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

# linenode.cpp Example File

scenegraph/graph/linenode.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** You may use this file under the terms of the BSD license as follows:
    **
    ** "Redistribution and use in source and binary forms, with or without
    ** modification, are permitted provided that the following conditions are
    ** met:
    **   * Redistributions of source code must retain the above copyright
    **     notice, this list of conditions and the following disclaimer.
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    **     notice, this list of conditions and the following disclaimer in
    **     the documentation and/or other materials provided with the
    **     distribution.
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    **     contributors may be used to endorse or promote products derived
    **     from this software without specific prior written permission.
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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 {  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);
    }