linenode.cpp Example File | Qt Quick 5.12.8

- Qt 5.12
- Qt Quick
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- linenode.cpp Example File
- Qt 5.12.8 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() {
             setShaderSourceFile(QOpenGLShader::Vertex, ":/scenegraph/graph/shaders/line.vsh");
             setShaderSourceFile(QOpenGLShader::Fragment, ":/scenegraph/graph/shaders/line.fsh");
         }

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

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

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

     private:
         int id_color = -1;
         int id_spread = -1;
         int id_size = -1;
     };

     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);
     }