Appearance panel: a stroke colour on an unpainted zero-width stroke restores 1 pt too (#1253)

The case #1297 also covered: appearance.setItem with a colour and no weight.

crates/engine/src/cmd/appearance.rs

@@ -522,6 +522,11 @@ fn set_item(s: &mut Session, p: &Value) -> Result<Value> {
     s.edit("Appearance", |d, _| {
         for id in &ids {
             let Some(n) = d.node_mut(*id) else { continue };
+            if p.get("weight").is_none()
+                && let Some(pa) = &paint
+            {
+                super::paint::restore_unpainted_stroke(&mut n.appearance, Some(idx), pa);
+            }
             let bounds = n.geometric_bounds();
             let Some(item) = n.appearance.items.get_mut(idx) else { continue };
             let (pp, op, bl, vis, bounds) = match item {

crates/engine/src/cmd/paint.rs

@@ -502,7 +502,7 @@ fn set_run_stroke(style: &mut CharStyle, paint: Paint) {
 }
 
 /// Use the existing 1 pt default when adding paint to an unpainted zero-width stroke.
-fn restore_unpainted_stroke(ap: &mut Appearance, index: Option<usize>, paint: &Paint) {
+pub(super) fn restore_unpainted_stroke(ap: &mut Appearance, index: Option<usize>, paint: &Paint) {
     if !paint.is_none()
         && let Some(stroke) = ap.stroke_at_mut(index)
         && stroke.paint.is_none()

crates/engine/tests/stroke_visibility.rs

@@ -105,3 +105,15 @@ fn existing_weights_and_explicitly_zero_painted_strokes_keep_their_widths() {
     s.execute("paint.setStroke", &json!({"none": true})).unwrap();
     assert_eq!(width(&s, id), 0.0, "fill edits and removing paint do not enable a stroke");
 }
+
+#[test]
+fn appearance_panel_stroke_colour_restores_an_unpainted_zero_width_stroke() {
+    let (mut s, id) = fixture();
+    s.execute("paint.setStroke", &json!({"none": true})).unwrap();
+    s.execute("stroke.set", &json!({"weight": 0})).unwrap();
+    s.execute("appearance.setItem", &json!({"index": 1, "color": "#00ff00"})).unwrap();
+    assert_eq!(width(&s, id), 1.0);
+    s.execute("appearance.setItem", &json!({"index": 1, "weight": 0})).unwrap();
+    s.execute("appearance.setItem", &json!({"index": 1, "color": "#0000ff"})).unwrap();
+    assert_eq!(width(&s, id), 0.0, "a painted stroke keeps an explicit zero width");
+}