Date: Mon, 11 Nov 2002 12:46:33 +0100
From: Manuel Collado <m DOT collado AT aaron DOT ls DOT fi DOT upm DOT es>
Subject: Re: Trying to hide cursor on a DOS box on WinNT
To: djgpp AT delorie DOT com
Message-id: <3DCF9899.DF49EB58@lml.ls.fi.upm.es>
MIME-version: 1.0
X-Mailer: Mozilla 4.75 [en] (WinNT; U)
Content-type: text/plain; charset=us-ascii
Content-transfer-encoding: 7bit
X-Accept-Language: en
References: <3DCB85E4 DOT A96AA73B AT lml DOT ls DOT fi DOT upm DOT es>
 <oj2nsu8sj8j0md029mvpl88qrlumerco7p AT 4ax DOT com>
Reply-To: djgpp AT delorie DOT com

Andrew Cottrell wrote:
> 
> >I'm trying to do that with conio funtions, but fail. I've searched the
> >FAQ with no luck. I'm using
> >
> >       _setcursortype (_NOCURSOR);
> >
> >But it only works in fullscreen mode, not inside a DOS window. In that
> >case
> >the behaviour is somehow erratic, and usually the cursor shows up all
> >the time.
> I have used this for a long long time and it has worked for me on
> everything from DOS, WIn 9x, NT 4.0 SP2 through SP6, 2K and XP.

Let me explain better. The problem appears only when executing the
program twice in sequence in a DOS windows (not in fullcreen mode) from
the 'cmd' or 'command' prompt. When invoking 'getkey' after
     _setcursortype (_NOCURSOR);
a spurious cursor appears at the position where the cursor was when the
program was started. This spurious cursor dissapears by momentarily
switching to fullscreen mode (Alt-Enter) and reappears when swtiching
bat to a DOS windows mode.

This behaviour can be reproduced in every machine running Windows NT or
2000 I can use (including a portable PC).
 
> Boot up using a DOS disk and try the app. If it works then the problem
> is with NT otherwise it is with the video card.
> 
> >Is this a known issue?
> Not as far as I can remember.
> >Is there a workaround?
> 
> >I'm using gcc 3.2 on WinnT 4.0 SP3.
> Have you tried it on another PC running NT 4.0? A long shot could be
> that it is an NT video driver or vidoe bios problem. Another thing to
> try is SP6 or SP6A for NT 4.0 as SP3 is very old.

I've experiment a bit, and the problem seems to be reproducible in the
following circumstances:

- the program is started in a DOS window.
- the first 'getkey' is issued after '_setcursortype (_NOCURSOR);'
- the last 'getkey' issued in the previously executed program in the
same DOS window also followed a '_setcursortype (_NOCURSOR);'

The following small program produces the explained effect:

#include <stdio.h>
#include <conio.h>
#include <keys.h>
#include <pc.h>

int main (int argc, char** argv) {
    int key;
    int turn = 2;

    clrscr ();
    cprintf ("Press any key to toggle cursor, Escape to exit\n");
    gotoxy (5, 10);
    cputs ("Cursor here -->");
    do {
        switch (turn++ % 3) {
        case 1:  _setcursortype (_SOLIDCURSOR);
                 break;
        case 2:  _setcursortype (_NOCURSOR);
                 break;
        default: _setcursortype (_NORMALCURSOR);
        }
        key = getkey ();
    } while (key != K_Escape);
    return 0;
}

To reproduce the bug, execute this program twice. The first time press
Escape whith the cursor hidden.

Perhaps this is a bug of the NTVDM emulator. Or it is a consequence of
an improper way (from Microsoft's point of view) of hiding the cursor.
-- 
To reply by e-mail, please remove the extra dot
in the given address:  m.collado -> mcollado