Hi !

I wrote a simple test program that scrolls 3 colored lines accross the
screen. I always draw the line, wait for vertical retrace and re-draw it
with same color like background.
(Black) My problem is, it only scrolls good, when one line is showed. By two
or more, the lines flickers on screen. I don't know what's wrong.

Thanx for help.

you may get the source from

http://www.centralnet.ch/userpages/omsec

create a virtual screen!

type

        virtualp=^virtuals;
        virtuals=array[1..64000] of byte;

get the memory and offset in mem of the virtual screen,
like:

var
      virtual:virtualp;
      virtseg:word;

getmem( virtual,64000 );
virtseg:=seg(virtual^);

then you should just write to the virtual screen
then swap your virtual page onto the real screen.

{ eg, swap(virtseg,vgaseg); vgaseg=$a000}
Procedure Swap( Source, Destination : Word ); Assembler;
Asm
    push    ds
    mov     ax,   [Destination]
    mov     es,   ax
    mov     ax,   [Source]
    mov     ds,   ax
    xor     si,   si
    xor     di,   di
    mov     cx,   32000
    rep     movsw
    pop     ds
End;

{ clear screen}
Procedure Cls(w:Word); Assembler;
Asm
        push    es
        mov     cx, 32000;
        mov     es,[w]
        xor     di,di
        mov     al,[0]
        mov     ah,al
        rep     stosw
        pop     es
End;