From:	ljchuang AT csie DOT nctu DOT edu DOT tw (Chuang Li-chung)
Newsgroups:	comp.os.msdos.djgpp
Subject:	[Allegro] Virtual Screen problem
Date:	5 Jun 1997 04:14:05 GMT
Organization:	Computer Science & Information Engineering NCTU
Lines:	23
Message-ID:	<5n5eed$nar@netnews.csie.nctu.edu.tw>
NNTP-Posting-Host:	ljchuang AT ccsun1 DOT csie DOT nctu DOT edu DOT tw
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

    
  hi, does anyone know how Allegro deal with the virtual screen 
  memory alloctaion?

  I have declared a screen of resolution 320x200 with 320x400 virtual
  screen, but when I executed the following funcion, it just return a
  mass of junk! ( this can be tested with Allegro example 2 )

  void move_block() {
    unsigned long waddress, raddress;
    _farsetsel(screen->seg);
    raddress = bmp_read_line(screen, now_y);
    waddress = bmp_write_line(screen, 0);    
    movedata(screen->seg, raddress, screen->seg, waddress, SCREEN_W*SCREEN_H);
  }

  I guess the problem is in my memory calculation, but I can't find the
  right way doing this. Any help would be highly appreciated!


  - Chuang Li-chung-

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