nhìn mà không ảnh hưởng đến các chức năng bất cứ điều gì cách, và kể từ khi người dùng hoàn toàn miễn phí để bỏ qua sự lựa chọn và có được công việc của họ thực hiện dù sao, đây là một sử dụng tốt các tùy chọn. | look without affecting the way anything functions and since users are completely free to ignore the choice and get their work done anyway this is a good use of options. 20 Chapter 4 Affordances and Metaphors Overview Developing a user interface where the program model matches the user model is not easy. Sometimes your users might not have a concrete expectation of how the program works and what it s supposed to do. There is no user model. When the user model is incomplete or wrong the program can use affordances or metaphors to show the user its model. In these cases you are going to have to find ways to give the user clues about how something works. With graphical interfaces a common way to solve this problem is with metaphors. But not all metaphors are created equal and it s important to understand why metaphors work so you know if you ve got a good one. The most famous metaphor is the desktop metaphor used in Windows and the Macintosh see Figure 4-1 . The computer screen behaves something like a real world desk. You have these little folders with little files in them which you can drag around into trash cans and cute little pictures of real world objects like printers. To the extent that this metaphor works it s because the little pictures of folders actually remind people of folders which makes them realize that they can put documents into them. J fM Ml Wfrw ĨỊMtOri Q jh Figure 4-1 The classic desktop metaphor Take a look at Figure 4-2 a screenshot from Kai s Photo Soap. Can you guess how to zoom in 21 Figure 4-2 Can you guess how to zoom in with Kai s Photo Soap It s not very hard. The magnifying glass is a real world metaphor. People know what magnifying glasses do. And there s no fear that the zoom operation is actually changing the size of the underlying image since that s not what magnifying glasses do. A metaphor even an imperfect one works a lot better than none at all. Can you figure out how to zoom in with Microsoft Word as shown in Figure 4-3 Figure .
