🚀 go-pugleaf

In <1992Oct15.033035.16753@dragon.acadiau.ca> James R. Skinner writes:
>
>I am trying to write a simple program to clear the monochrome monitor
>that I have attached to my system.  I am using the GCC compiler and the
>following code:
>
>
>
>main(int argc, char *argv[], char *envp[])
>{
>
>          for (  int *p=0x80000 ; *p <= (0x80000+4000)  ; (*p++) = 0x2007  );
>
>}
>
>This code causes an access violation exception when executed.
>How can I correct this?  How do I get access to this memory area?
>Any help will be appriciated..  Thanks.

First off, you are trying to access the 'physical' Display Buffer Address,
which you can't do under OS/2.  In order for you to do this, you will have
to use the 'Logical Video Buffer' which is a virtual address to this memory.
To get a pointer to the LVB use the ViogetBuf API:

/***************************************************************************
 * Structure defining the layout of the LVB Buffers.  The Buffer consists  *
 * of Host_Rows*Host_Cols 2-Byte Cells.                                    *
 ***************************************************************************/
typedef union {
  struct {
    BYTE Character;               /* ASCII Character                         */
    BYTE Color;                   /* Foreground/Background Color             */
  } Byte;
  UINT Cell;                      /* Allows access to the 2-byte cell        */
} LVB;

LVB     *lvb_Ptr;                /* Logical Video Buffer                    */
USHORT  lvb_Size;                /* Size of LVB in bytes                    */

VioGetBuf(&lvb_Ptr,&lvb_Size,0);

However, if all you want to do is clear the screen, all you have to do is
use the VioScrollUp API:

BYTE    Cell[2];
USHORT  CellCount = 2;

VioReadCellStr(Cell,&CellCount,1,1,0);
Cell[0] = 0x20;
VioScrollUp(0,0,-1,-1,-1,Cell,0);

the values -1 effectively clear the screen.  The VioReadCellStr is so you
can maintain the current Bg/Fg color attributes.