Features of Windows Vista - Part 4


Desktop Window Manager (DWM)

The Desktop Window Manager is the new windowing system which handles the drawing of all content to the screen. Instead of windows drawing directly to the video card's memory buffers, contents are instead rendered to back-buffers (technically Direct3D surfaces), which are then arranged in the appropriate Z-order, then displayed to the user. This drawing method uses significantly more video memory than the traditional window-drawing method used in previous versions of Windows, which only required enough memory to contain the composite of all currently visible windows at any given time. With the entire contents of windows being stored in video memory, a user can move windows around the screen smoothly, without having "tearing" artifacts be visible while the operating system asks applications to redraw the newly visible parts of their windows. Other features new to Windows Vista such as live thumbnail window previews and Flip 3D are implemented through the DWM.


Windows Vista includes a new version of Direct3D, called Direct3D 10. It adds scheduling and memory virtualization capabilities to the graphics subsystem and foregoes the current DirectX practice of using "capability bits" to indicate which features are active on the current hardware. Instead, Direct3D 10 defines a minimum standard of hardware capabilities which must be supported for a display system to be "Direct3D 10 compatible". Microsoft's goal is to create an environment for developers and designers where they can be assured that the input they provide will be rendered in exactly the same fashion on all supported graphics cards. This has been a recurring problem with the DirectX 9 model, where different video cards have produced different results, thus requiring fixes keyed to specific cards to be produced by developers.

According to Microsoft, Direct3D 10 will be able to display some graphics up to 8 times faster than DirectX 9.0c because of the new improved Windows Display Driver Model. In addition, Direct3D 10 incorporates Microsoft's High Level Shader Language 4.0. However, Direct3D 10 is not backward compatible like prior versions of DirectX. The same game will not be compatible with both Direct3D 10 and Direct3D 9 or below. Games would need to be developed for both APIs, one version for Direct3D 9 and below if targeting Windows versions prior to Windows Vista and another version using Direct3D 10 if targeting only Windows Vista. Windows Vista does, however, contain a backward compatible Direct3D 9 implementation.

In Windows Vista, only Direct3D features an overhaul. The DirectX SDK mentions that most of the other APIs have been deprecated. Direct Input and Direct Play have been deprecated and some of their components removed Direct Sound and therefore, Direct Music lack hardware abstraction and are emulated in software. The Direct Music kernel mode synthesizer that supplies the Direct Music components with a high-resolution timer has been removed.


Windows Imaging Component (WIC) is a new extensible imaging framework that allows applications supporting the framework to automatically get support of installed codecs for graphics file formats. Windows Presentation Foundation applications also automatically support the installed image codecs. Third party developers can write their own image codecs for their specific image file formats. By default, Windows Vista ships with the JPEG, TIFF, GIF, PNG, BMP and HD Photo codecs. Codecs for RAW image formats used generally by high-end digital cameras are also supported in this manner. Windows Explorer, Windows Photo Gallery and Windows Photo Gallery Viewer are based on this new framework and can thus view and export images in any format for which the necessary codecs are installed.

HD Photo (previously known as Windows Media Photo) is a photographic still image file format, that is introduced with Windows Vista. It supports features such as high dynamic range imaging, lossy as well as lossless compression, up to 32-bpp fixed or floating point representation, transparency, RGB, CMYK and n-channel color spaces, Radiance RGBE, embedded ICC color profiles, multiple images per file and support for Exif and XMP metadata formats. It is the preferred image format for XPS documents.

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