- Qt 5.5
- Qt Quick
- Scene Graph - Graph
- gridnode.cpp Example File
- Qt 5.5.1 Reference Documentation

# gridnode.cpp Example File

scenegraph/graph/gridnode.cpp

    /****************************************************************************
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    ** This file is part of the examples of the Qt Toolkit.
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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);
    }