Extend RGBA hex color parsing to support 3-value and 4-value variants (#3295)

Marshall Bowers created 2 years ago

This PR extends our support for parsing hex color codes to `Rgba` to
additionally support 3-value (`#rgb`) and 4-value (`#rgba`) formats.

See [here](https://developer.mozilla.org/en-US/docs/Web/CSS/hex-color)
for more details on these hex color variants.

Release Notes:

- N/A

Change summary

crates/gpui2/src/color.rs           | 127 ++++++++++++++++++++++++------
crates/theme2/src/default_colors.rs |   6 
2 files changed, 103 insertions(+), 30 deletions(-)

Detailed changes

crates/gpui2/src/color.rs

@@ -1,8 +1,8 @@
 #![allow(dead_code)]
 
+use anyhow::bail;
 use serde::de::{self, Deserialize, Deserializer, Visitor};
 use std::fmt;
-use std::num::ParseIntError;
 
 pub fn rgb<C: From<Rgba>>(hex: u32) -> C {
     let r = ((hex >> 16) & 0xFF) as f32 / 255.0;
@@ -19,7 +19,7 @@ pub fn rgba(hex: u32) -> Rgba {
     Rgba { r, g, b, a }
 }
 
-#[derive(Clone, Copy, Default)]
+#[derive(PartialEq, Clone, Copy, Default)]
 pub struct Rgba {
     pub r: f32,
     pub g: f32,
@@ -70,21 +70,7 @@ impl<'de> Visitor<'de> for RgbaVisitor {
     }
 
     fn visit_str<E: de::Error>(self, value: &str) -> Result<Rgba, E> {
-        if value.len() == 7 || value.len() == 9 {
-            let r = u8::from_str_radix(&value[1..3], 16).unwrap() as f32 / 255.0;
-            let g = u8::from_str_radix(&value[3..5], 16).unwrap() as f32 / 255.0;
-            let b = u8::from_str_radix(&value[5..7], 16).unwrap() as f32 / 255.0;
-            let a = if value.len() == 9 {
-                u8::from_str_radix(&value[7..9], 16).unwrap() as f32 / 255.0
-            } else {
-                1.0
-            };
-            Ok(Rgba { r, g, b, a })
-        } else {
-            Err(E::custom(
-                "Bad format for RGBA. Expected #rrggbb or #rrggbbaa.",
-            ))
-        }
+        Rgba::try_from(value).map_err(E::custom)
     }
 }
 
@@ -125,19 +111,59 @@ impl From<Hsla> for Rgba {
 }
 
 impl TryFrom<&'_ str> for Rgba {
-    type Error = ParseIntError;
+    type Error = anyhow::Error;
 
     fn try_from(value: &'_ str) -> Result<Self, Self::Error> {
-        let r = u8::from_str_radix(&value[1..3], 16)? as f32 / 255.0;
-        let g = u8::from_str_radix(&value[3..5], 16)? as f32 / 255.0;
-        let b = u8::from_str_radix(&value[5..7], 16)? as f32 / 255.0;
-        let a = if value.len() > 7 {
-            u8::from_str_radix(&value[7..9], 16)? as f32 / 255.0
-        } else {
-            1.0
+        const RGB: usize = "rgb".len();
+        const RGBA: usize = "rgba".len();
+        const RRGGBB: usize = "rrggbb".len();
+        const RRGGBBAA: usize = "rrggbbaa".len();
+
+        const EXPECTED_FORMATS: &'static str = "Expected #rgb, #rgba, #rrggbb, or #rrggbbaa";
+
+        let Some(("", hex)) = value.trim().split_once('#') else {
+            bail!("invalid RGBA hex color: '{value}'. {EXPECTED_FORMATS}");
+        };
+
+        let (r, g, b, a) = match hex.len() {
+            RGB | RGBA => {
+                let r = u8::from_str_radix(&hex[0..1], 16)?;
+                let g = u8::from_str_radix(&hex[1..2], 16)?;
+                let b = u8::from_str_radix(&hex[2..3], 16)?;
+                let a = if hex.len() == RGBA {
+                    u8::from_str_radix(&hex[3..4], 16)?
+                } else {
+                    0xf
+                };
+
+                /// Duplicates a given hex digit.
+                /// E.g., `0xf` -> `0xff`.
+                const fn duplicate(value: u8) -> u8 {
+                    value << 4 | value
+                }
+
+                (duplicate(r), duplicate(g), duplicate(b), duplicate(a))
+            }
+            RRGGBB | RRGGBBAA => {
+                let r = u8::from_str_radix(&hex[0..2], 16)?;
+                let g = u8::from_str_radix(&hex[2..4], 16)?;
+                let b = u8::from_str_radix(&hex[4..6], 16)?;
+                let a = if hex.len() == RRGGBBAA {
+                    u8::from_str_radix(&hex[6..8], 16)?
+                } else {
+                    0xff
+                };
+                (r, g, b, a)
+            }
+            _ => bail!("invalid RGBA hex color: '{value}'. {EXPECTED_FORMATS}"),
         };
 
-        Ok(Rgba { r, g, b, a })
+        Ok(Rgba {
+            r: r as f32 / 255.,
+            g: g as f32 / 255.,
+            b: b as f32 / 255.,
+            a: a as f32 / 255.,
+        })
     }
 }
 
@@ -311,3 +337,52 @@ impl<'de> Deserialize<'de> for Hsla {
         Ok(Hsla::from(rgba))
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use serde_json::json;
+
+    use super::*;
+
+    #[test]
+    fn test_deserialize_three_value_hex_to_rgba() {
+        let actual: Rgba = serde_json::from_value(json!("#f09")).unwrap();
+
+        assert_eq!(actual, rgba(0xff0099ff))
+    }
+
+    #[test]
+    fn test_deserialize_four_value_hex_to_rgba() {
+        let actual: Rgba = serde_json::from_value(json!("#f09f")).unwrap();
+
+        assert_eq!(actual, rgba(0xff0099ff))
+    }
+
+    #[test]
+    fn test_deserialize_six_value_hex_to_rgba() {
+        let actual: Rgba = serde_json::from_value(json!("#ff0099")).unwrap();
+
+        assert_eq!(actual, rgba(0xff0099ff))
+    }
+
+    #[test]
+    fn test_deserialize_eight_value_hex_to_rgba() {
+        let actual: Rgba = serde_json::from_value(json!("#ff0099ff")).unwrap();
+
+        assert_eq!(actual, rgba(0xff0099ff))
+    }
+
+    #[test]
+    fn test_deserialize_eight_value_hex_with_padding_to_rgba() {
+        let actual: Rgba = serde_json::from_value(json!(" #f5f5f5ff   ")).unwrap();
+
+        assert_eq!(actual, rgba(0xf5f5f5ff))
+    }
+
+    #[test]
+    fn test_deserialize_eight_value_hex_with_mixed_case_to_rgba() {
+        let actual: Rgba = serde_json::from_value(json!("#DeAdbEeF")).unwrap();
+
+        assert_eq!(actual, rgba(0xdeadbeef))
+    }
+}

crates/theme2/src/default_colors.rs

@@ -1,5 +1,3 @@
-use std::num::ParseIntError;
-
 use gpui::{hsla, Hsla, Rgba};
 
 use crate::colors::{StatusColors, SystemColors, ThemeColors};
@@ -413,10 +411,10 @@ struct StaticColorScaleSet {
 }
 
 impl TryFrom<StaticColorScaleSet> for ColorScaleSet {
-    type Error = ParseIntError;
+    type Error = anyhow::Error;
 
     fn try_from(value: StaticColorScaleSet) -> Result<Self, Self::Error> {
-        fn to_color_scale(scale: StaticColorScale) -> Result<ColorScale, ParseIntError> {
+        fn to_color_scale(scale: StaticColorScale) -> Result<ColorScale, anyhow::Error> {
             scale
                 .into_iter()
                 .map(|color| Rgba::try_from(color).map(Hsla::from))