/************************************************************************* * * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * Copyright 2008 by Sun Microsystems, Inc. * * OpenOffice.org - a multi-platform office productivity suite * * $RCSfile: b2dmultirange.cxx,v $ * $Revision: 1.8 $ * * This file is part of OpenOffice.org. * * OpenOffice.org is free software: you can redistribute it and/or modify * it under the terms of the GNU Lesser General Public License version 3 * only, as published by the Free Software Foundation. * * OpenOffice.org is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU Lesser General Public License version 3 for more details * (a copy is included in the LICENSE file that accompanied this code). * * You should have received a copy of the GNU Lesser General Public License * version 3 along with OpenOffice.org. If not, see * * for a copy of the LGPLv3 License. * ************************************************************************/ // MARKER(update_precomp.py): autogen include statement, do not remove #include "precompiled_basegfx.hxx" #include #include #include #include #include #include #include #include #include #include #include #include #include namespace basegfx { namespace { // Generating a poly-polygon from a bunch of rectangles // // Helper functionality for sweep-line algorithm // ==================================================== typedef std::vector VectorOfRanges; class ImplPolygon; typedef o3tl::vector_pool VectorOfPolygons; /** This class represents an active edge As the sweep line traverses across the overall area, rectangle edges parallel to it generate events, and rectangle edges orthogonal to it generate active edges. This class represents the latter. */ class ActiveEdge { public: /** The two possible active rectangle edges differ by one coordinate value - the upper edge has the lower, the lower edge the higher value. */ enum EdgeType { /// edge with lower coordinate value UPPER=0, /// edge with higher coordinate value LOWER=1 }; enum EdgeDirection { /// edge proceeds to the left PROCEED_LEFT=0, /// edge proceeds to the right PROCEED_RIGHT=1 }; /** Create active edge @param rRect Rectangle this edge is part of @param fInvariantCoord The invariant ccordinate value of this edge @param eEdgeType Is fInvariantCoord the lower or the higher value, for this rect? */ ActiveEdge( const B2DRectangle& rRect, const double& fInvariantCoord, std::ptrdiff_t nPolyIdx, EdgeType eEdgeType, EdgeDirection eEdgeDirection ) : mfInvariantCoord(fInvariantCoord), mpAssociatedRect( &rRect ), mnPolygonIdx( nPolyIdx ), meEdgeType( eEdgeType ), meEdgeDirection( eEdgeDirection ) {} double getInvariantCoord() const { return mfInvariantCoord; } const B2DRectangle& getRect() const { return *mpAssociatedRect; } std::ptrdiff_t getTargetPolygonIndex() const { return mnPolygonIdx; } void setTargetPolygonIndex( std::ptrdiff_t nIdx ) { mnPolygonIdx = nIdx; } EdgeType getEdgeType() const { return meEdgeType; } EdgeDirection getEdgeDirection() const { return meEdgeDirection; } /// For STL sort bool operator<( const ActiveEdge& rRHS ) const { return mfInvariantCoord < rRHS.mfInvariantCoord; } private: /** The invariant coordinate value of this edge (e.g. the common y value, for a horizontal edge) */ double mfInvariantCoord; /** Associated rectangle This on the one hand saves some storage space (the vector of rectangles is persistent, anyway), and on the other hand provides an identifier to match active edges and x events (see below) Ptr because class needs to be assignable */ const B2DRectangle* mpAssociatedRect; /** Index of the polygon this edge is currently involved with. Note that this can change for some kinds of edge intersection, as the algorithm tends to swap associated polygons there. -1 denotes no assigned polygon */ std::ptrdiff_t mnPolygonIdx; /// 'upper' or 'lower' edge of original rectangle. EdgeType meEdgeType; /// 'left' or 'right' EdgeDirection meEdgeDirection; }; // Needs to be list - various places hold ptrs to elements typedef std::list< ActiveEdge > ListOfEdges; /** Element of the sweep line event list As the sweep line traverses across the overall area, rectangle edges parallel to it generate events, and rectangle edges orthogonal to it generate active edges. This class represents the former. The class defines an element of the sweep line list. The sweep line's position jumps in steps defined by the coordinates of the sorted SweepLineEvent entries. */ class SweepLineEvent { public: /** The two possible sweep line rectangle edges differ by one coordinate value - the starting edge has the lower, the finishing edge the higher value. */ enum EdgeType { /// edge with lower coordinate value STARTING_EDGE=0, /// edge with higher coordinate value FINISHING_EDGE=1 }; /** The two possible sweep line directions */ enum EdgeDirection { PROCEED_UP=0, PROCEED_DOWN=1 }; /** Create sweep line event @param fPos Coordinate position of the event @param rRect Rectangle this event is generated for. @param eEdgeType Is fPos the lower or the higher value, for the rectangle this event is generated for? */ SweepLineEvent( double fPos, const B2DRectangle& rRect, EdgeType eEdgeType, EdgeDirection eDirection) : mfPos( fPos ), mpAssociatedRect( &rRect ), meEdgeType( eEdgeType ), meEdgeDirection( eDirection ) {} double getPos() const { return mfPos; } const B2DRectangle& getRect() const { return *mpAssociatedRect; } EdgeType getEdgeType() const { return meEdgeType; } EdgeDirection getEdgeDirection() const { return meEdgeDirection; } /// For STL sort bool operator<( const SweepLineEvent& rRHS ) const { return mfPos < rRHS.mfPos; } private: /// position of the event, in the direction of the line sweep double mfPos; /** Rectangle this event is generated for This on the one hand saves some storage space (the vector of rectangles is persistent, anyway), and on the other hand provides an identifier to match active edges and events (see below) Ptr because class needs to be assignable */ const B2DRectangle* mpAssociatedRect; /// 'upper' or 'lower' edge of original rectangle. EdgeType meEdgeType; /// 'up' or 'down' EdgeDirection meEdgeDirection; }; typedef std::vector< SweepLineEvent > VectorOfEvents; /** Smart point container for B2DMultiRange::getPolyPolygon() This class provides methods needed only here, and is used as a place to store some additional information per polygon. Also, most of the intersection logic is implemented here. */ class ImplPolygon { public: /** Create polygon */ ImplPolygon() : mpLeadingRightEdge(NULL), mnIdx(-1), maPoints(), mbIsFinished(false) { // completely ad-hoc. but what the hell. maPoints.reserve(11); } void setPolygonPoolIndex( std::ptrdiff_t nIdx ) { mnIdx = nIdx; } bool isFinished() const { return mbIsFinished; } /// Add point to the end of the existing points void append( const B2DPoint& rPoint ) { OSL_PRECOND( maPoints.empty() || maPoints.back().getX() == rPoint.getX() || maPoints.back().getY() == rPoint.getY(), "ImplPolygon::append(): added point violates 90 degree line angle constraint!" ); if( maPoints.empty() || maPoints.back() != rPoint ) { // avoid duplicate points maPoints.push_back( rPoint ); } } /** Perform the intersection of this polygon with an active edge. @param rEvent The vertical line event that generated the intersection @param rActiveEdge The active edge that generated the intersection @param rPolygonPool Polygon pool, we sometimes need to allocate a new one @param bIsFinishingEdge True, when this is hitting the last edge of the vertical sweep - every vertical sweep starts and ends with upper and lower edge of the _same_ rectangle. @return the new current polygon (that's the one processing must proceed with, when going through the list of upcoming active edges). */ std::ptrdiff_t intersect( SweepLineEvent& rEvent, ActiveEdge& rActiveEdge, VectorOfPolygons& rPolygonPool, B2DPolyPolygon& rRes, bool isFinishingEdge ) { OSL_PRECOND( !isFinished(), "ImplPolygon::intersect(): called on already finished polygon!" ); OSL_PRECOND( !isFinishingEdge || (isFinishingEdge && &rEvent.getRect() == &rActiveEdge.getRect()), "ImplPolygon::intersect(): inconsistent ending!" ); const B2DPoint aIntersectionPoint( rEvent.getPos(), rActiveEdge.getInvariantCoord() ); // intersection point, goes to our polygon // unconditionally append(aIntersectionPoint); const bool isSweepLineEnteringRect( rEvent.getEdgeType() == SweepLineEvent::STARTING_EDGE); if( isFinishingEdge ) { if( isSweepLineEnteringRect ) handleFinalOwnRightEdge(rActiveEdge); else handleFinalOwnLeftEdge(rActiveEdge, rPolygonPool, rRes); // we're done with this rect & sweep line return -1; } else if( metOwnEdge(rEvent,rActiveEdge) ) { handleInitialOwnEdge(rEvent, rActiveEdge); // point already added, all init done, continue // with same poly return mnIdx; } else { OSL_ENSURE( rActiveEdge.getTargetPolygonIndex() != -1, "ImplPolygon::intersect(): non-trivial intersection hit empty polygon!" ); const bool isHittingLeftEdge( rActiveEdge.getEdgeDirection() == ActiveEdge::PROCEED_LEFT); if( isHittingLeftEdge ) return handleComplexLeftEdge(rActiveEdge, aIntersectionPoint, rPolygonPool, rRes); else return handleComplexRightEdge(rActiveEdge, aIntersectionPoint, rPolygonPool); } } private: std::ptrdiff_t getPolygonPoolIndex() const { return mnIdx; } void handleInitialOwnEdge(SweepLineEvent& rEvent, ActiveEdge& rActiveEdge) { const bool isActiveEdgeProceedLeft( rActiveEdge.getEdgeDirection() == ActiveEdge::PROCEED_LEFT); const bool isSweepLineEnteringRect( rEvent.getEdgeType() == SweepLineEvent::STARTING_EDGE); (void)isActiveEdgeProceedLeft; (void)isSweepLineEnteringRect; OSL_ENSURE( isSweepLineEnteringRect == isActiveEdgeProceedLeft, "ImplPolygon::intersect(): sweep initial own edge hit: wrong polygon order" ); OSL_ENSURE( isSweepLineEnteringRect || mpLeadingRightEdge == &rActiveEdge, "ImplPolygon::intersect(): sweep initial own edge hit: wrong leading edge" ); } void handleFinalOwnRightEdge(ActiveEdge& rActiveEdge) { OSL_ENSURE( rActiveEdge.getEdgeDirection() == ActiveEdge::PROCEED_RIGHT, "ImplPolygon::handleInitialOwnRightEdge(): start edge wrong polygon order" ); rActiveEdge.setTargetPolygonIndex(mnIdx); mpLeadingRightEdge = &rActiveEdge; } void handleFinalOwnLeftEdge(ActiveEdge& rActiveEdge, VectorOfPolygons& rPolygonPool, B2DPolyPolygon& rRes) { OSL_ENSURE( rActiveEdge.getEdgeDirection() == ActiveEdge::PROCEED_LEFT, "ImplPolygon::handleFinalOwnLeftEdge(): end edge wrong polygon order" ); const bool isHittingOurTail( rActiveEdge.getTargetPolygonIndex() == mnIdx); if( isHittingOurTail ) finish(rRes); // just finish. no fuss. else { // temp poly hits final left edge const std::ptrdiff_t nTmpIdx=rActiveEdge.getTargetPolygonIndex(); ImplPolygon& rTmp=rPolygonPool.get(nTmpIdx); // active edge's polygon has points // already. ours need to go in front of them. maPoints.insert(maPoints.end(), rTmp.maPoints.begin(), rTmp.maPoints.end()); // adjust leading edges, we're switching the polygon ActiveEdge* const pFarEdge=rTmp.mpLeadingRightEdge; mpLeadingRightEdge = pFarEdge; pFarEdge->setTargetPolygonIndex(mnIdx); // nTmpIdx is an empty shell, get rid of it rPolygonPool.free(nTmpIdx); } } std::ptrdiff_t handleComplexLeftEdge(ActiveEdge& rActiveEdge, const B2DPoint& rIntersectionPoint, VectorOfPolygons& rPolygonPool, B2DPolyPolygon& rRes) { const bool isHittingOurTail( rActiveEdge.getTargetPolygonIndex() == mnIdx); if( isHittingOurTail ) { finish(rRes); // so "this" is done - need new polygon to collect // further points const std::ptrdiff_t nIdxNewPolygon=rPolygonPool.alloc(); rPolygonPool.get(nIdxNewPolygon).setPolygonPoolIndex(nIdxNewPolygon); rPolygonPool.get(nIdxNewPolygon).append(rIntersectionPoint); rActiveEdge.setTargetPolygonIndex(nIdxNewPolygon); return nIdxNewPolygon; } else { const std::ptrdiff_t nTmpIdx=rActiveEdge.getTargetPolygonIndex(); ImplPolygon& rTmp=rPolygonPool.get(nTmpIdx); // active edge's polygon has points // already. ours need to go in front of them. maPoints.insert(maPoints.end(), rTmp.maPoints.begin(), rTmp.maPoints.end()); rTmp.maPoints.clear(); rTmp.append(rIntersectionPoint); // adjust leading edges, we're switching the polygon ActiveEdge* const pFarEdge=rTmp.mpLeadingRightEdge; ActiveEdge* const pNearEdge=&rActiveEdge; rTmp.mpLeadingRightEdge = NULL; pNearEdge->setTargetPolygonIndex(nTmpIdx); mpLeadingRightEdge = pFarEdge; pFarEdge->setTargetPolygonIndex(mnIdx); return nTmpIdx; } } std::ptrdiff_t handleComplexRightEdge(ActiveEdge& rActiveEdge, const B2DPoint& rIntersectionPoint, VectorOfPolygons& rPolygonPool) { const std::ptrdiff_t nTmpIdx=rActiveEdge.getTargetPolygonIndex(); ImplPolygon& rTmp=rPolygonPool.get(nTmpIdx); rTmp.append(rIntersectionPoint); rActiveEdge.setTargetPolygonIndex(mnIdx); mpLeadingRightEdge = &rActiveEdge; rTmp.mpLeadingRightEdge = NULL; return nTmpIdx; } /// True when sweep line hits our own active edge bool metOwnEdge(const SweepLineEvent& rEvent, ActiveEdge& rActiveEdge) { const bool bHitOwnEdge=&rEvent.getRect() == &rActiveEdge.getRect(); return bHitOwnEdge; } /// Retrieve B2DPolygon from this object B2DPolygon getPolygon() const { B2DPolygon aRes; std::for_each( maPoints.begin(), maPoints.end(), boost::bind( &B2DPolygon::append, boost::ref(aRes), _1, 1 ) ); aRes.setClosed( true ); return aRes; } /** Finish this polygon, push to result set. */ void finish(B2DPolyPolygon& rRes) { OSL_PRECOND( maPoints.empty() || maPoints.front().getX() == maPoints.back().getX() || maPoints.front().getY() == maPoints.back().getY(), "ImplPolygon::finish(): first and last point violate 90 degree line angle constraint!" ); mbIsFinished = true; mpLeadingRightEdge = NULL; rRes.append(getPolygon()); } /** Refers to the current leading edge element of this polygon, or NULL. The leading edge denotes the 'front' of the polygon vertex sequence, i.e. the coordinates at the polygon's leading edge are returned from maPoints.front() */ ActiveEdge* mpLeadingRightEdge; /// current index into vector pool std::ptrdiff_t mnIdx; /// Container for the actual polygon points std::vector maPoints; /// When true, this polygon is 'done', i.e. nothing must be added anymore. bool mbIsFinished; }; /** Init sweep line event list This method fills the event list with the sweep line events generated from the input rectangles, and sorts them with increasing x. */ void setupSweepLineEventListFromRanges( VectorOfEvents& o_rEventVector, const std::vector& rRanges, const std::vector& rOrientations ) { // we need exactly 2*rectVec.size() events: one for the // left, and one for the right edge of each rectangle o_rEventVector.clear(); o_rEventVector.reserve( 2*rRanges.size() ); // generate events // =============== // first pass: add all left edges in increasing order std::vector::const_iterator aCurrRect=rRanges.begin(); std::vector::const_iterator aCurrOrientation=rOrientations.begin(); const std::vector::const_iterator aEnd=rRanges.end(); const std::vector::const_iterator aEndOrientation=rOrientations.end(); while( aCurrRect != aEnd && aCurrOrientation != aEndOrientation ) { const B2DRectangle& rCurrRect( *aCurrRect++ ); o_rEventVector.push_back( SweepLineEvent( rCurrRect.getMinX(), rCurrRect, SweepLineEvent::STARTING_EDGE, (*aCurrOrientation++) == ORIENTATION_POSITIVE ? SweepLineEvent::PROCEED_UP : SweepLineEvent::PROCEED_DOWN) ); } // second pass: add all right edges in reversed order std::vector::const_reverse_iterator aCurrRectR=rRanges.rbegin(); std::vector::const_reverse_iterator aCurrOrientationR=rOrientations.rbegin(); const std::vector::const_reverse_iterator aEndR=rRanges.rend(); const std::vector::const_reverse_iterator aEndOrientationR=rOrientations.rend(); while( aCurrRectR != aEndR ) { const B2DRectangle& rCurrRect( *aCurrRectR++ ); o_rEventVector.push_back( SweepLineEvent( rCurrRect.getMaxX(), rCurrRect, SweepLineEvent::FINISHING_EDGE, (*aCurrOrientationR++) == ORIENTATION_POSITIVE ? SweepLineEvent::PROCEED_DOWN : SweepLineEvent::PROCEED_UP ) ); } // sort events // =========== // since we use stable_sort, the order of events with the // same x value will not change. The elaborate two-pass // add above thus ensures, that for each two rectangles // with similar left and right x coordinates, the // rectangle whose left event comes first will have its // right event come last. This is advantageous for the // clip algorithm below, see handleRightEdgeCrossing(). // TODO(P3): Use radix sort (from // b2dpolypolygonrasterconverter, or have your own // templatized version). std::stable_sort( o_rEventVector.begin(), o_rEventVector.end() ); } /** Insert two active edge segments for the given rectangle. This method creates two active edge segments from the given rect, and inserts them into the active edge list, such that this stays sorted (if it was before). @param io_rEdgeList Active edge list to insert into @param io_rPolygons Vector of polygons. Each rectangle added creates one tentative result polygon in this vector, and the edge list entries holds a reference to that polygon (this _requires_ that the polygon vector does not reallocate, i.e. it must have at least the maximal number of rectangles reserved) @param o_CurrentPolygon The then-current polygon when processing this sweep line event @param rCurrEvent The actual event that caused this call */ void createActiveEdgesFromStartEvent( ListOfEdges& io_rEdgeList, VectorOfPolygons& io_rPolygonPool, SweepLineEvent& rCurrEvent ) { ListOfEdges aNewEdges; const B2DRectangle& rRect=rCurrEvent.getRect(); const bool bGoesDown=rCurrEvent.getEdgeDirection() == SweepLineEvent::PROCEED_DOWN; // start event - new rect starts here, needs polygon to // collect points into const std::ptrdiff_t nIdxPolygon=io_rPolygonPool.alloc(); io_rPolygonPool.get(nIdxPolygon).setPolygonPoolIndex(nIdxPolygon); // upper edge aNewEdges.push_back( ActiveEdge( rRect, rRect.getMinY(), bGoesDown ? nIdxPolygon : -1, ActiveEdge::UPPER, bGoesDown ? ActiveEdge::PROCEED_LEFT : ActiveEdge::PROCEED_RIGHT) ); // lower edge aNewEdges.push_back( ActiveEdge( rRect, rRect.getMaxY(), bGoesDown ? -1 : nIdxPolygon, ActiveEdge::LOWER, bGoesDown ? ActiveEdge::PROCEED_RIGHT : ActiveEdge::PROCEED_LEFT ) ); // furthermore, have to respect a special tie-breaking // rule here, for edges which share the same y value: // newly added upper edges must be inserted _before_ any // other edge with the same y value, and newly added lower // edges must be _after_ all other edges with the same // y. This ensures that the left vertical edge processing // below encounters the upper edge of the current rect // first, and the lower edge last, which automatically // starts and finishes this rect correctly (as only then, // the polygon will have their associated active edges // set). const double nMinY( rRect.getMinY() ); const double nMaxY( rRect.getMaxY() ); ListOfEdges::iterator aCurr( io_rEdgeList.begin() ); const ListOfEdges::iterator aEnd ( io_rEdgeList.end() ); while( aCurr != aEnd ) { const double nCurrY( aCurr->getInvariantCoord() ); if( nCurrY >= nMinY && aNewEdges.size() == 2 ) // only add, if not yet done. { // insert upper edge _before_ aCurr. Thus, it will // be the first entry for a range of equal y // values. Using splice here, since we hold // references to the moved list element! io_rEdgeList.splice( aCurr, aNewEdges, aNewEdges.begin() ); } if( nCurrY > nMaxY ) { // insert lower edge _before_ aCurr. Thus, it will // be the last entry for a range of equal y values // (aCurr is the first entry strictly larger than // nMaxY). Using splice here, since we hold // references to the moved list element! io_rEdgeList.splice( aCurr, aNewEdges, aNewEdges.begin() ); // done with insertion, can early-exit here. return; } ++aCurr; } // append remainder of aNewList (might still contain 2 or // 1 elements, depending of the contents of io_rEdgeList). io_rEdgeList.splice( aCurr, aNewEdges ); } inline bool isSameRect(ActiveEdge& rEdge, const basegfx::B2DRange& rRect) { return &rEdge.getRect() == &rRect; } // wow what a hack. necessary because stl's list::erase does // not eat reverse_iterator template Iter eraseFromList(Cont&, Iter); template<> inline ListOfEdges::iterator eraseFromList( ListOfEdges& rList, ListOfEdges::iterator aIter) { return rList.erase(aIter); } template<> inline ListOfEdges::reverse_iterator eraseFromList( ListOfEdges& rList, ListOfEdges::reverse_iterator aIter) { return ListOfEdges::reverse_iterator( rList.erase(boost::prior(aIter.base()))); } template inline void processActiveEdges( Iterator first, Iterator last, ListOfEdges& rActiveEdgeList, SweepLineEvent& rCurrEvent, VectorOfPolygons& rPolygonPool, B2DPolyPolygon& rRes ) { const basegfx::B2DRange& rCurrRect=rCurrEvent.getRect(); // fast-forward to rCurrEvent's first active edge (holds // for both starting and finishing sweep line events, a // rect is regarded _outside_ any rects whose events have // started earlier first = std::find_if(first, last, boost::bind( &isSameRect, _1, boost::cref(rCurrRect))); if(first == last) return; int nCount=0; std::ptrdiff_t nCurrPolyIdx=-1; while(first != last) { if( nCurrPolyIdx == -1 ) nCurrPolyIdx=first->getTargetPolygonIndex(); OSL_ASSERT(nCurrPolyIdx != -1); // second encounter of my rect -> second edge // encountered, done const bool bExit= nCount && isSameRect(*first, rCurrRect); // deal with current active edge nCurrPolyIdx = rPolygonPool.get(nCurrPolyIdx).intersect( rCurrEvent, *first, rPolygonPool, rRes, bExit); // prune upper & lower active edges, if requested if( bPerformErase && (bExit || !nCount) ) first = eraseFromList(rActiveEdgeList,first); else ++first; // delayed exit, had to prune first if( bExit ) return; ++nCount; } } template inline void processActiveEdgesTopDown( SweepLineEvent& rCurrEvent, ListOfEdges& rActiveEdgeList, VectorOfPolygons& rPolygonPool, B2DPolyPolygon& rRes ) { processActiveEdges( rActiveEdgeList. begin(), rActiveEdgeList. end(), rActiveEdgeList, rCurrEvent, rPolygonPool, rRes); } template inline void processActiveEdgesBottomUp( SweepLineEvent& rCurrEvent, ListOfEdges& rActiveEdgeList, VectorOfPolygons& rPolygonPool, B2DPolyPolygon& rRes ) { processActiveEdges( rActiveEdgeList. rbegin(), rActiveEdgeList. rend(), rActiveEdgeList, rCurrEvent, rPolygonPool, rRes); } enum{ NoErase=0, PerformErase=1 }; void handleStartingEdge( SweepLineEvent& rCurrEvent, ListOfEdges& rActiveEdgeList, VectorOfPolygons& rPolygonPool, B2DPolyPolygon& rRes) { // inject two new active edges for rect createActiveEdgesFromStartEvent( rActiveEdgeList, rPolygonPool, rCurrEvent ); if( SweepLineEvent::PROCEED_DOWN == rCurrEvent.getEdgeDirection() ) processActiveEdgesTopDown( rCurrEvent, rActiveEdgeList, rPolygonPool, rRes); else processActiveEdgesBottomUp( rCurrEvent, rActiveEdgeList, rPolygonPool, rRes); } void handleFinishingEdge( SweepLineEvent& rCurrEvent, ListOfEdges& rActiveEdgeList, VectorOfPolygons& rPolygonPool, B2DPolyPolygon& rRes) { if( SweepLineEvent::PROCEED_DOWN == rCurrEvent.getEdgeDirection() ) processActiveEdgesTopDown( rCurrEvent, rActiveEdgeList, rPolygonPool, rRes); else processActiveEdgesBottomUp( rCurrEvent, rActiveEdgeList, rPolygonPool, rRes); } inline void handleSweepLineEvent( SweepLineEvent& rCurrEvent, ListOfEdges& rActiveEdgeList, VectorOfPolygons& rPolygonPool, B2DPolyPolygon& rRes) { if( SweepLineEvent::STARTING_EDGE == rCurrEvent.getEdgeType() ) handleStartingEdge(rCurrEvent,rActiveEdgeList,rPolygonPool,rRes); else handleFinishingEdge(rCurrEvent,rActiveEdgeList,rPolygonPool,rRes); } } namespace tools { B2DPolyPolygon solveCrossovers(const std::vector& rRanges, const std::vector& rOrientations) { // sweep-line algorithm to generate a poly-polygon // from a bunch of rectangles // =============================================== // // This algorithm uses the well-known sweep line // concept, explained in every good text book about // computational geometry. // // We start with creating two structures for every // rectangle, one representing the left x coordinate, // one representing the right x coordinate (and both // referencing the original rect). These structs are // sorted with increasing x coordinates. // // Then, we start processing the resulting list from // the beginning. Every entry in the list defines a // point in time of the line sweeping from left to // right across all rectangles. VectorOfEvents aSweepLineEvents; setupSweepLineEventListFromRanges( aSweepLineEvents, rRanges, rOrientations ); B2DPolyPolygon aRes; VectorOfPolygons aPolygonPool; ListOfEdges aActiveEdgeList; // sometimes not enough, but a usable compromise aPolygonPool.reserve( rRanges.size() ); std::for_each( aSweepLineEvents.begin(), aSweepLineEvents.end(), boost::bind( &handleSweepLineEvent, _1, boost::ref(aActiveEdgeList), boost::ref(aPolygonPool), boost::ref(aRes)) ); return aRes; } } }