QT QML Model from C++ - Issue with Map Rendering - c++

Question

I am building an application to create and edit gpx files on a map. I want to be able to render a line and set of markers from a single model.
Each GPX point has a co-ordinate, elevation and a time. I am aiming to create a model that can be used to show it on the map and also show the elevation profile.
I have modified the answer to this question QT QmlMap PolyLine not updated properly when underlying model changes in order to base my model on a structure of GPX points.
main.c
#include "mainwindow.h"
#include <QApplication>
#include <QQmlApplicationEngine>
#include "mapmarker.h"
#include <QQmlContext>
int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
//Added for model registration
QQmlApplicationEngine engine;
qmlRegisterType<MarkerModel>("MarkerModel", 1, 0, "MarkerModel");
engine.load(QUrl(QStringLiteral("qrc:/mainWindow.qml")));
return app.exec();
}
mainWindow.qml
import QtQuick 2.3
import QtQuick.Window 2.3
import QtLocation 5.9
import MarkerModel 1.0
ApplicationWindow {
id: appWindow
width: 1512
height: 1512
visible: true
x:100
y:100
MarkerModel{
id: markerModel
}
Plugin {
id: mapPlugin
name: "osm"
}
Map {
id: mapView
anchors.fill: parent
plugin: mapPlugin
MapItemView {
model: markerModel
delegate: routeMarkers
}
MapPolyline {
line.width: 5
path: markerModel.path
}
Component {
id: routeMarkers
MapCircle {
radius: 10
center: positionRole
}
}
MouseArea {
anchors.fill: parent
onClicked: {
var coord = parent.toCoordinate(Qt.point(mouse.x,mouse.y))
markerModel.addMarker(coord)
}
}
}
}
mapmarker.h
#ifndef MAPMARKER_H
#define MAPMARKER_H
#include <QAbstractListModel>
#include <QGeoCoordinate>
#include <QDebug>
#include <QDate>
struct gpxCoordinate {
QGeoCoordinate latlon;
float ele;
QDateTime time;
};
class MarkerModel : public QAbstractListModel {
Q_OBJECT
Q_PROPERTY(QVariantList path READ path NOTIFY pathChanged)
public:
enum MarkerRoles{positionRole = Qt::UserRole, pathRole};
MarkerModel(QObject *parent=nullptr): QAbstractListModel(parent)
{
connect(this, &QAbstractListModel::rowsInserted, this, &MarkerModel::pathChanged);
connect(this, &QAbstractListModel::rowsRemoved, this, &MarkerModel::pathChanged);
connect(this, &QAbstractListModel::dataChanged, this, &MarkerModel::pathChanged);
connect(this, &QAbstractListModel::modelReset, this, &MarkerModel::pathChanged);
connect(this, &QAbstractListModel::rowsMoved, this, &MarkerModel::pathChanged);
}
Q_INVOKABLE void addMarker(const QGeoCoordinate &coordinate, float elevation = 0, QDateTime dateTime = QDateTime::currentDateTime()) {
gpxCoordinate item;
item.latlon = coordinate;
item.ele = elevation;
item.time = dateTime;
beginInsertRows(QModelIndex(), rowCount(), rowCount());
m_coordinates.append(item);
endInsertRows();
}
int rowCount(const QModelIndex &parent = QModelIndex()) const override {
if(parent.isValid()) return 0;
return m_coordinates.count();
}
bool removeRows(int row, int count, const QModelIndex &parent = QModelIndex()) override {
if(row + count > m_coordinates.count() || row < 0)
return false;
beginRemoveRows(parent, row, row+count-1);
for(int i = 0; i < count; ++i)
m_coordinates.removeAt(row + i);
endRemoveRows();
return true;
}
bool removeRow(int row, const QModelIndex &parent = QModelIndex()) {
return removeRows(row, 1, parent);
}
QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override {
if (index.row() < 0 || index.row() >= m_coordinates.count())
return QVariant();
if(role == Qt::DisplayRole)
return QVariant::fromValue(index.row());
else if(role == MarkerModel::positionRole){
return QVariant::fromValue(m_coordinates[index.row()].latlon);
}
return QVariant();
}
QHash<int, QByteArray> roleNames() const override{
QHash<int, QByteArray> roles;
roles[positionRole] = "positionRole";
return roles;
}
QVariantList path() const{
QVariantList path;
for(const gpxCoordinate & coord: m_coordinates){
path << QVariant::fromValue(coord.latlon);
}
return path;
}
signals:
void pathChanged();
private:
QVector<gpxCoordinate> m_coordinates;
};
#endif // MARKERMODEL_H
I think I have made a really basic mistake somewhere as I can click on the map and draw a polyline but the MapCircles are not rendering. I see the error:-
Unable to assign [undefined] to QGeoCoordinate
When I first click on the map.
Have I misunderstood how models/roles work in Qt QML?

Answer 1

I have tracked this down to a build issue. I had some additional paths in my .pro file and was including some libraries that were not being used (spatialite) removing these fixed the issue completely.
I will leave the question up as it may be useful to anyone wanting to do something similar.