Struct UndoStack 

pub struct UndoStack { /* private fields */ }

A bounded, linear undo stack.

items[..pos] are undoable and items[pos..] are redoable, so a fresh edit truncating the redo branch is one truncate.

Implementations

impl UndoStack

pub const DEFAULT_MAX: u32 = 10_000

The default capacity.

pub const MIN_MAX: u32 = 4

The smallest capacity that can hold the worst-case group: a boundary, a clear, an insert and a boundary.

pub fn with_max(max: u32) -> UndoStack

An empty, enabled stack holding at most max items.

max is clamped up to UndoStack::MIN_MAX, because a capacity below the worst-case group size could only be satisfied by evicting half a group, and a half-evicted group is not a state this type admits.

pub fn set_enabled(&mut self, enabled: bool)

Turns recording on or off. Does not discard what is already recorded.

A disabled stack receives no items, boundaries included — the check happens once, at the single entry point, rather than at each of the several call sites that would otherwise each have to remember it.

pub fn max(&self) -> usize

The capacity.

pub fn len(&self) -> usize

How many items are stored, undoable and redoable together.

pub fn is_empty(&self) -> bool

Whether nothing is stored.

pub fn can_undo(&self) -> bool

Whether there is anything to undo.

pub fn can_redo(&self) -> bool

Whether there is anything to redo.

pub fn clear(&mut self)

Forgets everything. What a focus change to another field does.

pub fn push(&mut self, item: UndoItem)

Records one item, truncating the redo branch and evicting from the head if the stack is full.

A disabled stack ignores the call.

pub fn undo(&mut self) -> Vec<UndoItem>

The items one undo would replay, newest first, and moves the cursor past them.

The order is the inverse-replay order and is deliberately the opposite of UndoStack::redo’s: undoing a group has to unwind its members from the last one backwards, while redoing one re-applies them from the first forwards.

Exactly one item when the top of the stack is an ordinary edit. When it is a group’s closing boundary, the whole group: the walk continues until it has consumed the opening boundary.

Returns an empty slice when there is nothing to undo, which is the same answer as “the cursor is at the bottom”.

pub fn redo(&mut self) -> Vec<UndoItem>

The items one redo would replay, oldest first, and moves the cursor past them. The mirror of UndoStack::undo, including in the order it hands them back.

pub fn items(&self) -> impl Iterator<Item = &UndoItem>

The stored items, oldest first. For tests and diagnostics.

pub fn position(&self) -> usize

How many items are undoable — the cursor’s position.

Trait Implementations

impl Clone for UndoStack

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for UndoStack

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for UndoStack

fn default() -> UndoStack

Returns the “default value” for a type.

impl Eq for UndoStack

impl PartialEq for UndoStack

Two stacks are equal when they hold the same items with the cursor in the same place. The capacity and the enable switch are configuration rather than content, so they do not participate.

fn eq(&self, other: &UndoStack) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.