Class: TTFunk::Table::Cmap::Subtable

Inherits:
Object
  • Object
show all
Includes:
Reader
Defined in:
lib/ttfunk/table/cmap/subtable.rb

Overview

Character to Glyph Index encoding record. This class can be extended with a format-specific

See Also:

Constant Summary collapse

ENCODING_MAPPINGS =

Most used encoding mappings.

{
  mac_roman: { platform_id: 1, encoding_id: 0 }.freeze,
  # Use microsoft unicode, instead of generic unicode, for optimal
  # Windows support
  unicode: { platform_id: 3, encoding_id: 1 }.freeze,
  unicode_ucs4: { platform_id: 3, encoding_id: 10 }.freeze,
}.freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(file, table_start) ⇒ Subtable

Returns a new instance of Subtable.

Parameters:



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# File 'lib/ttfunk/table/cmap/subtable.rb', line 86

def initialize(file, table_start)
  @file = file
  @platform_id, @encoding_id, @offset = read(8, 'nnN')
  @offset += table_start

  parse_from(@offset) do
    @format = read(2, 'n').first

    case @format
    when 0 then extend(TTFunk::Table::Cmap::Format00)
    when 4 then extend(TTFunk::Table::Cmap::Format04)
    when 6 then extend(TTFunk::Table::Cmap::Format06)
    when 10 then extend(TTFunk::Table::Cmap::Format10)
    when 12 then extend(TTFunk::Table::Cmap::Format12)
    end

    parse_cmap!
  end
end

Instance Attribute Details

#encoding_id ⇒ Integere (readonly)

Platform-specific encoding ID.

Returns:

  • (Integere) 


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# File 'lib/ttfunk/table/cmap/subtable.rb', line 25

def encoding_id
  @encoding_id
end

#format ⇒ Integer (readonly)

Record encoding format.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/cmap/subtable.rb', line 29

def format
  @format
end

#platform_id ⇒ Integer (readonly)

Platform ID.

Returns:

  • (Integer) 


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# File 'lib/ttfunk/table/cmap/subtable.rb', line 21

def platform_id
  @platform_id
end

Class Method Details

.encode(charmap, encoding) ⇒ Hash

Encode encoding record.

Parameters:

  • charmap (Hash{Integer => Integer}) —

    keys are code points in the used encoding, values are Unicode code points.

  • encoding (Symbol) —

    • one of the encodign mapping in

    ENCODING_MAPPINGS

Returns:

  • (Hash) —

    • ‘:platform_id` (Integer) - Platform ID of this encoding record.

    • ‘:encoding_id` (Integer) - Encodign ID of this encoding record.

    • ‘:subtable` (String) - encoded encoding record.

    • ‘:max_glyph_id` (Integer) - maximum glyph ID in this encoding record.

    • ‘:charmap` (Hash{Integer => Hash}) - keys are codepoints in this encoding record, values are hashes:

      • ‘:new` - new glyph ID.

      • ‘:old` - glyph ID in the original font.



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# File 'lib/ttfunk/table/cmap/subtable.rb', line 56

def self.encode(charmap, encoding)
  case encoding
  when :mac_roman
    result = Format00.encode(charmap)
  when :unicode
    result = Format04.encode(charmap)
  when :unicode_ucs4
    result = Format12.encode(charmap)
  else
    raise NotImplementedError,
      "encoding #{encoding.inspect} is not supported"
  end

  mapping = ENCODING_MAPPINGS[encoding]

  # platform-id, encoding-id, offset
  result.merge(
    platform_id: mapping[:platform_id],
    encoding_id: mapping[:encoding_id],
    subtable: [
      mapping[:platform_id],
      mapping[:encoding_id],
      12,
      result[:subtable],
    ].pack('nnNA*'),
  )
end

Instance Method Details

#[](_code) ⇒ Integer

Get glyph ID for character code.

Parameters:

  • _code (Integer) —

    character code.

Returns:

  • (Integer) —

    glyph ID.

Raises:

  • (NotImplementedError) 


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# File 'lib/ttfunk/table/cmap/subtable.rb', line 125

def [](_code)
  raise NotImplementedError, "cmap format #{@format} is not supported"
end

#supported? ⇒ Boolean

Is this encoding record format supported?

Returns:

  • (Boolean) 


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# File 'lib/ttfunk/table/cmap/subtable.rb', line 117

def supported?
  false
end

#unicode? ⇒ Boolean

Is this an encoding record for Unicode?

Returns:

  • (Boolean) 


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# File 'lib/ttfunk/table/cmap/subtable.rb', line 109

def unicode?
  (platform_id == 3 && (encoding_id == 1 || encoding_id == 10) && format != 0) ||
    (platform_id.zero? && format != 0)
end