Microsoft KB Archive/75005

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Handling NULL lpDrawMode in a Display Driver

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Q75005

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The information in this article applies to:


 * Microsoft Windows Device Development Kit (DDK) for Windows, versions 3.0, 3.1
 * Microsoft Windows for Workgroups version 3.11

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SUMMARY
In the Microsoft Windows graphical environment, the graphics device interface (GDI) should never pass a NULL lpDrawMode to a display driver. However, when a printer driver uses the brute interface to call the BitBlt routine in the display driver, the calling printer driver provides the parameters, including lpDrawMode, to the display driver. In this case, GDI cannot prevent the driver from sending incorrect parameters.

For this reason, a display driver must be robust and must not crash when it receives incorrect arguments.

The source code for the 8514/A display driver, included with the Microsoft Windows Device Development Kit (DDK), provides a good example of how to handle operations with a NULL lpDrawMode parameter.

Additional query words: 3.00 3.10 3.11 DDKDISPLAY

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