Meziantou.Framework

Introduction

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Meziantou.Framework.UndoRedo adds undo and redo to an application, such as an editor or a form. Each change the user makes is an action that knows how to apply itself and how to revert itself. UndoRedoManager runs the actions, keeps them in a history, and reverts or reapplies them when the user asks to undo or redo.

What you can do with it

  • Record a change from two delegates, one that applies it and one that reverts it, or from an action class of your own. See Getting started and Actions.
  • Group several changes into a single undo step, all applied or none. See Transactions.
  • Merge consecutive changes, such as the characters of a word or the moves of a drag, into one undo step. See Merging actions.
  • Bind the Undo and Redo commands of a user interface, show the undo history, and limit its size. See Undo history in the UI.

Principles

  • Asynchronous. Applying and reverting an action return a ValueTask and accept a CancellationToken, so an action can save a file or call a service. Synchronous delegates are accepted too.
  • One action, one state. An action is applied or reverted in turn, never twice in a row: the manager never applies an applied action, and UndoRedoActionBase throws when it would happen.
  • All or nothing. A transaction that fails while applying its actions reverts the ones that already ran. A transaction that is not committed is rolled back.
  • Single-threaded. UndoRedoManager is not thread-safe: use it from one logical flow, such as the UI thread.

Namespace

Every type is in the Meziantou.Framework.UndoRedo namespace.

Next steps