Of Mice and Pen

Of Mice and Pen

We now turn our attention to the hardware technology that pervades the Tablet PC experience and how it impacts the way we design software for tablet users.

Tablet hardware differs from traditional computer hardware in two ways: tablets often run in portrait screen orientation and tablets have pens with digitizers. Digitizers are the devices responsible for detecting the position, pressure, and tilt of a pen on the tablet s screen. The technology behind a pen is vastly different from the technology behind a mouse, and the pen introduces unique usability challenges. In addition, the user of a pen, by mere physiology, can inadvertently create additional usability challenges that the software has to address. We consider the challenges of screen orientation, pen technologies, and user physiology in the following sections.

Tablet Displays

Tablet PCs run primarily in portrait orientation, with the height of the screen greater than its width. This arrangement models the traditional orientation of paper, which is also usually taller than it is wide. Paper s orientation is optimized for readability because it s difficult to read long lines of text, wide paper doesn t make a lot of sense. It s better to pack more narrow lines of text onto a tall sheet of paper.

Running the display in portrait mode has a few noteworthy consequences, however, the foremost being that menus and toolbars have less space in which to display their content. This can result in menus wrapping over multiple lines or toolbars being cut off. An example of the latter is shown in Figure 2-2.

NOTE
When designing your application, be sure that toolbar buttons fall within the usable width of a portrait screen.

You can also have your toolbars wrap into more rows to accommodate the screen s limitations. In addition, you should test all your dialog boxes in portrait mode to verify that they are not cut off. Remember to check them in large-font mode as well.

Figure 2-2. Microsoft WordPad in 768 1024 portrait mode, with its toolbar cut off on the right.

Some graphics chips don t natively support portrait mode. In these cases, the graphics chips manufacturer can implement portrait mode screen rotation by rotating everything using software. Although this approach is valid, you should be aware of the tremendous performance penalties it entails. When a device driver rotates a screen in memory, it essentially intercepts every call to draw on the screen, transforming the call parameters so that it ends up drawing in portrait mode instead of landscape mode. For certain calls, such as the popular BitBlt (which renders a bitmap on the screen), the consequences of software screen rotation are disastrous, requiring the driver to remap the bitmap pixel by pixel. If your application uses a lot of graphics calls, you ll want to test its performance in portrait mode to see whether software rotation is an issue. Keep in mind that not all graphics chips will have this problem.