Class: Fontisan::OpenTypeFont

Inherits:
SfntFont
  • Object
show all
Defined in:
lib/fontisan/open_type_font.rb,
lib/fontisan/open_type_font_extensions.rb

Overview

Extensions to OpenTypeFont for table-based construction

Constant Summary collapse

PAGE_SIZE =

Page size for lazy loading alignment (typical filesystem page size)

4096

Constants inherited from SfntFont

SfntFont::SFNT_TABLE_CLASS_MAP, SfntFont::TABLE_CLASS_MAP

Instance Attribute Summary collapse

Attributes inherited from SfntFont

#io_source, #lazy_load_enabled, #loading_mode, #parsed_tables, #sfnt_tables, #table_data, #table_entry_cache

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from SfntFont

#all_sfnt_tables, #close, #family_name, finalize, #find_table_entry, from_collection, #full_name, #has_table?, #head_table, #post_script_name, #preferred_family_name, #preferred_subfamily_name, #read_metadata_tables_batched, #read_table_data, #setup_finalizer, #sfnt_table, #subfamily_name, #table, #table_available?, #table_names, #to_file, #units_per_em, #update_checksum_adjustment_in_file, #update_checksum_adjustment_in_io

Instance Attribute Details

#page_cache ⇒ Object

Page cache for lazy loading (maps page_start_offset => page_data)



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# File 'lib/fontisan/open_type_font.rb', line 30

def page_cache
  @page_cache
end

Class Method Details

.from_file(path, mode: LoadingModes::FULL, lazy: false) ⇒ OpenTypeFont

Read OpenType Font from a file

Parameters:

  • path (String) —

    Path to the OTF file

  • mode (Symbol) (defaults to: LoadingModes::FULL) —

    Loading mode (:metadata or :full, default: :full)

  • lazy (Boolean) (defaults to: false) —

    If true, load tables on demand (default: false)

Returns:

Raises:

  • (ArgumentError) —

    if path is nil or empty, or if mode is invalid

  • (Errno::ENOENT) —

    if file does not exist

  • (RuntimeError) —

    if file format is invalid



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# File 'lib/fontisan/open_type_font.rb', line 44

def self.from_file(path, mode: LoadingModes::FULL, lazy: false)
  if path.nil? || path.to_s.empty?
    raise ArgumentError,
          "path cannot be nil or empty"
  end
  raise Errno::ENOENT, "File not found: #{path}" unless File.exist?(path)

  # Validate mode
  LoadingModes.validate_mode!(mode)

  File.open(path, "rb") do |io|
    font = read(io)
    font.initialize_storage
    font.loading_mode = mode
    font.lazy_load_enabled = lazy

    if lazy
      # Keep file handle open for lazy loading
      font.io_source = File.open(path, "rb")
      font.setup_finalizer
    else
      # Read tables upfront
      font.read_table_data(io)
    end

    font
  end
rescue BinData::ValidityError, EOFError => e
  raise "Invalid OTF file: #{e.message}"
end

.from_tables(tables) ⇒ OpenTypeFont

Create font from hash of tables

This is used during font conversion when we have tables but not a file.

Parameters:

  • tables (Hash<String, String>) —

    Map of table tag to binary data

Returns:



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# File 'lib/fontisan/open_type_font_extensions.rb', line 12

def self.from_tables(tables)
  # Create minimal header structure
  font = new
  font.initialize_storage
  font.loading_mode = LoadingModes::FULL

  # Store table data
  font.table_data = tables

  # Build header from tables
  num_tables = tables.size
  max_power = 0
  n = num_tables
  while n > 1
    n >>= 1
    max_power += 1
  end

  search_range = (1 << max_power) * 16
  entry_selector = max_power
  range_shift = (num_tables * 16) - search_range

  font.header.sfnt_version = 0x4F54544F # 'OTTO' for OpenType/CFF
  font.header.num_tables = num_tables
  font.header.search_range = search_range
  font.header.entry_selector = entry_selector
  font.header.range_shift = range_shift

  # Build table directory
  font.tables.clear
  tables.each_key do |tag|
    entry = TableDirectory.new
    entry.tag = tag
    entry.checksum = 0 # Will be calculated on write
    entry.offset = 0 # Will be calculated on write
    entry.table_length = tables[tag].bytesize
    font.tables << entry
  end

  font
end

Instance Method Details

#cff? ⇒ Boolean

Check if font is CFF flavored

Returns:

  • (Boolean) —

    true for OpenType fonts



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# File 'lib/fontisan/open_type_font.rb', line 107

def cff?
  true
end

#initialize_storage ⇒ void

This method returns an undefined value.

Initialize storage hashes

Extends base class to add page_cache for lazy loading.



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# File 'lib/fontisan/open_type_font.rb', line 80

def initialize_storage
  super
  @page_cache = {}
end

#truetype? ⇒ Boolean

Check if font is TrueType flavored

Returns:

  • (Boolean) —

    false for OpenType fonts



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# File 'lib/fontisan/open_type_font.rb', line 100

def truetype?
  false
end

#valid? ⇒ Boolean

Validate format correctness

Extends base class to check for CFF table (OpenType-specific).

Returns:

  • (Boolean) —

    true if the OTF format is valid, false otherwise



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# File 'lib/fontisan/open_type_font.rb', line 90

def valid?
  return false unless super
  return false unless has_table?(Constants::CFF_TAG)

  true
end