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CHAPTER 1 GETTING TO KNOW THE WINDOWS PHONE 7 DEVICE
DirectX 9 Acceleration
I f you’ve been paying attention to the media hype about Windows Phone 7, you’ve probably seen
DirectX 9 acceleration mentioned a few times. Its an impressive bullet point, but what does it mean
for your game?
When you’re developing games (or any piece of software, for that matter), sometimes you
push the edges of performance. Eventually, you will hit a limit on just how much more you can
tweak your code to increase the performance. This is where hardware acceleration comes in and
takes over.
Intensive tasks such as video playback and three-dimensional (3D) rendering can be moved from
the CPU to the GPU, freeing the CPU for more of your game logic. Having a GPU that supports
DirectX 9 acceleration means that you can write intense, high-performance games.
You might think that this acceleration is important only for 3D games. And youd be right — sort of.
Hardware acceleration is traditionally thought of as an important feature for developing 3D games,
but it’s important for two-dimensional (2D) games as well. This is especially true because there
really isn’t any such thing as a 2D game in XNA! You can make 2D games, but behind the scenes
the XNA framework makes a 3D game with a fi xed camera. Because of this, even your “basic” 2D
games will benefi t from DirectX 9 acceleration.
Face Buttons
Every device marketed as Windows Phone 7 is required to have the following three buttons on the
face of the phone:
Back button
Start button
Search button
Back Button
This works exactly as you would expect it to, just like the famous browser button of the same name.
If you go to a new screen in your phone’s user interface (UI) and click the Back button, you are mag-
ically transported — wait for it — back to the previous screen. Pure genius! Games and applications
that you write can handle the Back button however you choose.
You will learn how to write code that responds to pressing the Back button in
Chapter 6.
Start Button
Pressing the Start button returns you to the main Start screen no matter where you are or what
application or game you are running. Applications exited in this manner go into a suspended state,
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