Fix #221: Effect > Pathfinder works on several selected objects

Choosing an Effect > Pathfinder item (Add, Intersect, Exclude, Subtract...)
with several loose objects selected now groups them and applies the live
effect to the group, in one undo step, so the result shows at once and stays
editable. A selection that already holds a group, or a single object, works
as before, and agents get `grouped: true` back when it happens.

Root cause: Pathfinder effects combine the contents of a group or layer.
Applied to loose objects, each one got an effect with nothing to combine, so
nothing visibly changed, while the Pathfinder panel's commands (found by the
command search) act on the selection directly.

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

crates/engine/src/cmd/effectcmd.rs

@@ -23,7 +23,7 @@ pub fn specs() -> Vec<CommandSpec> {
             "Apply Effect",
             [],
             None,
-            "{effect: id (see effect.list, e.g. \"stylize.dropShadow\", \"distort.roughen\", \"warp.arc\", or \"plugin.<id>\" for an installed effect plug-in), params?: {…} (missing keys take the dialog defaults), item?: appearance item index|null (apply to that fill/stroke only; omitted: the Appearance panel's active item, else the whole object), ids?: [..] (layers too), target?: \"object\"|\"contents\" (contents: the objects inside groups and layers)} append a live effect to each selected object's appearance (a group's or layer's apply to its members as one piece: one combined shadow) → {ids, index, item}",
+            "{effect: id (see effect.list, e.g. \"stylize.dropShadow\", \"distort.roughen\", \"warp.arc\", or \"plugin.<id>\" for an installed effect plug-in), params?: {…} (missing keys take the dialog defaults), item?: appearance item index|null (apply to that fill/stroke only; omitted: the Appearance panel's active item, else the whole object), ids?: [..] (layers too), target?: \"object\"|\"contents\" (contents: the objects inside groups and layers)} append a live effect to each selected object's appearance (a group's or layer's apply to its members as one piece: one combined shadow; a Pathfinder effect, which combines a group's contents, groups several loose selected objects first, in the same undo step) → {ids, index, item, grouped?}",
             has_doc,
             apply
         ),
@@ -130,6 +130,15 @@ pub(crate) fn apply(s: &mut Session, p: &Value) -> Result<Value> {
     }
     let effect = effects::new_effect(id, &params).ok_or_else(|| bad(C, format!("unknown effect `{id}`")))?;
     let label = effects::effect_info(id).map(|e| e.label.trim_end_matches('…').to_string()).unwrap_or_default();
+    if let Some(loose) = loose_for_pathfinder(s, p, id)? {
+        let gid = s.edit(&label, |d, sel| {
+            let gid = super::object::group_nodes(d, &loose)?;
+            d.node_mut(gid).ok_or(EngineError::NoNode(gid))?.appearance.effects.push(effect.clone());
+            sel.set([gid]);
+            Ok(gid)
+        })?;
+        return Ok(json!({ "ids": [gid.0], "index": 0, "item": null, "grouped": true }));
+    }
     let item = item_target(s, p, C)?;
     let mut index = 0;
     let ids = edit_effects(s, p, item, C, &label, "Apply Effect: select objects", |fx| {
@@ -143,6 +152,19 @@ pub(crate) fn apply(s: &mut Session, p: &Value) -> Result<Value> {
     Ok(json!({ "ids": ids_json(&ids), "index": index, "item": landed }))
 }
 
+/// The selected objects a Pathfinder effect should group before it applies: it combines the
+/// contents of a group or layer, so on several loose objects (none a group) it would do nothing.
+/// `None` when the effect isn't one, objects are named (`ids`) or another target is asked for.
+fn loose_for_pathfinder(s: &Session, p: &Value, id: &str) -> Result<Option<Vec<NodeId>>> {
+    if !effects::is_pathfinder(id) || ["ids", "id", "item", "target"].iter().any(|k| p.get(k).is_some()) {
+        return Ok(None);
+    }
+    let roots = super::appearance::subject_roots(s)?;
+    let d = &s.doc()?.doc;
+    let grouped = roots.iter().any(|r| d.node(*r).is_some_and(|n| matches!(n.kind, NodeKind::Group { clip: false, .. } | NodeKind::Layer { .. })));
+    Ok((roots.len() >= 2 && !grouped).then_some(roots))
+}
+
 fn list(s: &mut Session, p: &Value) -> Result<Value> {
     let catalog: Vec<Value> = effects::effect_catalog()
         .into_iter()
@@ -507,6 +529,34 @@ mod tests {
         assert!((b.x1 - 320.0).abs() < 1e-6, "{b:?}");
     }
 
+    #[test]
+    fn pathfinder_effect_on_loose_objects_groups_them_first() {
+        let (mut s, a) = session_with_rect();
+        let b = NodeId(s.execute("shape.rectangle", &json!({"x": 150, "y": 100, "width": 100, "height": 100})).unwrap()["id"].as_u64().unwrap());
+        s.execute("select.set", &json!({"ids": [a.0, b.0]})).unwrap();
+        let r = s.execute("effect.apply", &json!({"effect": "pathfinder.add"})).unwrap();
+        assert_eq!(r["grouped"], true);
+        let g = NodeId(r["ids"][0].as_u64().unwrap());
+        let gn = node(&s, g);
+        assert_eq!(gn.children().unwrap().iter().map(|c| c.id).collect::<Vec<_>>(), [a, b], "stacking order kept");
+        assert!(vectorcraft_render::effects::has_pathfinder(&gn));
+        assert_eq!(s.doc().unwrap().selection.objects, [g]);
+        // Live: one united shape, so expanding leaves a single path.
+        s.execute("effect.expandAppearance", &json!({})).unwrap();
+        assert_eq!(node(&s, g).children().unwrap().len(), 1);
+        // Grouping and applying are one undo step.
+        s.execute("edit.undo", &json!({})).unwrap();
+        s.execute("edit.undo", &json!({})).unwrap();
+        let d = &s.doc().unwrap().doc;
+        assert!(d.node(g).is_none());
+        assert!(d.node(a).is_some_and(|n| n.appearance.effects.is_empty()) && d.parent_of(a) == d.parent_of(b));
+        // A selection holding a group applies to each object as before; so does a single object.
+        s.execute("select.set", &json!({"ids": [a.0]})).unwrap();
+        let r = s.execute("effect.apply", &json!({"effect": "pathfinder.add"})).unwrap();
+        assert!(r.get("grouped").is_none());
+        assert_eq!(node(&s, a).appearance.effects.len(), 1);
+    }
+
     #[test]
     fn pathfinder_effect_on_a_group_renders_live_and_expands() {
         let (mut s, a) = session_with_rect();

crates/engine/src/cmd/object.rs

@@ -375,20 +375,26 @@ fn send_to_current_layer(s: &mut Session, _: &Value) -> Result<Value> {
 
 fn group(s: &mut Session, _: &Value) -> Result<Value> {
     let ids = selected_roots(s)?;
-    let Some(top) = ids.last().copied() else { return Err(EngineError::Other("nothing selected".into())) };
     let gid = s.edit("Group", |d, sel| {
-        let (par, idx, _) = d.position(top).ok_or(EngineError::NoNode(top))?;
-        let gid = d.alloc_id();
-        d.insert(par, idx + 1, Node::group(gid, vec![]))?;
-        for id in &ids {
-            d.move_node(*id, Some(gid), usize::MAX)?;
-        }
+        let gid = group_nodes(d, &ids)?;
         sel.set([gid]);
         Ok(gid)
     })?;
     Ok(json!({ "id": gid.0 }))
 }
 
+/// Put `ids` (top-level objects, in paint order) in a new group where the front-most one was.
+pub(crate) fn group_nodes(d: &mut Document, ids: &[NodeId]) -> Result<NodeId> {
+    let Some(top) = ids.last().copied() else { return Err(EngineError::Other("nothing selected".into())) };
+    let (par, idx, _) = d.position(top).ok_or(EngineError::NoNode(top))?;
+    let gid = d.alloc_id();
+    d.insert(par, idx + 1, Node::group(gid, vec![]))?;
+    for id in ids {
+        d.move_node(*id, Some(gid), usize::MAX)?;
+    }
+    Ok(gid)
+}
+
 fn ungroup(s: &mut Session, _: &Value) -> Result<Value> {
     let ids = selected_roots(s)?;
     s.edit("Ungroup", |d, sel| {

docs/mcp.md

@@ -67,7 +67,7 @@ objects' fills or strokes differ (`fillMixed` / `strokeMixed`, drawn as a "?" pr
 | `export` | `{path?, format?, scale?, artboard?, range?, selection?, outlineText?, options?}` | `svg`, `pdf`, `png`, `jpg`, `webp`, `gif`, `png8` (an indexed `.png`), `tiff`, `bmp`, `tga`, `psd` (layered), `txt` (the document's text) or `vectorcraft` (the list comes from `document.formats`). When `format` is omitted, it comes from the path's extension. PDF writes one page per artboard: all of them, or `artboard` (0-based) / `range` (`"1-3, 5"`, 1-based); the other formats write one artboard. `options` carries more format options (e.g. `{"quality": 80}` for JPEG). `selection: true` exports the selected objects cropped to their bounds; `outlineText: true` writes SVG text as paths. Template layers are left out, live effects are kept, and exporting `vectorcraft` never changes the document's path. Without `path` the bytes come back as `dataBase64`. Both backends run the same `document.export` call. |
 | `add_text` | `{text, x?, y?, width?, height?, path?, mode?, pathEffect?, size?, font?, color?}` | Point type at (x, y); area type with `width`/`height`; or `path` + `mode` (`area`/`onPath`) to flow text in or along a path, with `pathEffect` (`rainbow`, `skew`, `3dRibbon`, `stairStep`, `gravity`). |
 | `apply_effect` | `{effect?, params?, ids?}` | Appends a live effect. Without `effect`, returns the effect catalogue with parameters and defaults. |
-| `pathfinder` | `{operation, ids?}` | `unite`, `minusFront`, `intersect`, `exclude`, `divide`, `trim`, `merge`, `crop`, `outline`, `minusBack`. For a live version, apply the `pathfinder.*` effect to a group. |
+| `pathfinder` | `{operation, ids?}` | `unite`, `minusFront`, `intersect`, `exclude`, `divide`, `trim`, `merge`, `crop`, `outline`, `minusBack`. For a live version, apply the `pathfinder.*` effect to a group (`effect.apply` groups several loose selected objects first). |
 | `transform` | `{ids?, dx?, dy?, rotate?, scale?, scaleX?, scaleY?, reflect?, shear?, origin?, copy?}` | Runs move, rotate, scale, reflect, shear in that order. With `copy`, the first step duplicates. |
 | `create_graph` | `{type?, x, y, width, height, csv? \| series?, categories?, rows?}` | The nine Illustrator graph types: column, stacked column, bar, stacked bar, line, area, scatter, pie and radar. Edit later with `graph.setData` / `graph.setType` via `run_command`. |
 | `text_wrap` | `{ids?, offset?, invert?, release?}` | Area type below the objects (same layer) flows around them. |