Crate undo [−] [src]
An undo/redo library.
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
Redo | Undo | |
---|---|---|
Dispatch | Static | Dynamic |
State Handling | Yes | Yes |
Command Merging | Yes (manual) | Yes (automatic) |
undo
uses dynamic dispatch instead of static dispatch to store the commands, which means
it has some additional overhead compared to redo
. However, this has the benefit that you
can store multiple types of commands in a UndoStack
at a time. Both supports state handling
and command merging but undo
will automatically merge commands with the same id, while
in redo
you need to implement the merge method yourself.
I recommend using undo
by default and to use redo
when performance is important.
They have similar API, so it should be easy to switch between them if necessary.
Examples
use undo::{self, UndoCmd, UndoStack}; #[derive(Clone, Copy)] struct PopCmd { vec: *mut Vec<i32>, e: Option<i32>, } impl UndoCmd for PopCmd { type Err = (); 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; let e = self.e.ok_or(())?; vec.push(e); } 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(()) }
An unsafe implementation of redo
and undo
is used in examples since it is less verbose and
makes the examples easier to follow.
Structs
Id |
An unique id for an |
UndoGroup |
A collection of |
UndoStack |
Maintains a stack of |
Traits
UndoCmd |
Trait that defines the functionality of a command. |
Type Definitions
Result |
A specialized |