Q116462: BUG: Screen Corruption Can Occur with _setvideomode()

Article: Q116462
Product(s): Microsoft Programming Utilities
Version(s): 4.0,4.01,4.1
Operating System(s): 
Keyword(s): kb16bitonly
Last Modified: 26-JUN-2001

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The information in this article applies to:

- Microsoft CodeView for MS-DOS, versions 4.0, 4.01, 4.1 
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SYMPTOMS
========

When the CodeView video mode is set to be the same as the current MS-DOS video
mode, calls to _setvideomode(_DEFAULTMODE) can cause screen corruption.

RESOLUTION
==========

To work around the problem, start CodeView in a different mode than the one
MS-DOS is using.

STATUS
======

Microsoft has confirmed this to be a bug with CodeView for MS-DOS. We are
researching this problem and will post new information in the Microsoft
Knowledge Base as it becomes available.

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

The sample code below demonstrates the problem. Build a debug version and follow
these steps:

1. Install the ANSI.SYS driver. If ANSI.SYS is not already installed, you have
  to reboot your computer to install it. To install ANSI.SYS, add the following
  line to your CONFIG.SYS file:

  " DEVICE=C:\DOS\ANSI.SYS " (without the quotation marks)

2. Enter "mode co80, 50" (without the quotation marks) at the MS-DOS prompt.

3. Enter "CV /50 VIDEO" (without the quotation marks) to debug the VIDEO.EXE
  file in CodeView.

4. Type "t3" (without the quotation marks) in the CodeView command window.

There should now be a green border around the whole screen that does not go away
when you exit CodeView. You may also experience a certain amount of text loss in
the CodeView windows.

NOTE: Reissuing the mode command with different mode values at the MS-DOS prompt
restores the screen.

In step 2 above, using "CV /43 video" (without the quotation marks) or "CV /25
video" (without the quotation marks) prevents this problem from occurring.

Sample Code
-----------

  /* Compile options needed: Zi /Od
  */ 

  /* VIDEO.C */ 

     #include <graph.h>

     void main(void)
     {
      _setvideomode(_DEFAULTMODE);
     }

Additional query words: 4.00 4.10

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Keywords          : kb16bitonly 
Technology        : kbAudDeveloper kbCodeView kbZNotKeyword3 kbCodeView400DOS kbCodeView401DOS kbCodeView410DOS
Version           : :4.0,4.01,4.1

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