Struct ListDriver 

pub struct ListDriver {
    pub row_height: RowHeight,
    pub len: Box<dyn Fn() -> usize>,
    pub token_at: Box<dyn Fn(usize) -> u64>,
    pub build: Box<dyn Fn(usize, RNode) -> BuiltRow>,
    pub reorder: Option<ListReorderDriver>,
}

Supplied by the list() piece, type-erased over the item type. day-core invokes these to answer the native data-source and to build/rebind rows.

Fields

row_height: RowHeight

len: Box<dyn Fn() -> usize>

Current row count (reads the piece’s snapshot; no tree access).

token_at: Box<dyn Fn(usize) -> u64>

Stable identity token for row index (for native diffing).

build: Box<dyn Fn(usize, RNode) -> BuiltRow>

Build row index into anchor. Uses BuildCx internally, so it MUST be called with no with_tree borrow held. Returns the row’s scope + a rebind writer.

reorder: Option<ListReorderDriver>

Drag-to-reorder half, present when the piece is .reorderable() (docs/list.md).