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//! 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. If state handling is not needed, it can be disabled by setting the //! `no_state` feature flag. //! //! 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(()) //! } //! # foo().unwrap(); //! ``` //! //! *An unsafe implementation of `redo` and `undo` is used in examples since it is less verbose and //! makes the examples easier to follow.* //! //! [Command Pattern]: https://en.wikipedia.org/wiki/Command_pattern //! [`on_clean`]: struct.RedoStack.html#method.on_clean //! [`on_dirty`]: struct.RedoStack.html#method.on_dirty //! [static dispatch]: https://doc.rust-lang.org/stable/book/trait-objects.html#static-dispatch //! [dynamic dispatch]: https://doc.rust-lang.org/stable/book/trait-objects.html#dynamic-dispatch //! [`undo`]: https://crates.io/crates/undo //! [`merge`]: trait.RedoCmd.html#method.merge #![deny(missing_docs, missing_debug_implementations, unstable_features, unused_import_braces, unused_qualifications)] extern crate fnv; mod group; mod stack; pub use group::RedoGroup; pub use stack::RedoStack; use std::result; type Key = u32; /// An unique id for an `RedoStack`. #[derive(Debug)] pub struct Id(Key); /// A specialized `Result` that does not carry any data on success. pub type Result<E> = result::Result<(), E>; /// Trait that defines the functionality of a command. /// /// Every command needs to implement this trait to be able to be used with the `RedoStack`. pub trait RedoCmd { /// The error type. type Err; /// Executes the desired command and returns `Ok` if everything went fine, and `Err` if /// something went wrong. fn redo(&mut self) -> Result<Self::Err>; /// Restores the state as it was before [`redo`] was called and returns `Ok` if everything /// went fine, and `Err` if something went wrong. /// /// [`redo`]: trait.RedoCmd.html#tymethod.redo fn undo(&mut self) -> Result<Self::Err>; /// Used for manual merging of two `RedoCmd`s. /// /// Returns `Some(Ok)` if the merging was successful, `Some(Err)` if something went wrong when /// trying to merge, and `None` if it did not try to merge. /// This method is always called by the [`push`] method in `RedoStack`, with `self` being the top /// command on the stack and `cmd` being the new command. If `None` is returned from this /// method, `cmd` will be pushed on the stack as normal. However, if the return value is /// `Some(x)` it will not push the command on to the stack since either it was merged or an /// error has occurred, and then the stack returns the `x` value. /// /// Default implementation returns `None`. /// /// # Examples /// ``` /// use redo::{self, RedoCmd, RedoStack}; /// /// #[derive(Debug)] /// struct TxtCmd { /// txt: String, /// c: char, /// } /// /// impl TxtCmd { /// fn new(c: char) -> Self { /// TxtCmd { c: c, txt: String::new() } /// } /// } /// /// impl RedoCmd for TxtCmd { /// type Err = (); /// /// fn redo(&mut self) -> redo::Result<()> { /// Ok(()) /// } /// /// fn undo(&mut self) -> redo::Result<()> { /// Ok(()) /// } /// /// fn merge(&mut self, cmd: &Self) -> Option<redo::Result<()>> { /// // Merge cmd if not a space. /// if cmd.c != ' ' { /// self.txt.push(cmd.c); /// Some(Ok(())) /// } else { /// None /// } /// } /// } /// /// fn foo() -> redo::Result<()> { /// let mut stack = RedoStack::new(); /// stack.push(TxtCmd::new('a'))?; /// stack.push(TxtCmd::new('b'))?; /// stack.push(TxtCmd::new('c'))?; // 'a', 'b' and 'c' is merged. /// stack.push(TxtCmd::new(' '))?; /// stack.push(TxtCmd::new('d'))?; // ' ' and 'd' is merged. /// /// println!("{:#?}", stack); /// Ok(()) /// } /// # foo().unwrap(); /// ``` /// /// Output: /// /// ```txt /// RedoStack { /// stack: [ /// TxtCmd { /// txt: "bc", /// c: 'a' /// }, /// TxtCmd { /// txt: "d", /// c: ' ' /// } /// ], /// idx: 2, /// limit: None /// } /// ``` /// /// [`push`]: struct.RedoStack.html#method.push #[allow(unused_variables)] #[inline] fn merge(&mut self, cmd: &Self) -> Option<Result<Self::Err>> { None } }