diff --git a/include/mapnik/group/group_layout_manager.hpp b/include/mapnik/group/group_layout_manager.hpp
index 38ee30b5d..548e37bb6 100644
--- a/include/mapnik/group/group_layout_manager.hpp
+++ b/include/mapnik/group/group_layout_manager.hpp
@@ -31,43 +31,51 @@
 // stl
 #include <vector>
 
-using std::vector;
-
 namespace mapnik
 {
 
-using bound_box = box2d<double>;
-
 struct group_layout_manager
 {
-    group_layout_manager(group_layout const& layout)
+    using bound_box = box2d<double>;
+
+    group_layout_manager()
+        : update_layout_(false)
+    {}
+
+    explicit group_layout_manager(group_layout const& layout)
         : layout_(layout),
-          input_origin_(0, 0),
-          member_boxes_(vector<bound_box>()),
-          member_offsets_(vector<pixel_position>()),
-          update_layout_(true)
+          update_layout_(false)
     {
     }
 
     group_layout_manager(group_layout const& layout, pixel_position const& input_origin)
         : layout_(layout),
           input_origin_(input_origin),
-          member_boxes_(vector<bound_box>()),
-          member_offsets_(vector<pixel_position>()),
-          update_layout_(true)
+          update_layout_(false)
     {
     }
 
     group_layout_manager(group_layout const& layout, pixel_position const& input_origin,
-                         vector<bound_box> const& item_boxes)
+                         std::vector<bound_box> const& item_boxes)
         : layout_(layout),
           input_origin_(input_origin),
           member_boxes_(item_boxes),
-          member_offsets_(vector<pixel_position>()),
           update_layout_(true)
     {
     }
 
+    void set_input_origin(double x, double y)
+    {
+        input_origin_.set(x, y);
+        update_layout_ = true;
+    }
+
+    void set_input_origin(pixel_position const& input_origin)
+    {
+        input_origin_ = input_origin;
+        update_layout_ = true;
+    }
+
     inline void set_layout(group_layout const& layout)
     {
         layout_ = layout;
@@ -94,8 +102,8 @@ private:
 
     group_layout layout_;
     pixel_position input_origin_;
-    vector<bound_box> member_boxes_;
-    vector<pixel_position> member_offsets_;
+    std::vector<bound_box> member_boxes_;
+    std::vector<pixel_position> member_offsets_;
     bool update_layout_;
 };
 
diff --git a/include/mapnik/renderer_common/process_group_symbolizer.hpp b/include/mapnik/renderer_common/process_group_symbolizer.hpp
index e8da8d5c6..1c9de13c2 100644
--- a/include/mapnik/renderer_common/process_group_symbolizer.hpp
+++ b/include/mapnik/renderer_common/process_group_symbolizer.hpp
@@ -170,7 +170,7 @@ void render_group_symbolizer(group_symbolizer const& sym,
                 matches.emplace_back(rule, sub_feature);
 
                 // construct a bounding box around all symbolizers for the matched rule
-                bound_box bounds;
+                box2d<double> bounds;
                 render_thunk_list thunks;
                 render_thunk_extractor extractor(bounds, thunks, *sub_feature, common.vars_, prj_trans,
                                                  virtual_renderer, clipping_extent);
diff --git a/src/group/group_layout_manager.cpp b/src/group/group_layout_manager.cpp
index fe00e7d02..ad9aaad7c 100644
--- a/src/group/group_layout_manager.cpp
+++ b/src/group/group_layout_manager.cpp
@@ -34,19 +34,21 @@ namespace mapnik
 // This visitor will process offsets for the given layout
 struct process_layout
 {
+    using bound_box = box2d<double>;
+
     // The vector containing the existing, centered item bounding boxes
-    vector<bound_box> const& member_boxes_;
+    std::vector<bound_box> const& member_boxes_;
 
     // The vector to populate with item offsets
-    vector<pixel_position> & member_offsets_;
+    std::vector<pixel_position> & member_offsets_;
 
     // The origin point of the member boxes
     // i.e. The member boxes are positioned around input_origin,
     //      and the offset values should position them around (0,0)
     pixel_position const& input_origin_;
 
-    process_layout(vector<bound_box> const& member_bboxes,
-                   vector<pixel_position> &member_offsets,
+    process_layout(std::vector<bound_box> const& member_bboxes,
+                   std::vector<pixel_position> &member_offsets,
                    pixel_position const& input_origin)
        : member_boxes_(member_bboxes),
          member_offsets_(member_offsets),
@@ -54,9 +56,12 @@ struct process_layout
     {
     }
 
-    // arrange group memebers in centered, horizontal row
+    // arrange group members in centered, horizontal row
     void operator()(simple_row_layout const& layout) const
     {
+        member_offsets_.clear();
+        member_offsets_.reserve(member_boxes_.size());
+
         double total_width = (member_boxes_.size() - 1) * layout.get_item_margin();
         for (auto const& box : member_boxes_)
         {
@@ -66,7 +71,7 @@ struct process_layout
         double x_offset = -(total_width / 2.0);
         for (auto const& box : member_boxes_)
         {
-            member_offsets_.push_back(pixel_position(x_offset - box.minx(), -input_origin_.y));
+            member_offsets_.emplace_back(x_offset - box.minx(), -input_origin_.y);
             x_offset += box.width() + layout.get_item_margin();
         }
     }
@@ -150,7 +155,7 @@ private:
     }
 };
 
-bound_box group_layout_manager::offset_box_at(size_t i)
+box2d<double> group_layout_manager::offset_box_at(size_t i)
 {
     handle_update();
     pixel_position const& offset = member_offsets_.at(i);