Pointing to Objects

Overview of pointing to objects with a tablet pen and mouse.

Pointing with a tablet pen and pointing with a mouse are different. Pointing with a tablet pen is more difficult. Clicking a mouse is a purely vertical movement that is made with one finger. The user's muscle movement is captured by a spring-loaded mechanism that separates it from the horizontal pointing movement. With the tablet pen, the user points and taps by using the same arm, wrist, hand, and finger muscles. This affects the accuracy of using a tablet pen to tap an object or hover over an object. Tapping and hovering require precise muscle movements, which may be hard for new users of Tablet PC.

Provide larger user interface hot spots than you normally would for a mouse. Follow the size metrics guidelines documented in Visual Design Guidelines when you design controls. Examples of controls that provide a larger hot spot include:

• Spin boxes
• Text selection in text boxes
• Buttons
• Resize handles of a selection

A tap can sometimes result in a little drag movement if the tablet pen slips on the screen. Consider how your application can prevent unexpected behavior by carefully designing the interaction so it does not depend on minor slips or drags of the tablet pen. If you require a tablet pen drag to define a position on the screen, employ snapping to help the user to position the tablet pen more precisely.

Additionally, to reposition the cursor to tap menus or buttons on the screen, users must move a tablet pen a greater distance than they would move a mouse. Therefore, hand and arm muscle fatigue occurs more quickly with a tablet pen than it does with a mouse. Reduce hand movement by positioning menus carefully on the screen. Ensure that a shortcut menu and any submenus appear in the same location as the cursor, and not in the middle of the screen.

Also, when users hold a tablet pen, their hand may obscure menus, objects, or cursors. When considering tablet pen interaction, it is important to understand where users might rest their hand. Because of their ergonomic posture, users generally rest their hand in the lower half of the screen. Thus, any object or user interface (UI) that appears below the users hand may be partially obscured and hard to view.

Extending Mouse-Emulation Behaviors

Another approach is to exploit the tablet pen by extending mouse-emulation behaviors in a way that is consistent with both the Microsoft® Windows® and Tablet PC design guidelines. By taking advantage of the distinction between tablet pen and mouse messages in the Windows XP Tablet PC Edition ink services, you provide a better experience for tablet pen users without interfering with mouse behavior.

For example, spin boxes have small hot spots. This makes them easy to use with a mouse, but difficult to use with a tablet pen. This is because the mouse makes it simpler for the user to eliminate horizontal movement while clicking.

Using a Mouse to Hover over a Spin Box

You can make it easier to use a tablet pen to control a spin box by:

• Making the spin box large enough for tablet pens to work better. The downside of this is you reduce screen area and consistency for your mouse-only users.
• Replacing the spin boxes with controls such as sliders that are more suited to a tablet pen. However, this may not provide the precision that you want.
• Making a subclass of the spin control and expanding the spin box when the tablet pen hovers near (but not necessarily directly over) the spin control. This last method requires more development work than either of the first two, but it addresses their drawbacks.

Using a Tablet Pen to Hover over a Custom Spin Box Control

This approach does not affect how the application works on a traditional desktop, and it maintains the functionality of the original hot spot. Therefore, users who are proficient with the tablet pen are not slowed down by a hot spot that moves from beneath the tablet pen.