Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!rutgers!cbmvax!peter
From: peter@cbmvax.commodore.com (Peter Cherna)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Printing and the Layers Library... HELP!
Message-ID: <20688@cbmvax.commodore.com>
Date: 16 Apr 91 16:05:43 GMT
References: <1991Apr15.202049.24563@wehi.dn.mu.oz>
Reply-To: peter@cbmvax.commodore.com (Peter Cherna)
Organization: Commodore-Amiga, Inc.  West Chester, PA.
Lines: 63

In article <1991Apr15.202049.24563@wehi.dn.mu.oz> baxter_a@wehi.dn.mu.oz writes:
>Rather than handle all the extra clipping this involves myself, is
>it possible to use the layers library to protect memory outside the
>rastport strip being rendered to from being written into by the 
>drawing routines?

Here's some untested code to work from:

#define STRIP_WIDTH     whatever
#define STRIP_HEIGHT    whatever
#define DEPTH           whatever

struct BitMap stripBitMap;
struct Layer_Info *strip_layerinfo;
struct Layer *strip_layer;
ULONG ok = TRUE;

/* Start with a bitmap */
InitBitMap( &stripBitMap, DEPTH, STRIP_WIDTH, STRIP_HEIGHT );

/* Allocate bitmap planes */
for ( d = 0; d < DEPTH; d++ )
{
    if ( !( stripBitMap.Planes[d] = AllocRaster( STRIP_WIDTH, STRIP_HEIGHT ) ) )
    {
        ok = FALSE;
        break;
    }
}

/* A Layer_Info is somewhat like an underlying screen */
if (ok)
{
    ok = ( strip_layerinfo = NewLayerInfo() );
}

/* A Layer is what underlies a window.  It needs to be associated with
 * a Layer_Info, and its RastPort provides clipping.
 */
if (ok)
{
    /* Layer flags don't matter much since we're not going to change
     * the layers (move, size, etc.).  We're just using one for clipping.
     */
    ok = ( strip_layer = CreateUpfrontLayer( strip_layerinfo, &stripBitMap
        0, 0, STRIP_WIDTH, STRIP_HEIGHT,
        LAYERSIMPLE | LAYERBACKDROP, NULL ) );
}

if (ok)
{
    /* We're in fine shape now.  Render away... */
    render( layer->rp );
}

/* Free up and exit (exercise for the reader) */

     Peter
--
Peter Cherna, Operating Systems Development Group, Commodore-Amiga, Inc.
{uunet|rutgers}!cbmvax!peter    peter@cbmvax.commodore.com
My opinions do not necessarily represent the opinions of my employer.
"If all you have is a hammer, everything looks like a nail."