xref: /AOO41X/main/vcl/source/gdi/regband.cxx (revision 9f62ea84a806e17e6f2bbff75724a7257a0eb5d9)

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 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
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// MARKER(update_precomp.py): autogen include statement, do not remove
#include "precompiled_vcl.hxx"
#include <tools/debug.hxx>
#include <vcl/salbtype.hxx>
#include <vcl/regband.hxx>

#include <algorithm>


// =======================================================================
//
// ImplRegionBand
//
// Jedes Band enthaelt die zwischen der enthaltenen Ober- und Untergrenze
// enthaltenen Rechtecke. Bei den Operationen Union, Intersect, XOr und
// Exclude werden immer Rechtecke der gleichen Hoehe ausgewerte; die
// Grenzen der Baender sind immer so zu waehlen, dasz dies moeglich ist.
//
// Die Rechtecke in den Baendern werden nach Moeglichkeit zusammengefaszt.
//
// Bei der Umwandlung von Polygonen werden alle Punkte des Polygons
// in die einzelnen Baender eingetragen (sie stehen fuer jedes Band als
// Punkte in einer Liste). Nach dem Eintragen der Punkte werden diese
// in Rechtecke umgewandelt und die Liste der Punkte geloescht.
//
// -----------------------------------------------------------------------

ImplRegionBand::ImplRegionBand( long nTop, long nBottom )
{
	// save boundaries
	mnYTop				= nTop;
	mnYBottom			= nBottom;

	// initialize lists
	mpNextBand			= NULL;
	mpPrevBand			= NULL;
	mpFirstSep			= NULL;
	mpFirstBandPoint	= NULL;
	mbTouched			= sal_False;
}

// -----------------------------------------------------------------------

ImplRegionBand::ImplRegionBand(
    const ImplRegionBand& rRegionBand,
    const bool bIgnorePoints)
{
	// copy boundaries
	mnYTop				= rRegionBand.mnYTop;
	mnYBottom			= rRegionBand.mnYBottom;
	mbTouched			= rRegionBand.mbTouched;

	// initialisation
	mpNextBand			= NULL;
	mpPrevBand			= NULL;
	mpFirstSep			= NULL;
	mpFirstBandPoint	= NULL;

	// copy all elements of the list with separations
	ImplRegionBandSep* pNewSep;
	ImplRegionBandSep* pPrevSep = 0;
	ImplRegionBandSep* pSep = rRegionBand.mpFirstSep;
	while ( pSep )
	{
		// create new and copy data
		pNewSep 			= new ImplRegionBandSep;
		pNewSep->mnXLeft	= pSep->mnXLeft;
		pNewSep->mnXRight	= pSep->mnXRight;
		pNewSep->mbRemoved	= pSep->mbRemoved;
		pNewSep->mpNextSep	= NULL;
		if ( pSep == rRegionBand.mpFirstSep )
			mpFirstSep = pNewSep;
		else
			pPrevSep->mpNextSep = pNewSep;

		pPrevSep = pNewSep;
		pSep = pSep->mpNextSep;
	}

    if ( ! bIgnorePoints)
    {
    	// Copy points.
        ImplRegionBandPoint* pPoint = rRegionBand.mpFirstBandPoint;
        ImplRegionBandPoint* pPrevPointCopy = NULL;
        while (pPoint != NULL)
        {
            ImplRegionBandPoint* pPointCopy = new ImplRegionBandPoint();
            pPointCopy->mnX = pPoint->mnX;
            pPointCopy->mnLineId = pPoint->mnLineId;
            pPointCopy->mbEndPoint = pPoint->mbEndPoint;
            pPointCopy->meLineType = pPoint->meLineType;

            if (pPrevPointCopy != NULL)
                pPrevPointCopy->mpNextBandPoint = pPointCopy;
            else
                mpFirstBandPoint = pPointCopy;

            pPrevPointCopy = pPointCopy;
            pPoint = pPoint->mpNextBandPoint;
        }
    }
}

// -----------------------------------------------------------------------

ImplRegionBand::~ImplRegionBand()
{
	DBG_ASSERT( mpFirstBandPoint == NULL, "ImplRegionBand::~ImplRegionBand -> pointlist not empty" );

	// delete elements of the list
	ImplRegionBandSep* pSep = mpFirstSep;
	while ( pSep )
	{
		ImplRegionBandSep* pTempSep = pSep->mpNextSep;
		delete pSep;
		pSep = pTempSep;
	}

	// delete elements of the list
	ImplRegionBandPoint* pPoint = mpFirstBandPoint;
	while ( pPoint )
	{
		ImplRegionBandPoint* pTempPoint = pPoint->mpNextBandPoint;
		delete pPoint;
		pPoint = pTempPoint;
	}
}

// -----------------------------------------------------------------------
//
// generate separations from lines and process union with existing
// separations

void ImplRegionBand::ProcessPoints()
{
	// check Pointlist
	ImplRegionBandPoint* pRegionBandPoint = mpFirstBandPoint;
	while ( pRegionBandPoint )
	{
		// within list?
		if ( pRegionBandPoint && pRegionBandPoint->mpNextBandPoint )
		{
			// start/stop?
			if ( pRegionBandPoint->mbEndPoint && pRegionBandPoint->mpNextBandPoint->mbEndPoint )
			{
				// same direction? -> remove next point!
				if ( pRegionBandPoint->meLineType == pRegionBandPoint->mpNextBandPoint->meLineType )
				{
					ImplRegionBandPoint* pSaveRegionBandPoint = pRegionBandPoint->mpNextBandPoint;
					pRegionBandPoint->mpNextBandPoint = pRegionBandPoint->mpNextBandPoint->mpNextBandPoint;
					delete pSaveRegionBandPoint;
				}
			}
		}

		// continue with next element in the list
		pRegionBandPoint = pRegionBandPoint->mpNextBandPoint;
	}

	pRegionBandPoint = mpFirstBandPoint;
	while ( pRegionBandPoint && pRegionBandPoint->mpNextBandPoint )
	{
		Union( pRegionBandPoint->mnX, pRegionBandPoint->mpNextBandPoint->mnX );

		ImplRegionBandPoint* pNextBandPoint = pRegionBandPoint->mpNextBandPoint->mpNextBandPoint;

		// remove allready processed points
		delete pRegionBandPoint->mpNextBandPoint;
		delete pRegionBandPoint;

		// continue with next element in the list
		pRegionBandPoint = pNextBandPoint;
	}

	// remove last element if necessary
	if ( pRegionBandPoint )
		delete pRegionBandPoint;

	// list is now empty
	mpFirstBandPoint = NULL;
}

// -----------------------------------------------------------------------
//
// generate separations from lines and process union with existing
// separations

sal_Bool ImplRegionBand::InsertPoint( long nX, long nLineId,
								  sal_Bool bEndPoint, LineType eLineType )
{
	if ( !mpFirstBandPoint )
	{
		mpFirstBandPoint				  = new ImplRegionBandPoint;
		mpFirstBandPoint->mnX			  = nX;
		mpFirstBandPoint->mnLineId		  = nLineId;
		mpFirstBandPoint->mbEndPoint	  = bEndPoint;
		mpFirstBandPoint->meLineType	  = eLineType;
		mpFirstBandPoint->mpNextBandPoint = NULL;
		return sal_True;
	}

	// look if line allready touched the band
	ImplRegionBandPoint* pRegionBandPoint = mpFirstBandPoint;
	ImplRegionBandPoint* pLastTestedRegionBandPoint = NULL;
	while( pRegionBandPoint )
	{
		if ( pRegionBandPoint->mnLineId == nLineId )
		{
			if ( bEndPoint )
			{
				if( !pRegionBandPoint->mbEndPoint )
				{
					// remove old band point
					if( !mpFirstBandPoint->mpNextBandPoint )
					{
						// if we've only got one point => replace first point
						pRegionBandPoint->mnX = nX;
						pRegionBandPoint->mbEndPoint = sal_True;
						return sal_True;
					}
					else
					{
						// remove current point
						if( !pLastTestedRegionBandPoint )
						{
							// remove and delete old first point
							ImplRegionBandPoint* pSaveBandPoint = mpFirstBandPoint;
							mpFirstBandPoint = mpFirstBandPoint->mpNextBandPoint;
							delete pSaveBandPoint;
						}
						else
						{
							// remove and delete current band point
							pLastTestedRegionBandPoint->mpNextBandPoint = pRegionBandPoint->mpNextBandPoint;
							delete pRegionBandPoint;
						}

						break;
					}
				}
			}
			else
				return sal_False;
		}

		// use next element
		pLastTestedRegionBandPoint = pRegionBandPoint;
		pRegionBandPoint = pRegionBandPoint->mpNextBandPoint;
	}

	// search appropriate position and insert point into the list
	ImplRegionBandPoint* pNewRegionBandPoint;

	pRegionBandPoint = mpFirstBandPoint;
	pLastTestedRegionBandPoint = NULL;
	while ( pRegionBandPoint )
	{
		// new point completly left? -> insert as first point
		if ( nX <= pRegionBandPoint->mnX )
		{
			pNewRegionBandPoint 					= new ImplRegionBandPoint;
			pNewRegionBandPoint->mnX				= nX;
			pNewRegionBandPoint->mnLineId			= nLineId;
			pNewRegionBandPoint->mbEndPoint 		= bEndPoint;
			pNewRegionBandPoint->meLineType 		= eLineType;
			pNewRegionBandPoint->mpNextBandPoint	= pRegionBandPoint;

			// connections to the new point
			if ( !pLastTestedRegionBandPoint )
				mpFirstBandPoint = pNewRegionBandPoint;
			else
				pLastTestedRegionBandPoint->mpNextBandPoint = pNewRegionBandPoint;

			return sal_True;
		}

		// use next element
		pLastTestedRegionBandPoint = pRegionBandPoint;
		pRegionBandPoint = pRegionBandPoint->mpNextBandPoint;
	}

	// not inserted -> add to the end of the list
	pNewRegionBandPoint 					= new ImplRegionBandPoint;
	pNewRegionBandPoint->mnX				= nX;
	pNewRegionBandPoint->mnLineId			= nLineId;
	pNewRegionBandPoint->mbEndPoint 		= bEndPoint;
	pNewRegionBandPoint->meLineType 		= eLineType;
	pNewRegionBandPoint->mpNextBandPoint	= NULL;

	// connections to the new point
	pLastTestedRegionBandPoint->mpNextBandPoint = pNewRegionBandPoint;

	return sal_True;
}

// -----------------------------------------------------------------------

void ImplRegionBand::MoveX( long nHorzMove )
{
	// move all x-separations
	ImplRegionBandSep* pSep = mpFirstSep;
	while ( pSep )
	{
		pSep->mnXLeft  += nHorzMove;
		pSep->mnXRight += nHorzMove;
		pSep = pSep->mpNextSep;
	}
}

// -----------------------------------------------------------------------

void ImplRegionBand::ScaleX( double fHorzScale )
{
	ImplRegionBandSep* pSep = mpFirstSep;
	while ( pSep )
	{
		pSep->mnXLeft	= FRound( pSep->mnXLeft * fHorzScale );
		pSep->mnXRight	= FRound( pSep->mnXRight * fHorzScale );
		pSep = pSep->mpNextSep;
	}
}

// -----------------------------------------------------------------------
//
// combine overlaping sparations

sal_Bool ImplRegionBand::OptimizeBand()
{
	ImplRegionBandSep* pPrevSep = 0;
	ImplRegionBandSep* pSep = mpFirstSep;
	while ( pSep )
	{
		// remove?
		if ( pSep->mbRemoved || (pSep->mnXRight < pSep->mnXLeft) )
		{
			ImplRegionBandSep* pOldSep = pSep;
			if ( pSep == mpFirstSep )
				mpFirstSep = pSep->mpNextSep;
			else
				pPrevSep->mpNextSep = pSep->mpNextSep;
			pSep = pSep->mpNextSep;
			delete pOldSep;
			continue;
		}

		// overlaping separations? -> combine!
		if ( pSep->mpNextSep )
		{
			if ( (pSep->mnXRight+1) >= pSep->mpNextSep->mnXLeft )
			{
				if ( pSep->mpNextSep->mnXRight > pSep->mnXRight )
					pSep->mnXRight = pSep->mpNextSep->mnXRight;

				ImplRegionBandSep* pOldSep = pSep->mpNextSep;
				pSep->mpNextSep = pOldSep->mpNextSep;
				delete pOldSep;
				continue;
			}
		}

		pPrevSep = pSep;
		pSep = pSep->mpNextSep;
	}

	return sal_True;
}

// -----------------------------------------------------------------------

void ImplRegionBand::Union( long nXLeft, long nXRight )
{
	DBG_ASSERT( nXLeft <= nXRight, "ImplRegionBand::Union(): nxLeft > nXRight" );

	// band empty? -> add element
	if ( !mpFirstSep )
	{
		mpFirstSep				= new ImplRegionBandSep;
		mpFirstSep->mnXLeft 	= nXLeft;
		mpFirstSep->mnXRight	= nXRight;
		mpFirstSep->mbRemoved	= sal_False;
		mpFirstSep->mpNextSep	= NULL;
		return;
	}

	// process real union
	ImplRegionBandSep* pNewSep;
	ImplRegionBandSep* pPrevSep = 0;
	ImplRegionBandSep* pSep = mpFirstSep;
	while ( pSep )
	{
		// new separation completely inside? nothing to do!
		if ( (nXLeft >= pSep->mnXLeft) && (nXRight <= pSep->mnXRight) )
			return;

		// new separation completly left? -> new separation!
		if ( nXRight < pSep->mnXLeft )
		{
			pNewSep 			= new ImplRegionBandSep;
			pNewSep->mnXLeft	= nXLeft;
			pNewSep->mnXRight	= nXRight;
			pNewSep->mbRemoved	= sal_False;

			pNewSep->mpNextSep = pSep;
			if ( pSep == mpFirstSep )
				mpFirstSep = pNewSep;
			else
				pPrevSep->mpNextSep = pNewSep;
			break;
		}

		// new separation overlaping from left? -> extend boundary
		if ( (nXRight >= pSep->mnXLeft) && (nXLeft <= pSep->mnXLeft) )
			pSep->mnXLeft = nXLeft;

		// new separation overlaping from right? -> extend boundary
		if ( (nXLeft <= pSep->mnXRight) && (nXRight > pSep->mnXRight) )
		{
			pSep->mnXRight = nXRight;
			break;
		}

		// not inserted, but last element? -> add to the end of the list
		if ( !pSep->mpNextSep && (nXLeft > pSep->mnXRight) )
		{
			pNewSep 			= new ImplRegionBandSep;
			pNewSep->mnXLeft	= nXLeft;
			pNewSep->mnXRight	= nXRight;
			pNewSep->mbRemoved	= sal_False;

			pSep->mpNextSep 	= pNewSep;
			pNewSep->mpNextSep	= NULL;
			break;
		}

		pPrevSep = pSep;
		pSep = pSep->mpNextSep;
	}

	OptimizeBand();
}

// -----------------------------------------------------------------------

void ImplRegionBand::Intersect( long nXLeft, long nXRight )
{
	DBG_ASSERT( nXLeft <= nXRight, "ImplRegionBand::Intersect(): nxLeft > nXRight" );

	// band has been touched
	mbTouched = sal_True;

	// band empty? -> nothing to do
	if ( !mpFirstSep )
		return;

	// process real intersection
	ImplRegionBandSep* pSep = mpFirstSep;
	while ( pSep )
	{
		// new separation completly outside? -> remove separation
		if ( (nXRight < pSep->mnXLeft) || (nXLeft > pSep->mnXRight) )
			// will be removed from the optimizer
			pSep->mbRemoved = sal_True;

		// new separation overlaping from left? -> reduce right boundary
		if ( (nXLeft <= pSep->mnXLeft) &&
			 (nXRight <= pSep->mnXRight) &&
			 (nXRight >= pSep->mnXLeft) )
			pSep->mnXRight = nXRight;

		// new separation overlaping from right? -> reduce right boundary
		if ( (nXLeft >= pSep->mnXLeft) &&
			 (nXLeft <= pSep->mnXRight) &&
			 (nXRight >= pSep->mnXRight) )
			pSep->mnXLeft = nXLeft;

		// new separation within the actual one? -> reduce both boundaries
		if ( (nXLeft >= pSep->mnXLeft) && (nXRight <= pSep->mnXRight) )
		{
			pSep->mnXRight = nXRight;
			pSep->mnXLeft = nXLeft;
		}

		pSep = pSep->mpNextSep;
	}

	OptimizeBand();
}

// -----------------------------------------------------------------------

void ImplRegionBand::Exclude( long nXLeft, long nXRight )
{
	DBG_ASSERT( nXLeft <= nXRight, "ImplRegionBand::Exclude(): nxLeft > nXRight" );

	// band has been touched
	mbTouched = sal_True;

	// band empty? -> nothing to do
	if ( !mpFirstSep )
		return;

	// process real exclusion
	ImplRegionBandSep* pNewSep;
	ImplRegionBandSep* pPrevSep = 0;
	ImplRegionBandSep* pSep = mpFirstSep;
	while ( pSep  )
	{
		sal_Bool bSepProcessed = sal_False;

		// new separation completely overlapping? -> remove separation
		if ( (nXLeft <= pSep->mnXLeft) && (nXRight >= pSep->mnXRight) )
		{
			// will be removed from the optimizer
			pSep->mbRemoved = sal_True;
			bSepProcessed = sal_True;
		}

		// new separation overlaping from left? -> reduce boundary
		if ( !bSepProcessed )
		{
			if ( (nXRight >= pSep->mnXLeft) && (nXLeft <= pSep->mnXLeft) )
			{
				pSep->mnXLeft = nXRight+1;
				bSepProcessed = sal_True;
			}
		}

		// new separation overlaping from right? -> reduce boundary
		if ( !bSepProcessed )
		{
			if ( (nXLeft <= pSep->mnXRight) && (nXRight > pSep->mnXRight) )
			{
				pSep->mnXRight = nXLeft-1;
				bSepProcessed = sal_True;
			}
		}

		// new separation within the actual one? -> reduce boundary
		// and add new entry for reminder
		if ( !bSepProcessed )
		{
			if ( (nXLeft >= pSep->mnXLeft) && (nXRight <= pSep->mnXRight) )
			{
				pNewSep 			= new ImplRegionBandSep;
				pNewSep->mnXLeft	= pSep->mnXLeft;
				pNewSep->mnXRight	= nXLeft-1;
				pNewSep->mbRemoved	= sal_False;

				pSep->mnXLeft = nXRight+1;

				// connections from the new separation
				pNewSep->mpNextSep = pSep;

				// connections to the new separation
				if ( pSep == mpFirstSep )
					mpFirstSep = pNewSep;
				else
					pPrevSep->mpNextSep = pNewSep;
			}
		}

		pPrevSep = pSep;
		pSep = pSep->mpNextSep;
	}

	OptimizeBand();
}

// -----------------------------------------------------------------------

void ImplRegionBand::XOr( long nXLeft, long nXRight )
{
	DBG_ASSERT( nXLeft <= nXRight, "ImplRegionBand::XOr(): nxLeft > nXRight" );

    // #i46602# Reworked rectangle Xor
    //
    // In general, we can distinguish 11 cases of intersection
    // (details below). The old implementation explicitely handled 7
    // cases (numbered in the order of appearance, use CVS to get your
    // hands on the old version), therefore, I've sticked to that
    // order, and added four more cases. The code below references
    // those numbers via #1, #2, etc.
    //
    // Num Mnem        newX:oldX newY:oldY  Description                                             Result			Can quit?
    //
    // #1  Empty band      -         -      The band is empty, thus, simply add new bandSep         just add		Yes
    //
    // #2  apart           -         -      The rectangles are disjunct, add new one as is          just add		Yes
    //
    // #3  atop            ==        ==     The rectangles are _exactly_ the same, remove existing  just remove		Yes
    //
    // #4  around          <         >      The new rectangle extends the old to both sides         intersect		No
    //
    // #5  left            <         <      The new rectangle is left of the old (but intersects)   intersect		Yes
    //
    // #5b left-atop       <         ==     The new is left of the old, and coincides on the right  intersect		Yes
    //
    // #6  right           >         >      The new is right of the old (but intersects)			intersect		No
    //
    // #6b right-atop      ==        >      The new is right of the old, and coincides on the left	intersect		No
    //
    // #7 inside           >         <      The new is fully inside the old							intersect		Yes
    //
    // #8 inside-right     >         ==     The new is fully inside the old, coincides on the right	intersect		Yes
    //
    // #9 inside-left      ==        <      The new is fully inside the old, coincides on the left	intersect		Yes
    //
    //
    // Then, to correctly perform XOr, the segment that's switched off
    // (i.e. the overlapping part of the old and the new segment) must
    // be extended by one pixel value at each border:
    //           1   1
    // 0   4     0   4
    // 111100000001111
    //
    // Clearly, the leading band sep now goes from 0 to 3, and the
    // trailing band sep from 11 to 14. This mimicks the xor look of a
    // bitmap operation.
    //

	// band empty? -> add element
	if ( !mpFirstSep )
	{
		mpFirstSep				= new ImplRegionBandSep;
		mpFirstSep->mnXLeft 	= nXLeft;
		mpFirstSep->mnXRight	= nXRight;
		mpFirstSep->mbRemoved	= sal_False;
		mpFirstSep->mpNextSep	= NULL;
		return;
	}

	// process real xor
	ImplRegionBandSep* pNewSep;
	ImplRegionBandSep* pPrevSep = 0;
	ImplRegionBandSep* pSep = mpFirstSep;

    while ( pSep  )
    {
        long nOldLeft( pSep->mnXLeft );
        long nOldRight( pSep->mnXRight );

        // did the current segment actually touch the new rect? If
        // not, skip all comparisons, go on, loop and try to find
        // intersecting bandSep
        if( nXLeft <= nOldRight )
        {
            if( nXRight < nOldLeft )
            {
                // #2

                // add _before_ current bandSep
                pNewSep             = new ImplRegionBandSep;
                pNewSep->mnXLeft    = nXLeft;
                pNewSep->mnXRight   = nXRight;
                pNewSep->mpNextSep  = pSep;
                pNewSep->mbRemoved  = sal_False;

                // connections from the new separation
                pNewSep->mpNextSep = pSep;

                // connections to the new separation
                if ( pSep == mpFirstSep )
                    mpFirstSep = pNewSep;
                else
                    pPrevSep->mpNextSep = pNewSep;
                pPrevSep = NULL; // do not run accidentally into the "right" case when breaking the loop
                break;
            }
            else if( nXLeft == nOldLeft && nXRight == nOldRight )
            {
                // #3
                pSep->mbRemoved = sal_True;
                pPrevSep = NULL; // do not run accidentally into the "right" case when breaking the loop
                break;
            }
            else if( nXLeft != nOldLeft && nXRight == nOldRight )
            {
                // # 5b, 8
                if( nXLeft < nOldLeft )
                {
                    nXRight = nOldLeft; // 5b
                }
                else
                {
                    nXRight = nXLeft; // 8
                    nXLeft = nOldLeft;
                }

                pSep->mnXLeft = nXLeft;
                pSep->mnXRight = nXRight-1;

                pPrevSep = NULL; // do not run accidentally into the "right" case when breaking the loop
                break;
            }
            else if( nXLeft == nOldLeft && nXRight != nOldRight )
            {
                // # 6b, 9

                if( nXRight > nOldRight )
                {
                    nXLeft = nOldRight+1; // 6b

                    // cannot break here, simply mark segment as removed,
                    // and go on with adapted nXLeft/nXRight
                    pSep->mbRemoved = sal_True;
                }
                else
                {
                    pSep->mnXLeft = nXRight+1; // 9

                    pPrevSep = NULL; // do not run accidentally into the "right" case when breaking the loop
                    break;
                }
            }
            else // if( nXLeft != nOldLeft && nXRight != nOldRight ) follows automatically
            {
                // #4,5,6,7
                DBG_ASSERT( nXLeft != nOldLeft && nXRight != nOldRight,
                            "ImplRegionBand::XOr(): Case 4,5,6,7 expected all coordinates to be not equal!" );

                // The plain-jane check would look like this:
                //
                // if( nXLeft < nOldLeft )
                // {
                //     // #4,5
                //     if( nXRight > nOldRight )
                //     {
                //        // #4
                //     }
                //     else
                //     {
                //         // #5 done!
                //     }
                // }
                // else
                // {
                //     // #6,7
                //     if( nXRight > nOldRight )
                //     {
                //         // #6
                //     }
                //     else
                //     {
                //         // #7 done!
                //     }
                // }
                //
                // but since we generally don't have to care whether
                // it's 4 or 6 (only that we must not stop processing
                // here), condensed that in such a way that only the
                // coordinates get shuffled into correct ordering.

                if( nXLeft < nOldLeft )
                    ::std::swap( nOldLeft, nXLeft );

                bool bDone( false );

                if( nXRight < nOldRight )
                {
                    ::std::swap( nOldRight, nXRight );
                    bDone = true;
                }

                // now, nOldLeft<nXLeft<=nOldRight<nXRight always
                // holds. Note that we need the nXLeft<=nOldRight here, as
                // the intersection part might be only one pixel (original
                // nXLeft==nXRight)
                DBG_ASSERT( nOldLeft<nXLeft && nXLeft<=nOldRight && nOldRight<nXRight,
                            "ImplRegionBand::XOr(): Case 4,5,6,7 expected coordinates to be ordered now!" );

                pSep->mnXLeft = nOldLeft;
                pSep->mnXRight = nXLeft-1;

                nXLeft = nOldRight+1;
                // nxRight is already setup correctly

                if( bDone )
                {
                    // add behind current bandSep
                    pNewSep = new ImplRegionBandSep;

                    pNewSep->mnXLeft    = nXLeft;
                    pNewSep->mnXRight   = nXRight;
                    pNewSep->mpNextSep  = pSep->mpNextSep;
                    pNewSep->mbRemoved  = sal_False;

                    // connections from the new separation
                    pSep->mpNextSep = pNewSep;

                    pPrevSep = NULL; // do not run accidentally into the "right" case when breaking the loop
                    break;
                }
            }
        }

        pPrevSep = pSep;
        pSep = pSep->mpNextSep;
    }

    // new separation completely right of existing bandSeps ?
    if( pPrevSep && nXLeft >= pPrevSep->mnXRight )
    {
        pNewSep             = new ImplRegionBandSep;
        pNewSep->mnXLeft    = nXLeft;
        pNewSep->mnXRight   = nXRight;
        pNewSep->mpNextSep  = NULL;
        pNewSep->mbRemoved  = sal_False;

        // connections from the new separation
        pPrevSep->mpNextSep = pNewSep;
    }

	OptimizeBand();
}

// -----------------------------------------------------------------------

sal_Bool ImplRegionBand::IsInside( long nX )
{
	ImplRegionBandSep* pSep = mpFirstSep;
	while ( pSep )
	{
		if ( (pSep->mnXLeft <= nX) && (pSep->mnXRight >= nX) )
			return sal_True;

		pSep = pSep->mpNextSep;
	}

	return sal_False;
}

// -----------------------------------------------------------------------

sal_Bool ImplRegionBand::IsOver( long nLeft, long nRight )
{
	ImplRegionBandSep* pSep = mpFirstSep;
	while ( pSep )
	{
		if ( (pSep->mnXLeft < nRight) && (pSep->mnXRight > nLeft) )
			return sal_True;

		pSep = pSep->mpNextSep;
	}

	return sal_False;
}

// -----------------------------------------------------------------------

sal_Bool ImplRegionBand::IsInside( long nLeft, long nRight )
{
	ImplRegionBandSep* pSep = mpFirstSep;
	while ( pSep )
	{
		if ( (pSep->mnXLeft >= nLeft) && (nRight <= pSep->mnXRight) )
			return sal_True;

		pSep = pSep->mpNextSep;
	}

	return sal_False;
}

// -----------------------------------------------------------------------

long ImplRegionBand::GetXLeftBoundary() const
{
	DBG_ASSERT( mpFirstSep != NULL, "ImplRegionBand::XLeftBoundary -> no separation in band!" );

	return mpFirstSep->mnXLeft;
}

// -----------------------------------------------------------------------

long ImplRegionBand::GetXRightBoundary() const
{
	DBG_ASSERT( mpFirstSep != NULL, "ImplRegionBand::XRightBoundary -> no separation in band!" );

	// search last separation
	ImplRegionBandSep* pSep = mpFirstSep;
	while ( pSep->mpNextSep )
		pSep = pSep->mpNextSep;
	return pSep->mnXRight;
}

// -----------------------------------------------------------------------

sal_Bool ImplRegionBand::operator==( const ImplRegionBand& rRegionBand ) const
{
	ImplRegionBandSep*	 pOwnRectBandSep = mpFirstSep;
	ImplRegionBandSep*	 pSecondRectBandSep = rRegionBand.mpFirstSep;
	while ( pOwnRectBandSep && pSecondRectBandSep )
	{
		// get boundaries of current rectangle
		long nOwnXLeft = pOwnRectBandSep->mnXLeft;
		long nSecondXLeft = pSecondRectBandSep->mnXLeft;
		if ( nOwnXLeft != nSecondXLeft )
			return sal_False;

		long nOwnXRight = pOwnRectBandSep->mnXRight;
		long nSecondXRight = pSecondRectBandSep->mnXRight;
		if ( nOwnXRight != nSecondXRight )
			return sal_False;

		// get next separation from current band
		pOwnRectBandSep = pOwnRectBandSep->mpNextSep;

		// get next separation from current band
		pSecondRectBandSep = pSecondRectBandSep->mpNextSep;
	}

	// differnt number of separations?
	if ( pOwnRectBandSep || pSecondRectBandSep )
		return sal_False;

	return sal_True;
}

// -----------------------------------------------------------------------

ImplRegionBand* ImplRegionBand::SplitBand (const sal_Int32 nY)
{
    OSL_ASSERT(nY>mnYTop);
    OSL_ASSERT(nY<=mnYBottom);

    // Create a copy of the given band (we tell the constructor to copy the points together
    // with the seps.)
    ImplRegionBand* pLowerBand = new ImplRegionBand(*this, false);

    // Adapt vertical coordinates.
    mnYBottom = nY-1;
    pLowerBand->mnYTop = nY;

    // Insert new band into list of bands.
    pLowerBand->mpNextBand = mpNextBand;
    mpNextBand = pLowerBand;
    pLowerBand->mpPrevBand = this;
    if (pLowerBand->mpNextBand != NULL)
        pLowerBand->mpNextBand->mpPrevBand = pLowerBand;

    return pLowerBand;
}