Struct UndoStack 

pub struct UndoStack { /* private fields */ }

One undo history over the stores it UndoStack::watches: units are turns (everything one event’s dispatch changed), inverted, not snapshots. Enabling it turns on standing value capture; drop the stack and the capture stops.

Implementations

impl UndoStack

pub fn new(levels: usize) -> UndoStack

A stack holding at most levels units: the bound on what history keeps in RAM.

pub fn watch<T: ApplyField + Identified + Clone + 'static>( &self, store: Store<Keyed<T>>, )

Bring one store under this history. Only watched stores are captured; a change in any other store passes the stack by.

pub fn grouped(&self, label: &'static str, f: impl FnOnce())

Everything f changes lands as one unit named label: a multi-field commit, an inspector applying twelve properties.

pub fn begin_group(&self, label: &'static str) -> UndoGroup

Keep one undo unit open across event turns, until the returned guard is dropped. Nested groups join the outer unit and retain its label. Keep the guard only for the duration of the interaction: all watched edits in that interval belong to the group.

pub fn checkpoint(&self) -> UndoCheckpoint

Preserve history before an atomic persistence operation. Failed commits must restore both the database/cache and this checkpoint, including an existing redo branch.

pub fn restore_checkpoint(&self, checkpoint: UndoCheckpoint)

pub fn can_undo(&self) -> Signal<bool>

pub fn can_redo(&self) -> Signal<bool>

pub fn undo_label(&self) -> Signal<String>

The next undo unit’s display label (“Name”, or whatever the resolver makes of it), empty when there is nothing to undo. What a menu title interpolates.

pub fn redo_label(&self) -> Signal<String>

pub fn set_label_resolver(&self, f: impl Fn(&'static str) -> String + 'static)

How unit labels become display text (Fluent lookup, capitalization); the default capitalizes the raw label.

pub fn set_transient_context( &self, capture: impl Fn() -> Rc<dyn Any> + 'static, restore: impl Fn(&dyn Any) + 'static, )

Ride transient UI state (a selection, a scroll position) along the history: captured, never persisted (docs/model.md “Transient UI state”).

capture runs as each unit seals, so a snapshot is the UI state at that point of document history, including any selection writes the same turn made. Undo restores the snapshot of the unit history lands on: the previous unit’s, or the base snapshot (taken here, at install) once the last unit is undone; redo restores the redone unit’s own. UI changes between units restore nowhere: they are not history, which is what makes “select A, move it, select B, move it, undo” land on A (the state as it stood when A’s move sealed) rather than on B.

restore must not write a watched store (that would fork history from inside a replay); write plain signals. A unit sealed before this call carries no snapshot and restores nothing.

pub fn undo(&self) -> bool

pub fn redo(&self) -> bool

pub fn clear(&self)

Drop all history (a schema migration, a wholesale reload).

Trait Implementations

impl Clone for UndoStack

fn clone(&self) -> UndoStack

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.