Image Trace: Document Library links to a global swatch that shares a process swatch's color

When a process swatch listed before a global or spot swatch showed the
same color, a traced fill of that color took the process swatch and
stayed unlinked. Of the swatches that trace as one color, the first
linked one now gives the fill, and the first one otherwise.

crates/engine/src/cmd/buildcmds/trace.rs

@@ -585,10 +585,12 @@ pub(super) fn trace_make(s: &mut Session, p: &Value, expand: bool) -> Result<Val
                 *live = Some(Box::new(shape));
             }
             // A library color fills with the swatch's own color (its model kept), linked to a
-            // global or spot swatch of the document.
-            let solid = library
-                .iter()
-                .find(|(rgb, _)| *rgb == tp.color)
+            // global or spot swatch of the document. Of the swatches that trace as this color,
+            // the first linked one is taken, else the first.
+            let same = || library.iter().filter(|(rgb, _)| *rgb == tp.color);
+            let solid = same()
+                .find(|(_, p)| matches!(p, Paint::Solid { swatch: Some(_), .. }))
+                .or_else(|| same().next())
                 .map_or_else(|| Paint::solid(Color::rgb8(tp.color[0], tp.color[1], tp.color[2])), |l| l.1.clone());
             // Gradients: a path the tracer found to be a linear gradient is filled with it.
             let paint = tp.gradient.as_ref().map_or(solid, |g| traced_gradient(g, xf));

crates/engine/src/tests/build.rs

@@ -3178,6 +3178,43 @@ fn image_trace_document_library_links_fills_to_global_swatches() {
     assert!(!got.is_empty() && got.iter().all(|f| f.1.is_none()), "{got:?}");
 }
 
+#[test]
+fn image_trace_document_library_links_to_a_global_swatch_after_a_process_swatch_of_its_color() {
+    let mut s = session();
+    // A process swatch, then two global swatches, all of one color.
+    s.execute("swatch.new", &json!({"name": "Red", "color": "#c82828"})).unwrap();
+    s.execute("swatch.new", &json!({"name": "Ink", "color": "#c82828", "global": true})).unwrap();
+    s.execute("swatch.new", &json!({"name": "Ink 2", "color": "#c82828", "global": true})).unwrap();
+    s.execute("swatch.new", &json!({"name": "Leaf", "color": "#28a03c"})).unwrap();
+    s.execute("swatch.new", &json!({"name": "Sky", "color": "#2846c8", "global": true})).unwrap();
+    let [tr, tg, tb, _] = s.doc().unwrap().doc.tint_paint("Sky", 0.5).unwrap().color().unwrap().to_rgba8(1.0);
+    let tint_hex = format!("#{tr:02x}{tg:02x}{tb:02x}");
+    s.execute("swatch.new", &json!({"name": "Mist", "color": tint_hex})).unwrap();
+    s.execute("swatch.new", &json!({"swatch": "Sky", "tint": 50})).unwrap();
+    let r = vectorcraft_trace::Raster::from_fn(60, 60, |x, _| match x {
+        0..20 => [200, 40, 40, 255],
+        20..40 => [40, 160, 60, 255],
+        _ => [tr, tg, tb, 255],
+    });
+    add_image(&mut s, &r, Affine::IDENTITY);
+    let params = json!({"mode": "color", "palette": "documentLibrary", "library": "document", "colors": 8});
+    let res = s.execute("imageTrace.makeAndExpand", &json!({"params": params})).unwrap();
+    let g = node(&s, NodeId(res["id"].as_u64().unwrap()));
+    let got: Vec<Paint> = g.children().unwrap().iter().map(|n| n.appearance.fill_paint()).collect();
+    let red = Color::rgb8(200, 40, 40);
+    let reds: Vec<&Paint> = got.iter().filter(|p| p.color().map(|c| c.to_rgba8(1.0)) == Some(red.to_rgba8(1.0))).collect();
+    assert!(!reds.is_empty(), "{got:?}");
+    assert!(reds.iter().all(|p| matches!(p, Paint::Solid { swatch: Some(w), .. } if w == "Ink")), "{got:?}");
+    let tints: Vec<&Paint> = got.iter().filter(|p| p.color().map(|c| c.to_rgba8(1.0)) == Some([tr, tg, tb, 255])).collect();
+    assert!(!tints.is_empty(), "{got:?}");
+    assert!(tints.iter().all(|p| matches!(p, Paint::Solid { swatch: Some(w), tint, .. } if w == "Sky" && *tint == 0.5)), "{got:?}");
+    // Editing the global swatch recolors the trace.
+    s.execute("swatch.edit", &json!({"name": "Ink", "color": "#ff8800"})).unwrap();
+    let g = node(&s, NodeId(res["id"].as_u64().unwrap()));
+    let orange = Color::rgb8(255, 136, 0).to_rgba8(1.0);
+    assert!(g.children().unwrap().iter().any(|n| n.appearance.fill_paint().color().map(|c| c.to_rgba8(1.0)) == Some(orange)));
+}
+
 #[test]
 fn image_trace_document_library_matches_a_lab_spot_by_its_cmyk_equivalent() {
     let _g = crate::tests_colormgmt::GLOBAL.lock().unwrap_or_else(|e| e.into_inner());

docs/image-trace-adjustments.md

@@ -49,7 +49,9 @@ and traces as All.
 **Document Library linked colors.** With Library › Document Swatches, with or without a color group,
 a traced fill or stroke whose color comes from a global or spot swatch is linked to that swatch, and
 one whose color comes from a tint swatch is linked to its base at the tint. Editing the swatch
-recolors the trace. Colors from process swatches and from swatch libraries are not linked.
+recolors the trace. Colors from process swatches and from swatch libraries are not linked. When
+several swatches show the same color, the first of them in the list that is a global, spot or tint
+swatch gives the link.
 
 **Document Library** traces with the library's colors as they are. Each pixel takes the library
 color nearest to it in lightness and hue, with a difference in hue or chroma counted three times