basegfx/source/polygon/WaveLine.cxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  *
   9  */
  10
  11 #include <basegfx/polygon/WaveLine.hxx>
  12 #include <basegfx/point/b2dpoint.hxx>
  13
  14 namespace basegfx
  15 {
  16 BASEGFX_DLLPUBLIC B2DPolygon createWaveLinePolygon(basegfx::B2DRectangle const& rRectangle)
  17 {
  18     basegfx::B2DPolygon aPolygon;
  19
  20     double fWaveHeight = rRectangle.getHeight();
  21     // Wavelength depends on the wave height so it looks nice
  22     double fHalfWaveLength = fWaveHeight + 1.0;
  23     double fWaveAmplitude = fWaveHeight / 2.0;
  24
  25     double fLastX = rRectangle.getMinX();
  26     double fBaseY = rRectangle.getMinY() + fWaveAmplitude;
  27     double fDirection = 1.0;
  28
  29     // In quadratic bezier the curve is 1/2 of the control height
  30     // so we need to compensate for that.
  31     constexpr double fHeightCompensation = 2.0;
  32
  33     aPolygon.append(basegfx::B2DPoint(fLastX, fBaseY));
  34
  35     for (double fI = fHalfWaveLength; fI <= rRectangle.getWidth(); fI += fHalfWaveLength)
  36     {
  37         basegfx::B2DPoint aPoint(fLastX + fHalfWaveLength, fBaseY);
  38         basegfx::B2DPoint aControl(fLastX + (fHalfWaveLength / 2.0),
  39                                    fBaseY + fDirection * fWaveAmplitude * fHeightCompensation);
  40
  41         aPolygon.appendQuadraticBezierSegment(aControl, aPoint);
  42
  43         fLastX = aPoint.getX(); // next iteration
  44         fDirection *= -1.0; // fDirection iterates between 1 and -1
  45     }
  46
  47     return aPolygon;
  48 }
  49
  50 } // end of namespace basegfx
  51
  52 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */