Recolor: art a row leaves unchanged loses its link to a rewritten group swatch

When recolor.apply with a group rewrites a global swatch with another
color than the row of the art linked to it, and that row leaves the art's
color as it is, the art now keeps the row's color and is no longer linked
to the swatch. Before, the link stayed and the group's rewrite gave the
art the swatch's new color.

crates/engine/src/cmd/recolor.rs

@@ -31,7 +31,7 @@ pub fn specs() -> Vec<CommandSpec> {
             "Recolor Artwork",
             ["Edit", "Edit Colors"],
             None,
-            "{map: rows [{from: [colour keys (recolor.colors) or \"#rrggbb\" (every colour shown as that hex)], to: colour (hex, key, {c,m,y,k} or {l,a,b}) | null, exclude?: false (the row's colours are kept)}] | {\"key or #rrggbb\": colour, …} (one row per colour), method?: \"exact\" (default)|\"preserveTints\"|\"scaleTints\"|\"tintsShades\"|\"hueShift\" (how a row's colours take its new colour, relative to the row's darkest, average or most saturated colour), limitTo?: swatch library id or name; or \"document\" (the document's swatches): new colours snap to its nearest colour, group?: colour group to rewrite, groupColors?: [colour] (what `group` is rewritten with; default: the rows' new colours, in order, excluded rows left out), rename?: the group's new name, includeImages?: true, includePatterns?: true} recolour the selection (gradients, text, meshes, image pixels and pattern tiles included; each new colour keeps the model of the one it replaces (model?: \"keep\" default | \"new\" (the new colour's own model, so a CMYK colour replacing RGB art gives CMYK art) | \"document\" (the document's colour mode)), except a library swatch's with limitTo: art takes the swatch itself, linked to a global or spot colour at its tints, and the swatch joins the document's swatches; art linked to a global swatch of `group` that is rewritten with its row's new color stays linked to it, at its tint; other recolored art loses its swatch link) and the group, as one undo step → {changed, swatches: [names added to the document's swatches], relinked?: with group, the other paints linked to its global swatches that took their new colors, note?: set when a colour kept a model other than its new colour's (see model)}",
+            "{map: rows [{from: [colour keys (recolor.colors) or \"#rrggbb\" (every colour shown as that hex)], to: colour (hex, key, {c,m,y,k} or {l,a,b}) | null, exclude?: false (the row's colours are kept)}] | {\"key or #rrggbb\": colour, …} (one row per colour), method?: \"exact\" (default)|\"preserveTints\"|\"scaleTints\"|\"tintsShades\"|\"hueShift\" (how a row's colours take its new colour, relative to the row's darkest, average or most saturated colour), limitTo?: swatch library id or name; or \"document\" (the document's swatches): new colours snap to its nearest colour, group?: colour group to rewrite, groupColors?: [colour] (what `group` is rewritten with; default: the rows' new colours, in order, excluded rows left out), rename?: the group's new name, includeImages?: true, includePatterns?: true} recolour the selection (gradients, text, meshes, image pixels and pattern tiles included; each new colour keeps the model of the one it replaces (model?: \"keep\" default | \"new\" (the new colour's own model, so a CMYK colour replacing RGB art gives CMYK art) | \"document\" (the document's colour mode)), except a library swatch's with limitTo: art takes the swatch itself, linked to a global or spot colour at its tints, and the swatch joins the document's swatches; art linked to a global swatch of `group` that is rewritten with its row's new color stays linked to it, at its tint; other recolored art, and art in a row linked to a global swatch of `group` that is rewritten with another color, keeps its row's new color and loses its swatch link) and the group, as one undo step → {changed, swatches: [names added to the document's swatches], relinked?: with group, the other paints linked to its global swatches that took their new colors, note?: set when a colour kept a model other than its new colour's (see model)}",
             has_doc,
             apply
         ),
@@ -354,7 +354,8 @@ impl ColorMap {
     /// swatch links its colours to it (at their tints; shades and other hues stay unlinked), a
     /// process swatch gives its colour in its own model; a color linked to a global swatch of the
     /// rewritten group that takes the row's new color keeps its link (at its tint in the row);
-    /// other rows map the colour, which loses its link when it changes. True when anything changed.
+    /// other rows map the colour, which loses its link when it changes or when the group's rewrite
+    /// would change it. True when anything changed.
     fn map_link(&self, c: &mut Color, link: &mut Option<String>, tint: &mut f32) -> bool {
         let Some(i) = self.row_of(*c) else { return false };
         let (Some(row), Some(l)) = (self.rows.get(i), self.links.get(i)) else { return false };
@@ -385,7 +386,10 @@ impl ColorMap {
                 row.map(*c)
             }
         };
-        if new == *c {
+        // A color its row leaves as it is still loses its link to a swatch of the rewritten group
+        // when the rewrite would give it another color.
+        let rewritten = link.as_deref().and_then(|n| self.group.iter().find(|g| g.name == n)).is_some_and(|g| g.shown.tinted(*tint) != new);
+        if new == *c && !rewritten {
             return false;
         }
         *c = new;

crates/engine/src/tests_recolor.rs

@@ -430,6 +430,14 @@ fn apply_with_a_group_keeps_art_linked_to_its_global_swatches() {
     run(&mut s, "recolor.apply", json!({"map": {"#2878f0": "#ff6a00"}, "group": "Brand", "groupColors": ["#123456"]}));
     assert_eq!(link(&s, full), (orange, None, 1.0));
     assert_eq!(swatch_hex(&s), "#123456");
+    // A row that leaves the art's color as it is while the swatch is rewritten with another color:
+    // the art keeps its color, unlinked.
+    run(&mut s, "edit.undo", json!({}));
+    select_all(&mut s);
+    let blue = Color::from_hex("#2878f0").unwrap();
+    run(&mut s, "recolor.apply", json!({"map": {"#2878f0": "#2878f0"}, "group": "Brand", "groupColors": ["#123456"]}));
+    assert_eq!(link(&s, full), (blue, None, 1.0));
+    assert_eq!(swatch_hex(&s), "#123456");
     // Without a group the swatch is unchanged, so the art takes the new color unlinked.
     run(&mut s, "edit.undo", json!({}));
     select_all(&mut s);

docs/mcp.md

@@ -1694,7 +1694,9 @@ the others turn by the same hue). `limitTo` snaps new colours to a swatch librar
 step (art linked to its global swatches follows), and `recolor.apply` with `group` recolours the art and rewrites the
 group together. Art linked to one of the group's global swatches stays linked when the swatch is rewritten with its
 row's new color (the default without `groupColors` when the rows follow the group's order), so a later `swatch.edit` still
-reaches it; the reply's `relinked` counts the other linked paints that took the group's new colors. Without `group`,
+reaches it; the reply's `relinked` counts the other linked paints that took the group's new colors. Art in a row that
+is linked to a swatch rewritten with another color keeps its row's new color, even an unchanged one, and is no longer
+linked to the swatch. Without `group`,
 the swatch keeps its color and the recolored art is no longer linked to it.
 
 ```json