Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!ucsd!ucbvax!agate!shelby!neon!cm-next-9!grd
From: grd@cm-next-9.Stanford.EDU (glen diener)
Newsgroups: comp.sys.next
Subject: Re: transparent windows?
Message-ID: <1990May25.192737.14598@Neon.Stanford.EDU>
Date: 25 May 90 19:27:37 GMT
References: <177@heaven.woodside.ca.us>
Sender: news@Neon.Stanford.EDU (USENET News System)
Organization: CCRMA, Stanford University
Lines: 27

In article <177@heaven.woodside.ca.us> glenn@heaven.UUCP (Glenn C. Reid) writes:
>
>Do any of you have any ideas about how to keep a window from painting
>its backgroundGray color?  I would like to have a window that lets you
>see through to what's behind it, for positioning graphic elements.
 ...stuff deleted
>Thanks,
> Glenn Reid
> glenn@heaven.woodside.ca.us

I spent a lot of time on this, and concluded that there was no easy way to
do it: windows are opaque, and that's that.  Paul Hegarty from NeXT
also told me that it was impossible given the current window server
architecture.

One thing you can do, however, which will have the same effect (almost)
is to locate the window directly underneath the current window, then composite
it, or at least the part of it which intersects the current window, into the
current window (This lets you do nifty things using the dissolve operator
which you could never do with transparent windows).  I'm sure this is the
way that the screen grabbers in Icon and Scene do their work.  I found that
the compositing machinery was almost, but not quite, fast enough to allow
what we might call ``pseudo-transparent'' windows to appear smooth as they
are dragged around (provided they aren't too big!).

glen diener
grd@cm-next-9.stanford.edu