Multiple level undo/redo mechanism.

摘要

A multiple-level undo/redo mechanism is provided in an operating system and is available to application programs run on the operating system. The operating system provides a mechanism for keeping a log of user commands and providing a cursor to a position within the log. Each command may be encapsulated into an object that supports an interface for performing undo/redo operations. Similarly, the log may be encapsulated into an object that supports operations that facilitate a multiple-level undo/redo. A user may perform a single undo/redo operation, multiple successive undo/redo operations or complete undo/redo operations.