16: Understanding Undo in Java

Display Quick Response Code in Java 16: Understanding Undo
16: Understanding Undo
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Using this same knowledge, we could create different categories of incremental Undo, like a format-Undo function that would Undo only preceding format commands and other types of category-specific Undo actions. If a user entered some text, changed it to italic, entered some more text, increased the paragraph indentation, entered some more text, and then clicked the Format-Undo button, only the indentation increase would be undone. A second click of the Format-Undo button would reverse the italicize operation. Neither invocation of the format-Undo would affect the content. What are the implications of category-specific Undo in a nontext program In a drawing program, for example, there could be separate Undo commands for pigment application tools, transformations, and cut-and-paste. There is really no reason that we couldn t have independent Undo functions for each particular class of operation in a program. Pigment application tools include all drawing implements pencils, pens, fills, sprayers, brushes and all shape tools rectangles, lines, ellipses, arrows. Transformations include all image-manipulation tools shear, sharpness, hue, rotate, contrast, and line weight. Cut-and-paste tools include all lassos, marquees, clones, drags, and other repositioning tools. Unlike the Backspace function in the word processor, undoing a pigment application in a draw program would be temporal and would work independently of selection. That is, the pigment that is removed first would be the last pigment applied, regardless of the current selection. In text, there is an implied order from the upper left to the lower right. Deleting from the lower right to the upper left maps to a strong, intrinsic mental model, so it seems natural. In a drawing, no such conventional order exists so any deletion order other than one based on entry sequence would be disconcerting to users. A better alternative might be to Undo within the current selection only. A user selects a graphic object, for example, and requests a transformation-Undo. The last transformation to have been applied to that selected object would be reversed. Most software users are familiar with the incremental Undo and would find a category-specific Undo novel and possibly disturbing. However, the ubiquity of the Backspace key shows that incremental Undo is a learned behavior that users find to be helpful. If more programs had modal Undo tools, users would soon adapt to them. They would even come to expect them the way they expect to find the Backspace key on word processors.
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Part III: Designing Interaction Details
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Deleted data buffers
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As a user works on a document for an extended time, she may desire a repository of deleted text. Take for example, the six missing paragraphs. If they are separated from her by a couple of complex search-and-replaces, they can be as difficult to reclaim by Undo as they are to rekey. Our user is thinking, If the program would just remember the stuff I deleted and keep it in a special place, I could go get what I want directly. What the user is imagining is a repository of the data components of her actions, rather than merely a LIFO stack of procedurals a deleted data buffer. The user wants the missing text without regard to which function elided it. The usual manifest model forces her not only to be aware of every intermediate step but to reverse each of them, in turn. To create a facility more amenable to our user, we can create, in addition to the normal Undo stack, an independent buffer that collects all deleted text or data. At any time, she can open this buffer as a document and use standard cut-and-paste or click-and-drag idioms to examine and recover the desired text. If the entries in this deletion buffer are headed with simple date stamps and document names, navigation would be very simple and visual. Users can then browse the buffer of deleted data at will, randomly, rather than sequentially. Finding those six missing paragraphs would be a simple, visual procedure, regardless of the number or type of complex, intervening steps she had taken. A deleted data buffer should be offered in addition to the regular, incremental, multiple Undo because it complements it. The data must be saved in a buffer, anyway. This feature would be quite useful in most programs, too, whether spreadsheet, drawing program, or invoice generator.
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