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+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * This file incorporates work covered by the following license notice:
+ *
+ * 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 .
+ */
+
+#include <osl/diagnose.h>
+
+#include <basegfx/range/b2drange.hxx>
+#include <basegfx/range/b2drangeclipper.hxx>
+#include <basegfx/polygon/b2dpolypolygon.hxx>
+#include <basegfx/range/b2drectangle.hxx>
+
+#include <o3tl/vector_pool.hxx>
+
+#include <algorithm>
+#include <cassert>
+#include <list>
+#include <iterator>
+
+namespace basegfx
+{
+ namespace
+ {
+ // Generating a poly-polygon from a bunch of rectangles
+
+ // Helper functionality for sweep-line algorithm
+ // ====================================================
+
+ class ImplPolygon;
+ typedef o3tl::vector_pool<ImplPolygon> 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:
+
+ 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 coordinate 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,
+ EdgeDirection eEdgeDirection ) :
+ mfInvariantCoord(fInvariantCoord),
+ mpAssociatedRect( &rRect ),
+ mnPolygonIdx( nPolyIdx ),
+ 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; }
+ EdgeDirection getEdgeDirection() const { return meEdgeDirection; }
+
+ 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;
+
+ /// '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(nullptr),
+ mnIdx(-1),
+ mbIsFinished(false)
+ {
+ // completely ad-hoc. but what the hell.
+ maPoints.reserve(11);
+ }
+
+ void setPolygonPoolIndex( std::ptrdiff_t nIdx ) { mnIdx = nIdx; }
+
+ /// 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 const & rEvent,
+ ActiveEdge& rActiveEdge,
+ VectorOfPolygons& rPolygonPool,
+ B2DPolyPolygon& rRes,
+ bool isFinishingEdge )
+ {
+ OSL_PRECOND( !mbIsFinished,
+ "ImplPolygon::intersect(): called on already finished polygon!" );
+ OSL_PRECOND( !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);
+
+ if( isFinishingEdge )
+ {
+ // isSweepLineEnteringRect ?
+ if( rEvent.getEdgeType() == SweepLineEvent::STARTING_EDGE)
+ 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:
+ void handleInitialOwnEdge(SweepLineEvent const & rEvent,
+ ActiveEdge const & rActiveEdge) const
+ {
+ const bool isActiveEdgeProceedLeft(
+ rActiveEdge.getEdgeDirection() == ActiveEdge::PROCEED_LEFT);
+ const bool isSweepLineEnteringRect(
+ rEvent.getEdgeType() == SweepLineEvent::STARTING_EDGE);
+
+ 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 const & 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 = nullptr;
+ 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 = nullptr;
+
+ return nTmpIdx;
+ }
+
+ /// True when sweep line hits our own active edge
+ static bool metOwnEdge(SweepLineEvent const & rEvent,
+ ActiveEdge const & rActiveEdge)
+ {
+ const bool bHitOwnEdge=&rEvent.getRect() == &rActiveEdge.getRect();
+ return bHitOwnEdge;
+ }
+
+ /// Retrieve B2DPolygon from this object
+ B2DPolygon getPolygon() const
+ {
+ B2DPolygon aRes;
+ for (auto const& aPoint : maPoints)
+ aRes.append(aPoint, 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 = nullptr;
+
+ 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<B2DPoint> 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<B2DRange>& rRanges,
+ const std::vector<B2VectorOrientation>& 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<B2DRange>::const_iterator aCurrRect=rRanges.begin();
+ std::vector<B2VectorOrientation>::const_iterator aCurrOrientation=rOrientations.begin();
+ const std::vector<B2DRange>::const_iterator aEnd=rRanges.end();
+ const std::vector<B2VectorOrientation>::const_iterator aEndOrientation=rOrientations.end();
+ while( aCurrRect != aEnd && aCurrOrientation != aEndOrientation )
+ {
+ const B2DRectangle& rCurrRect( *aCurrRect++ );
+
+ o_rEventVector.emplace_back( rCurrRect.getMinX(),
+ rCurrRect,
+ SweepLineEvent::STARTING_EDGE,
+ (*aCurrOrientation++) == B2VectorOrientation::Positive ?
+ SweepLineEvent::PROCEED_UP : SweepLineEvent::PROCEED_DOWN );
+ }
+
+ // second pass: add all right edges in reversed order
+ std::vector<B2DRange>::const_reverse_iterator aCurrRectR=rRanges.rbegin();
+ std::vector<B2VectorOrientation>::const_reverse_iterator aCurrOrientationR=rOrientations.rbegin();
+ const std::vector<B2DRange>::const_reverse_iterator aEndR=rRanges.rend();
+ while( aCurrRectR != aEndR )
+ {
+ const B2DRectangle& rCurrRect( *aCurrRectR++ );
+
+ o_rEventVector.emplace_back( rCurrRect.getMaxX(),
+ rCurrRect,
+ SweepLineEvent::FINISHING_EDGE,
+ (*aCurrOrientationR++) == B2VectorOrientation::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().
+
+ 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 const & 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.emplace_back(
+ rRect,
+ rRect.getMinY(),
+ bGoesDown ? nIdxPolygon : -1,
+ bGoesDown ? ActiveEdge::PROCEED_LEFT : ActiveEdge::PROCEED_RIGHT );
+ // lower edge
+ aNewEdges.emplace_back(
+ rRect,
+ rRect.getMaxY(),
+ bGoesDown ? -1 : nIdxPolygon,
+ 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 );
+ }
+
+ bool isSameRect(ActiveEdge const & rEdge,
+ basegfx::B2DRange const & rRect)
+ {
+ return &rEdge.getRect() == &rRect;
+ }
+
+ // wow what a hack. necessary because stl's list::erase does
+ // not eat reverse_iterator
+ template<typename Cont, typename Iter> Iter eraseFromList(Cont&, const Iter&);
+ template<> ListOfEdges::iterator eraseFromList(
+ ListOfEdges& rList, const ListOfEdges::iterator& aIter)
+ {
+ return rList.erase(aIter);
+ }
+ template<> ListOfEdges::reverse_iterator eraseFromList(
+ ListOfEdges& rList, const ListOfEdges::reverse_iterator& aIter)
+ {
+ return ListOfEdges::reverse_iterator(
+ rList.erase(std::prev(aIter.base())));
+ }
+
+ template<int bPerformErase,
+ typename Iterator> void processActiveEdges(
+ Iterator first,
+ Iterator last,
+ ListOfEdges& rActiveEdgeList,
+ SweepLineEvent const & 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,
+ [&rCurrRect](ActiveEdge& anEdge) { return isSameRect(anEdge, rCurrRect); });
+
+ if(first == last)
+ return;
+
+ int nCount=0;
+ std::ptrdiff_t nCurrPolyIdx=-1;
+ while(first != last)
+ {
+ if( nCurrPolyIdx == -1 )
+ nCurrPolyIdx=first->getTargetPolygonIndex();
+
+ 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<int bPerformErase> void processActiveEdgesTopDown(
+ SweepLineEvent& rCurrEvent,
+ ListOfEdges& rActiveEdgeList,
+ VectorOfPolygons& rPolygonPool,
+ B2DPolyPolygon& rRes )
+ {
+ processActiveEdges<bPerformErase>(
+ rActiveEdgeList. begin(),
+ rActiveEdgeList. end(),
+ rActiveEdgeList,
+ rCurrEvent,
+ rPolygonPool,
+ rRes);
+ }
+
+ template<int bPerformErase> void processActiveEdgesBottomUp(
+ SweepLineEvent& rCurrEvent,
+ ListOfEdges& rActiveEdgeList,
+ VectorOfPolygons& rPolygonPool,
+ B2DPolyPolygon& rRes )
+ {
+ processActiveEdges<bPerformErase>(
+ 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( rCurrEvent.getEdgeDirection() == SweepLineEvent::PROCEED_DOWN )
+ processActiveEdgesTopDown<NoErase>(
+ rCurrEvent, rActiveEdgeList, rPolygonPool, rRes);
+ else
+ processActiveEdgesBottomUp<NoErase>(
+ rCurrEvent, rActiveEdgeList, rPolygonPool, rRes);
+ }
+
+ void handleFinishingEdge( SweepLineEvent& rCurrEvent,
+ ListOfEdges& rActiveEdgeList,
+ VectorOfPolygons& rPolygonPool,
+ B2DPolyPolygon& rRes)
+ {
+ if( rCurrEvent.getEdgeDirection() == SweepLineEvent::PROCEED_DOWN )
+ processActiveEdgesTopDown<PerformErase>(
+ rCurrEvent, rActiveEdgeList, rPolygonPool, rRes);
+ else
+ processActiveEdgesBottomUp<PerformErase>(
+ rCurrEvent, rActiveEdgeList, rPolygonPool, rRes);
+ }
+
+ void handleSweepLineEvent( SweepLineEvent& rCurrEvent,
+ ListOfEdges& rActiveEdgeList,
+ VectorOfPolygons& rPolygonPool,
+ B2DPolyPolygon& rRes)
+ {
+ if( rCurrEvent.getEdgeType() == SweepLineEvent::STARTING_EDGE )
+ handleStartingEdge(rCurrEvent,rActiveEdgeList,rPolygonPool,rRes);
+ else
+ handleFinishingEdge(rCurrEvent,rActiveEdgeList,rPolygonPool,rRes);
+ }
+ }
+
+ namespace utils
+ {
+ B2DPolyPolygon solveCrossovers(const std::vector<B2DRange>& rRanges,
+ const std::vector<B2VectorOrientation>& 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() );
+
+ for (auto& aSweepLineEvent : aSweepLineEvents)
+ handleSweepLineEvent(aSweepLineEvent, aActiveEdgeList, aPolygonPool, aRes);
+
+ return aRes;
+ }
+ }
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-14 09:59:57 +0000