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REVIEW

Undo Engine

Issue: 1.3 (December/January 2002)
Author: Daniel Howard
Article Description: No description available.
Article Length (in bytes): 3,484
Starting Page Number: 9
Article Number: 1304
Related Web Link(s):

http://www.belle-nuit.com/realbasic/undoengine.html

Excerpt of article text...

When you think of undo (and redo) functionality, what is the first type of application that pops into your head? A text editor, right? Well, as this class illustrates, Undo and Redo are not just for the text editor anymore. You can literally undo or redo anything you want in your application. Someone checks a CheckBox, you can uncheck it; someone switches rows in a PopupMenu, you can switch it back. The list goes on to include almost all interface elements.

Undo Engine is not one of the easiest classes to include in your own application; however, the example file that is included should provide enough help for most users to catch on quickly. Unfortunately, no documentation is included with the package. The example project included shows you how to make your own classes for a CheckBox undo, an EditField undo, and a Color Picker undo. Each works exceptionally well and paves the way for users to find methods of implementing the class for other controls. Due to the lack of documentation, it is not clear whether styled text is or is not supported. However, third party undo classes typically do not support styled text, so even if it is not supported this deficiency would not necessarily be a major weakness.

If you've ever tried to implement an undo function in your application, you know it can be a daunting task. Undo Engine can give you relatively powerful control over undo functionality in your REALbasic project, and in doing so it can knock a rather unpleasant problem off of your "To Do" list.

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