----- Original Message -----
From: "Bill J Gray" <pluto@...>
To: <guide-user@yahoogroups.com>
Sent: Wednesday, August 07, 2002 10:40 PM
Subject: [guide-user] Odd lines fixed/scope woes/new .TDFs


> One is that, if you zoom in far enough, the overlay lines start
> to curl up and create zingers all over the screen. This appears to
> happen because the endpoints of the lines are more than 2^16 = 65536
> pixels apart (may be half that, I'm not totally sure.) I think it's
> just some leftover 16-bit limitation in Windows' graphics routines.

The GDI (ie the graphics drawing bit) in Windows 95, 98 and ME is indeed 16
bit - ie the range of valid coordinates is -32768 to +32767. Go outside that
range and it "wraps around" to back inside the range again. GDI is "proper"
32-bit in Windows NT, 2000, and XP.

Regards,

Chris
---------------------------------------------------------------
Chris Marriott, SkyMap Software, UK
e-mail: chris@... Web site: http://www.skymap.com
Astronomy software written by astronomers, for astronomers