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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 <rtl/math.hxx>
#include <osl/diagnose.h>
#include <basegfx/tuple/b2dtuple.hxx>
#include <basegfx/range/b2drange.hxx>
#include <basegfx/range/b2drangeclipper.hxx>
#include <basegfx/range/b2dpolyrange.hxx>
#include <basegfx/polygon/b2dpolypolygon.hxx>
#include <basegfx/polygon/b2dpolygontools.hxx>
#include <basegfx/polygon/b2dpolypolygontools.hxx>
#include <o3tl/vector_pool.hxx>
#include <algorithm>
#include <deque>
#include <list>
#include <iterator>
namespace basegfx
{
namespace
{
// Generating a poly-polygon from a bunch of rectangles
// Helper functionality for sweep-line algorithm
// ====================================================
typedef std::vector<B2DRange> VectorOfRanges;
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),
maPoints(),
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& rActiveEdge)
{
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 );
}
inline 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<> inline ListOfEdges::iterator eraseFromList(
ListOfEdges& rList, const ListOfEdges::iterator& aIter)
{
return rList.erase(aIter);
}
template<> inline 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> 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,
[&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();
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<int bPerformErase> inline void processActiveEdgesTopDown(
SweepLineEvent& rCurrEvent,
ListOfEdges& rActiveEdgeList,
VectorOfPolygons& rPolygonPool,
B2DPolyPolygon& rRes )
{
processActiveEdges<bPerformErase>(
rActiveEdgeList. begin(),
rActiveEdgeList. end(),
rActiveEdgeList,
rCurrEvent,
rPolygonPool,
rRes);
}
template<int bPerformErase> inline 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);
}
inline 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;
}
}
}
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