Tablet PC Changes to Windows Interface Components

Description of Tablet PC changes to Microsoft® Windows® interface components.

A Tablet PC runs Microsoft® Windows® XP Tablet PC Edition, a version of the Windows XP operating system that is especially designed for use with a tablet pen. Tablet PC uses a high-density display, so one important difference to designers is some of the common controls are larger than those in other versions of Windows XP.

High-density displays are defined as having 106 or more dots per inch (dpi), depending on the resolution and the size of the display. The density of the pixels for a printer is not the same as that for a monitor. You must multiply the resolution of an LCD by about 3.5 to compare it to the resolution of a printed sheet. For example, a 200-dpi high-density LCD is equivalent to a 692-dpi printer. By the end of 2000, 51 different high-density notebook panels or LCDs were available, and even more are available today. A screen resolution of 122 dpi is the optimum resolution to run the Windows XP Tablet PC Edition operating system.

The evolution of LCD display is seen through the introduction of hand-held PCs, eBooks, notebook PCs, and, of course, Tablet PC. Unlike CRT displays, LCDs present a physical pixel for every logical pixel. A physical pixel is on the actual display and a logical pixel is on the screen area. For example, if the screen area is set to 640x480 on a 1024x768 LCD display, the projected area would appear only on a smaller portion of the screen.

Electronic printers operate from 300 to 1,200 pixels per inch, but displays do not need as much resolution because they can be gray scale devices. For example, a color ink-jet printer never prints more than two colors at a given pixel location. A 200-dpi high-density display that has full color (red-green-blue, or RGB) would be equivalent to a 692-dpi printer. The real resolution for LCD screens is about 3.5 times higher because it uses RGB subpixels where white is actually an optical illusion. This combined with the higher density of pixels, improves jagged line reduction. Because of this, text readability is closer to paper quality. People can even read novels on LCDs without eye strain.

Some common problems with applications on high-Tablet PC devices include:

• Icons and bitmaps do not scale or position properly even though the text, dialog boxes, and buttons are adjusting properly based upon the font settings. Bitmaps and icons are based upon pixel dimensions, and they shrink with higher resolutions.
• Some custom controls do not scale size properly. This is the same idea as the previous example, where the text is scaling correctly with font setting whereas the other elements sizes are probably fixed in the code.

For more information about physical sizing measurements, see Physical Sizing Measurements.

For details about metrics for applications running on high-dpi displays, see Tablet PC System Sizing Metrics for High DPI.