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

# graph.cpp Example File

scenegraph/graph/graph.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.
    **
    ** $QT_BEGIN_LICENSE:BSD$
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    #include "graph.h"

    #include "noisynode.h"
    #include "gridnode.h"
    #include "linenode.h"

    Graph::Graph()
        : m_samplesChanged(false)
        , m_geometryChanged(false)
    {
        setFlag(ItemHasContents, true);
    }

    void Graph::appendSample(qreal value)
    {
        m_samples << value;
        m_samplesChanged = true;
        update();
    }

    void Graph::removeFirstSample()
    {
        m_samples.removeFirst();
        m_samplesChanged = true;
        update();
    }

    void Graph::geometryChanged(const QRectF &newGeometry, const QRectF &oldGeometry)
    {
        m_geometryChanged = true;
        update();
        QQuickItem::geometryChanged(newGeometry, oldGeometry);
    }

    class GraphNode : public QSGNode
    {
    public:
        NoisyNode *background;
        GridNode *grid;
        LineNode *line;
        LineNode *shadow;
    };

    QSGNode *Graph::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *)
    {
        GraphNode *n= static_cast<GraphNode *>(oldNode);

        QRectF rect = boundingRect();

        if (rect.isEmpty()) {
            delete n;
            return 0;
        }

        if (!n) {
            n = new GraphNode();

            n->background = new NoisyNode(window());
            n->grid = new GridNode();
            n->line = new LineNode(10, 0.5, QColor("steelblue"));
            n->shadow = new LineNode(20, 0.2, QColor::fromRgbF(0.2, 0.2, 0.2, 0.4));

            n->appendChildNode(n->background);
            n->appendChildNode(n->grid);
            n->appendChildNode(n->shadow);
            n->appendChildNode(n->line);
        }

        if (m_geometryChanged) {
            n->background->setRect(rect);
            n->grid->setRect(rect);
        }

        if (m_geometryChanged || m_samplesChanged) {
            n->line->updateGeometry(rect, m_samples);
            // We don't need to calculate the geometry twice, so just steal it from the other one...
            n->shadow->setGeometry(n->line->geometry());
        }

        m_geometryChanged = false;
        m_samplesChanged = false;

        return n;
    }