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Q85596: BUG: SETCOLORTABLE Escape Disables Dithering

Article: Q85596
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:3.1
Operating System(s): 
Keyword(s): 
Last Modified: 06-NOV-1999

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The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) 3.1 
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SYMPTOMS
========

When the VGAPAL video driver is installed on a system, once an application calls
the SETCOLORTABLE escape to change an entry in the color table associated with a
device context, Windows does not create any dithered brushes for that device
context. Instead, Windows returns the solid brush that most closely matches the
requested color.

RESOLUTION
==========

To work around this problem, reset the color table to its original state by
specifying NULL as the value of the lpInData and lpOutData parameters in a call
to the SETCOLORTABLE escape, as follows:

     Escape(hDC, SETCOLORTABLE, 0, NULL, NULL)

STATUS
======

Microsoft has confirmed this to be a bug in Windows version 3.1. We are
researching this problem and will post new information here in the Microsoft
Knowledge Base as it becomes available.

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

The SETCOLORTABLE escape is documented on pages 500 and 501 of the "Microsoft
Software Development Kit: Programmer's Reference, Volume 3: Messages, Structures
and Macros" manual.

The comments regarding this escape state the following:

- The color-mapping algorithms in the display driver will most likely not work
  with a changed palette.

- If the color index pointed to by the lpInData parameter is 0xFFFF, the
  calling application performs all color mapping.

- Once an application restores the color table to its original state, an
  application can enable the color-mapping algorithms in the display driver.

However, with the VGAPAL driver, calling the SETCOLORTABLE escape with lpInData
pointing to the 0xFFFE value does not restore dithering.

Additional query words: buglist3.10 3.10

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Keywords          :  
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK310
Version           : WINDOWS:3.1

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