Merge #603: Part of #372: .ai files write layers and sublayers as PDF layers, hidden ones kept

# Conflicts:
#	ROADMAP.md

crates/engine/src/cmd/fileio/save.rs

@@ -306,11 +306,16 @@ fn blank_pages(doc: &Document) -> Document {
 const NOT_PDF_COMPATIBLE: &str = "saved without PDF content: VectorCraft opens it as before, other apps show empty pages";
 
 /// The encoder's params for a `.ai` file, from a save's or an export's: a PDF of every artboard
-/// with the PDF options, always carrying the native document; Use Compression compresses the
-/// PDF's content.
+/// with the PDF options, always carrying the native document, its layers and sublayers PDF layers
+/// (hidden ones off) unless asked otherwise; Use Compression compresses the PDF's content.
 pub(super) fn ai_params(params: &mut Value) {
     let Some(o) = params.as_object_mut() else { return };
     o.extend([("preserveEditing".into(), json!(true)), ("range".into(), json!("all"))]);
+    // Apps that read the PDF part (not the native document) then find the layers, the hidden ones
+    // with their art (#372); a PDF standard decides for itself.
+    if o.get("standard").is_none_or(Value::is_null) {
+        o.entry("createLayers").or_insert(json!(true));
+    }
     if let Some(c) = o.get("compress").and_then(Value::as_bool) {
         let compression = o.entry("compression").or_insert_with(|| json!({}));
         if let Some(m) = compression.as_object_mut() {

crates/engine/src/cmd/fileio/tests_pdflayers.rs

@@ -59,3 +59,35 @@ fn export_pdf_overprint_is_preserved_or_discarded() {
     assert_eq!(overprints(&mut s, json!({"compression": {"compressText": false}})), 1);
     assert_eq!(overprints(&mut s, json!({"advanced": {"overprint": "discard"}})), 0);
 }
+
+/// A `.ai` file's PDF part, which apps that don't read the native document open, has the layers
+/// and sublayers as PDF layers, the hidden ones with their art (#372).
+#[test]
+fn ai_files_write_their_layers_and_sublayers_as_pdf_layers() {
+    let mut s = session();
+    let layer1 = s.execute("document.inspect", &json!({})).unwrap()["layers"][1]["id"].as_u64().unwrap();
+    let sub = s.execute("layer.newSublayer", &json!({"parent": layer1, "name": "Sketch"})).unwrap()["id"].as_u64().unwrap();
+    s.execute("layer.setCurrent", &json!({"id": sub})).unwrap();
+    s.execute("shape.ellipse", &json!({"x": 10, "y": 40, "width": 20, "height": 20})).unwrap();
+    s.execute("layer.setProps", &json!({"id": sub, "visible": false})).unwrap();
+    // Name, shown and what it holds (sublayers by name), top-level layers in paint order.
+    fn rows(layers: &[std::sync::Arc<vectorcraft_doc::Node>]) -> Vec<(String, bool, Vec<String>)> {
+        layers
+            .iter()
+            .map(|l| {
+                let held =
+                    l.children().into_iter().flatten().map(|c| c.name.clone().filter(|_| c.is_layer()).unwrap_or_else(|| "art".into())).collect();
+                (l.name.clone().unwrap_or_default(), l.visible, held)
+            })
+            .collect()
+    }
+    let v = s.execute("document.export", &json!({"format": "ai"})).unwrap();
+    let back = vectorcraft_pdf::import(&b64(&v)).unwrap();
+    let art = || "art".to_string();
+    assert_eq!(rows(&back.layers), [("Layer 1".to_string(), true, vec![art(), "Sketch".into()]), ("Notes".to_string(), false, vec![art()])]);
+    let sketch = back.layers.first().and_then(|l| l.children()?.last().cloned()).unwrap();
+    assert_eq!(rows(&[sketch]), [("Sketch".to_string(), false, vec![art()])]);
+    // Asked not to, it writes none.
+    let v = s.execute("document.export", &json!({"format": "ai", "createLayers": false})).unwrap();
+    assert_eq!(vectorcraft_pdf::import(&b64(&v)).unwrap().layers.len(), 1);
+}