Module tree_model 

TreeModel — concrete reactive tree with shared, cloneable handles.

TreeModel<T> owns a hierarchy of T items in a flat SlotMap arena with parent-child links. Every structural mutation (insert_root, insert_child, remove, move_node, update) emits a TreeChange to all registered observers before returning. Node identity is a stable, versioned NodeId (a SlotMap key) that is never reused after removal.

Cloning produces a second handle to the same data — all handles see the same hierarchy and receive the same change notifications. Register observers via observe_changes; the returned [ObserverHandle] is RAII — dropping it unregisters the callback.

For per-view expand/collapse state wrap the model in a TreeSlice. For sort/filter projections use SortFilterTreeModel.

Example

let tree = TreeModel::new();
let root = tree.insert_root(0, "root");
let child = tree.insert_child(root, 0, "child");

assert_eq!(tree.root_count(), 1);
assert_eq!(tree.child_count(root), 1);
assert_eq!(tree.parent(child), Some(root));

let clone = tree.clone();
clone.insert_root(1, "root2");
assert_eq!(tree.root_count(), 2); // both handles share the same data

Structs

TreeModel

A concrete reactive tree that stores a hierarchy of T items in a flat arena.