class Prawn::SVG::TTF

Constants

LANGUAGE_IDS
SFNT_VERSION_STRINGS
UTF_16BE_PLATFORM_IDS

Attributes

family[R]
subfamily[R]

Public Class Methods

new(filename) click to toggle source
# File lib/prawn/svg/ttf.rb, line 8
def initialize(filename)
  load_data_from_file(filename)
end

Private Instance Methods

load_data_from_file(filename) click to toggle source
# File lib/prawn/svg/ttf.rb, line 14
def load_data_from_file(filename)
  File.open(filename, 'rb') do |f|
    offset_table = f.read(12)
    return unless offset_table && offset_table.length == 12 && SFNT_VERSION_STRINGS.include?(offset_table[0..3])

    table_count = (offset_table[4].ord * 256) + offset_table[5].ord
    tables = f.read(table_count * 16)
    return unless tables && tables.length == table_count * 16

    offset, length = table_count.times do |index|
      start = index * 16
      break tables[start + 8..start + 15].unpack('NNN') if tables[start..start + 3] == 'name'
    end

    return unless length

    f.seek(offset)
    data = f.read(length)
    return unless data && data.length == length

    _, name_count, string_offset = data[0..5].unpack('nnn')

    names = {}
    name_count.times do |index|
      start = 6 + (index * 12)
      platform_id, _, language_id, name_id, length, offset = data[start..start + 11].unpack('nnnnnn')
      next unless offset
      next unless LANGUAGE_IDS.include?(language_id)
      next unless [1, 2, 16, 17].include?(name_id)

      offset += string_offset
      field = data[offset..offset + length - 1]
      next unless field && field.length == length

      names[name_id] =
        if UTF_16BE_PLATFORM_IDS.include?(platform_id)
          begin
            field.force_encoding(Encoding::UTF_16BE).encode(Encoding::UTF_8)
          rescue StandardError
            field
          end
        else
          field
        end
    end

    @family = names[16] || names[1]
    @subfamily = names[17] || names[2]
  end
rescue Errno::ENOENT # in case the file disappears between the scan and the load, we don't want to crash
end