[traffic] Calculate filter list for active MWMs

Signed-off-by: mvglasow <michael -at- vonglasow.com>

traffxml/traff_model_xml.hpp

@@ -2,6 +2,11 @@
 
 #include "traffxml/traff_model.hpp"
 
+#include "geometry/rect2d.hpp"
+
+#include <string>
+#include <vector>
+
 namespace pugi
 {
 class xml_document;
@@ -11,4 +16,20 @@ class xml_node;
 namespace traffxml
 {
 bool ParseTraff(pugi::xml_document const & document, TraffFeed & feed);
+
+/**
+ * @brief Generates a list of XML `filter` elements from a vector of rects representing bboxes.
+ *
+ * The resulting string can be placed inside a TraFF XML `filter_list` element or can be passed as
+ * an extra to an Android intent.
+ *
+ * It will have one `filter` element for each element in `bboxRects`, although simplification may
+ * be applied to reduce the number of rects (currently not implemented).
+ *
+ * The `min_road_class` attribute is not used.
+ *
+ * @param bboxRects The rectangles, each of which represents a bounding box.
+ * @return A string of XML `filter` elements.
+ */
+std::string FiltersToXml(std::vector<m2::RectD> & bboxRects);
 }  // namespace traffxml