Placefile polygon rendering

wxdata/include/scwx/gr/placefile.hpp

@@ -1,5 +1,7 @@
 #pragma once
 
+#include <scwx/common/geographic.hpp>
+
 #include <istream>
 #include <memory>
 #include <optional>
@@ -157,6 +159,7 @@ public:
       };
 
       std::vector<std::vector<Element>> contours_ {};
+      scwx::common::Coordinate          center_ {};
    };
 
    bool IsValid() const;

wxdata/source/scwx/gr/placefile.cpp

@@ -729,17 +729,30 @@ void Placefile::Impl::ProcessElementEnd()
 {
    if (currentStatement_ == DrawingStatement::Polygon)
    {
+      auto di = std::static_pointer_cast<PolygonDrawItem>(currentDrawItem_);
+
       // Complete the current contour when ending the Polygon statement
       if (!currentPolygonContour_.empty())
       {
-         auto& contours =
-            std::static_pointer_cast<PolygonDrawItem>(currentDrawItem_)
-               ->contours_;
+         auto& contours = di->contours_;
 
          auto& newContour =
             contours.emplace_back(std::vector<PolygonDrawItem::Element> {});
          newContour.swap(currentPolygonContour_);
       }
+
+      if (!di->contours_.empty())
+      {
+         std::vector<common::Coordinate> coordinates {};
+         std::transform(di->contours_[0].cbegin(),
+                        di->contours_[0].cend(),
+                        std::back_inserter(coordinates),
+                        [](auto& element) {
+                           return common::Coordinate {element.latitude_,
+                                                      element.longitude_};
+                        });
+         di->center_ = GetCentroid(coordinates);
+      }
    }
 }