Follow-up to #2716: addItem applies in before out; anchor takes exactly [x, y]

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/layer/create.rs

@@ -279,6 +279,7 @@ fn anchor_param(p: &Value, cmd: &str) -> Result<Option<[f64; 2]>> {
         None | Some(Value::Null) => Ok(None),
         Some(v) => v
             .as_array()
+            .filter(|a| a.len() == 2)
             .and_then(|a| Some([a.first()?.as_f64()?, a.get(1)?.as_f64()?]))
             .filter(|c| c.iter().all(|x| x.is_finite() && x.abs() <= MAX_PLACEMENT))
             .map(Some)
@@ -361,12 +362,13 @@ pub(super) fn add_item(s: &mut Session, p: &Value) -> Result<Value> {
         l.out_point = fr.snap_nearest(end).max(start + fr.frame_duration());
         // `in` / `out` are comp times like `layer.timing`'s; each keeps at least one frame.
         let fd = fr.frame_duration();
-        if let Some(o) = out_p {
-            l.out_point = fr.snap_nearest(o).max(l.in_point + fd);
-        }
+        // In first, as `layer.timing` does, so an `out` before the layer's start still lands.
         if let Some(i) = in_p {
             l.in_point = fr.snap_nearest(i).min(l.out_point - fd);
         }
+        if let Some(o) = out_p {
+            l.out_point = fr.snap_nearest(o).max(l.in_point + fd);
+        }
         place(&mut l, position);
         set_anchor(&mut l, anchor);
         insert_layer_at(proj, st, cid, l, index)

crates/engine/src/tests/add_item_options.rs

@@ -82,3 +82,12 @@ fn invalid_values_are_errors_and_change_nothing() {
     }
     assert_eq!(s.active_comp().unwrap().layers.len(), n);
 }
+
+/// `in` applies before `out` (as `layer.timing`), so a range before the layer's start lands as asked.
+#[test]
+fn in_and_out_before_the_start_land_and_a_three_value_anchor_is_refused() {
+    let (mut s, item, _) = setup();
+    let id = s.execute_checked("layer.addItem", json!({"item": item, "time": 5.0, "in": 1.0, "out": 2.0})).unwrap()["layer"].as_u64().unwrap();
+    assert_eq!((secs(layer(&s, id).in_point), secs(layer(&s, id).out_point)), (1.0, 2.0));
+    assert!(s.execute_checked("layer.addItem", json!({"item": item, "anchor": [1.0, 2.0, 3.0]})).is_err());
+}