Emit accurate hex colors in generated themes (#3547)

This PR fixes an issues where the hex colors in the generated themes
were not correct.

We're using the [`palette`](https://crates.io/crates/palette) crate to
perform the conversions, as this gives us accurate hex codes that match
the VS Code source themes.

Release Notes:

- N/A

crates/theme_importer/Cargo.toml

@@ -13,6 +13,7 @@ gpui = { package = "gpui2", path = "../gpui2" }
 indexmap = "1.6.2"
 json_comments = "0.2.2"
 log.workspace = true
+palette = { version = "0.7.3", default-features = false, features = ["std"] }
 rust-embed.workspace = true
 serde.workspace = true
 simplelog = "0.9"

crates/theme_importer/src/color.rs

@@ -0,0 +1,54 @@
+use anyhow::Result;
+use gpui::Hsla;
+use palette::FromColor;
+
+pub(crate) fn try_parse_color(color: &str) -> Result<Hsla> {
+    let rgba = gpui::Rgba::try_from(color)?;
+    let rgba = palette::rgb::Srgba::from_components((rgba.r, rgba.g, rgba.b, rgba.a));
+    let hsla = palette::Hsla::from_color(rgba);
+
+    let hsla = gpui::hsla(
+        hsla.hue.into_positive_degrees() / 360.,
+        hsla.saturation,
+        hsla.lightness,
+        hsla.alpha,
+    );
+
+    Ok(hsla)
+}
+
+pub(crate) fn pack_color(color: Hsla) -> u32 {
+    let hsla = palette::Hsla::from_components((color.h * 360., color.s, color.l, color.a));
+    let rgba = palette::rgb::Srgba::from_color(hsla);
+    let rgba = rgba.into_format::<u8, u8>();
+
+    u32::from(rgba)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    pub fn test_serialize_color() {
+        let color = "#b4637aff";
+        let hsla = try_parse_color(color).unwrap();
+        let packed = pack_color(hsla);
+
+        assert_eq!(format!("#{:x}", packed), color);
+    }
+
+    #[test]
+    pub fn test_serialize_color_with_palette() {
+        let color = "#b4637aff";
+
+        let rgba = gpui::Rgba::try_from(color).unwrap();
+        let rgba = palette::rgb::Srgba::from_components((rgba.r, rgba.g, rgba.b, rgba.a));
+        let hsla = palette::Hsla::from_color(rgba);
+
+        let rgba = palette::rgb::Srgba::from_color(hsla);
+        let rgba = rgba.into_format::<u8, u8>();
+
+        assert_eq!(format!("#{:x}", rgba), color);
+    }
+}

crates/theme_importer/src/main.rs

@@ -1,3 +1,4 @@
+mod color;
 mod theme_printer;
 mod util;
 mod vscode;

crates/theme_importer/src/theme_printer.rs

@@ -1,12 +1,14 @@
 use std::fmt::{self, Debug};
 
-use gpui::{Hsla, Rgba};
+use gpui::Hsla;
 use theme::{
     Appearance, PlayerColor, PlayerColors, StatusColorsRefinement, SystemColors,
     ThemeColorsRefinement, UserHighlightStyle, UserSyntaxTheme, UserTheme, UserThemeFamily,
     UserThemeStylesRefinement,
 };
 
+use crate::color::pack_color;
+
 struct RawSyntaxPrinter<'a>(&'a str);
 
 impl<'a> Debug for RawSyntaxPrinter<'a> {
@@ -19,7 +21,7 @@ struct HslaPrinter(Hsla);
 
 impl Debug for HslaPrinter {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{:?}", IntoPrinter(&Rgba::from(self.0)))
+        write!(f, "rgba({:#010x}).into()", pack_color(self.0))
     }
 }
 

crates/theme_importer/src/vscode/converter.rs

@@ -1,5 +1,5 @@
 use anyhow::Result;
-use gpui::{rgba, Hsla, Rgba};
+use gpui::rgba;
 use indexmap::IndexMap;
 use strum::IntoEnumIterator;
 use theme::{
@@ -7,16 +7,13 @@ use theme::{
     UserHighlightStyle, UserSyntaxTheme, UserTheme, UserThemeStylesRefinement,
 };
 
+use crate::color::try_parse_color;
 use crate::util::Traverse;
 use crate::vscode::VsCodeTheme;
 use crate::ThemeMetadata;
 
 use super::ZedSyntaxToken;
 
-pub(crate) fn try_parse_color(color: &str) -> Result<Hsla> {
-    Ok(Rgba::try_from(color)?.into())
-}
-
 pub(crate) fn try_parse_font_weight(font_style: &str) -> Option<UserFontWeight> {
     match font_style {
         style if style.contains("bold") => Some(UserFontWeight::BOLD),