Crate undo[][src]

Expand description

A undo-redo library.

It is an implementation of the action pattern, where all modifications are done by creating objects of actions that applies the modifications. All actions knows how to undo the changes it applies, and by using the provided data structures it is easy to apply, undo, and redo changes made to a target.


  • Action provides the base functionality for all actions.
  • Record provides basic undo-redo functionality.
  • Timeline provides basic undo-redo functionality using a fixed size.
  • History provides non-linear undo-redo functionality that allows you to jump between different branches.
  • Queues wraps a record or history and extends them with queue functionality.
  • Checkpoints wraps a record or history and extends them with checkpoint functionality.
  • Actions can be merged into a single action by implementing the merge method on the action. This allows smaller actions to be used to build more complex operations, or smaller incremental changes to be merged into larger changes that can be undone and redone in a single step.
  • The target can be marked as being saved to disk and the data-structures can track the saved state and notify when it changes.
  • The amount of changes being tracked can be configured by the user so only the N most recent changes are stored.
  • Configurable display formatting using the display structure.
  • The library can be used as no_std.

Cargo Feature Flags

  • alloc: Enables the use of the alloc crate, enabled by default.
  • arrayvec: Required for the timeline module, enabled by default.
  • chrono: Enables time stamps and time travel.
  • serde: Enables serialization and deserialization.
  • colored: Enables colored output when visualizing the display structures.


use undo::{Action, History};

struct Add(char);

impl Action for Add {
    type Target = String;
    type Output = ();
    type Error = &'static str;

    fn apply(&mut self, s: &mut String) -> undo::Result<Add> {

    fn undo(&mut self, s: &mut String) -> undo::Result<Add> {
        self.0 = s.pop().ok_or("s is empty")?;

fn main() {
    let mut target = String::new();
    let mut history = History::new();
    history.apply(&mut target, Add('a')).unwrap();
    history.apply(&mut target, Add('b')).unwrap();
    history.apply(&mut target, Add('c')).unwrap();
    assert_eq!(target, "abc");
    history.undo(&mut target).unwrap().unwrap();
    history.undo(&mut target).unwrap().unwrap();
    history.undo(&mut target).unwrap().unwrap();
    assert_eq!(target, "");
    history.redo(&mut target).unwrap().unwrap();
    history.redo(&mut target).unwrap().unwrap();
    history.redo(&mut target).unwrap().unwrap();
    assert_eq!(target, "abc");


pub use self::timeline::Timeline;
pub use self::history::History;
pub use self::record::Record;


A history of actions.

A record of actions.

A timeline of actions.


Says if the action have been merged with another action.

The signal used for communicating state changes.


Base functionality for all actions.

Type Definitions

A specialized Result type for undo-redo operations.