Undo

An undo/redo library with dynamic dispatch, state handling and automatic command merging.

About

It uses the Command Pattern where the user implements the UndoCmd trait for each command.

The UndoStack has two states, clean and dirty. The stack is clean when no more commands can be redone, otherwise it is dirty. The stack will notice when it's state changes to either dirty or clean, and call the user defined methods set in on_clean and on_dirty. This is useful if you want to trigger some event when the state changes, eg. enabling and disabling buttons in an ui.

It also supports automatic merging of commands with the same id.

Redo vs Undo

Both supports command merging but undo will automatically merge commands with the same id, while in redo you need to implement the merge method yourself.

Examples

[dependencies]
undo = "0.7.2"

use undo::{self, UndoCmd, UndoStack};

#[derive(Clone, Copy, Debug)]
struct PopCmd {
    vec: *mut Vec<i32>,
    e: Option<i32>,
}

impl UndoCmd for PopCmd {
    fn redo(&mut self) -> undo::Result {
        self.e = unsafe {
            let ref mut vec = *self.vec;
            vec.pop()
        };
        Ok(())
    }

    fn undo(&mut self) -> undo::Result {
        unsafe {
            let ref mut vec = *self.vec;
            vec.push(self.e.unwrap());
        }
        Ok(())
    }
}

fn foo() -> undo::Result {
    let mut vec = vec![1, 2, 3];
    let mut stack = UndoStack::new();
    let cmd = PopCmd { vec: &mut vec, e: None };

    stack.push(cmd)?;
    stack.push(cmd)?;
    stack.push(cmd)?;

    assert!(vec.is_empty());

    stack.undo()?;
    stack.undo()?;
    stack.undo()?;

    assert_eq!(vec.len(), 3);
    Ok(())
}