engine: split layers above the original by default (#2083)

crates/engine/src/prefs.rs

@@ -110,7 +110,8 @@ page!(General {
     /// Synchronize Time of All Related Items.
     sync_time_related_items: bool = true,
     expression_pick_whip_compact: bool = true,
-    create_split_layers_above: bool = false,
+    /// Create Split Layers Above Original Layer (After Effects' default).
+    create_split_layers_above: bool = true,
     use_system_color_picker: bool = false,
     /// Number of projects in File ▸ Open Recent.
     recent_items: u32 = 10,

crates/engine/src/tests_m145.rs

@@ -42,14 +42,14 @@ fn split_layers_go_above_or_below_the_original() {
     let mut s = session();
     let a = solid(&mut s, "#ff0000");
     s.execute("time.set", json!({"time": 1.0})).unwrap();
-    let below = s.execute("edit.splitLayer", json!({"layers": [a]})).unwrap()[0].as_u64().unwrap();
-    let order: Vec<u64> = s.active_comp().unwrap().layers.iter().map(|l| l.id.0).collect();
-    assert_eq!(order, vec![a, below], "off (default): the new part goes below");
-    s.execute("edit.undo", json!({})).unwrap();
-    s.execute("prefs.set", json!({"key": "general.createSplitLayersAbove", "value": true})).unwrap();
     let above = s.execute("edit.splitLayer", json!({"layers": [a]})).unwrap()[0].as_u64().unwrap();
     let order: Vec<u64> = s.active_comp().unwrap().layers.iter().map(|l| l.id.0).collect();
-    assert_eq!(order, vec![above, a]);
+    assert_eq!(order, vec![above, a], "on (default): the new part goes above");
+    s.execute("edit.undo", json!({})).unwrap();
+    s.execute("prefs.set", json!({"key": "general.createSplitLayersAbove", "value": false})).unwrap();
+    let below = s.execute("edit.splitLayer", json!({"layers": [a]})).unwrap()[0].as_u64().unwrap();
+    let order: Vec<u64> = s.active_comp().unwrap().layers.iter().map(|l| l.id.0).collect();
+    assert_eq!(order, vec![a, below]);
 }
 
 #[test]

docs/preferences.md

@@ -91,7 +91,8 @@ Commands (CLI, MCP, control channel):
   one and in the comps that nest it (through the precomp layers' timing)
 - `general.expressionPickWhipCompact`: off, the pick whip writes match names
   (`thisComp.layer("A")("transform")("opacity")`)
-- `general.createSplitLayersAbove`: where Edit ▸ Split Layer puts the new layer
+- `general.createSplitLayersAbove`: where Edit ▸ Split Layer puts the new layer (on by default,
+  as in After Effects)
 - `startup.showHomeOnOpenProject`: the Home screen comes up after File ▸ Open / Open Recent
 - `composition.motionPath`, `composition.motionPathSeconds`, `composition.motionPathKeyframes`:
   how much of a position motion path the viewer draws (all, none, N seconds or N keyframes