Add serialisation of "topLeftCell" sheetView attribute

include/xlnt/worksheet/sheet_view.hpp

@@ -192,6 +192,30 @@ public:
         return type_;
     }
 
+    /// <summary>
+    /// has a  top left cell?
+    /// </summary>
+    bool has_top_left_cell() const
+    {
+        return top_left_cell_.is_set();
+    }
+
+    /// <summary>
+    /// Sets the top left cell of this view.
+    /// </summary>
+    void top_left_cell(const cell_reference& ref)
+    {
+        top_left_cell_.set(ref);
+    }
+
+    /// <summary>
+    /// Returns the top left cell of this view.
+    /// </summary>
+    cell_reference top_left_cell() const
+    {
+        return top_left_cell_.get();
+    }
+
     /// <summary>
     /// Returns true if this view is equal to rhs based on its id, grid lines setting,
     /// default grid color, pane, and selections.
@@ -202,7 +226,8 @@ public:
             && show_grid_lines_ == rhs.show_grid_lines_
             && default_grid_color_ == rhs.default_grid_color_
             && pane_ == rhs.pane_
-            && selections_ == rhs.selections_;
+            && selections_ == rhs.selections_
+            && top_left_cell_ == rhs.top_left_cell_;
     }
 
 private:
@@ -231,6 +256,11 @@ private:
     /// </summary>
     optional<xlnt::pane> pane_;
 
+    /// <summary>
+    /// The top left cell
+    /// </summary>
+    optional<cell_reference> top_left_cell_;
+
     /// <summary>
     /// The collection of selections
     /// </summary>

source/detail/serialization/xlsx_consumer.cpp

@@ -465,6 +465,10 @@ std::string xlsx_consumer::read_worksheet_begin(const std::string &rel_id)
                 {
                     new_view.show_grid_lines(is_true(parser().attribute("showGridLines")));
                 }
+                if (parser().attribute_present("topLeftCell"))
+                {
+                    new_view.top_left_cell(cell_reference(parser().attribute("topLeftCell")));
+                }
 
                 if (parser().attribute_present("defaultGridColor")) // default="true"
                 {

source/detail/serialization/xlsx_producer.cpp

@@ -2298,13 +2298,17 @@ void xlsx_producer::write_worksheet(const relationship &rel)
             write_attribute("tabSelected", write_bool(true));
         }
 
-        write_attribute("workbookViewId", view.id());
-
         if (view.type() != sheet_view_type::normal)
         {
             write_attribute("view", view.type() == sheet_view_type::page_break_preview
                 ? "pageBreakPreview" : "pageLayout");
         }
+        if (view.has_top_left_cell())
+        {
+            write_attribute("topLeftCell", view.top_left_cell().to_string());
+        }
+
+        write_attribute("workbookViewId", view.id());
 
         if (view.has_pane())
         {