devrgn.c

/*
 * Portions Copyright (c) 1999, 2000 Greg Haerr <greg@censoft.com>
 *	Somewhat less shamelessly ripped from the Wine distribution
 *
 * Device-independent multi-rectangle clipping routines.
 *
 * GDI region objects. Shamelessly ripped out from the X11 distribution
 * Thanks for the nice licence.
 *
 * Copyright 1993, 1994, 1995 Alexandre Julliard
 * Modifications and additions: Copyright 1998 Huw Davies
 */
/* **********************************************************************

Copyright (c) 1987, 1988  X Consortium

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Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts.

			All Rights Reserved

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************************************************************************/
/*
 * The functions in this file implement the Region abstraction, similar to one
 * used in the X11 sample server. A Region is simply an area, as the name
 * implies, and is implemented as a "y-x-banded" array of rectangles. To
 * explain: Each Region is made up of a certain number of rectangles sorted
 * by y coordinate first, and then by x coordinate.
 *
 * Furthermore, the rectangles are banded such that every rectangle with a
 * given upper-left y coordinate (y1) will have the same lower-right y
 * coordinate (y2) and vice versa. If a rectangle has scanlines in a band, it
 * will span the entire vertical distance of the band. This means that some
 * areas that could be merged into a taller rectangle will be represented as
 * several shorter rectangles to account for shorter rectangles to its left
 * or right but within its "vertical scope".
 *
 * An added constraint on the rectangles is that they must cover as much
 * horizontal area as possible. E.g. no two rectangles in a band are allowed
 * to touch.
 *
 * Whenever possible, bands will be merged together to cover a greater vertical
 * distance (and thus reduce the number of rectangles). Two bands can be merged
 * only if the bottom of one touches the top of the other and they have
 * rectangles in the same places (of the same width, of course). This maintains
 * the y-x-banding that's so nice to have...
 */
#include <stdlib.h>
#include <string.h>
#include "device.h"

typedef void (*REGION_OverlapBandFunctionPtr) (MWCLIPREGION * pReg, MWRECT * r1,
    MWRECT * r1End, MWRECT * r2, MWRECT * r2End, MWCOORD top, MWCOORD bottom);
typedef void (*REGION_NonOverlapBandFunctionPtr) (MWCLIPREGION * pReg, MWRECT * r,
    MWRECT * end, MWCOORD top, MWCOORD bottom);

/*  1 if two RECTs overlap.
 *  0 if two RECTs do not overlap.
 */
#define EXTENTCHECK(r1, r2) \
	((r1)->right > (r2)->left && \
	 (r1)->left < (r2)->right && \
	 (r1)->bottom > (r2)->top && \
	 (r1)->top < (r2)->bottom)

/*
 *   Check to see if there is enough memory in the present region.
 */
#define MEMCHECK(reg, rect, firstrect){\
        if ((reg)->numRects >= ((reg)->size - 1)){\
          (firstrect) = REALLOC(\
           (firstrect), ((sizeof(MWRECT)) * ((reg)->size)), \
           (2 * (sizeof(MWRECT)) * ((reg)->size)));\
          if ((firstrect) == 0)\
            return;\
          (reg)->size *= 2;\
          (rect) = &(firstrect)[(reg)->numRects];\
         }\
       }

#define REGION_NOT_EMPTY(pReg) pReg->numRects

#define EMPTY_REGION(pReg) { \
    (pReg)->numRects = 0; \
    (pReg)->extents.left = (pReg)->extents.top = 0; \
    (pReg)->extents.right = (pReg)->extents.bottom = 0; \
    (pReg)->type = MWREGION_NULL; \
 }

#define INRECT(r, x, y) \
      ( ( ((r).right >  x)) && \
        ( ((r).left <= x)) && \
        ( ((r).bottom >  y)) && \
        ( ((r).top <= y)) )

/**
 * return TRUE if point is in region
 *
 * @param rgn Region.
 * @param x X co-ordinate of point to check.
 * @param y Y co-ordinate of point to check.
 * @return TRUE iff point is in region
 */
MWBOOL
GdPtInRegion(MWCLIPREGION *rgn, MWCOORD x, MWCOORD y)
{
    int i;

    if (rgn->numRects > 0 && INRECT(rgn->extents, x, y))
	for (i = 0; i < rgn->numRects; i++)
	    if (INRECT (rgn->rects[i], x, y))
		return TRUE;
    return FALSE;
}

/**
 * return whether rectangle is all in, partly in, or out of region
 *
 * @param rgn Region.
 * @param rect Rectangle to check.
 * @return MWRECT_PARTIN, MWRECT_ALLIN, or MWRECT_OUT.
 */
int 
GdRectInRegion(MWCLIPREGION *rgn, const MWRECT *rect)
{
    MWRECT *	pCurRect;
    MWRECT *	pRectEnd;
    MWCOORD	rx, ry;
    MWBOOL	partIn, partOut;

    /* this is (just) a useful optimization */
    if (!rgn->numRects || !EXTENTCHECK(&rgn->extents, rect))
        return MWRECT_OUT;

    partOut = FALSE;
    partIn = FALSE;
    rx = rect->left;
    ry = rect->top;

    /* 
     * can stop when both partOut and partIn are TRUE,
     * or we reach rect->bottom
     */
    for (pCurRect = rgn->rects, pRectEnd = pCurRect + rgn->numRects;
		 pCurRect < pRectEnd; pCurRect++) {

	if (pCurRect->bottom <= ry)
	   continue;		/* not far enough down yet*/

	if (pCurRect->top > ry) {
	   partOut = TRUE;	/* missed part of rectangle above */
	   if (partIn || (pCurRect->top >= rect->bottom))
	      break;
	   ry = pCurRect->top;	/* x guaranteed to be == rect->left */
	}

	if (pCurRect->right <= rx)
	   continue;		/* not far enough over yet */

	if (pCurRect->left > rx) {
	   partOut = TRUE;	/* missed part of rectangle to left */
	   if (partIn)
	      break;
	}

	if (pCurRect->left < rect->right) {
	    partIn = TRUE;	/* definitely overlap */
	    if (partOut)
	       break;
	}

	if (pCurRect->right >= rect->right) {
	   ry = pCurRect->bottom;	/* finished with this band */
	   if (ry >= rect->bottom)
	      break;
	   rx = rect->left;	/* reset x out to left again */
	} else {
	    /*
	     * Because boxes in a band are maximal width, if the first box
	     * to overlap the rectangle doesn't completely cover it in that
	     * band, the rectangle must be partially out, since some of it
	     * will be uncovered in that band. partIn will have been set true
	     * by now...
	     */
	    break;
	}
    }

    return(partIn ? ((ry < rect->bottom) ? MWRECT_PARTIN : MWRECT_ALLIN) : 
		MWRECT_OUT);
}

#if 0000
/* Returns TRUE if rect is at least partly inside rgn*/
MWBOOL
GdRectInRegion(MWCLIPREGION *rgn, const MWRECT *rect)
{
    MWRECT *pCurRect, *pRectEnd;
    MWBOOL ret = FALSE;

    /* this is (just) a useful optimization */
	if ((rgn->numRects > 0) && EXTENTCHECK(&rgn->extents, rect))
	{
	    for (pCurRect = rgn->rects, pRectEnd = pCurRect +
	     rgn->numRects; pCurRect < pRectEnd; pCurRect++)
	    {
	        if (pCurRect->bottom <= rect->top)
			continue;             /* not far enough down yet */

		if (pCurRect->top >= rect->bottom) {
		    ret = FALSE;          /* too far down */
		    break;
		}

		if (pCurRect->right <= rect->left)
		    continue;              /* not far enough over yet */

		if (pCurRect->left >= rect->right) {
		    continue;
		}

		ret = TRUE;
		break;
	    }
	}
	return ret;
}
#endif

static MWBOOL
EQUALRECT(MWRECT *r1, MWRECT *r2)
{
	return ((r1->left == r2->left) && (r1->right == r2->right) &&
		(r1->top == r2->top) && (r1->bottom == r2->bottom));
}

/**
 * Test if two regions are identical.
 *
 * @param r1 First region.
 * @param r2 Second region.
 * @return TRUE iff the regions are exactly the same.
 */
MWBOOL
GdEqualRegion(MWCLIPREGION *r1, MWCLIPREGION *r2)
{
	int	i;

	if (r1->numRects != r2->numRects)
		return FALSE;
	if (r1->numRects == 0)
		return TRUE;
	if (!EQUALRECT(&r1->extents, &r2->extents))
		return FALSE;
	for (i = 0; i < r1->numRects; i++) {
		if (!EQUALRECT(r1->rects + i, r2->rects + i))
			return FALSE;
	}
	return TRUE;
}

/**
 * Test if a region is empty.
 *
 * @param rgn Region.
 * @return TRUE iff the region is empty.
 */
MWBOOL
GdEmptyRegion(MWCLIPREGION *rgn)
{
	return rgn->numRects == 0;
}

/**
 *            Create a new empty MWCLIPREGION.
 *
 * @return A new region.
 */
MWCLIPREGION *
GdAllocRegion(void)    
{
    MWCLIPREGION *rgn;

    if ((rgn = malloc(sizeof( MWCLIPREGION ))))
    {
	if ((rgn->rects = malloc(sizeof( MWRECT ))))
	{
	    rgn->size = 1;
	    EMPTY_REGION(rgn);
	    return rgn;
	}
	free(rgn);
    }
    return NULL;
}

/**
 * Create a new MWCLIPREGION which is a rectangular region.
 *
 * @param left Left edge of region.
 * @param top Top edge of region.
 * @param right Right edge of region.
 * @param bottom Bottom edge of region.
 * @return A new region.
 */
MWCLIPREGION *
GdAllocRectRegion(MWCOORD left, MWCOORD top, MWCOORD right, MWCOORD bottom)
{
	MWCLIPREGION *rgn;

	rgn = GdAllocRegion();
	if (rgn)
		GdSetRectRegion(rgn, left, top, right, bottom);
	return rgn;
}

/**
 * Create a new MWCLIPREGION which is a rectangular region.
 *
 * @param prc Rectangle defining the region.
 * @return A new region.
 */
MWCLIPREGION *
GdAllocRectRegionIndirect(MWRECT *prc)
{
	return GdAllocRectRegion(prc->left, prc->top, prc->right, prc->bottom);
}

/**
 * Redefine a region to be just a simple rectangular region.
 * The previous contents of the region are destroyed.
 *
 * @param rgn A region.
 * @param left Left edge of region.
 * @param top Top edge of region.
 * @param right Right edge of region.
 * @param bottom Bottom edge of region.
 */
void
GdSetRectRegion(MWCLIPREGION *rgn, MWCOORD left, MWCOORD top, MWCOORD right,
	MWCOORD bottom)
{
	if (left != right && top != bottom) {
		rgn->rects->left = rgn->extents.left = left;
		rgn->rects->top = rgn->extents.top = top;
		rgn->rects->right = rgn->extents.right = right;
		rgn->rects->bottom = rgn->extents.bottom = bottom;
		rgn->numRects = 1;
		rgn->type = MWREGION_SIMPLE;
	} else
		EMPTY_REGION(rgn);
}

/**
 * Redefine a region to be just a simple rectangular region.
 * The previous contents of the region are destroyed.
 *
 * @param rgn A region.
 * @param prc Rectangle defining the region.
 */
void
GdSetRectRegionIndirect(MWCLIPREGION *rgn, MWRECT *prc)
{
	GdSetRectRegion(rgn, prc->left, prc->top, prc->right, prc->bottom);
}

/**
 * Destroy a region.  Similar to free().
 *
 * @param rgn The region to destroy.
 */
void
GdDestroyRegion(MWCLIPREGION *rgn)
{
	if(rgn) {
		free(rgn->rects);
		free(rgn);
	}
}

/**
 * Translate a region by a specified offset.
 *
 * @param rgn The region to translate.
 * @param x The X offset.
 * @param y The Y offset.
 */
void
GdOffsetRegion(MWCLIPREGION *rgn, MWCOORD x, MWCOORD y)
{
	int	nbox = rgn->numRects;
	MWRECT *pbox = rgn->rects;

	if(nbox && (x || y)) {
		while(nbox--) {
			pbox->left += x;
			pbox->right += x;
			pbox->top += y;
			pbox->bottom += y;
			pbox++;
		}
		rgn->extents.left += x;
		rgn->extents.right += x;
		rgn->extents.top += y;
		rgn->extents.bottom += y;
	}
}

/**
 * get bounding box for region, return region type
 *
 * @param rgn The region to query.
 * @param prc On exit, contains the bounding box for the region.
 * @return The region type.  One of MWREGION_NULL (empty region),
 * MWREGION_SIMPLE (rectangular region), or MWREGION_COMPLEX (non-rectangular
 * region).
 */
int
GdGetRegionBox(MWCLIPREGION *rgn, MWRECT *prc)
{
	*prc = rgn->extents;
	return rgn->type;
}

/**
 *           Adds a rectangle to a MWCLIPREGION
 *
 * @param rect Rectangle to add to the region.
 * @param rgn The clip region to modify.
 */
void
GdUnionRectWithRegion(const MWRECT *rect, MWCLIPREGION *rgn)
{
    MWCLIPREGION region;

    region.rects = &region.extents;
    region.numRects = 1;
    region.size = 1;
    region.type = MWREGION_SIMPLE;
    region.extents = *rect;
    GdUnionRegion(rgn, rgn, &region);
}

/**
 *           Subtracts a rectangle from a MWCLIPREGION
 *
 * @param rect Rectangle to remove from the region.
 * @param rgn The clip region to modify.
 */
void
GdSubtractRectFromRegion(const MWRECT *rect, MWCLIPREGION *rgn)
{
    MWCLIPREGION region;

    region.rects = &region.extents;
    region.numRects = 1;
    region.size = 1;
    region.type = MWREGION_SIMPLE;
    region.extents = *rect;
    GdSubtractRegion(rgn, rgn, &region);
}


/**
 * Modify a region so that it is identical to another region.
 *
 * @param dst Region to copy to.
 * @param src Region to copy from.
 */
void
GdCopyRegion(MWCLIPREGION *dst, MWCLIPREGION *src)
{
    if (dst != src) /*  don't want to copy to itself */
    {  
	if (dst->size < src->numRects)
	{
	    if (! (dst->rects = REALLOC( dst->rects, dst->numRects * sizeof(MWRECT), src->numRects * sizeof(MWRECT))))
		return;
	    dst->size = src->numRects;
	}
	dst->numRects = src->numRects;
	dst->extents.left = src->extents.left;
	dst->extents.top = src->extents.top;
	dst->extents.right = src->extents.right;
	dst->extents.bottom = src->extents.bottom;
	dst->type = src->type;

	memcpy((char *) dst->rects, (char *) src->rects,
	       (int) (src->numRects * sizeof(MWRECT)));
    }
}


/* *********************************************************************
 *           REGION_SetExtents
 *           Re-calculate the extents of a region
 */
static void
REGION_SetExtents (MWCLIPREGION *pReg)
{
    MWRECT *pRect, *pRectEnd, *pExtents;

    if (pReg->numRects == 0)
    {
	pReg->extents.left = 0;
	pReg->extents.top = 0;
	pReg->extents.right = 0;
	pReg->extents.bottom = 0;
	return;
    }

    pExtents = &pReg->extents;
    pRect = pReg->rects;
    pRectEnd = &pRect[pReg->numRects - 1];

    /*
     * Since pRect is the first rectangle in the region, it must have the
     * smallest top and since pRectEnd is the last rectangle in the region,
     * it must have the largest bottom, because of banding. Initialize left and
     * right from pRect and pRectEnd, resp., as good things to initialize them
     * to...
     */
    pExtents->left = pRect->left;
    pExtents->top = pRect->top;
    pExtents->right = pRectEnd->right;
    pExtents->bottom = pRectEnd->bottom;

    while (pRect <= pRectEnd)
    {
	if (pRect->left < pExtents->left)
	    pExtents->left = pRect->left;
	if (pRect->right > pExtents->right)
	    pExtents->right = pRect->right;
	pRect++;
    }
}


/* *********************************************************************
 *           REGION_Coalesce
 *
 *      Attempt to merge the rects in the current band with those in the
 *      previous one. Used only by REGION_RegionOp.
 *
 * Results:
 *      The new index for the previous band.
 *
 * Side Effects:
 *      If coalescing takes place:
 *          - rectangles in the previous band will have their bottom fields
 *            altered.
 *          - pReg->numRects will be decreased.
 *
 */
static MWCOORD
REGION_Coalesce (
	     MWCLIPREGION *pReg, /* Region to coalesce */
	     MWCOORD prevStart,  /* Index of start of previous band */
	     MWCOORD curStart    /* Index of start of current band */
) {
    MWRECT *pPrevRect;          /* Current rect in previous band */
    MWRECT *pCurRect;           /* Current rect in current band */
    MWRECT *pRegEnd;            /* End of region */
    MWCOORD curNumRects;          /* Number of rectangles in current band */
    MWCOORD prevNumRects;         /* Number of rectangles in previous band */
    MWCOORD bandtop;               /* top coordinate for current band */

    pRegEnd = &pReg->rects[pReg->numRects];

    pPrevRect = &pReg->rects[prevStart];
    prevNumRects = curStart - prevStart;

    /*
     * Figure out how many rectangles are in the current band. Have to do
     * this because multiple bands could have been added in REGION_RegionOp
     * at the end when one region has been exhausted.
     */
    pCurRect = &pReg->rects[curStart];
    bandtop = pCurRect->top;
    for (curNumRects = 0;
	 (pCurRect != pRegEnd) && (pCurRect->top == bandtop);
	 curNumRects++)
    {
	pCurRect++;
    }
    
    if (pCurRect != pRegEnd)
    {
	/*
	 * If more than one band was added, we have to find the start
	 * of the last band added so the next coalescing job can start
	 * at the right place... (given when multiple bands are added,
	 * this may be pointless -- see above).
	 */
	pRegEnd--;
	while (pRegEnd[-1].top == pRegEnd->top)
	{
	    pRegEnd--;
	}
	curStart = pRegEnd - pReg->rects;
	pRegEnd = pReg->rects + pReg->numRects;
    }
	
    if ((curNumRects == prevNumRects) && (curNumRects != 0)) {
	pCurRect -= curNumRects;
	/*
	 * The bands may only be coalesced if the bottom of the previous
	 * matches the top scanline of the current.
	 */
	if (pPrevRect->bottom == pCurRect->top)
	{
	    /*
	     * Make sure the bands have rects in the same places. This
	     * assumes that rects have been added in such a way that they
	     * cover the most area possible. I.e. two rects in a band must
	     * have some horizontal space between them.
	     */
	    do
	    {
		if ((pPrevRect->left != pCurRect->left) ||
		    (pPrevRect->right != pCurRect->right))
		{
		    /*
		     * The bands don't line up so they can't be coalesced.
		     */
		    return (curStart);
		}
		pPrevRect++;
		pCurRect++;
		prevNumRects -= 1;
	    } while (prevNumRects != 0);

	    pReg->numRects -= curNumRects;
	    pCurRect -= curNumRects;
	    pPrevRect -= curNumRects;

	    /*
	     * The bands may be merged, so set the bottom of each rect
	     * in the previous band to that of the corresponding rect in
	     * the current band.
	     */
	    do
	    {
		pPrevRect->bottom = pCurRect->bottom;
		pPrevRect++;
		pCurRect++;
		curNumRects -= 1;
	    } while (curNumRects != 0);

	    /*
	     * If only one band was added to the region, we have to backup
	     * curStart to the start of the previous band.
	     *
	     * If more than one band was added to the region, copy the
	     * other bands down. The assumption here is that the other bands
	     * came from the same region as the current one and no further
	     * coalescing can be done on them since it's all been done
	     * already... curStart is already in the right place.
	     */
	    if (pCurRect == pRegEnd)
	    {
		curStart = prevStart;
	    }
	    else
	    {
		do
		{
		    *pPrevRect++ = *pCurRect++;
		} while (pCurRect != pRegEnd);
	    }
	    
	}
    }
    return (curStart);
}

/* *********************************************************************
 *           REGION_RegionOp
 *
 *      Apply an operation to two regions. Called by GdUnion,
 *      GdXor, GdSubtract, GdIntersect...
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      The new region is overwritten.
 *
 * Notes:
 *      The idea behind this function is to view the two regions as sets.
 *      Together they cover a rectangle of area that this function divides
 *      into horizontal bands where points are covered only by one region
 *      or by both. For the first case, the nonOverlapFunc is called with
 *      each the band and the band's upper and lower extents. For the
 *      second, the overlapFunc is called to process the entire band. It
 *      is responsible for clipping the rectangles in the band, though
 *      this function provides the boundaries.
 *      At the end of each band, the new region is coalesced, if possible,
 *      to reduce the number of rectangles in the region.
 *
 */
static void
REGION_RegionOp(
	    MWCLIPREGION *newReg, /* Place to store result */
	    MWCLIPREGION *reg1,   /* First region in operation */
            MWCLIPREGION *reg2,   /* 2nd region in operation */
	    REGION_OverlapBandFunctionPtr overlapFunc,     /* Function to call for over-lapping bands */
	    REGION_NonOverlapBandFunctionPtr nonOverlap1Func, /* Function to call for non-overlapping bands in region 1 */
	    REGION_NonOverlapBandFunctionPtr nonOverlap2Func  /* Function to call for non-overlapping bands in region 2 */
) {
    MWRECT *r1;                         /* Pointer into first region */
    MWRECT *r2;                         /* Pointer into 2d region */
    MWRECT *r1End;                      /* End of 1st region */
    MWRECT *r2End;                      /* End of 2d region */
    MWCOORD ybot;                         /* Bottom of intersection */
    MWCOORD ytop;                         /* Top of intersection */
    MWRECT *oldRects;                   /* Old rects for newReg */
    MWCOORD prevBand;                     /* Index of start of
						 * previous band in newReg */
    MWCOORD curBand;                      /* Index of start of current
						 * band in newReg */
    MWRECT *r1BandEnd;                  /* End of current band in r1 */
    MWRECT *r2BandEnd;                  /* End of current band in r2 */
    MWCOORD top;                          /* Top of non-overlapping band */
    MWCOORD bot;                          /* Bottom of non-overlapping band */
    
    /*
     * Initialization:
     *  set r1, r2, r1End and r2End appropriately, preserve the important
     * parts of the destination region until the end in case it's one of
     * the two source regions, then mark the "new" region empty, allocating
     * another array of rectangles for it to use.
     */
    r1 = reg1->rects;
    r2 = reg2->rects;
    r1End = r1 + reg1->numRects;
    r2End = r2 + reg2->numRects;
    

    /*
     * newReg may be one of the src regions so we can't empty it. We keep a 
     * note of its rects pointer (so that we can free them later), preserve its
     * extents and simply set numRects to zero. 
     */

    oldRects = newReg->rects;
    newReg->numRects = 0;

    /*
     * Allocate a reasonable number of rectangles for the new region. The idea
     * is to allocate enough so the individual functions don't need to
     * reallocate and copy the array, which is time consuming, yet we don't
     * have to worry about using too much memory. I hope to be able to
     * nuke the REALLOC() at the end of this function eventually.
     */
    newReg->size = MWMAX(reg1->numRects,reg2->numRects) * 2;

    if (! (newReg->rects = malloc( sizeof(MWRECT) * newReg->size )))
    {
	newReg->size = 0;
	return;
    }
    
    /*
     * Initialize ybot and ytop.
     * In the upcoming loop, ybot and ytop serve different functions depending
     * on whether the band being handled is an overlapping or non-overlapping
     * band.
     *  In the case of a non-overlapping band (only one of the regions
     * has points in the band), ybot is the bottom of the most recent
     * intersection and thus clips the top of the rectangles in that band.
     * ytop is the top of the next intersection between the two regions and
     * serves to clip the bottom of the rectangles in the current band.
     *  For an overlapping band (where the two regions intersect), ytop clips
     * the top of the rectangles of both regions and ybot clips the bottoms.
     */
    if (reg1->extents.top < reg2->extents.top)
	ybot = reg1->extents.top;
    else
	ybot = reg2->extents.top;
    
    /*
     * prevBand serves to mark the start of the previous band so rectangles
     * can be coalesced into larger rectangles. qv. miCoalesce, above.
     * In the beginning, there is no previous band, so prevBand == curBand
     * (curBand is set later on, of course, but the first band will always
     * start at index 0). prevBand and curBand must be indices because of
     * the possible expansion, and resultant moving, of the new region's
     * array of rectangles.
     */
    prevBand = 0;
    
    do
    {
	curBand = newReg->numRects;

	/*
	 * This algorithm proceeds one source-band (as opposed to a
	 * destination band, which is determined by where the two regions
	 * intersect) at a time. r1BandEnd and r2BandEnd serve to mark the
	 * rectangle after the last one in the current band for their
	 * respective regions.
	 */
	r1BandEnd = r1;
	while ((r1BandEnd != r1End) && (r1BandEnd->top == r1->top))
	{
	    r1BandEnd++;
	}
	
	r2BandEnd = r2;
	while ((r2BandEnd != r2End) && (r2BandEnd->top == r2->top))
	{
	    r2BandEnd++;
	}
	
	/*
	 * First handle the band that doesn't intersect, if any.
	 *
	 * Note that attention is restricted to one band in the
	 * non-intersecting region at once, so if a region has n
	 * bands between the current position and the next place it overlaps
	 * the other, this entire loop will be passed through n times.
	 */
	if (r1->top < r2->top)
	{
	    top = MWMAX(r1->top,ybot);
	    bot = MWMIN(r1->bottom,r2->top);

	    if ((top != bot) && nonOverlap1Func)
	    {
		(* nonOverlap1Func) (newReg, r1, r1BandEnd, top, bot);
	    }

	    ytop = r2->top;
	}
	else if (r2->top < r1->top)
	{
	    top = MWMAX(r2->top,ybot);
	    bot = MWMIN(r2->bottom,r1->top);

	    if ((top != bot) && nonOverlap2Func)
	    {
		(* nonOverlap2Func) (newReg, r2, r2BandEnd, top, bot);
	    }

	    ytop = r1->top;
	}
	else
	{
	    ytop = r1->top;
	}

	/*
	 * If any rectangles got added to the region, try and coalesce them
	 * with rectangles from the previous band. Note we could just do
	 * this test in miCoalesce, but some machines incur a not
	 * inconsiderable cost for function calls, so...
	 */
	if (newReg->numRects != curBand)
	{
	    prevBand = REGION_Coalesce (newReg, prevBand, curBand);
	}

	/*
	 * Now see if we've hit an intersecting band. The two bands only
	 * intersect if ybot > ytop
	 */
	ybot = MWMIN(r1->bottom, r2->bottom);
	curBand = newReg->numRects;
	if (ybot > ytop)
	{
	    (* overlapFunc) (newReg, r1, r1BandEnd, r2, r2BandEnd, ytop, ybot);

	}
	
	if (newReg->numRects != curBand)
	{
	    prevBand = REGION_Coalesce (newReg, prevBand, curBand);
	}

	/*
	 * If we've finished with a band (bottom == ybot) we skip forward
	 * in the region to the next band.
	 */
	if (r1->bottom == ybot)
	{
	    r1 = r1BandEnd;
	}
	if (r2->bottom == ybot)
	{
	    r2 = r2BandEnd;
	}
    } while ((r1 != r1End) && (r2 != r2End));

    /*
     * Deal with whichever region still has rectangles left.
     */
    curBand = newReg->numRects;
    if (r1 != r1End)
    {
	if (nonOverlap1Func)
	{
	    do
	    {
		r1BandEnd = r1;
		while ((r1BandEnd < r1End) && (r1BandEnd->top == r1->top))
		{
		    r1BandEnd++;
		}
		(* nonOverlap1Func) (newReg, r1, r1BandEnd,
				     MWMAX(r1->top,ybot), r1->bottom);
		r1 = r1BandEnd;
	    } while (r1 != r1End);
	}
    }
    else if ((r2 != r2End) && nonOverlap2Func)
    {
	do
	{
	    r2BandEnd = r2;
	    while ((r2BandEnd < r2End) && (r2BandEnd->top == r2->top))
	    {
		 r2BandEnd++;
	    }
	    (* nonOverlap2Func) (newReg, r2, r2BandEnd,
				MWMAX(r2->top,ybot), r2->bottom);
	    r2 = r2BandEnd;
	} while (r2 != r2End);
    }

    if (newReg->numRects != curBand)
    {
	(void) REGION_Coalesce (newReg, prevBand, curBand);
    }

    /*
     * A bit of cleanup. To keep regions from growing without bound,
     * we shrink the array of rectangles to match the new number of
     * rectangles in the region. This never goes to 0, however...
     *
     * Only do this stuff if the number of rectangles allocated is more than
     * twice the number of rectangles in the region (a simple optimization...).
     */
    if (newReg->numRects < (newReg->size >> 1))
    {
	if (REGION_NOT_EMPTY(newReg))
	{
	    MWRECT *prev_rects = newReg->rects;
	    newReg->rects = REALLOC( newReg->rects, sizeof(MWRECT) * newReg->size, sizeof(MWRECT) * newReg->numRects );
	    newReg->size = newReg->numRects;
	    if (! newReg->rects)
		newReg->rects = prev_rects;
	}
	else
	{
	    /*
	     * No point in doing the extra work involved in an Xrealloc if
	     * the region is empty
	     */
	    newReg->size = 1;
	    free( newReg->rects );
	    newReg->rects = malloc( sizeof(MWRECT) );
	}
    }
    free( oldRects );
}

/* *********************************************************************
 *          Region Intersection
 ***********************************************************************/


/* *********************************************************************
 *	     REGION_IntersectO
 *
 * Handle an overlapping band for REGION_Intersect.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      Rectangles may be added to the region.
 *
 */
static void
REGION_IntersectO(MWCLIPREGION *pReg,  MWRECT *r1, MWRECT *r1End,
			MWRECT *r2, MWRECT *r2End, MWCOORD top, MWCOORD bottom)

{
    MWCOORD       left, right;
    MWRECT      *pNextRect;

    pNextRect = &pReg->rects[pReg->numRects];

    while ((r1 != r1End) && (r2 != r2End))
    {
	left = MWMAX(r1->left, r2->left);
	right =	MWMIN(r1->right, r2->right);

	/*
	 * If there's any overlap between the two rectangles, add that
	 * overlap to the new region.
	 * There's no need to check for subsumption because the only way
	 * such a need could arise is if some region has two rectangles
	 * right next to each other. Since that should never happen...
	 */
	if (left < right)
	{
	    MEMCHECK(pReg, pNextRect, pReg->rects);
	    pNextRect->left = left;
	    pNextRect->top = top;
	    pNextRect->right = right;
	    pNextRect->bottom = bottom;
	    pReg->numRects += 1;
	    pNextRect++;
	}

	/*
	 * Need to advance the pointers. Shift the one that extends
	 * to the right the least, since the other still has a chance to
	 * overlap with that region's next rectangle, if you see what I mean.
	 */
	if (r1->right < r2->right)
	{
	    r1++;
	}
	else if (r2->right < r1->right)
	{
	    r2++;
	}
	else
	{
	    r1++;
	    r2++;
	}
    }
}

/**
 * Finds the intersection of two regions - i.e. the places where
 * they overlap.
 *
 * @param newReg Output region.  May be one of the source regions.
 * @param reg1 Source region.
 * @param reg2 Source region.
 */
void
GdIntersectRegion(MWCLIPREGION *newReg, MWCLIPREGION *reg1, MWCLIPREGION *reg2)
{
   /* check for trivial reject */
    if ( (!(reg1->numRects)) || (!(reg2->numRects))  ||
	(!EXTENTCHECK(&reg1->extents, &reg2->extents)))
	newReg->numRects = 0;
    else
	REGION_RegionOp (newReg, reg1, reg2,  REGION_IntersectO, NULL, NULL);
    
    /*
     * Can't alter newReg's extents before we call miRegionOp because
     * it might be one of the source regions and miRegionOp depends
     * on the extents of those regions being the same. Besides, this
     * way there's no checking against rectangles that will be nuked
     * due to coalescing, so we have to examine fewer rectangles.
     */
    REGION_SetExtents(newReg);
    newReg->type = (newReg->numRects) ? MWREGION_COMPLEX : MWREGION_NULL ;
}

/* *********************************************************************
 *	     Region Union
 ***********************************************************************/

/* *********************************************************************
 *	     REGION_UnionNonO
 *
 *      Handle a non-overlapping band for the union operation. Just
 *      Adds the rectangles into the region. Doesn't have to check for
 *      subsumption or anything.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      pReg->numRects is incremented and the final rectangles overwritten
 *      with the rectangles we're passed.
 *
 */
static void
REGION_UnionNonO(MWCLIPREGION *pReg,MWRECT *r,MWRECT *rEnd,MWCOORD top,
	MWCOORD bottom)
{
    MWRECT *pNextRect;

    pNextRect = &pReg->rects[pReg->numRects];

    while (r != rEnd)
    {
	MEMCHECK(pReg, pNextRect, pReg->rects);
	pNextRect->left = r->left;
	pNextRect->top = top;
	pNextRect->right = r->right;
	pNextRect->bottom = bottom;
	pReg->numRects += 1;
	pNextRect++;
	r++;
    }
}

/* *********************************************************************
 *	     REGION_UnionO
 *
 *      Handle an overlapping band for the union operation. Picks the
 *      left-most rectangle each time and merges it into the region.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      Rectangles are overwritten in pReg->rects and pReg->numRects will
 *      be changed.
 *
 */
static void
REGION_UnionO(MWCLIPREGION *pReg, MWRECT *r1, MWRECT *r1End,
	MWRECT *r2, MWRECT *r2End, MWCOORD top, MWCOORD bottom)
{
    MWRECT *pNextRect;
    
    pNextRect = &pReg->rects[pReg->numRects];

#define MERGERECT(r) \
    if ((pReg->numRects != 0) &&  \
	(pNextRect[-1].top == top) &&  \
	(pNextRect[-1].bottom == bottom) &&  \
	(pNextRect[-1].right >= r->left))  \
    {  \
	if (pNextRect[-1].right < r->right)  \
	{  \
	    pNextRect[-1].right = r->right;  \
	}  \
    }  \
    else  \
    {  \
	MEMCHECK(pReg, pNextRect, pReg->rects);  \
	pNextRect->top = top;  \
	pNextRect->bottom = bottom;  \
	pNextRect->left = r->left;  \
	pNextRect->right = r->right;  \
	pReg->numRects += 1;  \
	pNextRect += 1;  \
    }  \
    r++;
    
    while ((r1 != r1End) && (r2 != r2End))
    {
	if (r1->left < r2->left)
	{
	    MERGERECT(r1);
	}
	else
	{
	    MERGERECT(r2);
	}
    }
    
    if (r1 != r1End)
    {
	do
	{
	    MERGERECT(r1);
	} while (r1 != r1End);
    }
    else while (r2 != r2End)
    {
	MERGERECT(r2);
    }
}

/**
 * Finds the union of two regions - i.e. the places which are
 * in either reg1 or reg2 or both.
 *
 * @param newReg Output region.  May be one of the source regions.
 * @param reg1 Source region.
 * @param reg2 Source region.
 */
void
GdUnionRegion(MWCLIPREGION *newReg, MWCLIPREGION *reg1, MWCLIPREGION *reg2)
{
    /*  checks all the simple cases */

    /*
     * Region 1 and 2 are the same or region 1 is empty
     */
    if ( (reg1 == reg2) || (!(reg1->numRects)) )
    {
	if (newReg != reg2)
	    GdCopyRegion(newReg, reg2);
	return;
    }

    /*
     * if nothing to union (region 2 empty)
     */
    if (!(reg2->numRects))
    {
	if (newReg != reg1)
	    GdCopyRegion(newReg, reg1);
	return;
    }

    /*
     * Region 1 completely subsumes region 2
     */
    if ((reg1->numRects == 1) && 
	(reg1->extents.left <= reg2->extents.left) &&
	(reg1->extents.top <= reg2->extents.top) &&
	(reg1->extents.right >= reg2->extents.right) &&
	(reg1->extents.bottom >= reg2->extents.bottom))
    {
	if (newReg != reg1)
	    GdCopyRegion(newReg, reg1);
	return;
    }

    /*
     * Region 2 completely subsumes region 1
     */
    if ((reg2->numRects == 1) && 
	(reg2->extents.left <= reg1->extents.left) &&
	(reg2->extents.top <= reg1->extents.top) &&
	(reg2->extents.right >= reg1->extents.right) &&
	(reg2->extents.bottom >= reg1->extents.bottom))
    {
	if (newReg != reg2)
	    GdCopyRegion(newReg, reg2);
	return;
    }

	REGION_RegionOp (newReg, reg1, reg2, REGION_UnionO, 
		REGION_UnionNonO, REGION_UnionNonO);

    newReg->extents.left = MWMIN(reg1->extents.left, reg2->extents.left);
    newReg->extents.top = MWMIN(reg1->extents.top, reg2->extents.top);
    newReg->extents.right = MWMAX(reg1->extents.right, reg2->extents.right);
    newReg->extents.bottom = MWMAX(reg1->extents.bottom, reg2->extents.bottom);
    newReg->type = (newReg->numRects) ? MWREGION_COMPLEX : MWREGION_NULL ;
}

/* *********************************************************************
 *	     Region Subtraction
 ***********************************************************************/

/* *********************************************************************
 *	     REGION_SubtractNonO1
 *
 *      Deal with non-overlapping band for subtraction. Any parts from
 *      region 2 we discard. Anything from region 1 we add to the region.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      pReg may be affected.
 *
 */
static void
REGION_SubtractNonO1(MWCLIPREGION *pReg, MWRECT *r, MWRECT *rEnd,
	MWCOORD top, MWCOORD bottom)
{
    MWRECT *pNextRect;
	
    pNextRect = &pReg->rects[pReg->numRects];
	
    while (r != rEnd)
    {
	MEMCHECK(pReg, pNextRect, pReg->rects);
	pNextRect->left = r->left;
	pNextRect->top = top;
	pNextRect->right = r->right;
	pNextRect->bottom = bottom;
	pReg->numRects += 1;
	pNextRect++;
	r++;
    }
}


/* *********************************************************************
 *	     REGION_SubtractO
 *
 *      Overlapping band subtraction. x1 is the left-most point not yet
 *      checked.
 *
 * Results:
 *      None.
 *
 * Side Effects:
 *      pReg may have rectangles added to it.
 *
 */
static void
REGION_SubtractO(MWCLIPREGION *pReg, MWRECT *r1, MWRECT *r1End,
	MWRECT *r2, MWRECT *r2End, MWCOORD top, MWCOORD bottom)
{
    MWRECT *pNextRect;
    MWCOORD left;
    
    left = r1->left;
    pNextRect = &pReg->rects[pReg->numRects];

    while ((r1 != r1End) && (r2 != r2End))
    {
	if (r2->right <= left)
	{
	    /*
	     * Subtrahend missed the boat: go to next subtrahend.
	     */
	    r2++;
	}
	else if (r2->left <= left)
	{
	    /*
	     * Subtrahend preceeds minuend: nuke left edge of minuend.
	     */
	    left = r2->right;
	    if (left >= r1->right)
	    {
		/*
		 * Minuend completely covered: advance to next minuend and
		 * reset left fence to edge of new minuend.
		 */
		r1++;
		if (r1 != r1End)
		    left = r1->left;
	    }
	    else
	    {
		/*
		 * Subtrahend now used up since it doesn't extend beyond
		 * minuend
		 */
		r2++;
	    }
	}
	else if (r2->left < r1->right)
	{
	    /*
	     * Left part of subtrahend covers part of minuend: add uncovered
	     * part of minuend to region and skip to next subtrahend.
	     */
	    MEMCHECK(pReg, pNextRect, pReg->rects);
	    pNextRect->left = left;
	    pNextRect->top = top;
	    pNextRect->right = r2->left;
	    pNextRect->bottom = bottom;
	    pReg->numRects += 1;
	    pNextRect++;
	    left = r2->right;
	    if (left >= r1->right)
	    {
		/*
		 * Minuend used up: advance to new...
		 */
		r1++;
		if (r1 != r1End)
		    left = r1->left;
	    }
	    else
	    {
		/*
		 * Subtrahend used up
		 */
		r2++;
	    }
	}
	else
	{
	    /*
	     * Minuend used up: add any remaining piece before advancing.
	     */
	    if (r1->right > left)
	    {
		MEMCHECK(pReg, pNextRect, pReg->rects);
		pNextRect->left = left;
		pNextRect->top = top;
		pNextRect->right = r1->right;
		pNextRect->bottom = bottom;
		pReg->numRects += 1;
		pNextRect++;
	    }
	    r1++;
	    left = r1->left;
	}
    }

    /*
     * Add remaining minuend rectangles to region.
     */
    while (r1 != r1End)
    {
	MEMCHECK(pReg, pNextRect, pReg->rects);
	pNextRect->left = left;
	pNextRect->top = top;
	pNextRect->right = r1->right;
	pNextRect->bottom = bottom;
	pReg->numRects += 1;
	pNextRect++;
	r1++;
	if (r1 != r1End)
	{
	    left = r1->left;
	}
    }
}
	
/**
 * Finds the difference of two regions (regM - regS) - i.e. the
 * places which are in regM but not regS.
 *
 * @param regD Output (Difference) region.  May be one of the source regions.
 * @param regM Source (Minuend) region - the region to subtract from.
 * @param regS Source (Subtrahend) region - the region we subtract.
 */
void
GdSubtractRegion(MWCLIPREGION *regD, MWCLIPREGION *regM, MWCLIPREGION *regS )
{
   /* check for trivial reject */
    if ( (!(regM->numRects)) || (!(regS->numRects))  ||
	(!EXTENTCHECK(&regM->extents, &regS->extents)) )
    {
	GdCopyRegion(regD, regM);
	return;
    }
 
    REGION_RegionOp (regD, regM, regS, REGION_SubtractO, 
		REGION_SubtractNonO1, NULL);

    /*
     * Can't alter newReg's extents before we call miRegionOp because
     * it might be one of the source regions and miRegionOp depends
     * on the extents of those regions being the unaltered. Besides, this
     * way there's no checking against rectangles that will be nuked
     * due to coalescing, so we have to examine fewer rectangles.
     */
    REGION_SetExtents (regD);
    regD->type = (regD->numRects) ? MWREGION_COMPLEX : MWREGION_NULL ;
}

/**
 * Finds the XOR of two regions - i.e. the places which are
 * in either reg1 or reg2 but not both.
 *
 * @param dr Output region.  May be one of the source regions.
 * @param sra Source region.
 * @param srb Source region.
 */
void
GdXorRegion(MWCLIPREGION *dr, MWCLIPREGION *sra, MWCLIPREGION *srb)
{
    MWCLIPREGION *tra, *trb;

    if ((! (tra = GdAllocRegion())) || (! (trb = GdAllocRegion())))
	return;
    GdSubtractRegion(tra,sra,srb);
    GdSubtractRegion(trb,srb,sra);
    GdUnionRegion(dr,tra,trb);
    GdDestroyRegion(tra);
    GdDestroyRegion(trb);
}

MWCLIPREGION *
GdAllocBitmapRegion(MWIMAGEBITS *bitmap, MWCOORD width,	MWCOORD height)
{
	MWRECT		rect;
	MWIMAGEBITS	bits = bitmap[0];
	MWCLIPREGION *	rgn;
	int 		x, y, inrect = 0, bitnum = 0, i = 0;

	if(!(rgn = GdAllocRegion()))
		return NULL;

	/* Return an empty region if the bitmap is empty. */
	if(!bitmap || !width || !height)
		return rgn;

	for(y = 0; y < height; y++) {
		rect.top = y;
		rect.bottom = y + 1;
		for(x = 0; x < width; x++) {
			if(!bitnum--) {
				bitnum = 15;		/* FIXME no hardcoded bits */
				bits = bitmap[i++];
			}
			if(bits & 0x8000) {
				if(!inrect) {
					inrect = 1;
					rect.left = x;
				}
			} else {
				if(inrect) {
					inrect = 0;
					rect.right = x;
					GdUnionRectWithRegion(&rect, rgn);
				}
			}
			bits <<= 1;
		}
		if(inrect) {
			rect.right = x;
			GdUnionRectWithRegion(&rect, rgn);
		}
		inrect = 0;
		bitnum = 0;
	}

	return rgn;
}

#if 0
/* *********************************************************************
 *            DumpRegion
 *            Outputs the contents of a MWCLIPREGION
 */
void
DumpRegion(MWCLIPREGION *pReg)
{
    MWRECT *pRect, *pRectEnd = pReg->rects + pReg->numRects;

    DPRINTF("Region %p: %d,%d - %d,%d %d rects\n", pReg,
	    pReg->extents.left, pReg->extents.top,
	    pReg->extents.right, pReg->extents.bottom, pReg->numRects);
    for(pRect = pReg->rects; pRect < pRectEnd; pRect++)
        DPRINTF("\t%d,%d - %d,%d\n", pRect->left, pRect->top,
		pRect->right, pRect->bottom);
}
#endif