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Direct X

DirectDraw

DirectDraw provides a device-independent way for games and Windows subsystem software, such as 3-D graphics packages and digital video CODECS, to gain access to the features of specific display devices.

DirectDraw also allows applications to directly manipulate display memory. DirectDraw provides this functionality while maintaining compatibility with existing Microsoft Windows-based applications and device drivers.

DirectDraw works with a wide variety of display hardware, ranging from simple SVGA monitors to advanced hardware implementations that provide clipping, stretching, and non-RGB color format support. The interface is designed so that your applications can enumerate the capabilities of the underlying hardware and then use any supported hardware-accelerated features. DirectX emulates features that are not implemented in hardware.

Using DirectDraw, an application can manipulate video memory, taking full advantage of the block mode bit transfers ("bit-blitting"), page flipping, and color decompression capabilities of different types of video hardware without becoming dependent on any particular adapter.

This interaction between applications, DirectDraw, and the display adapter is summarized in the following table:

  1. The DirectDraw HAL (hardware abstraction layer) reports the capabilities of the underlying display adapter to DDRAW.DLL. The DirectDraw HAL is usually internal to a DirectDraw compliant video driver, however for some drivers it may exist as a separate component.
  2. DirectDraw applications send video requests to DDRAW.DLL when redrawing the screen
  3. DirectDraw application requests that the DirectDraw HAL has determined can be accomplished in hardware by the display adapter are passed directly through to the display driver.
  4. DirectDraw application requests that are not supported in hardware by the display adapter are instead processed in software by DDRAW.DLL and then passed on to GDI.