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// mapnik
#include <mapnik/feature_factory.hpp>
#include <mapnik/geometry.hpp>
// boost
#include <boost/make_shared.hpp>
#include "hello_featureset.hpp"
hello_featureset::hello_featureset(mapnik::box2d<double> const& box, std::string const& encoding)
: box_(box),
feature_id_(1),
tr_(new mapnik::transcoder(encoding)),
ctx_(boost::make_shared<mapnik::context_type>()) { }
hello_featureset::~hello_featureset() { }
mapnik::feature_ptr hello_featureset::next()
{
if (feature_id_ == 1)
{
// let us pretend it just has one column/attribute name
std::string attribute("key");
// the featureset context needs to know the field schema
ctx_->push(attribute);
// create a new feature
mapnik::feature_ptr feature(mapnik::feature_factory::create(ctx_,feature_id_));
// increment the count so that we only return one feature
++feature_id_;
// create an attribute pair of key:value
UnicodeString ustr = tr_->transcode("hello world!");
feature->put(attribute,ustr);
// we need a geometry to display so just for fun here
// we take the center of the bbox that was used to query
// since we don't actually have any data to pull from...
mapnik::coord2d center = box_.center();
// create a new point geometry
mapnik::geometry_type * pt = new mapnik::geometry_type(mapnik::Point);
// we use path type geometries in Mapnik to fit nicely with AGG and Cairo
// here we stick an x,y pair into the geometry using move_to()
pt->move_to(center.x,center.y);
// add the geometry to the feature
feature->add_geometry(pt);
// A feature usually will have just one geometry of a given type
// but mapnik does support many geometries per feature of any type
// so here we draw a line around the point
mapnik::geometry_type * line = new mapnik::geometry_type(mapnik::LineString);
line->move_to(box_.minx(),box_.miny());
line->line_to(box_.minx(),box_.maxy());
line->line_to(box_.maxx(),box_.maxy());
line->line_to(box_.maxx(),box_.miny());
line->line_to(box_.minx(),box_.miny());
feature->add_geometry(line);
// return the feature!
return feature;
}
// otherwise return an empty feature
return mapnik::feature_ptr();
}
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