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Creating Tablet PC Applications with VS .NET : Page 7

The Tablet PC platform supports applications with special tablet features enabled, such as ink input and pen-based operation. In order for this platform to become truly popular, third-party vendors will also have to ink-enable their applications. Find out how.


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A Real-world Application
The ink notepad application created so far (the complete code can be seen in Listing 1) demonstrates many of the features supported by the Tablet PC API. However, I also realize that many readers need to develop business applications and not notepads. For this reason, I decided to create a simple sample application that shows how to use many of the features already discussed and use them in a typical data-oriented application.

The sample application is made for a knowledge worker who spends most of the time in a warehouse, checking on inventory, adjusting amounts, and ordering additional merchandise. Figure 6 shows this application. The user can search for products by writing the name of the product into the top ink-panel (the area with the blue gradient background). The application then recognizes the handwriting and uses the result to query SQL Server. If the user is not happy with the result, more can be written to increase recognition accuracy and reduce the size of the result set. The user can also delete individual strokes using the end-of-pen eraser, or even the scratch-out gesture, which allows scratching out some of the written words to trigger an erase operation on the strokes covered up by the scratch out operation. If it all still fails, the user can start over by clearing out the entire input area with the click of a button.

 
Figure 6: A simple inventory management application can be used to search for products and set inventory amounts and order additional items.
Once a reasonable list of products is retrieved from the server, the user can pick the desired product from the list, specify the quantity currently in stock, and make adjustments. The user can also specify a new order amount. The two ink input areas at the bottom are similar to the one on top except that they are optimized toward recognizing numbers. Also, their behavior is slightly different. Once the user writes a number, the application attempts to recognize the number and immediately clears out the ink area. If the recognition fails, the user can rewrite the number without having to first clear out the input area. This provides a good experience for short numeric input.

Although this application is simple, it is also very amazing, as it provides a very good user experience that relies entirely on handwriting recognition. This is a combination of the operating system doing a very good job at recognizing handwriting and an interface designed to fix recognition problems quickly without causing frustrating moments for the user.

This application uses mostly techniques already discussed. The "inkable areas" are simple image controls with attached ink overlays. Note that there are no UI standards for ink-enabled controls. I thought the blue gradient provided a somewhat intuitive ink input control, as it looks very similar to the inkable areas provided by the Ink Input Panel.

All ink input panels use timers to initiate automatic recognition. The timer responsible for recognizing the ink in the top-most input panel operates on a 500 millisecond interval. However, the timer is disabled by default and is only enabled when the InkOverlayfires a Stroke event. This event occurs every time the user lifts the pen off the display after writing a stroke. The timer triggers ink recognition half a second after a stroke's completion (the timer fires only once by immediately disabling itself) unless another Stroke event occurs within that time and resets the timer. This triggers smooth recognition after the user is finished writing, and does not interfere with the writing operation itself. Also, this allows writing more text at any point, as this simply retriggers the recognition.

The two ink areas at the bottom of the panel work very similarly except for the fact that you clear out the ink areas after the recognition takes place. For this reason, the timers are on a slower interval, firing the recognition two seconds after the last stroke has been completed. It is important to give the user a bit more time in this case, as you wouldn't want to recognize text (and clear the input area) while the user is attempting to write more digits. Note that the two numeric input panels use recognizer factoids to limit the recognition results to numbers. This enhances recognition results and makes it almost impossible to trigger incorrect results unless it is done on purpose.

A more detailed description of this sample application is beyond the scope of this article. You can download the complete source code (C# and VB .NET versions) as well as a more detailed description of this application from the CoDe Magazine Web site.

With Visual Studio .NET, developing Tablet PC applications is quite straightforward. In fact, if you have architected your applications properly, you will be able to incorporate ink functionality at a level that makes it available throughout your applications, without having to use cumbersome input aids such as the Input Panel. In this article, I can only scratch the surface of what is possible, and explain the very basics, but with what you have learned here, you can already create sophisticated Tablet PC applications. For instance, you could attach an InkCollector class to a special TextBox class used throughout an application. That InkCollector class could be used to recognize the pen when it moves over the textbox and open up a larger "inkable" input area that stays "open" as long as the pen hovers within its range. Then, when the pen moves away, the control could automatically recognize the written text and paste it into the textbox before the inkable area fades away. This way, an application could support advanced inking and regular keyboard interaction, without having to provide different versions (most textboxes that support ink have to be larger in dimension to provide enough room for the user to write). But retrofitting existing applications with ink functionality may be the topic of a future article.

The big question that remains is whether or not Tablet PCs will be as successful in the market as Microsoft hopes. Will computing be revolutionized by this technology within a few years? My personal opinion is that it will not replace the way we use computers today. However, when you consider that all it takes for a Notebook computer to become a Tablet PC is a swivel display with an integrated digitizer, I wonder why it would make sense to build another notebook computer that does not support this functionality. This way, Tablet PC functionality will always be available when needed, but will not interfere with regular, keyboard-driven computing when pen input is not adequate. Furthermore, I believe that there are a lot of people that can benefit from Tablet PC functionality no matter what. Knowledge workers could benefit from using a full-featured computer with capabilities beyond those of Pocket PCs, without the luxury of sitting down to use a notebook computer.

Since initial publication of this article, Microsoft has released an updated SDK as well as merged the Tablet PC API into the latest edition of Windows XP. Some features and functions in this article may therefore have changed and improved with the latest tools.



Markus Egger  is the President and Chief Software Architect of EPS Software Corp., located in Houston, Texas. He is also the founder of EPS Software Austria, located in Salzburg. He concentrates in consulting and development of custom software based on Microsoft technologies. Markus' passion lies with object-oriented technology. He is an international author and speaker, and is the publisher of CoDe Magazine. For the past 8 years, Markus has received the Microsoft MVP award, originally for Visual FoxPro, and now for C#. Several applications he has worked on (mostly as project manager) have received Microsoft Excellence Award nominations. A full bio can be found on the Web at www.eps-cs.com and www.MarkusEgger.com. You can reach Markus at megger@eps-software.com.
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