text: // g2o - General Graph Optimization
  // Copyright (C) 2011 R. Kuemmerle, G. Grisetti, W. Burgard
  // All rights reserved.
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  // * Redistributions of source code must retain the above copyright notice,
  //   this list of conditions and the following disclaimer.
  // * Redistributions in binary form must reproduce the above copyright
  //   notice, this list of conditions and the following disclaimer in the
  //   documentation and/or other materials provided with the distribution.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
  // IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  // TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  // PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
  // TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  // PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  // LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  // NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  #include "edge_se2_odom_differential_calib.h"
  
  #ifdef G2O_HAVE_OPENGL
  #include "g2o/stuff/opengl_wrapper.h"
  #endif
  
  namespace g2o {
  
  EdgeSE2OdomDifferentialCalib::EdgeSE2OdomDifferentialCalib()
      : BaseFixedSizedEdge<3, VelocityMeasurement, VertexSE2, VertexSE2,
                           VertexOdomDifferentialParams>() {}
  
  bool EdgeSE2OdomDifferentialCalib::read(std::istream& is) {
    number_t vl, vr, dt;
    is >> vl >> vr >> dt;
    VelocityMeasurement vm(vl, vr, dt);
    setMeasurement(vm);
    return readInformationMatrix(is);
  }
  
  bool EdgeSE2OdomDifferentialCalib::write(std::ostream& os) const {
    os << measurement().vl() << " " << measurement().vr() << " "
       << measurement().dt() << " ";
    return writeInformationMatrix(os);
  }
  
  #ifdef G2O_HAVE_OPENGL
  EdgeSE2OdomDifferentialCalibDrawAction::EdgeSE2OdomDifferentialCalibDrawAction()
      : DrawAction(typeid(EdgeSE2OdomDifferentialCalib).name()) {}
  
  HyperGraphElementAction* EdgeSE2OdomDifferentialCalibDrawAction::operator()(
      HyperGraph::HyperGraphElement* element,
      HyperGraphElementAction::Parameters*) {
    if (typeid(*element).name() != _typeName) return nullptr;
    EdgeSE2OdomDifferentialCalib* e =
        static_cast<EdgeSE2OdomDifferentialCalib*>(element);
    VertexSE2* fromEdge = static_cast<VertexSE2*>(e->vertex(0));
    VertexSE2* toEdge = static_cast<VertexSE2*>(e->vertex(1));
    glColor3f(0.5f, 0.5f, 0.5f);
    glPushAttrib(GL_ENABLE_BIT);
    glDisable(GL_LIGHTING);
    glBegin(GL_LINES);
    glVertex3f((float)fromEdge->estimate().translation().x(),
               (float)fromEdge->estimate().translation().y(), 0.f);
    glVertex3f((float)toEdge->estimate().translation().x(),
               (float)toEdge->estimate().translation().y(), 0.f);
    glEnd();
    glPopAttrib();
    return this;
  }
  #endif
  
  }  // namespace g2o
  