(If you??™re
using an older video card, these out-of-date drivers are quite possibly the only ones that were
provided in the retail package.) WPF also provides better performance under the Windows
Vista operating system, where it can take advantage of the new Windows Vista Display Driver
Model (WDDM). WDDM offers several important enhancements beyond the Windows XP Display
Driver Model (XPDM). Most importantly, WDDM allows several GPU operations to be
scheduled at once, and it allows video card memory to be paged to normal system memory if
you exceed what??™s available on the video card.
As a general rule of thumb, WPF offers some sort of hardware acceleration to all WDDM
(Windows Vista) drivers and to XPDM (Windows XP) drivers that were created after November
2004, which is when Microsoft released new driver development guidelines. Of course, the
level of support differs. When the WPF infrastructure first starts up, it evaluates your video
card and assigns it a rating from 0 to 2, as described in the sidebar ???WPF Tiers.???
Part of the promise of WPF is that you don??™t need to worry about the details and idiosyncrasies
of specific hardware. WPF is intelligent enough to use hardware optimizations where
possible, but it has a software fallback for everything. So if you run a WPF application on a
computer with a legacy video card, the interface will still appear the way you designed it.
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