Xref: utzoo comp.sys.amiga.tech:110 comp.sys.amiga:16663
Path: utzoo!mnetor!uunet!husc6!tut.cis.ohio-state.edu!bloom-beacon!gatech!hubcap!ncrcae!usceast!baldwin
From: baldwin@usceast.UUCP (Chuck Baldwin)
Newsgroups: comp.sys.amiga.tech,comp.sys.amiga
Subject: Multiple viewports
Message-ID: <2554@usceast.UUCP>
Date: 25 Mar 88 07:11:40 GMT
Lines: 36
Keywords: two viewports for every bitmap


[Not being entirely sure where this should go, I post to both]

I am trying to perform a conceptually simple task, of showing two
different views of a large bitmap by using two ViewPorts.  My code
is not in obvious error, and I get bizarre but repeatable results.

Allocate a View, two ViewPorts, two RasInfos, one RastPort, and one BitMap
Initialize these items appropriately:
   Point both RasInfo to BitMap
   Give each ViewPort it's own RasInfo
   Link two ViewPorts through vp.Next field
   Link ViewPorts into View
Do arcane things to generate copper lists
ON_DISPLAY;


The problem is this ... the first ViewPort has graphics correctly
rendered, but the second doesn't. In fact, the second ViewPort is black, which
is not the currently defined background color.  It's as if the display 
is not spewing electrons for the bottom half of the screen.

The program exits okay, so it's not as if I were corrupting system structures
or anything similarly catastrophic.

Anybody able to shed some light on this?  If you really need to see the
code, I can post it, but it's almost exactly like the example code in
RKM vol1 about using Views and ViewPorts.  Really!

                                         Mitch

(Hiding out here under an assumed name ...)

BITNET:   {SXA00051, SXAA00052} @ BAGAMCOK
UUCP:     seismo!ncr-sd!ncrcae!usceast!baldwin
          nosc!crash!pro-carolina!mitch