Add QGeoJson: a GeoJSON parser

Add a Class to convert a GeoJSON document to a QVariantList ready to be
used as Model in a MapItemView. It comes with autotests, example and
detailed documentation.

[ChangeLog][QtLocation] Added a GeoJSON parser which can be used to
annotate maps with tracks, polygonal boundaries, etc.

Fixes: QTBUG-64111
Change-Id: Ib06d3902a052f69f75ae40be5c9ab56023cad916
Reviewed-by: Paolo Angelelli <paolo.angelelli@qt.io>

1 files changed, 263 insertions, 0 deletions

diff --git a/examples/location/geojson_viewer/main.cpp b/examples/location/geojson_viewer/main.cpp
new file mode 100644
index 00000000..451df7ed
--- /dev/null
+++ b/examples/location/geojson_viewer/main.cpp
@@ -0,0 +1,263 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2018 Julian Sherollari <jdotsh@gmail.com>
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** 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 https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** BSD License Usage
+** Alternatively, you may use this file under the terms of the BSD license
+** as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of The Qt Company Ltd nor the names of its
+**     contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QGuiApplication>
+#include <QQmlApplicationEngine>
+#include <QDebug>
+#include <QFile>
+#include <QJsonDocument>
+#include <QVariantMap>
+#include <QQmlContext>
+#include <QtLocation/private/qgeojson_p.h>
+#include <QGeoCircle>
+#include <QGeoPath>
+#include <QGeoPolygon>
+#include <QtLocation/private/qdeclarativegeomapitemview_p.h>
+#include <QtLocation/private/qdeclarativegeomapquickitem_p.h>
+#include <QtLocation/private/qdeclarativecirclemapitem_p.h>
+#include <QtLocation/private/qdeclarativepolylinemapitem_p.h>
+#include <QtLocation/private/qdeclarativepolygonmapitem_p.h>
+#include <QtLocation/private/qdeclarativerectanglemapitem_p.h>
+#include <QJsonObject>
+#include <QJsonArray>
+
+class extractor
+{
+public:
+    extractor();
+
+    static bool hasProperties(QQuickItem *item)
+    {
+        QVariant props = item->property("props");
+        return !props.isNull();
+    }
+
+    static bool isFeatureCollection(QQuickItem *item)
+    {
+        QVariant geoJsonType = item->property("geojsonType");
+        return geoJsonType.toString() == QStringLiteral("FeatureCollection");
+    }
+
+    static bool isGeoJsonEntry(QQuickItem *item)
+    {
+        QVariant geoJsonType = item->property("geojsonType");
+        return !geoJsonType.toString().isEmpty();
+    }
+
+    static QVariantMap toVariant(QDeclarativePolygonMapItem *mapPolygon)
+    {
+        QVariantMap ls;
+        ls["type"] = "Polygon";
+        ls["data"] = QVariant::fromValue(mapPolygon->geoShape());
+        if (hasProperties(mapPolygon))
+            ls["properties"] = mapPolygon->property("props").toMap();
+        return ls;
+    }
+    static QVariantMap toVariant(QDeclarativePolylineMapItem *mapPolyline)
+    {
+        QVariantMap ls;
+        ls["type"] = "LineString";
+        ls["data"] = QVariant::fromValue(mapPolyline->geoShape());
+        if (hasProperties(mapPolyline))
+            ls["properties"] = mapPolyline->property("props").toMap();
+        return ls;
+    }
+    static QVariantMap toVariant(QDeclarativeCircleMapItem *mapCircle)
+    {
+        QVariantMap pt;
+        pt["type"] = "Point";
+        pt["data"] = QVariant::fromValue(mapCircle->geoShape());
+        if (hasProperties(mapCircle))
+            pt["properties"] = mapCircle->property("props").toMap();
+        return pt;
+    }
+
+    static QVariantMap toVariant(QDeclarativeGeoMapItemView *mapItemView)
+    {
+        // bool featureCollecton = isFeatureCollection(mapItemView);
+
+        // If not a feature collection, this must be a geometry collection,
+        // or a multilinestring/multipoint/multipolygon.
+        // To disambiguate, one could check for heterogeneity.
+        // For simplicity, in this example, we expect the property "geojsonType" to be injected in the mapItemView
+        // by the delegate, and to be correct.
+
+        QString nodeType = mapItemView->property("geojsonType").toString();
+        QVariantMap root;
+        if (!nodeType.isEmpty())  // Empty nodeType can happen only for the root MIV
+            root["type"] = nodeType;
+        if (hasProperties(mapItemView)) // Features are converted to regular types w properties.
+            root["properties"] = mapItemView->property("props").toMap();
+
+        QVariantList features;
+        const QList<QQuickItem *> &quickChildren = mapItemView->childItems();
+        for (auto kid : quickChildren) {
+            QVariant entry;
+            if (QDeclarativeGeoMapItemView *miv = qobject_cast<QDeclarativeGeoMapItemView *>(kid)) {
+                // Handle nested miv
+                entry = toVariant(miv);
+            } else if (QDeclarativePolylineMapItem *polyline = qobject_cast<QDeclarativePolylineMapItem *>(kid)) {
+                entry = toVariant(polyline);
+            } else if (QDeclarativePolygonMapItem *polygon = qobject_cast<QDeclarativePolygonMapItem *>(kid)) {
+                entry = toVariant(polygon);
+            } else if (QDeclarativeCircleMapItem *circle = qobject_cast<QDeclarativeCircleMapItem *>(kid)) {
+                entry = toVariant(circle); // If GeoJSON Point type is visualized in other ways, handle those types here instead.
+            }
+            features.append(entry);
+        }
+        if (nodeType.isEmpty()) // Dirty hack to handle (=skip) the first MIV used to process the fictitious list with 1 element
+            return features.first().toMap();
+        root["data"] = features;
+        return root;
+    }
+};
+
+class GeoJsoner: public QObject
+{
+    Q_OBJECT
+    Q_PROPERTY(QVariant model MEMBER m_importedGeoJson NOTIFY modelChanged)
+
+public:
+    GeoJsoner(QObject *parent = nullptr) : QObject(parent)
+    {
+
+    }
+
+public slots:
+
+    Q_INVOKABLE bool load(QUrl url)
+    {
+        // Reading GeoJSON file
+        QFile loadFile(url.toLocalFile());
+        if (!loadFile.open(QIODevice::ReadOnly)) {
+            qWarning() << "Error while opening the file: " << url;
+            qWarning() << loadFile.error() <<  loadFile.errorString();
+            return false;
+        }
+
+        // Load the GeoJSON file using Qt's API
+        QJsonParseError err;
+        QJsonDocument loadDoc(QJsonDocument::fromJson(loadFile.readAll(), &err));
+        if (err.error) {
+             qWarning() << "Parsing while importing the JSON document:\n" << err.errorString();
+             return false;
+        }
+
+        // Import geographic data to a QVariantList
+        QVariantList modelList = QGeoJson::importGeoJson(loadDoc);
+        qDebug() << "Testing instant export for bbox and id members: " << QGeoJson::exportGeoJson(modelList);
+        m_importedGeoJson =  modelList;
+        emit modelChanged();
+        return true;
+    }
+
+    // Used by the MapItemView Extractor to identify a Feature
+    Q_INVOKABLE QVariantList toGeoJson(QDeclarativeGeoMapItemView *mapItemView)
+    {
+        QVariantList res;
+        QDeclarativeGeoMapItemView *root = mapItemView;
+        QVariantMap miv = extractor::toVariant(root);
+        if (!miv.isEmpty())
+            res.append(miv);
+        return res;
+    }
+
+    Q_INVOKABLE void dumpGeoJSON(QVariantList geoJson, QUrl url)
+    {
+        QJsonDocument json = QGeoJson::exportGeoJson(geoJson);
+        QFile jsonFile(url.toLocalFile());
+        jsonFile.open(QIODevice::WriteOnly);
+        jsonFile.write(json.toJson());
+        jsonFile.close();
+    }
+
+    Q_INVOKABLE void writeDebug(QVariantList geoJson, QUrl url)
+    {
+        QString prettyPrint = QGeoJson::toString(geoJson);
+        QFile debugFile(url.toLocalFile());
+        debugFile.open(QIODevice::WriteOnly);
+        debugFile.write(prettyPrint.toUtf8());
+        debugFile.close();
+    }
+
+    Q_INVOKABLE void print(QDeclarativeGeoMapItemView *view)
+    {
+        QVariantList list;
+        list.append(extractor::toVariant(view));
+        QString prettyPrint =
+                QGeoJson::toString(list);
+        qDebug().noquote() << prettyPrint;
+    }
+
+signals:
+    void modelChanged();
+
+public:
+    QVariant m_importedGeoJson;
+};
+
+#include "main.moc"
+
+int main(int argc, char *argv[])
+{
+    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
+    QGuiApplication app(argc, argv);
+
+    // Switch to QML app
+    QQmlApplicationEngine engine;
+    qmlRegisterType<GeoJsoner>("Qt.GeoJson", 1, 0, "GeoJsoner");
+    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
+
+    if (engine.rootObjects().isEmpty())
+        return -1;
+
+    return app.exec();
+}