Building Tablet PC Applications (Pro-Developer)

Even Better than the Real Thing

A majority of existing applications work just fine on the Tablet PC, indicating that integration with the Tablet PC Platform isn t necessarily a requirement for a great tablet application. After all, a major design goal of the Tablet PC Platform was that legacy applications would work without modification, using the platform s mouse emulation and the Tablet PC Input Panel for mouse and keyboard input.

However, the fact that you re reading this book is an indicator that your application is most likely different from the ones just mentioned. You probably already suspect that your application might benefit from tighter integration with the Tablet PC Platform. Let s get right into the reasons why your application might be better off leveraging the platform, and what level of integration is appropriate for your needs.

User Benefits of Integration

A user who purchases a Tablet PC will reap all the hardware-related benefits of the device, such as its portability and pen-based mouse emulation, without any intervention from your software. The question of whether to change your application to work better on the Tablet PC instead revolves around two issues: pen-friendly user interfaces and digital ink features.

Pen-Friendly User Interfaces

Even if your application will not support digital ink, there are significant user interface challenges that you must surmount in order to make it truly usable on a Tablet PC. The pen is great as a natural and intuitive manipulator users are adept at directly interacting with the visible user interface elements in an application. However, you can add functionality to your application that the pen can take advantage of to fully realize its value as a direct manipulator. Some of the problems that existing user interfaces might pose were discussed in Chapter 2, and included:

• Inadequate control size

  Controls that are several pixels wide are simply too hard to target with a pen.

• Parallax

  The difference between where the user thinks the pen is and where the system thinks it is can be significant.

• Physical obscuration

  The user s hand and the pen itself will often block large portions of the user interface.

• Hover sensitivity

  Features relying on the user to hold the cursor still, such as tool tips, are problematic when using a pen.

When updating an existing application for use on a Tablet PC, these user interface issues need to be addressed. However, it s not all bad news! Pens also open up a new world of possibilities for your application s user interface, including:

• Advanced pen features

  Many Tablet PCs support querying some pretty fancy pen features, such as hover distance, rotation, tilt, and pressure. This allows your application to pioneer new, more intuitive user interfaces. For instance, a 3-D modeling application might use a pen s rotation and tilt to decide how to orient an object in space. It might even use pressure and hover distance to determine how far into a scene an object should be placed. The possibilities are quite exciting given these new axes of freedom.

• Pen buttons and tips

  A Tablet PC pen might also have barrel buttons and even sensitivity on both tips (ends). Their availability opens the door to more natural user interfaces. Perhaps the best example of this is using the tail end of a pen as the eraser, but there are many other opportunities (such as using tips and buttons for highlighter or selection functions).

You should decide which of these user interface problems and possibilities to tackle and exploit in your application. You can usually overcome problems in your applications without having to use the Tablet PC Platform SDK because control size, parallax, physical obscuration, and hover sensitivity do not involve Tablet PC Platform specific APIs. However, you can often capitalize on opportunities to use the new pen capabilities through the Tablet PC Platform SDK.

Digital Ink Features

If you want digital ink features, updating your application to work with the Tablet PC Platform SDK is the right way to go. The platform and the SDK take care of a host of ink-related problems for you, making your job much easier. Here are a few ways in which your application might use digital ink:

• As a replacement for physical ink

  Perhaps one of the greatest draws of digital ink is its ability to replace physical pen and paper. Currently, annotating, note taking, and transcribing are largely done on paper. However, the ease with which digital ink is manipulated, searched, and stored outmatches traditional paper in many usage scenarios.

• As an alternative input methodology

  The pen and digital ink are intuitive alternatives for entering data. For instance, a parcel carrier might find it easier to fill out forms with a pen instead of a keyboard while on a route. A graphic designer might prefer sketching logo ideas using a pen instead of constructing them slowly with a mouse. A musician might want to draw notes on a digital staff. There are many other applications that could profit from allowing digital ink as a natural method of input.

And what if your application already supports digital ink? This is not that far-fetched of a possibility because there have been many tablet-like PC devices before Microsoft s Tablet PC. Furthermore, some niche market applications have long been using pens and digitizer tablets as their primary input device. If your application currently accepts digital ink, the remaining question is whether it would be better off converting its features implementations to use the Tablet PC Platform SDK. This is a difficult question only you can answer, but we aim to provide you with the necessary information to make a knowledgeable decision. Benefits of using the platform with the SDK include:

• Standardization

  Using the SDK will automatically afford basic interoperability (by means of the Clipboard, for instance) with other applications that support digital ink.

• Effortless improvements

  As further advances are made in areas such as handwriting recognition, new platform binaries will automatically improve your application without requiring it to be changed.

• Built-in features

  B zier curve fitting, antialiased ink, high-throughput pen data, and ink recognition are just a few of the advanced features that come bundled in the Tablet PC Platform. Chances are good that replicating these features would require a significant investment of time on your part.

Business Benefits of Integration

Now that we ve explored some possible user benefits of integrating your application with the Tablet PC Platform, we ll turn our attention to the business-driven reasons why you might want your application to shine on the Tablet PC. As this is a book meant for programmers, not for marketers, we ll keep the business reasoning simple. Three basic factors that affect the decision to invest in building Tablet PC features in your application are:

• Business cost

  How many developers and testers will it take to integrate pen and ink features? This cost will fluctuate depending on how pen-friendly and ink-ready your application is currently.

• User benefit

  Earlier we discussed the various user benefits of applications designed for the Tablet PC. Your application s purpose and usage scenarios will influence the amount your users will benefit.

• Tablet PC adoption rate

  The number of Tablet PCs sold and the speed at which they re sold are important factors that unfortunately you have little control over (unless, of course, you write the killer application that single-handedly drives sales of Tablet PCs through the roof). A more accurate forecast of the adoption rate can be given only after Tablet PCs start selling in many markets worldwide.

The specifics of cost and user benefit will depend on your business. Intimate knowledge of your own situation will help you to choose correctly for your application.