Qt 5.6 | Qt Quick | Scene Graph - Graph | gridnode.cpp Example File

Qt 5.6.2 Reference Documentation

# gridnode.cpp Example File

scenegraph/graph/gridnode.cpp

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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);
      }