linenode.cpp Example File

  /****************************************************************************
  **
  ** Copyright (C) 2015 The Qt Company Ltd.
  ** Contact: http://www.qt.io/licensing/
  **
  ** This file is part of the examples of the Qt Toolkit.
  **
  ** $QT_BEGIN_LICENSE:BSD$
  ** You may use this file under the terms of the BSD license as follows:
  **
  ** "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.
  **   * Neither the name of The Qt Company Ltd nor the names of its
  **     contributors may be used to endorse or promote products derived
  **     from this software without specific prior written permission.
  **
  **
  ** 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
  ** OWNER 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."
  **
  ** $QT_END_LICENSE$
  **
  ****************************************************************************/

  #include "linenode.h"

  #include <QtGui/QColor>

  #include <QtQuick/QSGSimpleMaterial>

  struct LineMaterial
  {
      QColor color;
      float spread;
      float size;
  };

  class LineShader : public QSGSimpleMaterialShader<LineMaterial>
  {
      QSG_DECLARE_SIMPLE_SHADER(LineShader, LineMaterial)

  public:
      LineShader() : id_color(-1), id_spread(-1), id_size(-1) {
          setShaderSourceFile(QOpenGLShader::Vertex, ":/scenegraph/graph/shaders/line.vsh");
          setShaderSourceFile(QOpenGLShader::Fragment, ":/scenegraph/graph/shaders/line.fsh");
      }

      QList<QByteArray> attributes() const {  return QList<QByteArray>() << "pos" << "t"; }

      void updateState(const LineMaterial *m, const LineMaterial *) {
          program()->setUniformValue(id_color, m->color);
          program()->setUniformValue(id_spread, m->spread);
          program()->setUniformValue(id_size, m->size);
      }

      void resolveUniforms() {
          id_spread = program()->uniformLocation("spread");
          id_size = program()->uniformLocation("size");
          id_color = program()->uniformLocation("color");
      }

  private:
      int id_color;
      int id_spread;
      int id_size;
  };

  struct LineVertex {
      float x;
      float y;
      float t;
      inline void set(float xx, float yy, float tt) { x = xx; y = yy; t = tt; }
  };

  static const QSGGeometry::AttributeSet &attributes()
  {
      static QSGGeometry::Attribute attr[] = {
          QSGGeometry::Attribute::create(0, 2, GL_FLOAT, true),
          QSGGeometry::Attribute::create(1, 1, GL_FLOAT)
      };
      static QSGGeometry::AttributeSet set = { 2, 3 * sizeof(float), attr };
      return set;
  }

  LineNode::LineNode(float size, float spread, const QColor &color)
      : m_geometry(attributes(), 0)
  {
      setGeometry(&m_geometry);
      m_geometry.setDrawingMode(GL_TRIANGLE_STRIP);

      QSGSimpleMaterial<LineMaterial> *m = LineShader::createMaterial();
      m->state()->color = color;
      m->state()->size = size;
      m->state()->spread = spread;
      m->setFlag(QSGMaterial::Blending);
      setMaterial(m);
      setFlag(OwnsMaterial);
  }

  /*
   * Assumes that samples have values in the range of 0 to 1 and scales them to
   * the height of bounds. The samples are stretched out horizontally along the
   * width of the bounds.
   *
   * The position of each pair of points is identical, but we use the third value
   * "t" to shift the point up or down and to add antialiasing.
   */
  void LineNode::updateGeometry(const QRectF &bounds, const QList<qreal> &samples)
  {
      m_geometry.allocate(samples.size() * 2);

      float x = bounds.x();
      float y = bounds.y();
      float w = bounds.width();
      float h = bounds.height();

      float dx = w / (samples.size() - 1);

      LineVertex *v = (LineVertex *) m_geometry.vertexData();
      for (int i=0; i<samples.size(); ++i) {
          v[i*2+0].set(x + dx * i, y + samples.at(i) * h, 0);
          v[i*2+1].set(x + dx * i, y + samples.at(i) * h, 1);
      }

      markDirty(QSGNode::DirtyGeometry);
  }