Module: Prawn::Rtl::Bidi

Extended by:
FFI::Library
Defined in:
lib/prawn/rtl/bidi.rb

Overview

FFI BiDi wrapper for Unicode Bidirectional Algorithm support

This module provides direct FFI bindings to ICU’s ubidi functions for bidirectional text processing.

Defined Under Namespace

Classes: BiDiError

Constant Summary collapse

UBIDI_DEFAULT_LTR =

Constants from ubidi.h

0xfe
UBIDI_DEFAULT_RTL = 
0xff
UBIDI_LTR = 
0
UBIDI_RTL = 
1
UBIDI_MIXED = 
2
UBIDI_NEUTRAL = 
3
UBIDI_DO_MIRRORING =

Reorder options

2
UBIDI_OUTPUT_REVERSE = 
16

Class Method Summary collapse

Class Method Details

.attach_icu_function(ruby_name, icu_name, args, return_type) ⇒ Object

Helper to attach function with detected suffix



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# File 'lib/prawn/rtl/bidi.rb', line 108

def self.attach_icu_function(ruby_name, icu_name, args, return_type)
  suffixed_name = "#{icu_name}#{detect_icu_suffix}"
  attach_function ruby_name, suffixed_name.to_sym, args, return_type
end

.contains_rtl?(text) ⇒ Boolean

Checks if a string contains RTL characters

Parameters:

  • text (String) —

    the text to check

Returns:

  • (Boolean) —

    true if the text contains RTL characters



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# File 'lib/prawn/rtl/bidi.rb', line 197

def self.contains_rtl?(text)
  return false if text.nil? || text.empty?

  bidi = nil
  begin
    bidi = ubidi_open
    return false if bidi.null?

    utf16_text = text.encode('UTF-16LE')
    text_length = utf16_text.bytesize / 2

    text_buffer = FFI::MemoryPointer.new(:uint16, text_length + 1)
    text_buffer.put_bytes(0, utf16_text)

    status = FFI::MemoryPointer.new(:int32)
    status.put_int32(0, 0)

    ubidi_setPara(bidi, text_buffer, text_length, UBIDI_DEFAULT_LTR, nil, status)

    return false if status.get_int32(0).positive?

    direction = ubidi_getDirection(bidi)
    [UBIDI_RTL, UBIDI_MIXED].include?(direction)
  ensure
    ubidi_close(bidi) if bidi && !bidi.null?
  end
end

.detect_icu_suffix ⇒ Object

Detect ICU version suffix by checking for a known function



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# File 'lib/prawn/rtl/bidi.rb', line 86

def self.detect_icu_suffix
  @detect_icu_suffix ||= begin
    # Try common suffixes from newer to older versions
    # Some versions use _4_2 format, others use _42 format
    suffixes = [''] + 90.downto(4).flat_map { |v| ["_#{v}", "_#{v / 10}_#{v % 10}"] }

    # Find suffix by checking if ubidi_open function exists
    suffix = suffixes.find do |s|
      # Try to find the function
      func_name = :"ubidi_open#{s}"
      ffi_libraries.any? do |lib|
        lib.find_function(func_name.to_s)
      end
    rescue StandardError
      false
    end

    suffix || ''
  end
end

.find_icu_lib ⇒ Object

Find ICU library files



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# File 'lib/prawn/rtl/bidi.rb', line 53

def self.find_icu_lib
  candidates = []
  lib_name = 'icuuc'

  search_paths.each do |path|
    Dir.glob(File.expand_path(path)).each do |dir|
      # Try versioned libraries first (newer to older)
      # ICU versions from 4.0 (2009) to potential future versions
      90.downto(4).each do |version|
        case platform
        when :osx
          candidates << File.join(dir, "lib#{lib_name}.#{version}.dylib")
          candidates << File.join(dir, "lib#{lib_name}.dylib")
        when :windows
          candidates << File.join(dir, "#{lib_name}#{version}.dll")
          candidates << File.join(dir, "#{lib_name}.dll")
        else
          candidates << File.join(dir, "lib#{lib_name}.so.#{version}")
          candidates << File.join(dir, "lib#{lib_name}.so")
        end
      end
    end
  end

  # Find the first existing library
  found = candidates.find { |path| File.exist?(path) }
  found || ["lib#{lib_name}.so", "lib#{lib_name}.dylib", "#{lib_name}.dll", lib_name]
end

.platform ⇒ Object

Detect platform



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# File 'lib/prawn/rtl/bidi.rb', line 18

def self.platform
  os = RbConfig::CONFIG['host_os']
  case os
  when /darwin/
    :osx
  when /linux/
    :linux
  when /bsd/
    :bsd
  when /mswin|msys|mingw|cygwin|bccwin|wince|emc/
    :windows
  else
    :linux
  end
end

.reorder(text, direction: :auto) ⇒ String

Reorders text according to the Unicode Bidirectional Algorithm

Parameters:

  • text (String) —

    the text to reorder

  • direction (Symbol) (defaults to: :auto) —

    :ltr, :rtl, or :auto (default)

Returns:

  • (String) —

    the visually reordered text



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# File 'lib/prawn/rtl/bidi.rb', line 140

def self.reorder(text, direction: :auto)
  return text if text.nil? || text.empty?

  # Convert direction to ubidi constant
  para_level =
    case direction
    when :ltr then UBIDI_LTR
    when :rtl then UBIDI_RTL
    else UBIDI_DEFAULT_LTR
    end

  bidi = nil
  begin
    # Open BiDi object
    bidi = ubidi_open
    raise BiDiError, 'Failed to create BiDi object' if bidi.null?

    # Convert string to UTF-16 for ICU
    utf16_text = text.encode('UTF-16LE')
    text_length = utf16_text.bytesize / 2

    # Create buffer for UTF-16 string
    text_buffer = FFI::MemoryPointer.new(:uint16, text_length + 1)
    text_buffer.put_bytes(0, utf16_text)

    # Error status
    status = FFI::MemoryPointer.new(:int32)
    status.put_int32(0, 0)

    # Set paragraph
    ubidi_setPara(bidi, text_buffer, text_length, para_level, nil, status)

    error_code = status.get_int32(0)
    raise BiDiError, "ubidi_setPara failed with error code: #{error_code}" if error_code.positive?

    # Get required size for output
    output_length = text_length * 2
    output_buffer = FFI::MemoryPointer.new(:uint16, output_length)

    # Write reordered text
    written = ubidi_writeReordered(bidi, output_buffer, output_length, UBIDI_DO_MIRRORING, status)

    error_code = status.get_int32(0)
    raise BiDiError, "ubidi_writeReordered failed with error code: #{error_code}" if error_code.positive?

    # Convert back from UTF-16 to UTF-8
    result_bytes = output_buffer.get_bytes(0, written * 2)
    result_bytes.force_encoding('UTF-16LE').encode('UTF-8')
  ensure
    ubidi_close(bidi) if bidi && !bidi.null?
  end
end

.search_paths ⇒ Object

Search paths for ICU libraries



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# File 'lib/prawn/rtl/bidi.rb', line 35

def self.search_paths
  @search_paths ||=
    if ENV['ICU_LIB_PATH']
      [ENV['ICU_LIB_PATH']]
    elsif FFI::Platform::IS_WINDOWS
      ENV['PATH'].split(File::PATH_SEPARATOR)
    else
      [
        '/usr/local/{lib64,lib}',
        '/usr/local/opt/icu4c/{lib64,lib}',
        '/opt/local/{lib64,lib}',
        '/opt/homebrew/{lib64,lib}',
        '/usr/{lib64,lib}'
      ] + Dir['/usr/lib/*-linux-gnu'] + Dir['/lib/*-linux-gnu']
    end
end