feat: allow hidden sheets

example.exs

@@ -145,7 +145,11 @@ sheet6 =
   # nest further
   |> Sheet.group_cols("C", "D")
 
+# Sheets can also be hidden.
+sheet7 = Sheet.with_name("Hidden", state: :hidden)
+
 Workbook.append_sheet(workbook, sheet4)
 |> Workbook.append_sheet(sheet5)
 |> Workbook.append_sheet(sheet6)
+|> Workbook.append_sheet(sheet7)
 |> Elixlsx.write_to("example.xlsx")

lib/elixlsx/sheet.ex

@@ -28,6 +28,7 @@ defmodule Elixlsx.Sheet do
             group_rows: [],
             merge_cells: [],
             pane_freeze: nil,
+            state: :visible,
             show_grid_lines: true,
             data_validations: []
 
@@ -40,6 +41,7 @@ defmodule Elixlsx.Sheet do
           group_rows: list(rowcol_group),
           merge_cells: [{String.t(), String.t()}],
           pane_freeze: {number, number} | nil,
+          state: :visible | :hidden | :very_hidden,
           show_grid_lines: boolean(),
           data_validations: list({String.t(), String.t(), list(String.t()) | String.t()})
         }
@@ -49,10 +51,18 @@ defmodule Elixlsx.Sheet do
   Create a sheet with a sheet name.
 
   The name can be up to 31 characters long.
+
+  ## Options
+
+  * `state` - sets the default visibility of the sheet. Can be one of:
+        - `:visible` (default)
+        - `:hidden`
+        - `:very_hidden`
   """
-  @spec with_name(String.t()) :: Sheet.t()
-  def with_name(name) do
-    %Sheet{name: name}
+  @spec with_name(String.t(), Keyword.t()) :: Sheet.t()
+  def with_name(name, opts \\ []) do
+    state = Keyword.get(opts, :state, :visible)
+    %Sheet{name: name, state: state}
   end
 
   defp split_cell_content_props(cell) do

lib/elixlsx/xml_templates.ex

@@ -123,8 +123,14 @@ defmodule Elixlsx.XMLTemplates do
       }
     end
 
+    state = case sheet_info.state do
+      :hidden -> "hidden"
+      :very_hidden -> "veryHidden"
+      _ -> "visible"
+    end
+
     """
-    <sheet name="#{xml_escape(sheet_info.name)}" sheetId="#{sheet_comp_info.sheetId}" state="visible" r:id="#{
+    <sheet name="#{xml_escape(sheet_info.name)}" sheetId="#{sheet_comp_info.sheetId}" state="#{state}" r:id="#{
       sheet_comp_info.rId
     }"/>
     """