Undo Toolkit 4.5.1 is a powerful, flexible implementation of the Undo
command that can be added to existing projects, providing unlimited
multiple Undo and Redo with minimal memory footprint.

The Undo Toolkit includes:

* The UndoableAction class and subclasses, which store the information
needed to undo an action.

* The UndoProvider class interface, which specifies how a class sends and
receives UndoableActions.

* The UndoStack class, which stores UndoableActions and handles the Undo
and Redo menu items.

Sample UndoProvider classes in this toolkit include the UndoableCheckBox,
UndoableSlider, UndoablePopupMenu, UndoableRadioButton, UndoableGroupBox,
UndoableListBox, and UndoableEditField classes. All are one-to-one
replacements for the built-in REALbasic controls, and the developer can
create additional UndoProvider classes and seamlessly integrate them into
the toolkit.

The UndoStack class allows for implementation of single or multiple Undo
(and, optionally, Redo) on a per-window, per-application, or other basis as
desired. The toolkit is designed for localization and includes hooks for
language-specific strings.

All classes in the Undo Toolkit are documented using the REALbasic 4.5
“Notes” feature. The toolkit may be backward-compatible with earlier
releases of the compiler, but has only been tested with REALbasic 4.5.1.

Undo Toolkit 4.5.1 is open source software, released under the GNU General
Public License. It’s available for download from
(http://www.ravenna.com/~forbes/yonk/source/). Please feel free to
contribute code or additional UndoProvider classes to this project.

— Scott Forbes