From: varobert AT colba DOT net
Message-Id: <3.0.32.19990718003516.007a55e0@mail.colba.net>
X-Sender: varobert AT mail DOT colba DOT net
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Date: Sun, 18 Jul 1999 00:35:27 -0400
To: djgpp AT delorie DOT com
Subject: Re: still got double buffering prob. in 13h mode.
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Reply-To: djgpp AT delorie DOT com

At 11:47 AM 7/18/99 +0800, you wrote:
>Hi,
>
>I added the memset(double_buffer,0,320*200) before I draw to my buffer but
>still gives me garbage instead of a single red dot at position (10,10).
>
>Any idee what goes wrong ?
>(source below)
>
>Thanks;
>Mark.
>
>
>
>
>#include <stdlib.h>
>#include <dos.h>
>#include <sys/movedata.h>
>#include <dpmi.h>
>
>typedef unsigned char byte;
>
>short screen;
>byte *double_buffer;
>
>void mode(byte mode){
>   union REGS regs;
>   regs.h.ah=0x00;
>   regs.h.al=mode;
>   int86(0x10, &regs, &regs);
>}
>  
>main(){
>   mode(0x13);
>
>   screen = __dpmi_segment_to_descriptor(0xa000);
>   if (screen == -1){
>      printf("error getting a selector.\n");
>      exit(1);
>   }
>
>   double_buffer = (byte *)malloc(320*200);
>   if (double_buffer==NULL){
>      printf("Not enough memory for double buffer.\n");
>      exit(1);
>   }
>
>   memset(double_buffer,0,320*200);
>
>   double_buffer[10*320+10] = 4;
>
>   while (inportb(0x3da) & 8);
>   while (!(inportb(0x3da) & 8));
>   movedata(_my_ds(),*double_buffer,screen,0,320*200);


Try:
movedata(_my_ds(),double_buffer,screen,0,320*200);

The problem is that *double_buffer is the value of the first pixel in your
dbl buffer, which is 0, so in essence, you're dumping your program code on
your screen !

-GodOfWar


>
>   getch();
>   mode(0x03);
>}
>   
>
>
>