1Fall 2005 6.831 UI Design and Implementation 1 2Fall 2005 6.831 UI Design and Implementation 2 This is the Windows XP Search Companion. It appears when you press the Search button on a Windows Explorer toolbar, and is primarily intended for finding files on your hard disk.An interesting feature of this interface is that, rather than giving a textbox for search keywords right away, it first asks you to specify what kind of file you’re looking for. There’s some logic to this design decision, because it turns out that different search criteria are appropriate for different kinds of files. For example, if you select “Picture, music, and video”, the next step of the dialog won’t both asking for a word or phrase inside the file, since these kinds of files are not textual. Similarly, if you select “Documents”, the next step of the dialog will ask not only for search keywords, but also for the approximate time since you last edited the file, since most documents are sought for editing purposes (while most media files are sought for playing purposes).Unfortunately, to a frequent user, the demand that you specify the file’s type first feels jarring and hard to answer. The categories are not disjoint, so the decision isn’t always easy. Are HTML files and simple text files included in “Documents”, or only Microsoft Office files? Some of the categories are bizarre – “computers or people”? Why is “Internet” a completely separate category, and why does Help get a different icon than the rest? Perhaps the worst problem in the category list is that the answer that frequent users are most likely to want – “All files and folders”, to be sure that the search won’t miss anything – is actually buried in the middle of the list, where it’s hardest to find and click.This interface is clearly designed for novice users. Hence the wizard design, a fixed sequence of carefully guided steps. And hence the cute animated cartoon dog, which some people in class found condescending by its mere presence. It’s still an open question whether cartoon characters like this dog and the Paperclip are more helpful or harmful to good user interface design. So far, experiments with characters in serious commercial interfaces (designed for productivity rather than entertainment) have been largely unsuccessful.The animated dog does have one advantage: it’s a very visible mode status indicator. You won’t accidentally leave the Windows Explorer in search mode, because the dog will get your attention and motivate you to find a way to get rid of it -- which is not trivial, since there’s no obvious Cancel button.Another problem with this wizard is that the Back button on toolbar is easy to confuse with the Back button in the dialog. The user thinks “this isn’t what I want, I’ll go Back”, but then reaches habitually for the Back button in the toolbar, which backs up the main Explorer window instead of the Search Companion pane. This is probably a capture error, because of the effect of habit, but it also has some features of a description error.3Fall 2005 6.831 UI Design and Implementation 3 In contrast to the previous example, here’s Google’s start page. Google is an outstanding example of a heuristic we’ll see today: Aesthetic and minimalist design. Its interface is as simple as possible. Unnecessary features and hyperlinks are omitted, lots of whitespace is used. Google is fast to load and trivial to use.But maybe Google goes a little too far! Take the perspective of a completely novice user coming to Google for the first time. •What does Google actually do? The front page doesn’t say. •What should be typed into the text box? It has no caption at all. •The button labels are almost gibberish. “Google Search” isn’t meaningful English (although it’s gradually becoming more meaningful as Google enters the language as a noun, verb, and adjective). And what does “I’m Feeling Lucky” mean?•Where is Help? Turns out it’s buried at the bottom, along with “Jobs & Press”.Although these problems would be easy for Google to fix, they are actually minor, because Google’s interface is simple enough that it can be learned by only a small amount of exploration. (Except perhaps for the I’m Feeling Lucky button, which probably remains a mystery until a user is curious enough to hunt for the help. After all, maybe it does a random choice from the search results!)Notice that Google does not ask you to choose your search domain first. It picks a good default, and makes it easy to change.4Fall 2005 6.831 UI Design and Implementation 4 Antialiasing Alpha compositing Transforms Clipping Painting tricks5Fall 2005 6.831 UI Design and Implementation 5!! Alpha is a pixels transparency from 0.0 (transparent) to 1.0 (opaque) 32-bit RGBA pixels: each pixel has red, green, blue, and alpha values Uses for alpha Antialiasing Nonrectangular images Translucent componentsIn many graphics toolkits, the pixel model includes a fourth channel in addition to red, green, and blue: the pixel’s alpha value, which represents its degree of transparency.6Fall 2005 6.831 UI Design and Implementation 6"! !# !$ % &! !#SimpleAntialiasedSubpixel renderingOne use of the alpha channel is antialiasing, which is a way to make an edge look smoother. Instead of making a binary decision between whether to draw a pixel (opaque) or not (transparent), antialiasing uses an alpha value determined by the fraction of the pixel that is covered by the edge. The overall effect is a fuzzier but less jagged edge.Subpixel rendering takes this a step further. Every pixel on an LCD screen consists of three discrete pixels side-by-side: red, green, and blue. So we can get a horizontal resolution which is three times the nominal pixel resolution of the screen, simply by choosing the colors of the pixels along the edge so that the appropriate subpixels are light or dark. It only works on LCD screens, not CRTs, because CRT pixels are often arranged in triangles, and because CRTs
View Full Document
Unlocking...