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APPLE_LEGACY_FONTS.adoc

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Apple Legacy Font Format Support

General

Fontisan provides support for Apple’s legacy font formats that predate modern OpenType standards:

  • 'true' signature TrueType fonts - Older Mac fonts with 'true' sfnt version

  • dfont (Data Fork Font) - Mac suitcase format with fonts in data fork

These formats require special handling due to their unique structures and historical platform-specific conventions.

'true' signature TrueType fonts

Traditional TrueType fonts use 'true' (0x74727565) as the SFNT version instead of the modern 0x00010000. These were common on classic Mac OS.

$ fontisan info legacy_font.ttf

Font type:                TrueType (Not Variable)
SFNT Version:             'true' (legacy)
Family:                   Legacy Font
...

Detection:
  Fontisan automatically detects 'true' signature fonts
  Treats them as standard TrueType for all operations
  Preserves signature format when writing

dfont (Data Fork Font) format

The dfont format stores complete Mac font suitcases in the data fork, supporting multiple fonts in a single file with resource-fork style structure.

$ fontisan ls family.dfont

Font 0: Arial
  Family: Arial
  Subfamily: Regular

Font 1: Arial
  Family: Arial
  Subfamily: Bold

Font 2: Arial
  Family: Arial
  Subfamily: Italic
Example 1. dfont structure
dfont format structure:

Data Fork Map:
  Resource data: Contains all font resources
  Resource map: Index of resources by type and ID
  Postscript names: Font name mapping

Supported fonts in dfont:
  - TrueType fonts ('true' signature)
  - OpenType fonts (CFF or TrueType outlines)
  - Mixed formats in single dfont

Features:
  - Automatic resource fork extraction
  - Font list with metadata
  - Extract individual fonts by index
  - Unpack all fonts to directory
  - Validate fonts within dfont
=== Working with dfont files

==== List fonts in dfont

[source,shell]

$ fontisan ls family.dfont

Font 0: Arial Regular Family: Arial Subfamily: Regular PostScript: Arial

Font 1: Arial Bold Family: Arial Subfamily: Bold PostScript: Arial-Bold

==== Show dfont info

[source,shell]

$ fontisan info family.dfont

Collection: family.dfont Type: dfont Fonts: 3

Font 0 (offset: 256): Font type: TrueType (Not Variable) Family: Arial Subfamily: Regular …​

==== Extract fonts from dfont

[source,shell]

Extract all fonts

$ fontisan unpack family.dfont extracted_fonts/

Extract specific font

$ fontisan unpack family.dfont --font-index 0 Arial.ttf

==== Validate dfont

[source,shell]

$ fontisan validate family.dfont -t indexability

Collection: family.dfont Type: dfont Fonts: 3

Summary: Total Errors: 0 Total Warnings: 2

Font 0: Arial Regular

Font: family.dfont:0 Status: VALID_WITH_WARNINGS …​

=== Ruby API for dfont

[source,ruby]

require 'fontisan'

Load dfont collection

dfont = Fontisan::FontLoader.load('family.dfont')

Access as collection

puts "Font count: #{dfont.font_count}" File.open('family.dfont', 'rb') do |io| fonts = dfont.extract_fonts(io) fonts.each_with_index do |font, i| puts "Font #{i}: #{font.family_name}" end end

Extract specific font

font = Fontisan::FontLoader.load('family.dfont', font_index: 0)

Validate dfont

report = Fontisan.validate('family.dfont') puts report.valid? # ⇒ true/false