Crate undo [−] [src]

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. When it's state changes to either dirty or clean, it calls the user defined methods set in on_state_change. This is useful if you want to trigger some event when the state changes, eg. enabling and disabling undo and redo buttons.

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

Redo vs Undo

	Redo	Undo
Dispatch	Static	Dynamic
State Handling	Yes	Yes
Command Merging	Manual	Auto

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

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(())
}

Structs

Key	A key for an `UndoStack` in an `UndoGroup`.
UndoGroup	A collection of `UndoStack`s.
UndoGroupBuilder	Builder for `UndoGroup`.
UndoStack	Maintains a stack of `UndoCmd`s.
UndoStackBuilder	Builder for `UndoStack`.

Traits

UndoCmd

Trait that defines the functionality of a command.

Type Definitions

Result

A specialized Result that does not carry any data on success.