DirectDraw calls the DirectDraw driver for supported hardware functions, or the hardware emulation layer (HEL) for functions that must be emulated in software. When DirectDraw is invoked, it accesses the graphics card directly through the DirectDraw driver. The device independent bitmap (DIB) engine portion of GDI emulates functionality when it is not supported by the display driver. The display driver always supports GDI calls and, usually, DirectDraw and Direct3D calls.
The following figure shows a diagram of the DirectDraw driver architecture.Īs shown in the preceding figure, an application accesses the display card through GDI (user and kernel-mode portions) and the display driver.
This document generically refers to both of the system-supplied components as DirectDraw. Other portions of the display driver handle GDI and other non-DirectDraw related calls. This component is referred to as the DirectDraw driver in this document. The DirectDraw portion of the display driver, which, along with the rest of the display driver, is implemented by graphics hardware vendors. Kernel-mode DirectDraw also handles synchronization with GDI and all cross-process states.
#DIRECTDRAW DRIVER DRIVERS#
This is a critical design goal because display drivers are trusted components of the Microsoft Windows 2000 and later operating systems. This portion of DirectDraw performs parameter validation for the driver, making it easier to implement more robust drivers. Kernel-mode DirectDraw, which is an integral part of win32k.sys, the system-supplied graphics engine that is loaded by a kernel-mode display driver. This component provides hardware emulation, manages the various DirectDraw objects, and provides display memory and display hardware management services. User-mode DirectDraw ( ddraw.dll), which is a system-supplied dynamic-link library (DLL) that is loaded and called by DirectDraw applications. Microsoft DirectDraw includes the following components:
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