/*--------------------------------------------------------------------------------------

//

//  File:       OffscreenUtils.c

//

//  Contents:   Procedures for the creation, manipulation, and disposal of offscreen bit structures.

//

//

//  By Georgiann ("George") Delaney

//  ©Ê1989 - 1990, Apple Computer, Inc.

//

//--------------------------------------------------------------------------------------*/

#pragma segment OffscreenSeg

#include "MacHeaders.h"

/*--------------------------------------------------------------------------------------*/

Boolean  CreateOSBitmap(GrafPtr *theOSBitmap, Rect *bounds)

/*

    CreateOSBitmap returns, in the specified pointer, an offscreen bitmap whose size is

    that which was specified in the bounds parameter.

*/

{

    GrafPtr     bitsPort;                   /*  temporary storage for new bitmap    */

    GrafPtr     holdPort;                   /*  storage for current port            */

    Rect        bitsRect;                   /*  local copy of specified boundary    */

    Boolean     theReturn    = false;       /*  temp storage for return value       */

                    /*  Save off the current port so that it can be restored after OpenPort()  */

    GetPort(&holdPort);             

                    /*  Convert the rect so that is is zero-based. */

    bitsRect = *bounds;

    OffsetRect(&bitsRect, -bitsRect.top, -bitsRect.left);

                    /*  Allocate memory for the offscreen bitmap's */

    bitsPort  = (GrafPtr) NewPtr(sizeof(GrafPort));

    if (MemError() == noErr) {

                    /*  Allocate and initialize the offscreen bitmap's clipRgn, visRgn,  etc... */

        OpenPort(bitsPort);     

        bitsPort->portRect  = bitsRect;

        RectRgn(bitsPort->clipRgn,&bitsRect);

        RectRgn(bitsPort->visRgn, &bitsRect);

                    /*  Allocate and initialize the offscreen bitmap    */

        bitsPort->portBits.bounds   = bitsRect;

        bitsPort->portBits.rowBytes = ((bitsRect.right  + 15) >> 4) << 1;

        bitsPort->portBits.baseAddr = NewPtr(bitsPort->portBits.rowBytes * (long)bitsRect.bottom);

        if (MemError() == noErr) {

                    /*  Clear the bitmap's original contents  */

            EraseRect(&bitsRect);   

            *theOSBitmap = bitsPort;

            theReturn = true;

            }

        else  {

                    /*  Offscreen bitmap alloaction failed.  Dispose all allocated memory  */

            ClosePort(bitsPort);

            DisposPtr((Ptr)bitsPort->portBits.baseAddr);

            }

                    /*  Restore the port to that which was set before OpenPort()  */

        SetPort(holdPort);  

        }

    return(theReturn);

}

/*--------------------------------------------------------------------------------------*/

void  DisposeOSBitmap(GrafPtr theOSBitmap)

/*

    DisposeOSBitmap disposes of an offscreen bitmap created with the above offscreen bitmap

    creation function.

*/

{

            /*  Close the offscreen bitmap's port  */

    ClosePort(theOSBitmap);

            /*  Dispose the offscreen bitmap  */

    DisposPtr((Ptr)theOSBitmap->portBits.baseAddr);

            /*  Dispose the offscreen bitmap's port  */

    DisposPtr((Ptr)theOSBitmap);

}