use css classes for colors, number down to 6

Author: ThierryBerger

src/librustdoc/html/render/print_item.rs

@@ -58,8 +58,8 @@ struct NotableTraitBadgeVars {
     full_path: String,
     /// Relative URL to the trait page, or `None` when not linkable.
     href: Option<String>,
-    /// Pre-rendered `style="..."` attribute.
-    style_attr: String,
+    /// Index of the `.notable-trait-badge-{n}` color class.
+    color_index: u64,
 }
 
 #[derive(Template)]
@@ -132,15 +132,13 @@ pub(super) fn print_item(cx: &Context<'_>, item: &clean::Item) -> impl fmt::Disp
                 // This won't be stable between releases though.
                 let mut h = DefaultHasher::new();
                 info.full_path.hash(&mut h);
-                // Evenly-spaced OKLCH hues at fixed light/chroma.
-                const BADGE_HUES: u64 = 8;
-                let hue = (h.finish() % BADGE_HUES) * 360 / BADGE_HUES;
-                let style_attr = format!("style=\"background: oklch(0.55 0.21 {hue})\"");
+                const BADGE_COLORS: u64 = 6;
+                let color_index = h.finish() % BADGE_COLORS;
                 NotableTraitBadgeVars {
                     name: info.name,
                     full_path: info.full_path,
                     href: info.href,
-                    style_attr,
+                    color_index,
                 }
             })
             .collect();

src/librustdoc/html/static/css/rustdoc.css

@@ -1667,6 +1667,13 @@ so that we can apply CSS-filters to change the arrow color in themes */
 	color: white;
 }
 
+.notable-trait-badge-0 { background: oklch(0.55 0.21 0); }
+.notable-trait-badge-1 { background: oklch(0.55 0.21 60); }
+.notable-trait-badge-2 { background: oklch(0.55 0.21 120); }
+.notable-trait-badge-3 { background: oklch(0.55 0.21 180); }
+.notable-trait-badge-4 { background: oklch(0.55 0.21 240); }
+.notable-trait-badge-5 { background: oklch(0.55 0.21 300); }
+
 .rightside {
 	padding-left: 12px;
 	float: right;

src/librustdoc/html/templates/print_item.html

@@ -23,9 +23,9 @@ <h1>
         {% if !notable_trait_badges.is_empty() %}
         <div class="notable-trait-badge-container">
             {% for badge in notable_trait_badges.iter() %}
-            <a class="notable-trait-badge" {# #} {% if let Some(href) = badge.href
-                %}href="{{href|safe}}" {% endif %} {#+ #} title="{{badge.full_path}}" {#+ #}
-                {{badge.style_attr|safe}}>{{badge.name}}</a>
+            <a class="notable-trait-badge notable-trait-badge-{{badge.color_index}}" {# #}
+                {% if let Some(href) = badge.href %}href="{{href|safe}}" {% endif %} {#+ #}
+                title="{{badge.full_path}}">{{badge.name}}</a>
             {% endfor %}
         </div>
         {% endif %}