Struct UndoStatus 

pub struct UndoStatus {
    pub can_undo: bool,
    pub can_redo: bool,
    pub undo_summary: Option<String>,
    pub redo_summary: Option<String>,
}

What the live undo history can do right now, as a widget sees it.

Published by the host once per frame. Every field is derived from the real UndoLog at publish time and is scoped to the local author exactly as Ctrl+Z is — so can_undo is false precisely when pressing Ctrl+Z would do nothing, and a control rendered from it cannot promise an action the shortcut would refuse.

Fields

can_undo: bool

There is an action this user can undo.

can_redo: bool

There is an action this user can redo.

undo_summary: Option<String>

Short description of the action undo would revert, derived from the change itself ("+12 -3 chars", "+1 item", "2 fields") by the same producer the history pane uses — see history_source::change_summary.

None when there is nothing to undo. It is deliberately never a guess: a change whose effect cannot be described reports NO_VISIBLE_CHANGE.

redo_summary: Option<String>

The mirror of undo_summary for redo: what re-applying would put back.

Implementations

impl UndoStatus

pub fn empty() -> UndoStatus

The status of a history in which nothing has happened yet.

pub fn can(&self, which: UndoRequest) -> bool

Whether the verb which is available.

pub fn summary(&self, which: UndoRequest) -> Option<&str>

The summary for the verb which, if any.

pub fn description(&self, which: UndoRequest) -> String

The sentence an assistive technology should hear as the control’s description: what the verb would do, or the reason it is unavailable.

"Nothing to undo" when unavailable — never a description of an action that is not there.

Trait Implementations

impl Clone for UndoStatus

fn clone(&self) -> UndoStatus

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for UndoStatus

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

Formats the value using the given formatter.

impl Default for UndoStatus

fn default() -> UndoStatus

Returns the “default value” for a type.

impl PartialEq for UndoStatus

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for UndoStatus

impl StructuralPartialEq for UndoStatus