Class: Xlsxtream::Columns

Inherits:
Object
  • Object
show all
Defined in:
lib/xlsxtream/columns.rb

Instance Method Summary collapse

Constructor Details

#initialize(column_options_array) ⇒ Columns

Pass an Array of column options Hashes. Symbol Hash keys and associated values are as follows:

width_chars

Approximate column with in characters, calculated per MSDN docs as if using a default 11 point Calibri font for a 96 DPI target. Specify as an integer.

width_pixels

Exact with of column in pixels. Specify as a Float. Overrides width_chars if that is also provided.



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# File 'lib/xlsxtream/columns.rb', line 15

def initialize(column_options_array)
  @columns = column_options_array
end

Instance Method Details

#to_xml ⇒ Object 



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# File 'lib/xlsxtream/columns.rb', line 19

def to_xml
  xml = String.new('<cols>')

  @columns.each_with_index do |column, index|
    width_chars  = column[ :width_chars  ]
    width_pixels = column[ :width_pixels ]

    if width_chars.nil? && width_pixels.nil?
      xml << %Q{<col min="#{index + 1}" max="#{index + 1}"/>}
    else

      # https://msdn.microsoft.com/en-us/library/office/documentformat.openxml.spreadsheet.column.aspx
      #
      # Truncate(
      #   [{Number of Characters} * {Maximum Digit Width} + {5 pixel padding}]
      #   /{Maximum Digit Width}*256
      # )/256
      #
      # "Using the Calibri font as an example, the maximum digit width of
      #  11 point font size is 7 pixels (at 96 dpi)"
      #
      # By observation, though, I note that a different spreadsheet-wide
      # font size selected via the Workbook's ":font => { :size => ... }"
      # options Hash entry results in Excel, at least, scaling the given
      # widths in proportion with the requested font size change. We do
      # not, apparently, need to do that ourselves and run the calculation
      # based on the reference 11 point -> 7 pixel figure.
      #
      width_pixels ||= ((((width_chars * 7.0) + 5) / 7) * 256).truncate() / 256.0

      xml << %Q{<col min="#{index + 1}" max="#{index + 1}" width="#{width_pixels}" customWidth="1"/>}
    end
  end

  xml << '</cols>'
end