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 space. CJK runs get a kinsoku shori post-pass (no line starts or ends with a forbidden character).

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 29

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 13

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

  CjkLayout.apply_kinsoku(lines)
end

Instance Method Details

#break(glyphs) ⇒ Object 



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# File 'lib/idml/text_engine/line_breaker.rb', line 41

def break(glyphs)
  lines = []
  current = []
  current_width = 0
  last_space_idx = -1
  width_at_space = 0

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

    if glyph.is_space
      last_space_idx = current.length - 1
      width_at_space = current_width
    end

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

    if last_space_idx >= 0
      line_glyphs = current[0..last_space_idx]
      lines << Line.new(line_glyphs, width_at_space, 0)
      current = current[(last_space_idx + 1)..]
      current_width = current.sum(&:width)
      last_space_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