Example for reading shapefiles with GDAL and displaying the geometry.

CMakeLists.txt

@@ -4,6 +4,7 @@ project(QGeoView LANGUAGES C CXX)
 
 option(BUILD_EXAMPLES "Build examples" ON)
 
+find_package(GDAL CONFIG)
 add_subdirectory(lib)
 if (${BUILD_EXAMPLES})
   message(STATUS "Enabled building of examples")
@@ -22,6 +23,9 @@ if (${BUILD_EXAMPLES})
   add_subdirectory(samples/moving-objects)
   add_subdirectory(samples/mouse-actions)
   add_subdirectory(samples/camera-actions)
+  if(GDAL_FOUND)
+    add_subdirectory(samples/shapefile)
+  endif()
 else ()
   message(STATUS "Disabled building of examples")
 endif ()

samples/shapefile/CMakeLists.txt

@@ -0,0 +1,40 @@
+set(CMAKE_CXX_STANDARD 11)
+
+set(CMAKE_AUTOMOC ON)
+set(CMAKE_AUTORCC ON)
+set(CMAKE_AUTOUIC ON)
+set(CMAKE_INCLUDE_CURRENT_DIR ON)
+
+# Set the QT version
+find_package(Qt6 COMPONENTS Core QUIET)
+if (NOT Qt6_FOUND)
+    set(QT_VERSION 5 CACHE STRING "Qt version for QGeoView")
+else()
+    set(QT_VERSION 6 CACHE STRING "Qt version for QGeoView")
+endif()
+
+find_package(Qt${QT_VERSION} REQUIRED COMPONENTS
+    Core
+    Gui
+    Widgets
+    Network
+)
+
+add_executable(qgeoview-samples-shapefile
+    main.cpp
+    mainwindow.h
+    mainwindow.cpp
+    polygon.cpp
+    polygon.h
+)
+
+target_link_libraries(qgeoview-samples-shapefile
+    PRIVATE
+    Qt${QT_VERSION}::Core
+    Qt${QT_VERSION}::Network
+    Qt${QT_VERSION}::Gui
+    Qt${QT_VERSION}::Widgets
+    QGeoView
+    qgeoview-samples-shared
+    GDAL::GDAL
+)

samples/shapefile/main.cpp

@@ -0,0 +1,37 @@
+/***************************************************************************
+ * QGeoView is a Qt / C ++ widget for visualizing geographic data.
+ * Copyright (C) 2018-2023 Andrey Yaroshenko.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, see https://www.gnu.org/licenses.
+ ****************************************************************************/
+
+#include <QApplication>
+#include <QCommandLineParser>
+
+#include "mainwindow.h"
+
+int main(int argc, char* argv[])
+{
+    QApplication app(argc, argv);
+    app.setApplicationName("QGeoView Samples");
+
+    QCommandLineParser parser;
+    parser.addHelpOption();
+    parser.addVersionOption();
+    parser.process(app);
+
+    MainWindow window;
+    window.show();
+    return app.exec();
+}

samples/shapefile/mainwindow.cpp

@@ -0,0 +1,121 @@
+/***************************************************************************
+ * QGeoView is a Qt / C ++ widget for visualizing geographic data.
+ * Copyright (C) 2018-2023 Andrey Yaroshenko.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, see https://www.gnu.org/licenses.
+ ****************************************************************************/
+
+#include "mainwindow.h"
+
+#include <QTimer>
+#include <QApplication>
+#include <QDir>
+
+#include <QGeoView/QGVLayerOSM.h>
+#include <helpers.h>
+#include "polygon.h"
+
+#include "cpl_conv.h"
+#include "ogrsf_frmts.h"
+
+QList<QGV::GeoPos> convert(OGRPolygon* poPolygon)
+{
+    OGRPoint ptTemp;
+    QList<QGV::GeoPos> result;
+    OGRLinearRing* poExteriorRing = poPolygon->getExteriorRing();
+    int NumberOfExteriorRingVertices = poExteriorRing->getNumPoints();
+    for (int k = 0; k < NumberOfExteriorRingVertices; k++) {
+        poExteriorRing->getPoint(k, &ptTemp);
+        result << QGV::GeoPos(ptTemp.getY(), ptTemp.getX());
+    }
+    return result;
+}
+
+MainWindow::MainWindow()
+{
+    setWindowTitle("QGeoView Samples - Shapefile");
+
+    mMap = new QGVMap(this);
+    setCentralWidget(mMap);
+
+    Helpers::setupCachedNetworkAccessManager(this);
+
+    // Background layer
+    auto osmLayer = new QGVLayerOSM();
+    mMap->addItem(osmLayer);
+
+    // Please adapt the following two points to your system:
+    //  1. GDAL data path
+    QDir gdalData(QApplication::applicationDirPath());
+    gdalData.cd("gdal");
+    //  2. PROJ data path
+    QDir projData(gdalData);
+
+    // GDAL configuration (https://gdal.org/user/configoptions.html)
+    std::string GDAL_DATA = QDir::toNativeSeparators(gdalData.absolutePath()).toStdString();
+    CPLSetConfigOption("GDAL_DATA", GDAL_DATA.c_str());
+    std::string PROJ_DATA = QDir::toNativeSeparators(projData.absolutePath()).toStdString();
+    CPLSetConfigOption("PROJ_DATA", PROJ_DATA.c_str());
+
+    GDALAllRegister(); // Load GDAL drivers
+    GDALDataset *poDS = static_cast<GDALDataset*>(GDALOpenEx("countries.shp", GDAL_OF_VECTOR, NULL, NULL, NULL)); // Open vector file
+    if (poDS == NULL) {
+        printf("Open failed.\n");
+        exit(1);
+    }
+
+    for (int iLayer = 0; iLayer < poDS->GetLayerCount(); iLayer++)
+    {
+        OGRLayer* poLayer = poDS->GetLayer(iLayer);
+        OGRFeatureDefn* poFDefn = poLayer->GetLayerDefn();
+        poLayer->ResetReading();
+        OGRFeature* poFeature;
+        while ((poFeature = poLayer->GetNextFeature()) != NULL) {
+            OGRGeometry* poGeometry = poFeature->GetGeometryRef();
+            auto type = wkbFlatten(poGeometry->getGeometryType());
+            if (poGeometry != NULL && wkbFlatten(poGeometry->getGeometryType()) == wkbPolygon) {
+                OGRPolygon* poPolygon = (OGRPolygon*)poGeometry;
+                if (poPolygon->IsValid()) {
+                    QList<QGV::GeoPos> points = convert(poPolygon);
+                    if (points.count() > 2)
+                        mMap->addItem(new Polygon(points, Qt::red, Qt::blue));
+                }
+            } else if (poGeometry != NULL && wkbFlatten(poGeometry->getGeometryType()) == wkbMultiPolygon) {
+                OGRMultiPolygon* poMultiPolygon = (OGRMultiPolygon*)poGeometry;
+                for (int i = 0; i < poMultiPolygon->getNumGeometries(); i++) {
+                    OGRPolygon* poPolygon = (OGRPolygon*)poMultiPolygon->getGeometryRef(i);
+                    if (poPolygon->IsValid()) {
+                        QList<QGV::GeoPos> points = convert(poPolygon);
+                        if (points.count() > 2)
+                            mMap->addItem(new Polygon(points, Qt::red, Qt::blue));
+                    }
+                }
+            } else {
+                printf("no polygon geometry\n");
+            }
+            OGRFeature::DestroyFeature(poFeature);
+        }
+    }
+    GDALClose(poDS);
+
+    // Show whole world
+    QTimer::singleShot(100, this, [this]() {
+        auto target = mMap->getProjection()->boundaryGeoRect();
+        mMap->cameraTo(QGVCameraActions(mMap).scaleTo(target));
+    });
+}
+
+MainWindow::~MainWindow()
+{
+}

samples/shapefile/mainwindow.h

@@ -0,0 +1,35 @@
+/***************************************************************************
+ * QGeoView is a Qt / C ++ widget for visualizing geographic data.
+ * Copyright (C) 2018-2023 Andrey Yaroshenko.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, see https://www.gnu.org/licenses.
+ ****************************************************************************/
+
+#pragma once
+
+#include <QMainWindow>
+
+#include <QGeoView/QGVMap.h>
+
+class MainWindow : public QMainWindow
+{
+    Q_OBJECT
+
+public:
+    MainWindow();
+    ~MainWindow();
+
+private:
+    QGVMap* mMap;
+};