mapnik/plugins/input/templates/helloworld/hello_datasource.cpp

// file plugin
#include "hello_datasource.hpp"
#include "hello_featureset.hpp"

// boost
#include <boost/make_shared.hpp>


using mapnik::datasource;
using mapnik::parameters;

DATASOURCE_PLUGIN(hello_datasource)

hello_datasource::hello_datasource(parameters const& params, bool bind)
: datasource(params),
    type_(datasource::Vector),
    desc_(*params_.get<std::string>("type"), *params_.get<std::string>("encoding","utf-8")),
    extent_()
{
    if (bind)
    {
        this->bind();
    }
}

void hello_datasource::bind() const
{
    if (is_bound_) return;

    // every datasource must have some way of reporting its extent
    // in this case we are not actually reading from any data so for fun
    // let's just create a world extent in Mapnik's default srs:
    // '+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs' (equivalent to +init=epsg:4326)
    // see http://spatialreference.org/ref/epsg/4326/ for more details
    extent_.init(-180,-90,180,90);

    // declare that this datasource is going to provide points
    // options are point,polygon,linestring, and collection
    desc_.set_geometry_type("point");

    is_bound_ = true;
}

hello_datasource::~hello_datasource() { }

// This name must match the plugin filename, eg 'hello.input'
std::string const hello_datasource::name_="hello";

std::string hello_datasource::name()
{
    return name_;
}

int hello_datasource::type() const
{
    return type_;
}

mapnik::box2d<double> hello_datasource::envelope() const
{
    if (!is_bound_) bind();

    return extent_;
}

mapnik::layer_descriptor hello_datasource::get_descriptor() const
{
    if (!is_bound_) bind();

    return desc_;
}

mapnik::featureset_ptr hello_datasource::features(mapnik::query const& q) const
{
    if (!is_bound_) bind();

    // if the query box intersects our world extent then query for features
    if (extent_.intersects(q.get_bbox()))
    {
        return boost::make_shared<hello_featureset>(q.get_bbox(),desc_.get_encoding());
    }

    // otherwise return an empty featureset pointer
    return mapnik::featureset_ptr();
}

mapnik::featureset_ptr hello_datasource::features_at_point(mapnik::coord2d const& pt) const
{
    if (!is_bound_) bind();

    // features_at_point is rarely used - only by custom applications,
    // so for this sample plugin let's do nothing...
    return mapnik::featureset_ptr();
}