WaveLine.cxx

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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/.
 *
 */
 
#include <basegfx/polygon/WaveLine.hxx>
#include <basegfx/point/b2dpoint.hxx>
 
namespace basegfx
{
BASEGFX_DLLPUBLIC B2DPolygon createWaveLinePolygon(basegfx::B2DRectangle const& rRectangle)
{
    basegfx::B2DPolygon aPolygon;
 
    double fWaveHeight = rRectangle.getHeight();
    // Wavelength depends on the wave height so it looks nice
    double fHalfWaveLength = fWaveHeight + 1.0;
    double fWaveAmplitude = fWaveHeight / 2.0;
 
    double fLastX = rRectangle.getMinX();
    double fBaseY = rRectangle.getMinY() + fWaveAmplitude;
    double fDirection = 1.0;
 
    // In quadratic bezier the curve is 1/2 of the control height
    // so we need to compensate for that.
    constexpr double fHeightCompensation = 2.0;
 
    aPolygon.append(basegfx::B2DPoint(fLastX, fBaseY));
 
    for (double fI = fHalfWaveLength; fI <= rRectangle.getWidth(); fI += fHalfWaveLength)
    {
        basegfx::B2DPoint aPoint(fLastX + fHalfWaveLength, fBaseY);
        basegfx::B2DPoint aControl(fLastX + (fHalfWaveLength / 2.0),
                                   fBaseY + fDirection * fWaveAmplitude * fHeightCompensation);
 
        aPolygon.appendQuadraticBezierSegment(aControl, aPoint);
 
        fLastX = aPoint.getX(); // next iteration
        fDirection *= -1.0; // fDirection iterates between 1 and -1
    }
 
    return aPolygon;
}
 
} // end of namespace basegfx
 
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