DOCUMENT:Q75005 03-NOV-1999 [win16ddk] TITLE :Handling NULL lpDrawMode in a Display Driver PRODUCT :Microsoft Windows Device Driver Kit PROD/VER::3.0,3.1; WINDOWS:3.11 OPER/SYS: KEYWORDS: ====================================================================== ------------------------------------------------------------------------------- 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 ------------------------------------------------------------------------------- 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 ====================================================================== Keywords : Technology : kbAudDeveloper kbWin3xSearch kbWinDDKSearch kbWFWSearch kbWinDDK300 kbWinDDK310 kbWFW311 Version : :3.0,3.1; WINDOWS:3.11 ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 1999.