825 lines
37 KiB
C++
825 lines
37 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/*
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* This file is part of the LibreOffice project.
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* This file incorporates work covered by the following license notice:
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed
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* with this work for additional information regarding copyright
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* ownership. The ASF licenses this file to you under the Apache
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* License, Version 2.0 (the "License"); you may not use this file
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* except in compliance with the License. You may obtain a copy of
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* the License at http://www.apache.org/licenses/LICENSE-2.0 .
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*/
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#include <basegfx/polygon/b2dpolygonclipper.hxx>
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#include <basegfx/polygon/b2dpolygontools.hxx>
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#include <basegfx/numeric/ftools.hxx>
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#include <basegfx/polygon/b2dpolypolygoncutter.hxx>
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#include <basegfx/polygon/b2dpolygoncutandtouch.hxx>
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#include <basegfx/polygon/b2dpolypolygontools.hxx>
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#include <basegfx/curve/b2dcubicbezier.hxx>
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#include <basegfx/utils/rectcliptools.hxx>
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#include <sal/log.hxx>
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namespace basegfx::utils
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{
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B2DPolyPolygon clipPolygonOnParallelAxis(const B2DPolygon& rCandidate, bool bParallelToXAxis, bool bAboveAxis, double fValueOnOtherAxis, bool bStroke)
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{
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B2DPolyPolygon aRetval;
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if(rCandidate.count())
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{
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const B2DRange aCandidateRange(getRange(rCandidate));
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if(bParallelToXAxis && fTools::moreOrEqual(aCandidateRange.getMinY(), fValueOnOtherAxis))
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{
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// completely above and on the clip line. also true for curves.
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if(bAboveAxis)
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{
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// add completely
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aRetval.append(rCandidate);
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}
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}
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else if(bParallelToXAxis && fTools::lessOrEqual(aCandidateRange.getMaxY(), fValueOnOtherAxis))
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{
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// completely below and on the clip line. also true for curves.
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if(!bAboveAxis)
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{
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// add completely
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aRetval.append(rCandidate);
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}
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}
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else if(!bParallelToXAxis && fTools::moreOrEqual(aCandidateRange.getMinX(), fValueOnOtherAxis))
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{
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// completely right of and on the clip line. also true for curves.
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if(bAboveAxis)
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{
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// add completely
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aRetval.append(rCandidate);
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}
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}
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else if(!bParallelToXAxis && fTools::lessOrEqual(aCandidateRange.getMaxX(), fValueOnOtherAxis))
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{
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// completely left of and on the clip line. also true for curves.
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if(!bAboveAxis)
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{
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// add completely
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aRetval.append(rCandidate);
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}
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}
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else
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{
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// add cuts with axis to polygon, including bezier segments
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// Build edge to cut with. Make it a little big longer than needed for
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// numerical stability. We want to cut against the edge seen as endless
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// ray here, but addPointsAtCuts() will limit itself to the
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// edge's range ]0.0 .. 1.0[.
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const double fSmallExtension((aCandidateRange.getWidth() + aCandidateRange.getHeight()) * (0.5 * 0.1));
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const B2DPoint aStart(
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bParallelToXAxis ? aCandidateRange.getMinX() - fSmallExtension : fValueOnOtherAxis,
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bParallelToXAxis ? fValueOnOtherAxis : aCandidateRange.getMinY() - fSmallExtension);
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const B2DPoint aEnd(
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bParallelToXAxis ? aCandidateRange.getMaxX() + fSmallExtension : fValueOnOtherAxis,
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bParallelToXAxis ? fValueOnOtherAxis : aCandidateRange.getMaxY() + fSmallExtension);
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const B2DPolygon aCandidate(addPointsAtCuts(rCandidate, aStart, aEnd));
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const sal_uInt32 nPointCount(aCandidate.count());
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const sal_uInt32 nEdgeCount(aCandidate.isClosed() ? nPointCount : nPointCount - 1);
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B2DCubicBezier aEdge;
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B2DPolygon aRun;
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for(sal_uInt32 a(0); a < nEdgeCount; a++)
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{
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aCandidate.getBezierSegment(a, aEdge);
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const B2DPoint aTestPoint(aEdge.interpolatePoint(0.5));
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const bool bInside(bParallelToXAxis ?
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fTools::moreOrEqual(aTestPoint.getY(), fValueOnOtherAxis) == bAboveAxis :
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fTools::moreOrEqual(aTestPoint.getX(), fValueOnOtherAxis) == bAboveAxis);
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if(bInside)
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{
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const sal_uInt16 nRunCount = aRun.count();
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if (!nRunCount || !aRun.getB2DPoint(nRunCount - 1).equal(aEdge.getStartPoint()))
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{
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aRun.append(aEdge.getStartPoint());
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}
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if(aEdge.isBezier())
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{
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aRun.appendBezierSegment(aEdge.getControlPointA(), aEdge.getControlPointB(), aEdge.getEndPoint());
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}
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else
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{
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aRun.append(aEdge.getEndPoint());
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}
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}
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else
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{
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if(bStroke && aRun.count())
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{
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aRetval.append(aRun);
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aRun.clear();
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}
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}
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}
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if(aRun.count())
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{
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if(bStroke)
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{
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// try to merge this last and first polygon; they may have been
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// the former polygon's start/end point
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if(aRetval.count())
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{
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const B2DPolygon aStartPolygon(aRetval.getB2DPolygon(0));
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if(aStartPolygon.count() && aStartPolygon.getB2DPoint(0).equal(aRun.getB2DPoint(aRun.count() - 1)))
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{
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// append start polygon to aRun, remove from result set
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aRun.append(aStartPolygon); aRun.removeDoublePoints();
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aRetval.remove(0);
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}
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}
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aRetval.append(aRun);
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}
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else
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{
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// set closed flag and correct last point (which is added double now).
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closeWithGeometryChange(aRun);
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aRetval.append(aRun);
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}
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}
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}
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}
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return aRetval;
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}
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B2DPolyPolygon clipPolyPolygonOnParallelAxis(const B2DPolyPolygon& rCandidate, bool bParallelToXAxis, bool bAboveAxis, double fValueOnOtherAxis, bool bStroke)
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{
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B2DPolyPolygon aRetval;
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for(const auto& rB2DPolygon : rCandidate )
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{
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const B2DPolyPolygon aClippedPolyPolygon(clipPolygonOnParallelAxis(rB2DPolygon, bParallelToXAxis, bAboveAxis, fValueOnOtherAxis, bStroke));
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if(aClippedPolyPolygon.count())
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{
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aRetval.append(aClippedPolyPolygon);
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}
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}
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return aRetval;
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}
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B2DPolyPolygon clipPolygonOnRange(const B2DPolygon& rCandidate, const B2DRange& rRange, bool bInside, bool bStroke)
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{
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const sal_uInt32 nCount(rCandidate.count());
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B2DPolyPolygon aRetval;
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if(!nCount)
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{
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// source is empty
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return aRetval;
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}
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if(rRange.isEmpty())
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{
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if(bInside)
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{
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// nothing is inside an empty range
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return aRetval;
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}
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else
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{
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// everything is outside an empty range
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return B2DPolyPolygon(rCandidate);
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}
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}
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const B2DRange aCandidateRange(getRange(rCandidate));
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if(rRange.isInside(aCandidateRange))
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{
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// candidate is completely inside given range
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if(bInside)
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{
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// nothing to do
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return B2DPolyPolygon(rCandidate);
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}
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else
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{
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// nothing is outside, then
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return aRetval;
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}
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}
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if(!bInside)
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{
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// cutting off the outer parts of filled polygons at parallel
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// lines to the axes is only possible for the inner part, not for
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// the outer part which means cutting a hole into the original polygon.
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// This is because the inner part is a logical AND-operation of
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// the four implied half-planes, but the outer part is not.
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// It is possible for strokes, but with creating unnecessary extra
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// cuts, so using clipPolygonOnPolyPolygon is better there, too.
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// This needs to be done with the topology knowledge and is unfortunately
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// more expensive, too.
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const B2DPolygon aClip(createPolygonFromRect(rRange));
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return clipPolygonOnPolyPolygon(rCandidate, B2DPolyPolygon(aClip), bInside, bStroke);
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}
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// clip against the four axes of the range
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// against X-Axis, lower value
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aRetval = clipPolygonOnParallelAxis(rCandidate, true, bInside, rRange.getMinY(), bStroke);
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if(aRetval.count())
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{
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// against Y-Axis, lower value
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if(aRetval.count() == 1)
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{
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aRetval = clipPolygonOnParallelAxis(aRetval.getB2DPolygon(0), false, bInside, rRange.getMinX(), bStroke);
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}
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else
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{
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aRetval = clipPolyPolygonOnParallelAxis(aRetval, false, bInside, rRange.getMinX(), bStroke);
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}
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if(aRetval.count())
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{
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// against X-Axis, higher value
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if(aRetval.count() == 1)
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{
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aRetval = clipPolygonOnParallelAxis(aRetval.getB2DPolygon(0), true, false, rRange.getMaxY(), bStroke);
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}
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else
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{
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aRetval = clipPolyPolygonOnParallelAxis(aRetval, true, false, rRange.getMaxY(), bStroke);
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}
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if(aRetval.count())
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{
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// against Y-Axis, higher value
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if(aRetval.count() == 1)
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{
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aRetval = clipPolygonOnParallelAxis(aRetval.getB2DPolygon(0), false, false, rRange.getMaxX(), bStroke);
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}
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else
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{
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aRetval = clipPolyPolygonOnParallelAxis(aRetval, false, false, rRange.getMaxX(), bStroke);
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}
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}
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}
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}
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return aRetval;
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}
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B2DPolyPolygon clipPolyPolygonOnRange(const B2DPolyPolygon& rCandidate, const B2DRange& rRange, bool bInside, bool bStroke)
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{
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B2DPolyPolygon aRetval;
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if(!rCandidate.count())
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{
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// source is empty
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return aRetval;
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}
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if(rRange.isEmpty())
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{
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if(bInside)
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{
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// nothing is inside an empty range
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return aRetval;
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}
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else
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{
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// everything is outside an empty range
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return rCandidate;
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}
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}
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if(bInside)
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{
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for( const auto& rClippedPoly : rCandidate)
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{
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const B2DPolyPolygon aClippedPolyPolygon(clipPolygonOnRange(rClippedPoly , rRange, bInside, bStroke));
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if(aClippedPolyPolygon.count())
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{
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aRetval.append(aClippedPolyPolygon);
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}
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}
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}
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else
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{
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// for details, see comment in clipPolygonOnRange for the "cutting off
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// the outer parts of filled polygons at parallel lines" explanations
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const B2DPolygon aClip(createPolygonFromRect(rRange));
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return clipPolyPolygonOnPolyPolygon(rCandidate, B2DPolyPolygon(aClip), bInside, bStroke);
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}
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return aRetval;
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}
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B2DPolyPolygon clipPolyPolygonOnPolyPolygon(const B2DPolyPolygon& rCandidate, const B2DPolyPolygon& rClip,
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bool bInside, bool bStroke, size_t* pPointLimit)
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{
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B2DPolyPolygon aRetval;
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if(rCandidate.count() && rClip.count())
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{
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// one or both are no rectangle - go the hard way and clip PolyPolygon
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// against PolyPolygon...
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if(bStroke)
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{
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// line clipping, create line snippets by first adding all cut points and
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// then marching along the edges and detecting if they are inside or outside
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// the clip polygon
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for(const auto& rPolygon : rCandidate)
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{
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// add cuts with clip to polygon, including bezier segments
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const B2DPolygon aCandidate(addPointsAtCuts(rPolygon, rClip));
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const sal_uInt32 nPointCount(aCandidate.count());
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const sal_uInt32 nEdgeCount(aCandidate.isClosed() ? nPointCount : nPointCount - 1);
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B2DCubicBezier aEdge;
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B2DPolygon aRun;
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for(sal_uInt32 b(0); b < nEdgeCount; b++)
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{
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aCandidate.getBezierSegment(b, aEdge);
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const B2DPoint aTestPoint(aEdge.interpolatePoint(0.5));
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const bool bIsInside(utils::isInside(rClip, aTestPoint) == bInside);
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if(bIsInside)
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{
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if(!aRun.count())
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{
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aRun.append(aEdge.getStartPoint());
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}
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if(aEdge.isBezier())
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{
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aRun.appendBezierSegment(aEdge.getControlPointA(), aEdge.getControlPointB(), aEdge.getEndPoint());
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}
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else
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{
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aRun.append(aEdge.getEndPoint());
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}
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}
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else
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{
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if(aRun.count())
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{
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aRetval.append(aRun);
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aRun.clear();
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}
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}
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}
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if(aRun.count())
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{
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// try to merge this last and first polygon; they may have been
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// the former polygon's start/end point
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if(aRetval.count())
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{
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const B2DPolygon aStartPolygon(aRetval.getB2DPolygon(0));
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if(aStartPolygon.count() && aStartPolygon.getB2DPoint(0).equal(aRun.getB2DPoint(aRun.count() - 1)))
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{
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// append start polygon to aRun, remove from result set
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aRun.append(aStartPolygon); aRun.removeDoublePoints();
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aRetval.remove(0);
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}
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}
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aRetval.append(aRun);
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}
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}
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}
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else
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{
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// check for simplification with ranges if !bStroke (handling as stroke is more simple),
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// but also only when bInside, else the simplification may lead to recursive calls (see
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// calls to clipPolyPolygonOnPolyPolygon in clipPolyPolygonOnRange and clipPolygonOnRange)
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if (bInside && basegfx::utils::isRectangle(rClip))
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{
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// #i125349# detect if both given PolyPolygons are indeed ranges
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if (basegfx::utils::isRectangle(rCandidate))
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{
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// both are rectangle
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if(rCandidate.getB2DRange().equal(rClip.getB2DRange()))
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{
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// if both are equal -> no change
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return rCandidate;
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}
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else
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{
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// not equal -> create new intersection from both ranges,
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// but much cheaper based on the ranges
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basegfx::B2DRange aIntersectionRange(rCandidate.getB2DRange());
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aIntersectionRange.intersect(rClip.getB2DRange());
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if(aIntersectionRange.isEmpty())
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{
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// no common IntersectionRange -> the clip will be empty
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return B2DPolyPolygon();
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}
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else
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{
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// use common aIntersectionRange as result, convert
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// to expected utils::PolyPolygon form
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return basegfx::B2DPolyPolygon(
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basegfx::utils::createPolygonFromRect(aIntersectionRange));
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}
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}
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}
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else
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{
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// rClip is rectangle -> clip rCandidate on rRectangle, use the much
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// cheaper and numerically more stable clipping against a range
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return clipPolyPolygonOnRange(rCandidate, rClip.getB2DRange(), bInside, bStroke);
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}
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}
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// area clipping
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// First solve all polygon-self and polygon-polygon intersections.
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// Also get rid of some not-needed polygons (neutral, no area -> when
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// no intersections, these are tubes).
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// Now it is possible to correct the orientations in the cut-free
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// polygons to values corresponding to painting the utils::PolyPolygon with
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// a XOR-WindingRule.
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B2DPolyPolygon aMergePolyPolygonA = solveCrossovers(rClip);
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aMergePolyPolygonA = stripNeutralPolygons(aMergePolyPolygonA);
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aMergePolyPolygonA = correctOrientations(aMergePolyPolygonA);
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if(!bInside)
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{
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// if we want to get the outside of the clip polygon, make
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// it a 'Hole' in topological sense
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aMergePolyPolygonA.flip();
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}
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// prepare 2nd source polygon in same way
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B2DPolyPolygon aMergePolyPolygonB = solveCrossovers(rCandidate, pPointLimit);
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if (pPointLimit && !*pPointLimit)
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{
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SAL_WARN("basegfx", "clipPolyPolygonOnPolyPolygon hit point limit");
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return aRetval;
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}
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aMergePolyPolygonB = stripNeutralPolygons(aMergePolyPolygonB);
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aMergePolyPolygonB = correctOrientations(aMergePolyPolygonB);
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// to clip against each other, concatenate and solve all
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// polygon-polygon crossovers. polygon-self do not need to
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// be solved again, they were solved in the preparation.
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aRetval.append(aMergePolyPolygonA);
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aRetval.append(aMergePolyPolygonB);
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aRetval = solveCrossovers(aRetval, pPointLimit);
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// now remove neutral polygons (closed, but no area). In a last
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// step throw away all polygons which have a depth of less than 1
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// which means there was no logical AND at their position. For the
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// not-inside solution, the clip was flipped to define it as 'Hole',
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// so the removal rule is different here; remove all with a depth
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// of less than 0 (aka holes).
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aRetval = stripNeutralPolygons(aRetval);
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aRetval = stripDispensablePolygons(aRetval, bInside);
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}
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}
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return aRetval;
|
|
}
|
|
|
|
B2DPolyPolygon clipPolygonOnPolyPolygon(const B2DPolygon& rCandidate, const B2DPolyPolygon& rClip, bool bInside, bool bStroke)
|
|
{
|
|
B2DPolyPolygon aRetval;
|
|
|
|
if(rCandidate.count() && rClip.count())
|
|
{
|
|
aRetval = clipPolyPolygonOnPolyPolygon(B2DPolyPolygon(rCandidate), rClip, bInside, bStroke);
|
|
}
|
|
|
|
return aRetval;
|
|
}
|
|
|
|
namespace {
|
|
|
|
/*
|
|
* let a plane be defined as
|
|
*
|
|
* v.n+d=0
|
|
*
|
|
* and a ray be defined as
|
|
*
|
|
* a+(b-a)*t=0
|
|
*
|
|
* substitute and rearranging yields
|
|
*
|
|
* t = -(a.n+d)/(n.(b-a))
|
|
*
|
|
* if the denominator is zero, the line is either
|
|
* contained in the plane or parallel to the plane.
|
|
* in either case, there is no intersection.
|
|
* if numerator and denominator are both zero, the
|
|
* ray is contained in the plane.
|
|
*
|
|
*/
|
|
struct scissor_plane {
|
|
double nx,ny; // plane normal
|
|
double d; // [-] minimum distance from origin
|
|
sal_uInt32 clipmask; // clipping mask, e.g. 1000 1000
|
|
};
|
|
|
|
}
|
|
|
|
/*
|
|
*
|
|
* polygon clipping rules (straight out of Foley and Van Dam)
|
|
* ===========================================================
|
|
* current |next |emit
|
|
* ____________________________________
|
|
* inside |inside |next
|
|
* inside |outside |intersect with clip plane
|
|
* outside |outside |nothing
|
|
* outside |inside |intersect with clip plane followed by next
|
|
*
|
|
*/
|
|
static sal_uInt32 scissorLineSegment( ::basegfx::B2DPoint *in_vertex, // input buffer
|
|
sal_uInt32 in_count, // number of verts in input buffer
|
|
::basegfx::B2DPoint *out_vertex, // output buffer
|
|
scissor_plane const *pPlane, // scissoring plane
|
|
const ::basegfx::B2DRectangle &rR ) // clipping rectangle
|
|
{
|
|
|
|
sal_uInt32 out_count=0;
|
|
|
|
// process all the verts
|
|
for(sal_uInt32 i=0; i<in_count; i++) {
|
|
|
|
// vertices are relative to the coordinate
|
|
// system defined by the rectangle.
|
|
::basegfx::B2DPoint *curr = &in_vertex[i];
|
|
::basegfx::B2DPoint *next = &in_vertex[(i+1)%in_count];
|
|
|
|
// perform clipping judgement & mask against current plane.
|
|
sal_uInt32 clip = pPlane->clipmask & ((getCohenSutherlandClipFlags(*curr,rR)<<4)|getCohenSutherlandClipFlags(*next,rR));
|
|
|
|
if(clip==0) { // both verts are inside
|
|
out_vertex[out_count++] = *next;
|
|
}
|
|
else if((clip&0x0f) && (clip&0xf0)) { // both verts are outside
|
|
}
|
|
else if((clip&0x0f) && (clip&0xf0)==0) { // curr is inside, next is outside
|
|
|
|
// direction vector from 'current' to 'next', *not* normalized
|
|
// to bring 't' into the [0<=x<=1] interval.
|
|
::basegfx::B2DPoint dir((*next)-(*curr));
|
|
|
|
double denominator = pPlane->nx*dir.getX() +
|
|
pPlane->ny*dir.getY();
|
|
double numerator = pPlane->nx*curr->getX() +
|
|
pPlane->ny*curr->getY() +
|
|
pPlane->d;
|
|
double t = -numerator/denominator;
|
|
|
|
// calculate the actual point of intersection
|
|
::basegfx::B2DPoint intersection( curr->getX()+t*dir.getX(),
|
|
curr->getY()+t*dir.getY() );
|
|
|
|
out_vertex[out_count++] = intersection;
|
|
}
|
|
else if((clip&0x0f)==0 && (clip&0xf0)) { // curr is outside, next is inside
|
|
|
|
// direction vector from 'current' to 'next', *not* normalized
|
|
// to bring 't' into the [0<=x<=1] interval.
|
|
::basegfx::B2DPoint dir((*next)-(*curr));
|
|
|
|
double denominator = pPlane->nx*dir.getX() +
|
|
pPlane->ny*dir.getY();
|
|
double numerator = pPlane->nx*curr->getX() +
|
|
pPlane->ny*curr->getY() +
|
|
pPlane->d;
|
|
double t = -numerator/denominator;
|
|
|
|
// calculate the actual point of intersection
|
|
::basegfx::B2DPoint intersection( curr->getX()+t*dir.getX(),
|
|
curr->getY()+t*dir.getY() );
|
|
|
|
out_vertex[out_count++] = intersection;
|
|
out_vertex[out_count++] = *next;
|
|
}
|
|
}
|
|
|
|
return out_count;
|
|
}
|
|
|
|
B2DPolygon clipTriangleListOnRange( const B2DPolygon& rCandidate,
|
|
const B2DRange& rRange )
|
|
{
|
|
B2DPolygon aResult;
|
|
|
|
if( !(rCandidate.count()%3) )
|
|
{
|
|
const int scissor_plane_count = 4;
|
|
|
|
scissor_plane sp[scissor_plane_count];
|
|
|
|
sp[0].nx = +1.0;
|
|
sp[0].ny = +0.0;
|
|
sp[0].d = -(rRange.getMinX());
|
|
sp[0].clipmask = (RectClipFlags::LEFT << 4) | RectClipFlags::LEFT; // 0001 0001
|
|
sp[1].nx = -1.0;
|
|
sp[1].ny = +0.0;
|
|
sp[1].d = +(rRange.getMaxX());
|
|
sp[1].clipmask = (RectClipFlags::RIGHT << 4) | RectClipFlags::RIGHT; // 0010 0010
|
|
sp[2].nx = +0.0;
|
|
sp[2].ny = +1.0;
|
|
sp[2].d = -(rRange.getMinY());
|
|
sp[2].clipmask = (RectClipFlags::TOP << 4) | RectClipFlags::TOP; // 0100 0100
|
|
sp[3].nx = +0.0;
|
|
sp[3].ny = -1.0;
|
|
sp[3].d = +(rRange.getMaxY());
|
|
sp[3].clipmask = (RectClipFlags::BOTTOM << 4) | RectClipFlags::BOTTOM; // 1000 1000
|
|
|
|
// retrieve the number of vertices of the triangulated polygon
|
|
const sal_uInt32 nVertexCount = rCandidate.count();
|
|
|
|
if(nVertexCount)
|
|
{
|
|
// Upper bound for the maximal number of vertices when intersecting an
|
|
// axis-aligned rectangle with a triangle in E2
|
|
|
|
// The rectangle and the triangle are in general position, and have 4 and 3
|
|
// vertices, respectively.
|
|
|
|
// Lemma: Since the rectangle is a convex polygon ( see
|
|
// http://mathworld.wolfram.com/ConvexPolygon.html for a definition), and
|
|
// has no holes, it follows that any straight line will intersect the
|
|
// rectangle's border line at utmost two times (with the usual
|
|
// tie-breaking rule, if the intersection exactly hits an already existing
|
|
// rectangle vertex, that this intersection is only attributed to one of
|
|
// the adjoining edges). Thus, having a rectangle intersected with
|
|
// a half-plane (one side of a straight line denotes 'inside', the
|
|
// other 'outside') will at utmost add _one_ vertex to the resulting
|
|
// intersection polygon (adding two intersection vertices, and removing at
|
|
// least one rectangle vertex):
|
|
|
|
// *
|
|
// +--+-----------------+
|
|
// | * |
|
|
// |* |
|
|
// + |
|
|
// *| |
|
|
// * | |
|
|
// +--------------------+
|
|
|
|
// Proof: If the straight line intersects the rectangle two
|
|
// times, it does so for distinct edges, i.e. the intersection has
|
|
// minimally one of the rectangle's vertices on either side of the straight
|
|
// line (but maybe more). Thus, the intersection with a half-plane has
|
|
// minimally _one_ rectangle vertex removed from the resulting clip
|
|
// polygon, and therefore, a clip against a half-plane has the net effect
|
|
// of adding at utmost _one_ vertex to the resulting clip polygon.
|
|
|
|
// Theorem: The intersection of a rectangle and a triangle results in a
|
|
// polygon with at utmost 7 vertices.
|
|
|
|
// Proof: The inside of the triangle can be described as the consecutive
|
|
// intersection with three half-planes. Together with the lemma above, this
|
|
// results in at utmost 3 additional vertices added to the already existing 4
|
|
// rectangle vertices.
|
|
|
|
// This upper bound is attained with the following example configuration:
|
|
|
|
// *
|
|
// ***
|
|
// ** *
|
|
// ** *
|
|
// ** *
|
|
// ** *
|
|
// ** *
|
|
// ** *
|
|
// ** *
|
|
// ** *
|
|
// ** *
|
|
// ----*2--------3 *
|
|
// | ** |*
|
|
// 1* 4
|
|
// **| *|
|
|
// ** | * |
|
|
// **| * |
|
|
// 7* * |
|
|
// --*6-----5-----
|
|
// ** *
|
|
// **
|
|
|
|
// As we need to scissor all triangles against the
|
|
// output rectangle we employ an output buffer for the
|
|
// resulting vertices. the question is how large this
|
|
// buffer needs to be compared to the number of
|
|
// incoming vertices. this buffer needs to hold at
|
|
// most the number of original vertices times '7'. see
|
|
// figure above for an example. scissoring triangles
|
|
// with the cohen-sutherland line clipping algorithm
|
|
// as implemented here will result in a triangle fan
|
|
// which will be rendered as separate triangles to
|
|
// avoid pipeline stalls for each scissored
|
|
// triangle. creating separate triangles from a
|
|
// triangle fan produces (n-2)*3 vertices where n is
|
|
// the number of vertices of the original triangle
|
|
// fan. for the maximum number of 7 vertices of
|
|
// resulting triangle fans we therefore need 15 times
|
|
// the number of original vertices.
|
|
|
|
//const size_t nBufferSize = sizeof(vertex)*(nVertexCount*16);
|
|
//vertex *pVertices = (vertex*)alloca(nBufferSize);
|
|
//sal_uInt32 nNumOutput = 0;
|
|
|
|
// we need to clip this triangle against the output rectangle
|
|
// to ensure that the resulting texture coordinates are in
|
|
// the valid range from [0<=st<=1]. under normal circumstances
|
|
// we could use the BORDERCOLOR renderstate but some cards
|
|
// seem to ignore this feature.
|
|
::basegfx::B2DPoint stack[3];
|
|
unsigned int clipflag = 0;
|
|
|
|
for(sal_uInt32 nIndex=0; nIndex<nVertexCount; ++nIndex)
|
|
{
|
|
// rotate stack
|
|
stack[0] = stack[1];
|
|
stack[1] = stack[2];
|
|
stack[2] = rCandidate.getB2DPoint(nIndex);
|
|
|
|
// clipping judgement
|
|
clipflag |= unsigned(!(rRange.isInside(stack[2])));
|
|
|
|
if(nIndex > 1)
|
|
{
|
|
// consume vertices until a single separate triangle has been visited.
|
|
if(!((nIndex+1)%3))
|
|
{
|
|
// if any of the last three vertices was outside
|
|
// we need to scissor against the destination rectangle
|
|
if(clipflag & 7)
|
|
{
|
|
::basegfx::B2DPoint buf0[16];
|
|
::basegfx::B2DPoint buf1[16];
|
|
|
|
sal_uInt32 vertex_count = 3;
|
|
|
|
// clip against all 4 planes passing the result of
|
|
// each plane as the input to the next using a double buffer
|
|
vertex_count = scissorLineSegment(stack,vertex_count,buf1,&sp[0],rRange);
|
|
vertex_count = scissorLineSegment(buf1,vertex_count,buf0,&sp[1],rRange);
|
|
vertex_count = scissorLineSegment(buf0,vertex_count,buf1,&sp[2],rRange);
|
|
vertex_count = scissorLineSegment(buf1,vertex_count,buf0,&sp[3],rRange);
|
|
|
|
if(vertex_count >= 3)
|
|
{
|
|
// convert triangle fan back to triangle list.
|
|
::basegfx::B2DPoint v0(buf0[0]);
|
|
::basegfx::B2DPoint v1(buf0[1]);
|
|
for(sal_uInt32 i=2; i<vertex_count; ++i)
|
|
{
|
|
::basegfx::B2DPoint v2(buf0[i]);
|
|
aResult.append(v0);
|
|
aResult.append(v1);
|
|
aResult.append(v2);
|
|
v1 = v2;
|
|
}
|
|
}
|
|
}
|
|
else
|
|
{
|
|
// the last triangle has not been altered, simply copy to result
|
|
for(const basegfx::B2DPoint & i : stack)
|
|
aResult.append(i);
|
|
}
|
|
}
|
|
}
|
|
|
|
clipflag <<= 1;
|
|
}
|
|
}
|
|
}
|
|
|
|
return aResult;
|
|
}
|
|
|
|
} // end of namespace
|
|
|
|
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
|