Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!rutgers!bpa!cbmvax!peter
From: peter@cbmvax.commodore.com (Peter Cherna)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Clipping? Questions and recommendations.
Message-ID: <10056@cbmvax.commodore.com>
Date: 8 Mar 90 17:34:48 GMT
References: <27831.AA27831@slaka.sirius.se>
Reply-To: peter@cbmvax (Peter Cherna)
Organization: Commodore, West Chester, PA
Lines: 30

In article <27831.AA27831@slaka.sirius.se> micke@slaka.sirius.se (Mikael Karlsson) writes:
>I want to write a program with one user interface task and one drawer
>task. The UI task sends drawing commands to the drawer task.
>The UI task opens a window and initializes the drawer task by giving
>it a copy of the window's RastPort.
>
>Now for the question:
>Is it possible to have two tasks draw into the same window (RastPort)
>where each task uses different clipping regions?

The graphics library call InstallClipRegion() operates on a per-layer
basis.  Since your two tasks share a layer, they would share a clip
region.  So to have them use different clipping regions, there would
have to be some kind of locking protocol between them, say a semaphore,
which each of your tasks would have to obtain before installing its
clipping region and hold through its rendering operations, then remove
the clipping region and release the semaphore.

>--
>
> \_/   Mikael Karlsson, Lovsattersvagen 10, S-585 98  LINKOPING, SWEDEN
>  V                           | micke@slaka.sirius.se
>  |      Absolut Software     | micke@slaka.UUCP
> ~~~                          | {mcvax,seismo}!sunic!liuida!slaka!micke

     Peter
--
     Peter Cherna, Software Engineer, Commodore-Amiga, Inc.
     {uunet|rutgers}!cbmvax!peter    peter@cbmvax.cbm.commodore.com
My opinions do not necessarily represent the opinions of my employer.