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Q116460: BUG: Debugging With Mono And VGA Can Cause Screen Corruption

Article: Q116460
Product(s): Microsoft Programming Utilities
Version(s): 
Operating System(s): 
Keyword(s): kb16bitonly
Last Modified: 26-JUN-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft CodeView for MS-DOS 
-------------------------------------------------------------------------------

SYMPTOMS
========

When using the MS-DOS "mode mono" command to debug a graphics application on a
secondary monochrome monitor (VGA being the primary monitor), screen corruption
can result on both monitors.

RESOLUTION
==========

To work around the problem, do not use the mode mono command. Instead, either
debug on the primary VGA monitor or use the /2 command line option to display
Codeview's windows on the monochrome monitor (instead of on the VGA monitor).

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. We are researching this problem and will post new
information here in the Microsoft Knowledge Base as it becomes available.

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

The sample program below demonstrates the problem. Build a debug version and
enter the following commands at the DOS prompt:

  msherc
  mode mono
  cv /b /s modes

Once you have started Codeview, enter the following commands in the command
window:

  bp .49
  g
g

At this point both the VGA monitor and the monochrome monitor may display corrupt
information.

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

  /* Compiler Options Needed:  /AL /Zi /Od
  */ 

  #include <conio.h>
  #include <stdio.h>
  #include <graph.h>

  short modes[] = { _TEXTBW40,     _TEXTC40,      _TEXTBW80,
                    _TEXTC80,      _MRES4COLOR,   _MRESNOCOLOR,
                    _HRESBW,       _TEXTMONO,     _HERCMONO,
                    _MRES16COLOR,  _HRES16COLOR,  _ERESNOCOLOR,
                    _ERESCOLOR,    _VRES2COLOR,   _VRES16COLOR,
                    _MRES256COLOR, _ORESCOLOR
                  };
  char *names[] = { "TEXTBW40",    "TEXTC40",     "TEXTBW80",
                    "TEXTC80",     "MRES4COLOR",  "MRESNOCOLOR",
                    "HRESBW",      "TEXTMONO",    "HERCMONO",
                    "MRES16COLOR", "HRES16COLOR", "ERESNOCOLOR",
                    "ERESCOLOR",   "VRES2COLOR",  "VRES16COLOR",
                    "MRES256COLOR","ORESCOLOR"
                  };
  short rows[] = { 60, 50, 43, 30, 25 };  /* Possible number of rows */ 

  void main(void)
  {
   short c, i, j, x, y, row, num = sizeof(modes) / sizeof(modes[0]);
   struct _videoconfig vc;
   char b[500];              /* Buffer for string */ 

   _displaycursor( _GCURSOROFF );

   /* Try each mode. */ 
   for( i = 0; i <= num; i++ )
   {
    for (j = 0; j < 5; j++ )
    {
     /* Try each possible number of rows. */ 
     row = _setvideomoderows( modes[i], rows[j] );
     if( (!row) || (rows[j] != row) )
      continue;
     else
     {
      _getvideoconfig( &vc );
      y = (vc.numtextrows - 12) / 2;
      x = (vc.numtextcols - 25) / 2;

      /* Use text window to place output in middle of screen. */ 
      _settextwindow( y, x, vc.numtextrows - y, vc.numtextcols - x );

      /* Write all information to a string, then output string */ 
      c  = sprintf( b,     "Video mode: %s\n", names[i] );
      c += sprintf( b + c, "X pixels:   %d\n", vc.numxpixels );
      c += sprintf( b + c, "Y pixels:   %d\n", vc.numypixels );
      c += sprintf( b + c, "Columns:    %d\n", vc.numtextcols );
      c += sprintf( b + c, "Rows:       %d\n", vc.numtextrows );
      c += sprintf( b + c, "Colors:     %d\n", vc.numcolors );
      c += sprintf( b + c, "Bits/pixel: %d\n", vc.bitsperpixel );
      c += sprintf( b + c, "Pages:      %d\n", vc.numvideopages );
      c += sprintf( b + c, "Mode:       %d\n", vc.mode );
      c += sprintf( b + c, "Adapter:    %d\n", vc.adapter );
      c += sprintf( b + c, "Monitor:    %d\n", vc.monitor );
      c += sprintf( b + c, "Memory:     %d",   vc.memory );
      _outtext( b );
      _getch();
     }
    }
   }
   _displaycursor( _GCURSORON );
   _setvideomode( _DEFAULTMODE );
  }

Additional query words: 4.00 4.01 4.10

======================================================================
Keywords          : kb16bitonly 
Technology        : kbAudDeveloper kbCodeView kbZNotKeyword3
Version           : :

=============================================================================

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