Qt 5.6 | Qt Quick | Scene Graph - Custom Geometry | beziercurve.cpp Example File

Qt 5.6.3 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
      ** Licensees holding valid commercial Qt licenses may use this file in
      ** accordance with the commercial license agreement provided with the
      ** Software or, alternatively, in accordance with the terms contained in
      ** a written agreement between you and The Qt Company. For licensing terms
      ** and conditions see http://www.qt.io/terms-conditions. For further
      ** information use the contact form at http://www.qt.io/contact-us.
      **
      ** 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
      ** following information to ensure the GNU Lesser General Public License
      ** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
      ** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
      **
      ** As a special exception, The Qt Company gives you certain additional
      ** rights. These rights are described in The Qt Company LGPL Exception
      ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
      **
      ** $QT_END_LICENSE$
      **
      ****************************************************************************/

      #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;
      }