .assert()
+            .success()
+            .stdout(expected);
+    }
+
+    #[test]
+    fn groupsize_colors() {
+        let input = b"He\x11\0 \xff\0\xdd";
+        let expected_text = "\
+            ┌────────┬─────────────────────┬────────┐\n\
+            │00000000│ 4865 1100 20ff 00dd │He•⋄ ×⋄×│\n\
+            └────────┴─────────────────────┴────────┘\n";
+        let expected = ColorMap::from(
+            "\
+            ┌────────┬─────────────────────┬────────┐\n\
+            │r.......d y... b.c. g.m. c.m.d│y.bcgmcmd\n\
+            └────────┴─────────────────────┴────────┘\n",
+        )
+        .with::<colors::Red>('r')
+        .with::<colors::Default>('d')
+        .with::<colors::Yellow>('y')
+        .with::<colors::Blue>('b')
+        .with::<colors::Green>('g')
+        .with::<colors::BrightMagenta>('m')
+        .with::<colors::CustomColor<0xab, 0xcd, 0xef>>('c')
+        .colorize(expected_text);
+
+        hexyl()
+            .write_stdin(input)
+            .arg("--color=always")
+            .arg("--panels=1")
+            .arg("--groupsize=2")
+            .env("HEXYL_COLOR_OFFSET", "red")
+            .env("HEXYL_COLOR_ASCII_PRINTABLE", "yellow")
+            .env("HEXYL_COLOR_ASCII_WHITESPACE", "green")
+            .env("HEXYL_COLOR_ASCII_OTHER", "blue")
+            .env("HEXYL_COLOR_NONASCII", "bright magenta")
+            .env("HEXYL_COLOR_NULL", "#abcdef")
+            .assert()
+            .success()
+            .stdout(expected);
+    }
+}