region.c

realvnc是一个非常流行的远程控制程序

    {
        miRegionCopy(newReg, reg1);
        return TRUE;
    }

    /*   could put an extent check to see if add above or below */

    if ((reg1->extents.y1 >= reg2->extents.y2) ||
        (reg2->extents.y1 >= reg1->extents.y2) )
    {
        combineRegs(newReg, reg1, reg2);
        return TRUE;
    }
    return FALSE;
}

/*   TopRects(rects, reg1, reg2)
 * N.B. We now assume that reg1 and reg2 intersect.  Therefore we are
 * NOT checking in the two while loops for stepping off the end of the
 * region.  
 */ 

static int
TopRects(newReg, rects, reg1, reg2, FirstRect)
    register XRegion newReg;
    register BOX *rects;
    register XRegion reg1;
    register XRegion reg2; 
    BOX *FirstRect;
{
    register BOX *tempRects;

    /*  need to add some rects from region 1 */
    if (reg1->extents.y1 < reg2->extents.y1)
    {
        tempRects = reg1->rects;
        while(tempRects->y1 < reg2->extents.y1)
	{
	    MEMCHECK(newReg, rects, FirstRect);
            ADDRECTNOX(newReg,rects, tempRects->x1, tempRects->y1, 
		       tempRects->x2, MIN(tempRects->y2, reg2->extents.y1));
            tempRects++;
	}
    }
    /*  need to add some rects from region 2 */
    if (reg2->extents.y1 < reg1->extents.y1)
    {
        tempRects = reg2->rects;
        while (tempRects->y1 < reg1->extents.y1)
        {
            MEMCHECK(newReg, rects, FirstRect);
            ADDRECTNOX(newReg, rects, tempRects->x1,tempRects->y1, 
		       tempRects->x2, MIN(tempRects->y2, reg1->extents.y1));
            tempRects++;
	}
    }
    return 1;
}
#endif

/*======================================================================
 *	    Generic Region Operator
 *====================================================================*/

/*-
 *-----------------------------------------------------------------------
 * miCoalesce --
 *	Attempt to merge the boxes in the current band with those in the
 *	previous one. Used only by miRegionOp.
 *
 * Results:
 *	The new index for the previous band.
 *
 * Side Effects:
 *	If coalescing takes place:
 *	    - rectangles in the previous band will have their y2 fields
 *	      altered.
 *	    - pReg->numRects will be decreased.
 *
 *-----------------------------------------------------------------------
 */
/* static int*/
static int
miCoalesce (pReg, prevStart, curStart)
    register XRegion	pReg;	    	/* Region to coalesce */
    int	    	  	prevStart;  	/* Index of start of previous band */
    int	    	  	curStart;   	/* Index of start of current band */
{
    register BoxPtr	pPrevBox;   	/* Current box in previous band */
    register BoxPtr	pCurBox;    	/* Current box in current band */
    register BoxPtr	pRegEnd;    	/* End of region */
    int	    	  	curNumRects;	/* Number of rectangles in current
					 * band */
    int	    	  	prevNumRects;	/* Number of rectangles in previous
					 * band */
    int	    	  	bandY1;	    	/* Y1 coordinate for current band */

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

    pPrevBox = &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 miRegionOp
     * at the end when one region has been exhausted.
     */
    pCurBox = &pReg->rects[curStart];
    bandY1 = pCurBox->y1;
    for (curNumRects = 0;
	 (pCurBox != pRegEnd) && (pCurBox->y1 == bandY1);
	 curNumRects++)
    {
	pCurBox++;
    }
    
    if (pCurBox != 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].y1 == pRegEnd->y1)
	{
	    pRegEnd--;
	}
	curStart = pRegEnd - pReg->rects;
	pRegEnd = pReg->rects + pReg->numRects;
    }
	
    if ((curNumRects == prevNumRects) && (curNumRects != 0)) {
	pCurBox -= curNumRects;
	/*
	 * The bands may only be coalesced if the bottom of the previous
	 * matches the top scanline of the current.
	 */
	if (pPrevBox->y2 == pCurBox->y1)
	{
	    /*
	     * Make sure the bands have boxes in the same places. This
	     * assumes that boxes have been added in such a way that they
	     * cover the most area possible. I.e. two boxes in a band must
	     * have some horizontal space between them.
	     */
	    do
	    {
		if ((pPrevBox->x1 != pCurBox->x1) ||
		    (pPrevBox->x2 != pCurBox->x2))
		{
		    /*
		     * The bands don't line up so they can't be coalesced.
		     */
		    return (curStart);
		}
		pPrevBox++;
		pCurBox++;
		prevNumRects -= 1;
	    } while (prevNumRects != 0);

	    pReg->numRects -= curNumRects;
	    pCurBox -= curNumRects;
	    pPrevBox -= curNumRects;

	    /*
	     * The bands may be merged, so set the bottom y of each box
	     * in the previous band to that of the corresponding box in
	     * the current band.
	     */
	    do
	    {
		pPrevBox->y2 = pCurBox->y2;
		pPrevBox++;
		pCurBox++;
		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 (pCurBox == pRegEnd)
	    {
		curStart = prevStart;
	    }
	    else
	    {
		do
		{
		    *pPrevBox++ = *pCurBox++;
		} while (pCurBox != pRegEnd);
	    }
	    
	}
    }
    return (curStart);
}

/*-
 *-----------------------------------------------------------------------
 * miRegionOp --
 *	Apply an operation to two regions. Called by miUnion, miInverse,
 *	miSubtract, miIntersect...
 *
 * 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*/
static void
miRegionOp(newReg, reg1, reg2, overlapFunc,  nonOverlap1Func, nonOverlap2Func)
    register XRegion 	newReg;	    	    	/* Place to store result */
    XRegion	  	reg1;	    	    	/* First region in operation */
    XRegion	  	reg2;	    	    	/* 2d region in operation */
    void    	  	(*overlapFunc)();   	/* Function to call for over-
						 * lapping bands */
    void    	  	(*nonOverlap1Func)();	/* Function to call for non-
						 * overlapping bands in region
						 * 1 */
    void    	  	(*nonOverlap2Func)();	/* Function to call for non-
						 * overlapping bands in region
						 * 2 */
{
    register BoxPtr	r1; 	    	    	/* Pointer into first region */
    register BoxPtr	r2; 	    	    	/* Pointer into 2d region */
    BoxPtr  	  	r1End;	    	    	/* End of 1st region */
    BoxPtr  	  	r2End;	    	    	/* End of 2d region */
    register short  	ybot;	    	    	/* Bottom of intersection */
    register short  	ytop;	    	    	/* Top of intersection */
    BoxPtr  	  	oldRects;   	    	/* Old rects for newReg */
    int	    	  	prevBand;   	    	/* Index of start of
						 * previous band in newReg */
    int	    	  	curBand;    	    	/* Index of start of current
						 * band in newReg */
    register BoxPtr 	r1BandEnd;  	    	/* End of current band in r1 */
    register BoxPtr 	r2BandEnd;  	    	/* End of current band in r2 */
    short     	  	top;	    	    	/* Top of non-overlapping
						 * band */
    short     	  	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;
    
    oldRects = newReg->rects;
    
    EMPTY_REGION(newReg);

    /*
     * 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 Xrealloc() at the end of this function eventually.
     */
    newReg->size = max(reg1->numRects,reg2->numRects) * 2;

    if (! (newReg->rects = (BoxPtr)
	   Xmalloc ((unsigned) (sizeof(BoxRec) * 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.y1 < reg2->extents.y1)
	ybot = reg1->extents.y1;
    else
	ybot = reg2->extents.y1;
    
    /*
     * 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->y1 == r1->y1))
	{
	    r1BandEnd++;
	}
	
	r2BandEnd = r2;
	while ((r2BandEnd != r2End) && (r2BandEnd->y1 == r2->y1))
	{
	    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->y1 < r2->y1)
	{
	    top = max(r1->y1,ybot);
	    bot = min(r1->y2,r2->y1);

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

	    ytop = r2->y1;
	}
	else if (r2->y1 < r1->y1)
	{
	    top = max(r2->y1,ybot);
	    bot = min(r2->y2,r1->y1);

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

	    ytop = r1->y1;
	}
	else
	{
	    ytop = r1->y1;
	}

	/*
	 * 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 = miCoalesce (newReg, prevBand, curBand);
	}

	/*
	 * Now see if we've hit an intersecting band. The two bands only
	 * intersect if ybot > ytop
	 */
	ybot = min(r1->y2, r2->y2);
	curBand = newReg->numRects;
	if (ybot > ytop)
	{
	    (* overlapFunc) (newReg, r1, r1BandEnd, r2, r2BandEnd, ytop, ybot);

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

	/*
	 * If we've finished with a band (y2 == ybot) we skip forward
	 * in the region to the next band.
	 */
	if (r1->y2 == ybot)
	{
	    r1 = r1BandEnd;
	}
	if (r2->y2 == ybot)
	{
	    r2 = r2BandEnd;
	}
    } while ((r1 != r1End) && (r2 != r2End));

    /*
     * Deal with whichever region still has rectangles left.
     */
    curBand = newReg->numRects;
    if (r1 != r1End)
    {
	if (nonOverlap1Func != (void (*)())NULL)
	{
	    do
	    {
		r1BandEnd = r1;
		while ((r1BandEnd < r1End) && (r1BandEnd->y1 == r1->y1))
		{
		    r1BandEnd++;
		}
		(* nonOverlap1Func) (newReg, r1, r1BandEnd,
				     max(r1->y1,ybot), r1->y2);
		r1 = r1BandEnd;
	    } while (r1 != r1End);
	}
    }
    else if ((r2 != r2End) && (nonOverlap2Func != (void (*)())NULL))
    {
	do
	{
	    r2BandEnd = r2;
	    while ((r2BandEnd < r2End) && (r2BandEnd->y1 == r2->y1))
	    {
		 r2BandEnd++;
	    }
	    (* nonOverlap2Func) (newReg, r2, r2BandEnd,
				max(r2->y1,ybot), r2->y2);
	    r2 = r2BandEnd;
	} while (r2 != r2End);
    }

    if (newReg->numRects != curBand)
    {
	(void) miCoalesce (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))
	{
	    BoxPtr prev_rects = newReg->rects;
	    newReg->size = newReg->numRects;
	    newReg->rects = (BoxPtr) Xrealloc ((char *) newReg->rects,
				   (unsigned) (sizeof(BoxRec) * newReg->size));
	    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;
	    Xfree((char *) newReg->rects);
	    newReg->rects = (BoxPtr) Xmalloc(sizeof(BoxRec));
	}
    }
    Xfree ((char *) oldRects);
    return;
}

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

/*-
 *-----------------------------------------------------------------------
 * miUnionNonO --
 *	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*/
static int
miUnionNonO (pReg, r, rEnd, y1, y2)
    register XRegion	pReg;
    register BoxPtr	r;
    BoxPtr  	  	rEnd;
    register short  	y1;
    register short  	y2;
{
    register BoxPtr	pNextRect;

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

    assert(y1 < y2);

    while (r != rEnd)
    {
	assert(r->x1 < r->x2);
	MEMCHECK(pReg, pNextRect, pReg->rects);
	pNextRect->x1 = r->x1;
	pNextRect->y1 = y1;
	pNextRect->x2 = r->x2;
	pNextRect->y2 = y2;
	pReg->numRects += 1;
	pNextRect++;

	assert(pReg->numRects<=pReg->size);
	r++;
    }