Groups and nesting

Group membership is evaluated at settle points: initial measurement, node drops, group moves, resize commits, and group removal.

• Every node has at most one direct parent.
• Ordinary nodes join when their center is inside a group.
• A nested group must fit completely inside its parent.
• The smallest eligible group wins, producing an innermost-first hierarchy.
• Dragging an outer group carries all descendants without adding them to the current selection.

group.members contains direct members. group.descendants contains the deduplicated recursive subtree, and getParentGroup(node) returns the settled direct parent.

Use canContain to reject application-specific node types. For overlapping policies, configure one resolver per engine:

import { setGroupMembershipResolver } from "@snap-engine/snapline/group";

const disposePolicy = setGroupMembershipResolver(engine, (event) => {
  const pinned = event.candidates.find(
    (group) => group.metadata.role === "pinned",
  );
  return pinned ?? event.defaultParent;
});

A resolver may return one of the safe candidates or null. Persistence remains application-owned: use membership deltas to update group IDs in your document.