gridnode.cpp Example File

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  #include "gridnode.h"

  #include "qmath.h"

  #define GRID_SIZE 32

  GridNode::GridNode()
      : m_geometry(QSGGeometry::defaultAttributes_Point2D(), 0)
  {
      setGeometry(&m_geometry);
      m_geometry.setDrawingMode(GL_LINES);

      setMaterial(&m_material);
      m_material.setColor(Qt::gray);
  }

  /*
   * The function hardcodes a fixed set of grid lines and scales
   * those to the bounding rect.
   */
  void GridNode::setRect(const QRectF &rect)
  {
      int vCount = int((rect.width() - 1) / GRID_SIZE);
      int hCount = int((rect.height() - 1) / GRID_SIZE);

      int lineCount = vCount + hCount;

      QSGGeometry *g = geometry();

      g->allocate(lineCount * 2);

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

      QSGGeometry::Point2D *v = g->vertexDataAsPoint2D();

      // Then write the vertical lines
      for (int i=0; i<vCount; ++i)  {
          float dx = (i + 1) * GRID_SIZE;
          v[i*2].set(dx, y);
          v[i*2+1].set(dx, y + h);
      }
      v += vCount * 2;
      // Then write the horizontal lines
      for (int i=0; i<hCount; ++i)  {
          float dy = (i + 1) * GRID_SIZE;
          v[i*2].set(x, dy);
          v[i*2+1].set(x + w, dy);
      }

      // Tell the scenegraph we updated the geometry..
      markDirty(QSGNode::DirtyGeometry);
  }