Trait UndoControl 

pub trait UndoControl {
    // Provided methods
    fn set_undo_status(&mut self, _status: &mut dyn FnMut() -> UndoStatus) { ... }
    fn take_undo_request(&mut self) -> Option<UndoRequest> { ... }
}

A control that shows or drives the document’s undo history (an Undo button). The host reaches every laid-out widget through its node_map, so a control works at any depth with no container forwarding.

Provided Methods

fn set_undo_status(&mut self, _status: &mut dyn FnMut() -> UndoStatus)

Host → widget: the live undo state, published once per frame. Call the provider only when the status is shown; a historical summary can need a document diff.

fn take_undo_request(&mut self) -> Option<UndoRequest>

Widget → host: an undo or redo the user asked for, performed through the same path as Ctrl+Z. Rising-edge: reading clears it.

Implementors

impl UndoControl for UndoButton