Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!ut-emx!hcobb
From: hcobb@walt.cc.utexas.edu (Henry J. Cobb)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Clipping? Questions and recommendations.
Keywords: graphics
Message-ID: <25745@ut-emx.UUCP>
Date: 9 Mar 90 01:35:11 GMT
References: <27831.AA27831@slaka.sirius.se> <10056@cbmvax.commodore.com>
Sender: news@ut-emx.UUCP
Reply-To: hcobb@walt.cc.utexas.edu (Henry J. Cobb)
Organization: The University of Texas at Austin
Lines: 26
In-reply-to: peter@cbmvax.commodore.com (Peter Cherna)

In article <10056@cbmvax.commodore.com>, peter@cbmvax (Peter Cherna) writes:
>
<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.
<

	My copy of RKM: Includes & Autodocs shows this to be a function
in layers.library.

	The Autodoc says to call InstallClipRegion(l,NULL) to "tidy up"
when through.  Is there anyway to tell if the Clip region is set to its
default (NULL) value?

	Does this NULL value indicate that there is some sort of array 
somewhere where we can store our "commonly used" clipping regions and
rapidly select from them?

	Lastly, how much "effort" does this call require?  Would it hurt
alot to call it before drawing each line?

	Henry J. Cobb	hcobb@ccwf.cc.utexas.edu