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Q77402: INFO: Do Not Call the Display Driver Directly

Article: Q77402
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:3.1,95; winnt:
Operating System(s): 
Keyword(s): kbOSWinNT400 kbDSupport kbSDKWin16
Last Modified: 16-DEC-2000

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The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) 3.1 
- Microsoft Win32 Application Programming Interface (API), used with:
   - Microsoft Windows 95 
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SUMMARY
=======

In general, a Windows-based application cannot call the Windows display driver
directly to perform graphics primitives. This article details the reasons this
restriction is in place.

MORE INFORMATION
================

The Windows display driver communicates with the Graphics Device Interface (GDI)
to perform primitive graphics operations. The parameters of the entry points (or
exported functions) in the display driver are set up according to the standard
interface between GDI and the display driver. The parameters passed by GDI to
the display driver are only meaningful to GDI and to the display driver. A
Windows-based application has no way to obtain these parameters. For example,
the parameter most-commonly passed by GDI to the display driver is a pointer to
a structure called PDEVICE. Memory for this structure is allocated by GDI, and
its contents are specified by the display driver during the driver's
initialization. The pointer to the PDEVICE structure is private to GDI;
furthermore, the structure of PDEVICE varies among display drivers.

To give another example, when a primitive is to be done to a memory bitmap,
instead of passing a pointer to PDEVICE, GDI passes to the display driver a
pointer to a structure; the structure is usually referred to as a physical
bitmap. Note that this physical bitmap structure is also called "BITMAP"; do not
confuse it with the BITMAP structure defined in the Windows Software Development
Kit. Again, this physical bitmap structure is not designed to be used by a
Windows-based application. Although the information described in this structure
is somewhat related to the bitmap that the application uses, the pointer to the
physical bitmap structure is private to GDI and cannot be obtained by the
application.

Additional query words: nowinnt win16sdk

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Keywords          : kbOSWinNT400 kbDSupport kbSDKWin16 
Technology        : kbAudDeveloper kbSDKSearch kbWin32sSearch kbWin32API kbWinSDKSearch
Version           : WINDOWS:3.1,95; winnt:
Issue type        : kbinfo

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