Marble/Routing/BasicRouting: Difference between revisions

Revision as of 19:41, 19 December 2011

Editing Projects/Marble/MarbleCPlusPlus

Basic Routing

Tutorial Series	Marble C++ Tutorial
Previous	[Projects/Marble/LayerInterface
What's Next	Tutorial 7 - Customized Routing
Further Reading	n/a

Basic Routing

The Marble library 0.13 and later (KDE 4.8, Marble 1.3) has an API to calculate and manage routes. Let's start with a brief overview of the important classes and their interaction. The class RouteRequest holds parameters that are constraints for the route to be calculated: Start and destination, optional via points and further parameters (e.g. transport type). The RoutingManager passes such a request to backends (routing plugins) that calculate possible routes from it. The best route is chosen and displayed in a special layer in the MarbleWidget. Additionally you can access the route data via the RoutingModel. This model can be passed directly to e.g. a QListView to show the turn instructions, but also exposes further data like the waypoints of the route via the Route class. This one consists of a set of RouteSegment instances, each representing a number of waypoints and an optional turn instruction (Maneuver) at the end.

#include <QtGui/QApplication>
#include <marble/MarbleWidget.h>
#include <marble/MarbleModel.h>
#include <marble/RouteRequest.h>
#include <marble/RoutingManager.h>

using namespace Marble;

int main(int argc, char** argv)
{
    QApplication app(argc,argv);

    // Create a Marble QWidget without a parent
    MarbleWidget *mapWidget = new MarbleWidget();

    // Load the OpenStreetMap map
    mapWidget->setMapThemeId( "earth/openstreetmap/openstreetmap.dgml" );
    mapWidget->setProjection( Mercator );

    // Access the shared route request (start, destination and parameters)
    RoutingManager* manager = mapWidget->model()->routingManager();
    RouteRequest* request = manager->routeRequest();

    // Use default routing settings for cars
    request->setRoutingProfile( manager->defaultProfile( RoutingProfile::Motorcar ) );

    // Set start and destination
    request->append( GeoDataCoordinates( 8.38942, 48.99738, 0.0, GeoDataCoordinates::Degree ) );
    request->append( GeoDataCoordinates( 8.42002, 49.0058, 0.0, GeoDataCoordinates::Degree ) );

    // Calculate the route
    manager->retrieveRoute();

    // Center the map on the route start point and show it
    mapWidget->centerOn( request->at( 0 ) );
    mapWidget->setDistance( 0.75 );
    mapWidget->show();

    return app.exec();
}

Copy and paste the code above into a text editor. Then save it as my_marble.cpp and compile it by entering the following command on the command line:

 g++ -I /usr/include/qt4/ -o my_marble my_marble.cpp -lmarblewidget -lQtGui -lQtCore

If things go fine, execute ./my_marble and you end up with a fully usable OpenStreetMap application:

Tip

Here's a little checklist to tackle some problems that might arise when compiling the code above:

You need Qt and Marble development packages (or comparable git installations), version 1.3 (Marble library 0.13), shipped e.g. with KDE 4.8
If Qt headers are not installed in /usr/include/qt4 on your system, change the path in the g++ call above accordingly.
Likewise, add -I /path/to/marble/headers if they're not to be found in /usr/include

Note

If you provide maps in your application please check the Terms of Use of the map material. The map material that is shipped with Marble is licensed in the spirit of Free Software. This usually means at least that the authors should be credited and that the license is mentioned. E.g. for OpenStreetMap the license is CC-BY-SA. Other map data shipped with Marble is either public domain or licensed in the spirit of the BSD license.