M8.6: Puppet Warp pins appear at once, warp from the rest shape and follow Undo

- Pins show as soon as the tool has art selected: automatic ones at the
  centre and the middle of each limb's end (at least three), until pins are
  placed. They stay across tool switches while the selection is unchanged and
  a new selection starts afresh.
- The pins live in the document (Document.puppet, never saved) with the rest
  shape they started from: every warp starts from it, so warps don't stack and
  dragging a pin back restores the original; Undo/Redo take the pins back with
  the art. Adding and deleting pins are undo steps too.
- object.puppetWarp gains rest: true (the tool's pins); the new query
  object.puppetWarp.pins reads them. A click off the mesh adds nothing and
  says so (not-allowed cursor, canvas label); the command refuses such pins.
- The mesh grid covers the expanded art, so tiny art with a wide Expand no
  longer allocates millions of cells.
- Tests on groups, compound paths and open strokes.

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

crates/doc/src/lib.rs

@@ -23,6 +23,7 @@ pub mod pattern;
 pub mod perspective;
 mod pixels;
 pub mod profiles;
+pub mod puppet;
 pub mod range;
 pub mod rastersettings;
 mod reach;
@@ -69,6 +70,7 @@ pub use orient::OrientedBox;
 pub use pattern::{Overlap, PatternDef, PatternEdit, RepeatKind, RepeatSpec, TileType};
 pub use perspective::PerspectiveAttachment;
 pub use profiles::ColorProfiles;
+pub use puppet::{PuppetPin, PuppetPins};
 pub use rastersettings::{RasterColorModel, RasterEffectsSettings};
 pub use selection::{AnchorRef, Selection};
 pub use setup::{Background, DocSetup, ExportText, GridSize, Quotes};
@@ -566,6 +568,10 @@ pub struct Document {
     /// export settings are Export for Screens' ([`Document::export_settings`]).
     #[serde(default, skip_serializing_if = "Vec::is_empty")]
     pub assets: Vec<ExportAsset>,
+    /// Puppet Warp pins on the selected artwork while the tool edits it ([`PuppetPins`]): editing
+    /// state, never saved.
+    #[serde(skip)]
+    pub puppet: Option<Arc<PuppetPins>>,
 }
 
 fn ppi72() -> f64 {
@@ -633,6 +639,7 @@ impl Document {
             slices_clip_to_artboard: true,
             print_setup: None,
             assets: vec![],
+            puppet: None,
         };
         let id = d.alloc_id();
         d.layers.push(Arc::new(Node::layer(id, "Layer 1", LayerColor::Preset(0))));

crates/doc/src/puppet.rs

@@ -0,0 +1,89 @@
+//! Puppet Warp pins: editing state the Puppet Warp tool and `object.puppetWarp` share while the
+//! same artwork stays selected. It lives in the document (never saved) so Undo and Redo take the
+//! pins back with the warps they made.
+
+use std::sync::Arc;
+
+use vectorcraft_geom::Point;
+
+use crate::{Document, Node, NodeId};
+
+/// One pin: where it sits on the rest shape, where it is now, and the turn it holds.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct PuppetPin {
+    pub rest: Point,
+    pub at: Point,
+    /// Radians the art is turned around the pin; `None`: free to turn.
+    pub angle: Option<f64>,
+}
+
+/// The pins on some objects and the shape they warp from.
+#[derive(Clone, Debug, PartialEq)]
+pub struct PuppetPins {
+    /// The warped objects.
+    pub ids: Vec<NodeId>,
+    /// Their rest shape: the objects as they were when pinning began (the warp always starts
+    /// from it, so warps don't stack and dragging a pin back restores the original).
+    pub rest: Vec<Arc<Node>>,
+    /// The objects as the last warp left them: once anything else edits them, the pins start
+    /// again from the objects as they are.
+    pub result: Vec<Arc<Node>>,
+    pub pins: Vec<PuppetPin>,
+}
+
+impl PuppetPins {
+    /// The pins are still those of `ids` in `doc`: the same objects, as the last warp left them.
+    pub fn holds(&self, doc: &Document, ids: &[NodeId]) -> bool {
+        self.ids == ids
+            && self.ids.len() == self.result.len()
+            && ids.iter().zip(&self.result).all(|(id, r)| doc.node_arc(*id).is_some_and(|a| Arc::ptr_eq(a, r)))
+    }
+}
+
+impl Document {
+    /// The node `id` as the document holds it (shared: comparing pointers says whether it changed).
+    pub fn node_arc(&self, id: NodeId) -> Option<&Arc<Node>> {
+        fn find(nodes: &[Arc<Node>], id: NodeId) -> Option<&Arc<Node>> {
+            for n in nodes {
+                if n.id == id {
+                    return Some(n);
+                }
+                if let Some(f) = n.children().and_then(|ch| find(ch, id)) {
+                    return Some(f);
+                }
+            }
+            None
+        }
+        find(&self.layers, id)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::Appearance;
+    use vectorcraft_geom::{Rect, shapes};
+
+    #[test]
+    fn pins_hold_until_their_objects_change_and_are_never_saved() {
+        let mut d = Document::new(200.0, 200.0);
+        let l = d.layers[0].id;
+        let id = d.alloc_id();
+        d.insert(Some(l), 0, Node::path(id, shapes::rectangle(Rect::new(0.0, 0.0, 10.0, 10.0)), Appearance::default_art())).unwrap();
+        let node = d.node_arc(id).cloned().unwrap();
+        let pin = PuppetPin { rest: Point::new(5.0, 5.0), at: Point::new(6.0, 5.0), angle: Some(0.5) };
+        d.puppet = Some(Arc::new(PuppetPins { ids: vec![id], rest: vec![node.clone()], result: vec![node], pins: vec![pin] }));
+        let pins = d.puppet.clone().unwrap();
+        assert!(pins.holds(&d, &[id]));
+        assert!(!pins.holds(&d, &[id, l]), "other objects");
+        // Saved and read back without them (editing state).
+        let json = serde_json::to_string(&d).unwrap();
+        assert!(!json.contains("puppet"));
+        let back: Document = serde_json::from_str(&json).unwrap();
+        assert!(back.puppet.is_none());
+        assert_eq!(back.node(id), d.node(id));
+        // An edit by anything else: the pins no longer hold.
+        d.node_mut(id).unwrap().name = Some("moved".into());
+        assert!(!pins.holds(&d, &[id]));
+    }
+}