Validation Helpers

Fontisan includes 56 validation helpers organized into categories.

Table Validation

required_tables

Checks for required OpenType tables.

# Required: name, head, maxp, hhea, post
# Optional but common: cmap, hmtx, loca, glyf/cff

table_checksums

Validates table checksums.

table_lengths

Verifies table lengths match headers.

Name Table Validation

name_version

Validates version string format.

family_name

Checks family name presence and format.

postscript_name

Validates PostScript name compliance.

name_completeness

Verifies all required name records.

name_encoding

Validates name record encoding.

Head Table Validation

head_magic

Validates magic number (0x5F0F3CF5).

head_version

Checks head table version.

head_units_per_em

Validates UPM value (typically 1000 or 2048).

head_timestamps

Checks created/modified timestamps.

Metrics Validation

hhea_metrics

Validates horizontal header metrics.

vhea_metrics

Validates vertical header metrics.

os2_metrics

Validates OS/2 table metrics.

line_gap

Checks line gap values.

Glyph Validation

glyph_count

Verifies glyph count consistency.

glyph_bounds

Validates glyph bounding boxes.

composite_glyphs

Checks composite glyph structure.

glyph_names

Validates glyph naming.

CMAP Validation

cmap_presence

Checks cmap table presence.

cmap_format

Validates cmap format.

cmap_coverage

Checks Unicode coverage.

cmap_duplicates

Detects duplicate mappings.

Layout Table Validation

gsub_validity

Validates GSUB table structure.

gpos_validity

Validates GPOS table structure.

feature_list

Checks feature list validity.

script_list

Validates script list.

Advanced Validation

hint_validity

Validates TrueType hints.

cff_validity

Validates CFF table structure.

glyf_loca_consistency

Checks glyf/loca consistency.

maxp_accuracy

Verifies maxp values accuracy.

Using Helpers Programmatically

require 'fontisan'

font = Fontisan::FontLoader.load('font.ttf')
validator = Fontisan::Validators::FontValidator.new(font)

# Run specific helper
result = validator.check_required_tables
puts result.valid?  # => true or false

# Get all helper results
results = validator.run_all_helpers
results.each do |check_id, result|
  puts "#{check_id}: #{result.status}"
end

Helper Categories

Category	Helpers	Focus
Table	12	Table structure
Name	8	Name records
Head	6	Header validation
Metrics	10	Font metrics
Glyph	8	Glyph data
CMAP	6	Character mapping
Layout	6	GSUB/GPOS
Advanced	10	Complex checks