Crate redo [−] [src]
An undo/redo library.
About
It uses the Command Pattern where the user implements the RedoCmd
trait for a command.
The RedoStack
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 merging of commands by implementing the merge
method for a command.
Redo vs Undo
Redo | Undo | |
---|---|---|
Dispatch | Static | Dynamic |
State Handling | Yes | Yes |
Command Merging | Yes (manual) | Yes (automatic) |
redo
uses static dispatch instead of dynamic dispatch to store the commands, which means
it should be faster than undo
. However, this means that you can only store one type of
command in a RedoStack
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 redo::{self, RedoCmd, RedoStack}; #[derive(Clone, Copy)] struct PopCmd { vec: *mut Vec<i32>, e: Option<i32>, } impl RedoCmd for PopCmd { type Err = (); fn redo(&mut self) -> redo::Result<()> { self.e = unsafe { let ref mut vec = *self.vec; vec.pop() }; Ok(()) } fn undo(&mut self) -> redo::Result<()> { unsafe { let ref mut vec = *self.vec; let e = self.e.ok_or(())?; vec.push(e); } Ok(()) } } fn foo() -> redo::Result<()> { let mut vec = vec![1, 2, 3]; let mut stack = RedoStack::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 |
RedoGroup |
A collection of |
RedoStack |
Maintains a stack of |
Traits
RedoCmd |
Trait that defines the functionality of a command. |
Type Definitions
Result |
A specialized |