HUMAN-COMPUTER INTERACTION
SECOND EDITION
HUMAN-COMPUTER INTERACTION
SECOND EDITION
We have already noted the four key features of the WIMP interface that give it its name -- windows, icons, pointers and menus -- and we will now describe these in turn. There are also many additional interaction objects and techniques commonly used in WIMP interfaces, some designed for specific purposes and others more general. We will look at buttons, toolbars, palettes and dialog boxes. Most of these elements can be seen in Figure 3.15.
Together, these elements of the WIMP interfaces are called widgets, and they comprise the toolkit for interaction between user and system. In Chapter 10 we will describe windowing systems and interaction widgets more from the programmer's perspective. There we will discover that though most modern windowing systems provide the same set of basic widgets, the 'look and feel' -- how widgets are physically displayed and how users can interact with them to access their functionality -- of different windowing systems and toolkits can differ drastically.
The pointer is an important component of the WIMP interface, since the interaction style required by WIMP relies very much on pointing and selecting things such as icons. The mouse provides an input device capable of such tasks, although joysticks and trackballs are other alternatives, as we have previously seen in Chapter 2.
Another approach to menu selection is to arrange the options in a circular fashion. The pointer appears in the centre of the circle, and so there is the same distance to travel to any of the selections. This has the advantages that it is easier to select items, since they can each have a larger target area, and that the selection time for each item is the same, since the pointer is equidistant from them all. Compare this with a standard menu: remembering Fitts' law from Chapter 1, we can see that it will take longer to select items near the bottom of the menu than at the top. However, these pie menus, as they are known [35], take up more screen space and are less common in interfaces.
However, when the user presses function key F3 nothing happens. F3 only works when the menu is not displayed -- when the menu is there you must press 'F' instead! This is an example of an interface that is dishonest (see also Chapter 5).
It is not possible to cover all of graphic design in a single section, but we can look at a few examples. One of the worst features in many interfaces is the appalling use of colour. This is partly because many monitors only support a limited range of primary colours and partly because, as with the overuse of different fonts in word processors, the designer got carried away. Aside from issues of good taste an overuse of colour can be distracting and, remembering from Chapter 1 that a significant proportion of the population are colour blind, may mean that parts of the text are literally invisible to some users. In general, colour should be used sparingly and not relied upon to give information, but rather to reinforce other attributes.
The increasing use of 3D effects in interfaces has posed a whole new set of problems for text and numerical information. Whilst excellent for presenting physical information and certain sorts of graphs, text presented in perspective can be very difficult to read.
Some of the most complicated and difficult screen layouts are found in forms-based interfaces and dialog boxes. In each case the screen consists not only of information presented to the user, but also of places for the user to enter information or select options. Actually many of the same layout issues for data presentation also apply to fields for data entry. Alignment is still important. It is especially common to see the text entry boxes aligned in a jagged fashion because the field names are of different lengths. This is an occasion where right-justified text for the field labels may be best or, alternatively, in a graphical interface a smaller font can be used for field labels and the labels placed just above and to the left of the field they refer to.
Remember that a pretty interface is not necessarily a good interface. Ideally, as with any well-designed item, an interface should be aesthetically pleasing. Indeed, good graphic design and attractive displays can increase users' satisfaction and thus improve productivity.
It is clear that words have to change and many interface construction toolkits make this easy by using resources. When the program uses names of menu items, error messages and other text, it does not use the text directly, but instead uses a resource identifier, usually simply a number. A simple database is constructed separately that binds these identifiers to particular words and phrases. A different resource database is constructed for each language, and so the program can be customized to use in a particular country by simply choosing the appropriate resource database.
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