Class: Idml::TextEngine::LineBreaker

Inherits:
Object
  • Object
show all
Defined in:
lib/idml/text_engine/line_breaker.rb

Overview

Greedy word-wrap line breaker. Accumulates glyphs until exceeding the frame width, then breaks at the last break opportunity: a space, or a hyphen (compound words wrap after the hyphen, which stays on the first line). CJK runs get a kinsoku shori post-pass (no line starts or ends with a forbidden character).

Constant Summary collapse

HYPHEN_CODEPOINTS =

Break-after opportunities besides spaces: hyphen-minus, the Unicode hyphens, and the soft hyphen (which breaks without adding a visible hyphen).

[0x2D, 0x2010, 0x2011, 0x00AD].freeze

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(frame_width) ⇒ LineBreaker

CJK text wraps per character (no word boundaries): an overflow whose trailing glyph is CJK breaks before it instead of emitting an overlong line.



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# File 'lib/idml/text_engine/line_breaker.rb', line 37

def initialize(frame_width)
  @frame_width = frame_width
end

Class Method Details

.break(glyphs:, frame_width:) ⇒ Object 



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# File 'lib/idml/text_engine/line_breaker.rb', line 19

def self.break(glyphs:, frame_width:)
  lines = new(frame_width).break(glyphs)
  return lines unless cjk_run?(glyphs)

  lines = CjkLayout.apply_kinsoku(lines)
  CjkLayout.apply_pair_compression(lines)
  CjkLayout.apply_line_end_compression(lines)
end

Instance Method Details

#break(glyphs) ⇒ Object 



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# File 'lib/idml/text_engine/line_breaker.rb', line 49

def break(glyphs)
  lines = []
  current = []
  current_width = 0
  break_idx = -1
  width_at_break = 0

  glyphs.each_with_index do |glyph, _idx|
    current << glyph
    current_width += glyph.width

    if break_after?(glyph)
      break_idx = current.length - 1
      width_at_break = current_width
    end

    next unless current_width > @frame_width && current.length > 1

    if break_idx >= 0
      line_glyphs = current[0..break_idx]
      lines << Line.new(line_glyphs, width_at_break, 0)
      current = current[(break_idx + 1)..]
      current_width = current.sum(&:width)
      break_idx = -1
    elsif cjk_break?(current)
      lines << Line.new(current[0..-2], current_width - glyph.width, 0)
      current = [glyph]
      current_width = glyph.width
    else
      lines << Line.new(current, current_width, 0)
      current = []
      current_width = 0
    end
  end

  lines << Line.new(current, current_width, 0) if current.any?
  lines
end