Module: Idml::TextEngine::CjkLayout

Defined in:
lib/idml/text_engine/cjk_layout.rb

Overview

CJK text layout utilities: character classification, kinsoku shori (line-breaking rules), and vertical writing-mode helpers.

Constant Summary collapse

SCRIPT_SPACING_EM =

Mojikumi subset: automatic inter-script spacing — an eighth em is inserted between adjacent CJK and ASCII alphanumeric glyphs (widenning the leading glyph of each pair), matching InDesign's default CJK/Latin auto spacing. A named mojikumi set's OverrideMojikumiAki entries take precedence when given: the Desired value (em units) applies to each matching class pair (TODO 145).

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CLASS_IDEOGRAPH =

Mojikumi character classes (InDesign mojikumi table rows).

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CLASS_OPENING = 
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CLASS_CLOSING = 
3
CLASS_COMMA_PERIOD = 
4
CLASS_MIDDLE_DOT = 
5
CLASS_DIGIT = 
6
CLASS_LATIN = 
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COMMA_PERIOD_CODEPOINTS = 
[
  0x3001, # 、 ideographic comma
  0x3002, # 。 ideographic full stop
].freeze
CLOSING_CODEPOINTS = 
[
  0x3009, # 〉
  0x300B, # 》
  0x300D, # 」
  0x300F, # 』
  0x3011, # 】
  0x3015, # 〕
  0xFF09, # ）fullwidth right paren
  0xFF3D, # ］
  0xFF5D, # ｝
].freeze
TRAILING_COMPRESSION_CODEPOINTS =

Mojikumi subset 2: line-end punctuation compression — full-width closing punctuation occupying a line's final position renders at half advance (行末約物半角詰め), tightening the line as InDesign's default mojikumi does.

[
  0x3001, # 、 ideographic comma
  0x3002, # 。 ideographic full stop
  0x3009, # 〉
  0x300B, # 》
  0x300D, # 」
  0x300F, # 』
  0x3011, # 】
  0x3015, # 〕
  0xFF09, # ）fullwidth right paren
  0xFF3D, # ］
  0xFF5D, # ｝
  0x30FC, # ー prolonged sound mark
].freeze
OPENING_CODEPOINTS =

Class-based mojikumi pair compression: a full-width closing/middle glyph followed by another full-width punctuation glyph compresses to half advance within the line (。」、ー） … pairs), matching InDesign's default mojikumi behavior for consecutive 約物.

[
  0x300C, # 「
  0x300E, # 『
  0x3008, # 〈
  0x300A, # 《
  0x3010, # 【
  0x3014, # 〔
  0xFF08, # （fullwidth left paren
  0xFF3B, # ［
  0xFF5B, # ｛
].freeze
MIDDLE_CODEPOINTS = 
[
  0x30FB, # ・ fullwidth middle dot
  0x30FC, # ー prolonged sound mark
  0x2025, # ‥ two-dot leader
  0x2026, # … ellipsis
].freeze
CJK_RANGES = 
[
  0x3000..0x303F, # CJK Symbols and Punctuation
  0x3040..0x309F, # Hiragana
  0x30A0..0x30FF, # Katakana
  0x3400..0x4DBF, # CJK Extension A
  0x4E00..0x9FFF, # CJK Unified Ideographs
  0xAC00..0xD7AF, # Hangul Syllables
  0xF900..0xFAFF, # CJK Compatibility Ideographs
  0xFF00..0xFFEF, # Halfwidth and Fullwidth Forms
].freeze
FORBIDDEN_LINE_START =

Characters forbidden at line start (kinsoku shori).

%w[
  、 。， ． ｡ ： ； ？ ｿ ﾞ ﾟ ! ！ ” 〉 》 」 』 】
  〕 ｝ ） ｣ ゛ ゝ ゞ 〃 々 〆 〇 ー 〜
  ぁ ぃ ぅ ぇ ぉ っ ゃ ゅ ょ ゎ
  ァ ィ ゥ ェ ォ ッ ャ ュ ョ ヮ
  ぁ ぃ ぅ ぇ ぉ
].map(&:codepoints).flatten.freeze
FORBIDDEN_LINE_END =

Characters forbidden at line end (kinsoku shori).

%w[
  “ 〈 《 「 『 【 〔 ｛ （ ｢
].map(&:codepoints).flatten.freeze

Class Method Summary collapse

Class Method Details

.adjust_boundary(prev_line, current_line) ⇒ Object

Adjust the boundary between two lines according to kinsoku rules.



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# File 'lib/idml/text_engine/cjk_layout.rb', line 277

def adjust_boundary(prev_line, current_line)
  prev = dup_line(prev_line)
  curr = dup_line(current_line)

  # Move forbidden-start chars from current line start to prev line end.
  until curr.glyphs.empty? || !forbidden_start?(curr.glyphs.first.codepoint)
    moved = curr.glyphs.shift
    prev.glyphs << moved
    prev.width += moved.width
    curr.width -= moved.width
  end

  # Move forbidden-end chars from prev line end to current line start.
  until prev.glyphs.empty? || !forbidden_end?(prev.glyphs.last.codepoint)
    moved = prev.glyphs.pop
    prev.width -= moved.width
    curr.glyphs.unshift(moved)
    curr.width += moved.width
  end

  [prev, curr]
end

.aki_em(left, right, aki_overrides) ⇒ Object

Spacing (em units) between an adjacent pair: the named set's Desired aki for a matching class-pair override, else the default eighth-em at CJK/Latin script boundaries, else none.



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# File 'lib/idml/text_engine/cjk_layout.rb', line 62

def aki_em(left, right, aki_overrides)
  override = aki_overrides.find do |entry|
    entry.side_is_after_target &&
      entry.target_mojikumi_class == mojikumi_class(left) &&
      entry.side_mojikumi_class == mojikumi_class(right)
  end
  return override.desired if override&.desired

  return SCRIPT_SPACING_EM if script_boundary?(left, right)

  nil
end

.apply_kinsoku(lines) ⇒ Object

Apply kinsoku shori to an array of Line objects. Moves forbidden-start chars from the beginning of a line to the end of the previous line, and forbidden-end chars from the end of a line to the beginning of the next line.



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# File 'lib/idml/text_engine/cjk_layout.rb', line 258

def apply_kinsoku(lines)
  return lines if lines.length < 2

  result = [dup_line(lines.first)]
  lines[1..].each do |line|
    prev = result.last
    curr = dup_line(line)
    adjusted_prev, adjusted_current = adjust_boundary(prev, curr)
    result[-1] = adjusted_prev
    result << adjusted_current
  end
  result
end

.apply_line_end_compression(lines) ⇒ Object 



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# File 'lib/idml/text_engine/cjk_layout.rb', line 134

def apply_line_end_compression(lines)
  lines.each do |line|
    last = line.glyphs.last
    next unless last
    next unless compressible?(last.codepoint)

    last.width /= 2.0
    line.width = line.glyphs.sum(&:width)
  end
  lines
end

.apply_pair_compression(lines) ⇒ Object 



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# File 'lib/idml/text_engine/cjk_layout.rb', line 174

def apply_pair_compression(lines)
  lines.each do |line|
    glyphs = line.glyphs
    (0...(glyphs.length - 1)).each do |index|
      leading = glyphs[index]
      following = glyphs[index + 1]
      next unless pair_compressible?(leading, following)

      leading.width /= 2.0
    end
    line.width = glyphs.sum(&:width)
  end
  lines
end

.apply_script_spacing(glyphs, size, aki_overrides = []) ⇒ Object 



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# File 'lib/idml/text_engine/cjk_layout.rb', line 45

def apply_script_spacing(glyphs, size, aki_overrides = [])
  (0...(glyphs.length - 1)).each do |index|
    leading = glyphs[index]
    following = glyphs[index + 1]
    em = aki_em(leading.codepoint, following.codepoint,
                aki_overrides)
    next unless em&.positive?

    leading.width += em * size
  end
  glyphs
end

.ascii_alnum?(codepoint) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/idml/text_engine/cjk_layout.rb', line 109

def ascii_alnum?(codepoint)
  (0x30..0x39).cover?(codepoint) ||
    (0x41..0x5A).cover?(codepoint) ||
    (0x61..0x7A).cover?(codepoint)
end

.cjk?(codepoint) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/idml/text_engine/cjk_layout.rb', line 237

def cjk?(codepoint)
  CJK_RANGES.any? { |range| range.include?(codepoint) }
end

.closing?(codepoint) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/idml/text_engine/cjk_layout.rb', line 199

def closing?(codepoint)
  TRAILING_COMPRESSION_CODEPOINTS.include?(codepoint)
end

.compressible?(codepoint) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/idml/text_engine/cjk_layout.rb', line 146

def compressible?(codepoint)
  TRAILING_COMPRESSION_CODEPOINTS.include?(codepoint)
end

.contains_cjk?(text) ⇒ Boolean

Check if text contains any CJK characters.

Returns:

  • (Boolean) 


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# File 'lib/idml/text_engine/cjk_layout.rb', line 250

def contains_cjk?(text)
  text.each_codepoint.any? { |cp| cjk?(cp) }
end

.digit_class?(codepoint) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/idml/text_engine/cjk_layout.rb', line 90

def digit_class?(codepoint)
  (0x30..0x39).cover?(codepoint) ||
    (0xFF10..0xFF19).cover?(codepoint)
end

.dup_line(line) ⇒ Object 



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# File 'lib/idml/text_engine/cjk_layout.rb', line 272

def dup_line(line)
  Line.new(line.glyphs.dup, line.width, line.x_offset)
end

.forbidden_end?(codepoint) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/idml/text_engine/cjk_layout.rb', line 245

def forbidden_end?(codepoint)
  FORBIDDEN_LINE_END.include?(codepoint)
end

.forbidden_start?(codepoint) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/idml/text_engine/cjk_layout.rb', line 241

def forbidden_start?(codepoint)
  FORBIDDEN_LINE_START.include?(codepoint)
end

.fullwidth_digit?(codepoint) ⇒ Boolean

Detect if a codepoint is a CJK full-width digit (０-９).

Returns:

  • (Boolean) 


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# File 'lib/idml/text_engine/cjk_layout.rb', line 301

def fullwidth_digit?(codepoint)
  codepoint.between?(0xFF10, 0xFF19)
end

.fullwidth_punct?(codepoint) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/idml/text_engine/cjk_layout.rb', line 207

def fullwidth_punct?(codepoint)
  closing?(codepoint) || middle?(codepoint) ||
    OPENING_CODEPOINTS.include?(codepoint)
end

.latin_class?(codepoint) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/idml/text_engine/cjk_layout.rb', line 95

def latin_class?(codepoint)
  (0x41..0x5A).cover?(codepoint) ||
    (0x61..0x7A).cover?(codepoint) ||
    (0xFF21..0xFF3A).cover?(codepoint) ||
    (0xFF41..0xFF5A).cover?(codepoint)
end

.middle?(codepoint) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/idml/text_engine/cjk_layout.rb', line 203

def middle?(codepoint)
  MIDDLE_CODEPOINTS.include?(codepoint)
end

.mojikumi_class(codepoint) ⇒ Object

The mojikumi class of a codepoint, or nil outside the CJK punctuation / script classes. Ideographs (the default CJK class) win only when no special class matches.



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# File 'lib/idml/text_engine/cjk_layout.rb', line 78

def mojikumi_class(codepoint)
  return CLASS_OPENING if OPENING_CODEPOINTS.include?(codepoint)
  return CLASS_COMMA_PERIOD if COMMA_PERIOD_CODEPOINTS.include?(codepoint)
  return CLASS_CLOSING if CLOSING_CODEPOINTS.include?(codepoint)
  return CLASS_MIDDLE_DOT if MIDDLE_CODEPOINTS.include?(codepoint)
  return CLASS_DIGIT if digit_class?(codepoint)
  return CLASS_LATIN if latin_class?(codepoint)
  return CLASS_IDEOGRAPH if cjk?(codepoint)

  nil
end

.pair_compressible?(leading, following) ⇒ Boolean

Closing/middle glyph followed by full-width punctuation compresses the leading glyph to half advance.

Returns:

  • (Boolean) 


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# File 'lib/idml/text_engine/cjk_layout.rb', line 191

def pair_compressible?(leading, following)
  return false unless fullwidth_punct?(following.codepoint)

  closing?(leading.codepoint) ||
    (middle?(leading.codepoint) &&
     !OPENING_CODEPOINTS.include?(following.codepoint))
end

.script_boundary?(left, right) ⇒ Boolean

True when exactly one of the pair is CJK and the other is an ASCII letter or digit.

Returns:

  • (Boolean) 


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# File 'lib/idml/text_engine/cjk_layout.rb', line 104

def script_boundary?(left, right)
  (cjk?(left) && ascii_alnum?(right)) ||
    (ascii_alnum?(left) && cjk?(right))
end

.tate_chu_yoko?(codepoint) ⇒ Boolean

Tate-Chu-Yoko candidate: 1-2 digit horizontal runs in vertical text.

Returns:

  • (Boolean) 


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# File 'lib/idml/text_engine/cjk_layout.rb', line 306

def tate_chu_yoko?(codepoint)
  codepoint.between?(0x30, 0x39) || fullwidth_digit?(codepoint)
end

.vertical_mode?(orientation) ⇒ Boolean

Check if a StoryOrientation value indicates vertical writing.

Returns:

  • (Boolean) 


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# File 'lib/idml/text_engine/cjk_layout.rb', line 311

def vertical_mode?(orientation)
  ["TopToBottom", "RightToLeftTopToBottom"].include?(orientation)
end