Class: Fontisan::Tables::Gpos

Inherits:
Binary::BaseRecord show all
Defined in:
lib/fontisan/tables/gpos.rb

Overview

GPOS (Glyph Positioning) table parser Parses OpenType GPOS table to extract scripts and features

Instance Method Summary collapse

Methods inherited from Binary::BaseRecord

#raw_data, read, #valid?

Instance Method Details

#features(script_tag: "latn") ⇒ Array<String>

Get all feature tags for a given script

Parameters:

  • script_tag (String) (defaults to: "latn") —

    4-character script tag (e.g., ‘latn’)

Returns:

  • (Array<String>) —

    Array of 4-character feature tags



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# File 'lib/fontisan/tables/gpos.rb', line 34

def features(script_tag: "latn")
  return [] if script_list_offset.zero? || feature_list_offset.zero?

  # Get feature indices from the script's LangSys
  feature_indices = feature_indices_for_script(script_tag)
  return [] if feature_indices.empty?

  # Get feature list
  feature_list_data = table_data[(feature_list_offset - 10)..]
  return [] if feature_list_data.nil? || feature_list_data.empty?

  feature_list = LayoutCommon::FeatureList.read(feature_list_data)

  # Collect features referenced by the script
  features = []
  feature_indices.each do |idx|
    next if idx >= feature_list.feature_count

    features << feature_list.feature_records[idx].feature_tag
  end

  features.uniq
rescue StandardError
  []
end

#scripts ⇒ Array<String>

Get all script tags supported by this font

Returns:

  • (Array<String>) —

    Array of 4-character script tags



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# File 'lib/fontisan/tables/gpos.rb', line 19

def scripts
  return [] if script_list_offset.zero?

  script_list_data = table_data[(script_list_offset - 10)..]
  return [] if script_list_data.nil? || script_list_data.empty?

  script_list = LayoutCommon::ScriptList.read(script_list_data)
  script_list.script_tags
rescue StandardError
  []
end