- Qt 5.5
- Qt Quick
- Scene Graph - Custom Geometry
- beziercurve.cpp Example File
- Qt 5.5.1 Reference Documentation

# beziercurve.cpp Example File

scenegraph/customgeometry/beziercurve.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the demonstration applications of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:LGPL21$
    ** Commercial License Usage
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    ** GNU Lesser General Public License Usage
    ** Alternatively, this file may be used under the terms of the GNU Lesser
    ** General Public License version 2.1 or version 3 as published by the Free
    ** Software Foundation and appearing in the file LICENSE.LGPLv21 and
    ** LICENSE.LGPLv3 included in the packaging of this file. Please review the
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    #include "beziercurve.h"

    #include <QtQuick/qsgnode.h>
    #include <QtQuick/qsgflatcolormaterial.h>

    BezierCurve::BezierCurve(QQuickItem *parent)
        : QQuickItem(parent)
        , m_p1(0, 0)
        , m_p2(1, 0)
        , m_p3(0, 1)
        , m_p4(1, 1)
        , m_segmentCount(32)
    {
        setFlag(ItemHasContents, true);
    }

    BezierCurve::~BezierCurve()
    {
    }

    void BezierCurve::setP1(const QPointF &p)
    {
        if (p == m_p1)
            return;

        m_p1 = p;
        emit p1Changed(p);
        update();
    }

    void BezierCurve::setP2(const QPointF &p)
    {
        if (p == m_p2)
            return;

        m_p2 = p;
        emit p2Changed(p);
        update();
    }

    void BezierCurve::setP3(const QPointF &p)
    {
        if (p == m_p3)
            return;

        m_p3 = p;
        emit p3Changed(p);
        update();
    }

    void BezierCurve::setP4(const QPointF &p)
    {
        if (p == m_p4)
            return;

        m_p4 = p;
        emit p4Changed(p);
        update();
    }

    void BezierCurve::setSegmentCount(int count)
    {
        if (m_segmentCount == count)
            return;

        m_segmentCount = count;
        emit segmentCountChanged(count);
        update();
    }

    QSGNode *BezierCurve::updatePaintNode(QSGNode *oldNode, UpdatePaintNodeData *)
    {
        QSGGeometryNode *node = 0;
        QSGGeometry *geometry = 0;

        if (!oldNode) {
            node = new QSGGeometryNode;
            geometry = new QSGGeometry(QSGGeometry::defaultAttributes_Point2D(), m_segmentCount);
            geometry->setLineWidth(2);
            geometry->setDrawingMode(GL_LINE_STRIP);
            node->setGeometry(geometry);
            node->setFlag(QSGNode::OwnsGeometry);
            QSGFlatColorMaterial *material = new QSGFlatColorMaterial;
            material->setColor(QColor(255, 0, 0));
            node->setMaterial(material);
            node->setFlag(QSGNode::OwnsMaterial);
        } else {
            node = static_cast<QSGGeometryNode *>(oldNode);
            geometry = node->geometry();
            geometry->allocate(m_segmentCount);
        }

        QRectF bounds = boundingRect();
        QSGGeometry::Point2D *vertices = geometry->vertexDataAsPoint2D();
        for (int i = 0; i < m_segmentCount; ++i) {
            qreal t = i / qreal(m_segmentCount - 1);
            qreal invt = 1 - t;

            QPointF pos = invt * invt * invt * m_p1
                        + 3 * invt * invt * t * m_p2
                        + 3 * invt * t * t * m_p3
                        + t * t * t * m_p4;

            float x = bounds.x() + pos.x() * bounds.width();
            float y = bounds.y() + pos.y() * bounds.height();

            vertices[i].set(x, y);
        }
        node->markDirty(QSGNode::DirtyGeometry);

        return node;
    }