16: Understanding Undo in Java

Implementation qr barcode in Java 16: Understanding Undo
16: Understanding Undo
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interfaces. It allows users to reverse one or more previous actions if they decide to change their mind. A significant benefit of Undo is purely psychological: It reassures users. It is much easier to enter a cave if you are confident that you can get back out of it at any time. The Undo function is that comforting rope ladder to the surface, supporting a user s willingness to explore further by assuring him that he can back out of any dead-end caverns. Curiously, users often don t think about Undo until they need it, in much the same way that homeowners don t think about their insurance policies until a disaster strikes. Users frequently charge into the cave half prepared, and only start looking for the rope ladder for Undo after they have encountered trouble.
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Designing an Undo Facility
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Although users need Undo, it doesn t directly support any particular goal that underlies their tasks. Rather, it supports a necessary condition trustworthiness on the way to a real goal. It doesn t contribute positively to attaining users goals, but keeps negative occurrences from spoiling the effort. Users visualize the Undo facility in different ways, depending on the situation and their expectations. If a user is very computer-naive, he might see it as an unconditional panic button for extricating himself from a hopelessly tangled misadventure. A more experienced computer user might visualize Undo as a storage facility for deleted data. A really computer-sympathetic user with a logical mind might see it as a stack of procedures that can be undone one at a time in reverse order. To create an effective Undo facility, we must satisfy as many of these mental models as we expect our personas will bring to bear. The secret to designing a successful Undo system is to make sure that it supports typically used tools and avoids any hint that Undo signals (whether visually, audibly, or textually) a failure by a user. It should be less a tool for reversing errors and more one for supporting exploration. Errors are generally single, incorrect actions. Exploration, by contrast, is a long series of probes and steps, some of which are keepers and others that must be abandoned. Undo works best as a global, programwide function that undoes the last action regardless of whether it was done by direct manipulation or through a dialog box. One of the biggest problems in current implementations of Undo functionality is when users lose the ability to reverse their actions after they save the document (in Excel, for example). Just because a user has saved her work to avoid losing it in a
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Part III: Designing Interaction Details
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crash doesn t necessarily mean that she wants to commit to all the changes she has made. Furthermore, with our large disk drives, there is no reason not to save the Undo buffer with the document. Undo can also be problematic for documents with embedded objects. If a user makes changes to a spreadsheet embedded in a Word document, clicks on the Word document, and then invokes Undo, then the most recent Word action is undone instead of the most recent spreadsheet action. Users have a difficult time with this. It forces them to abandon their mental model of a single unified document and forces them to think in terms of the implementation model that there is one document embedded within another, and each has a separate editor with a separate Undo buffer.
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Types and Variants of Undo
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As is so common in the world of software, there is no adequate terminology to describe the different types of Undo that exist they are uniformly referred to as Undo and left at that. This language gap contributes to the lack of innovation to produce new and better variants of Undo. In this section, we define several Undo variants and explain their differences.
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