Metawriter: Only write features that are actually rendered.

include/mapnik/feature_style_processor.hpp

@@ -94,6 +94,7 @@ public:
         for (;metaItr!=metaItrEnd; ++metaItr)
         {
             metaItr->second->start(m_.metawriter_output_properties);
+            metaItr->second->set_size(m_.width(), m_.height());
         }
                        
         try

include/mapnik/metawriter.hpp

@@ -80,10 +80,13 @@ class metawriter
                              CoordTransform const &t,
                              metawriter_properties const& properties = metawriter_properties())=0;
         virtual void start(metawriter_property_map const& properties) {};
+        void set_size(int width, int height) { width_ = width; height_ = height; }
         virtual void stop() {};
         metawriter_properties const& get_default_properties() const { return dflt_properties_;}
     protected:
         metawriter_properties dflt_properties_;
+        int width_;
+        int height_;
 };
 
 typedef boost::shared_ptr<metawriter> metawriter_ptr;

src/metawriter.cpp

@@ -105,6 +105,9 @@ void metawriter_json_stream::add_box(box2d<double> box, Feature const &feature,
        output: WGS84
     */
 
+    /* Check if feature is in bounds. */
+    if (box.maxx() < 0 || box.maxy() < 0 || box.minx() > width_ || box.miny() > height_) return;
+
     proj_transform trans(prj_trans.source(), projection("+proj=latlong +datum=WGS84"));
     //t_ coord transform has transform for box2d combined with prj_trans
     box = t.backward(box, trans);