Path: utzoo!attcan!uunet!aplcen!uakari.primate.wisc.edu!zaphod.mps.ohio-state.edu!uwm.edu!dogie.macc.wisc.edu!decwrl!polyslo!rcfische
From: rcfische@polyslo.CalPoly.EDU (Raymond C. Fischer)
Newsgroups: comp.sys.mac.programmer
Subject: Re: who caps the window list with nil and when?
Message-ID: <25d0a2fa.7177@polyslo.CalPoly.EDU>
Date: 7 Feb 90 22:36:42 GMT
References: <3858@hub.UUCP>
Reply-To: rcfische@polyslo.CalPoly.EDU (Raymond C. Fischer)
Organization: Cal Poly State University -- San Luis Obispo
Lines: 21


In article <3858@hub.UUCP> 6600pete@ucsbuxa.ucsb.edu writes:
>In the midst of throwing together a quick FKEY, I needed to see if there
>were at least two windows open. So I checked FrontWindow and if it wasn't
>NIL I checked WindowPeek(FrontWindow)^.nextWindow to see if IT was NIL.
>
>Turns out that NewWindow doesn't cap the end of the window list with NIL
>like I would have expected it to. Lots of existing apps don't know about
>this and don't care.

I think you're mis-interpreting the results your seeing from this test.
It is not uncommon to see 0-1 windows on the screen, and yet find that
FrontWindow points to another WindowRecord, which then points to another
WindowRecord.  What's the explanation?

To check for more than one _visible_ window, not only do you need to 
follow the links, but you also need to make sure each window is visible.
The list _is_ capped with a NIL, but not all windows on the list are visible.

Ray Fischer
rcfische@polyslo.calpoly.edu