[traffxml] Fix location matching on dual carriageway roads

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

traffxml/traff_decoder.hpp

@@ -188,6 +188,31 @@ public:
                   std::unique_ptr<m4::Tree<routing::NumMwmId>> numMwmTree,
                   DataSource & dataSource);
   protected:
+    /**
+     * @brief Whether the set of fake endings generated for the check points is restricted.
+     *
+     * The return value is used internally when snapping checkpoints to edges. If this function
+     * returns true, this instructs the `PointsOnEdgesSnapping` instance to consider only edges which
+     * are not fenced off, i.e. can be reached from the respective checkpoint without crossing any
+     * other edges. If it returns false, this restriction does not apply, and all nearby edges are
+     * considered.
+     *
+     * Restricting the set of fake endings in this manner decreases the options considered for routing
+     * and thus processing time, which is desirable for regular routing and has no side effects.
+     * For TraFF location matching, simplification has undesirable side effects: if reference points
+     * are located on one side of the road, the other carriageway may not be considered. This would
+     * lead to situations like these:
+     *
+     * --<--<-+<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<==<+-<--<--
+     * -->-->-+>==>==>==>==>==>==>-->-->-->-->-->-->-->-->-->-->-->==>==>==>==>==>==>==>==>+->-->--
+     *                          *<                               <*
+     *
+     * (-- carriageway, + junction, < > direction, *< end point, <* start point, == route)
+     *
+     * To avoid this, the `DecoderRouter` implementation always returns false.
+     */
+    bool IsFakeEndingSetSimplified() override { return false; }
+
   private:
   };