Qt 5.9 | Qt Quick | Scene Graph - Graph | linenode.cpp Example File

Qt 5.9.9 Reference Documentation

# linenode.cpp Example File

scenegraph/graph/linenode.cpp

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      #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);
      }