Fix calculation of worksheet name length

- The previous change caused unnecessary issues
- We approximate that Excel calculates the character length with UTF-16
- Fixes https://github.com/caxlsx/caxlsx/issues/67

1 files changed, 3 insertions, 1 deletions

diff --git a/lib/axlsx/workbook/worksheet/worksheet.rb b/lib/axlsx/workbook/worksheet/worksheet.rb
index aae91947..9f3966f8 100644
--- a/lib/axlsx/workbook/worksheet/worksheet.rb
+++ b/lib/axlsx/workbook/worksheet/worksheet.rb
@@ -663,7 +663,9 @@ module Axlsx
 
     def validate_sheet_name(name)
       DataTypeValidator.validate :worksheet_name, String, name
-      raise ArgumentError, (ERR_SHEET_NAME_TOO_LONG % name) if name.bytesize > 31
+      # ignore first character (BOM) after encoding to utf16 because Excel does so, too.
+      character_length = name.encode("utf-16")[1..-1].encode("utf-16").bytesize / 2
+      raise ArgumentError, (ERR_SHEET_NAME_TOO_LONG % name) if character_length > 31
       raise ArgumentError, (ERR_SHEET_NAME_CHARACTER_FORBIDDEN % name) if '[]*/\?:'.chars.any? { |char| name.include? char }
       name = Axlsx::coder.encode(name)
       sheet_names = @workbook.worksheets.reject { |s| s == self }.map { |s| s.name }