BUG: Screen Corruption Can Occur with _setvideomode()

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

2. Enter mode co80, 50 at the MS-DOS prompt.
3. Enter CV /50 VIDEO to debug the VIDEO.EXE file in CodeView.
4. Type t3 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 or CV /25 video prevents this problem from occurring.

Sample Code

/* Compile options needed: Zi /Od
*/ 

/* VIDEO.C */ 

   #include <graph.h>

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