QML Map with many items takes a long time to shut down

[izeilstra]

I am currently working on a small test application which uses QML Map to display a collection of paths. Each path is a list of coordinates. For each path, I create a MapPolyline with the coordinates as its path property, and then for each coordinate on the path, I create a MapQuickItem with that coordinate as its coordinate property. I am currently rendering 500 paths each containing 100 coordinates. The application starts up reasonably quickly but does not ever seem to finish shutting down on close. I am wondering if my approach is somehow unreasonably inefficient.

mymap.qml:

import QtQuick 2.0
import QtPositioning 5.6
import QtLocation 5.6
import com.plexsys.fpscounter 1.0

Map {
  id: myMap

  zoomLevel: 4
  center { latitude: 0; longitude: 0 }

  Plugin {
    id: myPlugin
    name: "itemsoverlay"
  }

  plugin: myPlugin

  MapPolyline {
    id: primeMeridian
    line.width: 3
    line.color: "green"
    path: [
      { latitude: -90, longitude: 0 },
      { latitude: 0, longitude: 0 },
      { latitude: 90, longitude: 0}
    ]
  }

  MapPolyline {
    id: equator
    line.width: 3
    line.color: "green"
    path: [
      { latitude: 0, longitude: -180 },
      { latitude: 0, longitude: -90 },
      { latitude: 0, longitude: 0 },
      { latitude: 0, longitude: 90 },
      { latitude: 0, longitude: 180 },
    ]
  }

  FpsCounter {
    id: fps_text
    x: 0
    y: 0
    z: parent.z + 1
    width: 50
    height: 25
    Text {
      anchors.centerIn: parent
      text: fps_text.fps.toFixed(2)
    }
  }

  Repeater {
    model: randomPathModel

    MapPolyline {
      line.width: 2
      line.color: "blue"
      path: randomPath.points
      Component.onCompleted: {
        myMap.addMapItem(this)
      }
    }
  }

  Repeater {
    model: randomPathModel

    Repeater {
      model: randomPath

      MapQuickItem {
        coordinate: randomPoint
        sourceItem: Rectangle {
          width: 16
          height: 16
          color: "red"
        }
        anchorPoint.x: sourceItem.width / 2
        anchorPoint.y: sourceItem.height / 2
        Component.onCompleted: {
          myMap.addMapItem(this)
        }
      }
    }
  }
}

QMLMapTester.cpp:

#include <QtCore/QUrl>

#include <QtWidgets/QApplication>
#include <QtWidgets/QMainWindow>
#include <QtWidgets/QHBoxLayout>

#include <QtQuick/QQuickView>

#include <QtQml/QQmlContext>

#include "RandomPathModel.h"
#include "FpsCounter.h"

////////////////////////////////////////////////////////////////////////////////

class MyMainWindow : public QMainWindow
{
public:
  MyMainWindow(QWidget* parent = nullptr) : QMainWindow(parent)
  {
    QWidget* mainWidget = new QWidget(this);
    setCentralWidget(mainWidget);
    QHBoxLayout* layout = new QHBoxLayout(mainWidget);

    m_view = new QQuickView;
    m_view->setResizeMode(QQuickView::SizeRootObjectToView);
    
    QWidget* container = QWidget::createWindowContainer(m_view, this);
    layout->addWidget(container);
  }

  QQuickView* getView() { return m_view; }

private:
  QQuickView* m_view;
};

////////////////////////////////////////////////////////////////////////////////

int main(int argc, char** argv)
{
  qmlRegisterType<FpsCounter>("com.plexsys.fpscounter", 1, 0, "FpsCounter");

  QApplication app(argc, argv);
  
  MyMainWindow mainWindow;

  RandomPathModel rpm;
  rpm.addPaths(500, 100);

  QQuickView* view = mainWindow.getView();
  QQmlContext* context = view->rootContext();
  context->setContextProperty("randomPathModel", &rpm);
  view->setSource(QUrl("mymap.qml"));

  mainWindow.show();

  return app.exec();
}

RandomPathModel.h:

#ifndef _QMLMAPTESTER_RANDOMPATHMODEL_H
#define _QMLMAPTESTER_RANDOMPATHMODEL_H
////////////////////////////////////////////////////////////////////////////////

#include "RandomPointModel.h"
#include <QtCore/QSharedPointer>

////////////////////////////////////////////////////////////////////////////////

class RandomPathModel : public QAbstractListModel
{
  Q_OBJECT

public:
  RandomPathModel(QObject* parent = nullptr);
  ~RandomPathModel();

  Q_PROPERTY(int length READ length CONSTANT)

  enum Roles
  {
    PathRole = Qt::UserRole + 1
  };

  int rowCount(const QModelIndex& parent) const override;

  int length() const;

  QVariant data(const QModelIndex& index, int role = Qt::DisplayRole) const override;

  void addPaths(int iNumPaths, int iNumPoints);

protected:
  QHash<int, QByteArray> roleNames() const override;

private:
  typedef QSharedPointer<RandomPointModel> RandomPointModelSharedPointer;
  typedef QList<RandomPointModelSharedPointer> PathList;
  PathList m_paths;
};

////////////////////////////////////////////////////////////////////////////////
#endif // _QMLMAPTESTER_RANDOMPATHMODEL_H

RandomPointModel.h:

#ifndef _QMLMAPTESTER_RANDOMPOINTMODEL_H
#define _QMLMAPTESTER_RANDOMPOINTMODEL_H
////////////////////////////////////////////////////////////////////////////////

#include <QtCore/QAbstractListModel>
#include <QtCore/QList>
#include <QtCore/QVariantList>
#include <QtPositioning/QGeoCoordinate>

////////////////////////////////////////////////////////////////////////////////

class RandomPointModel : public QAbstractListModel
{
  Q_OBJECT

public:
  RandomPointModel(QObject* parent = nullptr);
  ~RandomPointModel();

  enum Roles
  {
    PointRole = Qt::UserRole + 1
  };

  int rowCount(const QModelIndex& parent) const override;

  QVariant data(const QModelIndex& index, int role = Qt::DisplayRole) const override;

  void addPoints(int iNumPoints);

  Q_PROPERTY(QVariantList points READ points NOTIFY pointsChanged);

  const QVariantList& points() const;

signals:
  void pointsChanged(const QVariantList&);

protected:
  QHash<int, QByteArray> roleNames() const override;

private:
  QVariantList m_points;
};

////////////////////////////////////////////////////////////////////////////////
#endif // _QMLMAPTESTER_RANDOMPOINTMODEL_H

The model implementations are fairly obvious but I can include them if they matter.