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VALIDATION.adoc

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Font Validation Framework

General

Fontisan provides a comprehensive validation framework for ensuring font quality, structural integrity, and compliance with OpenType specifications.

The framework uses a declarative DSL for defining validation checks and supports multiple validation profiles for different use cases.

Validation profiles

Fontisan includes predefined validation profiles:

indexability

Fast font discovery and indexing (8 checks, metadata-only, ~5x faster)

usability

Font installation compatibility (26 checks, macOS Font Book focused)

production

Comprehensive production quality (37 checks, OpenType spec compliance - default)

web

Web font embedding readiness (18 checks for web deployment)

spec_compliance

Full OpenType specification compliance (detailed analysis mode)

$ fontisan validate --list
Available validation profiles:
  indexability         - Fast validation for font discovery and indexing
  usability            - Basic usability for installation
  production           - Comprehensive quality checks
  web                  - Web embedding and optimization
  spec_compliance      - Full OpenType spec compliance
  default              - Default validation profile (alias for production)

Command-line validation

Example 1. Validate with default profile
$ fontisan validate font.ttf

Font: font.ttf
Status: VALID

Summary:
  Checks performed: 37
  Passed: 37
  Failed: 0

Errors: 0
Warnings: 0
Info: 0
Example 2. Validate for web use with summary
$ fontisan validate font.ttf -t web -S

Font: font.ttf
Status: VALID

Summary:
  Checks performed: 18
  Passed: 17
  Failed: 1

Errors: 1
Warnings: 0

Failed checks:
  web_font_tables      - Missing required GSUB table
Example 3. Validation with table format output
$ fontisan validate font.ttf -T

CHECK_ID                    | STATUS | SEVERITY | TABLE
------------------------------------------------------------
required_tables             | PASS   | error    | N/A
name_version                | PASS   | error    | name
family_name                 | PASS   | error    | name

== Ruby API usage

=== Using predefined profiles

require 'fontisan'

# Validate with default profile (production)
report = Fontisan.validate('font.ttf')
puts report.valid?  # => true or false

# Validate with specific profile
report = Fontisan.validate('font.ttf', profile: :web)
puts "Errors: #{report.summary.errors}"
puts "Warnings: #{report.summary.warnings}"

# Check validation status
if report.valid?
  puts "Font is valid for web use!"
else
  puts "Font has #{report.summary.errors} errors"
end

=== Query validation results

report = Fontisan.validate('font.ttf', profile: :production)

# Get issues by severity
fatal_issues = report.fatal_errors
error_issues = report.errors_only
warning_issues = report.warnings_only
info_issues = report.info_only

# Get issues by category
table_issues = report.issues_by_category('table_validation')

# Get check results
failed_ids = report.failed_check_ids
pass_rate = report.pass_rate

# Export to different formats
yaml_output = report.to_yaml
json_output = report.to_json
summary = report.to_summary  # "2 errors, 3 warnings, 0 info"

== Creating custom validators

=== General

Custom validators inherit from Fontisan::Validators::Validator and define validation logic using the DSL.

The DSL provides 6 check methods:

  • check_table - Validate table-level properties

  • check_field - Validate specific field values

  • check_structure - Validate font structure and relationships

  • check_usability - Validate usability and best practices

  • check_instructions - Validate TrueType instructions/hinting

  • check_glyphs - Validate individual glyphs

require 'fontisan/validators/validator'

class MyFontValidator < Fontisan::Validators::Validator
  private

  def define_checks
    # Check name table
    check_table :name_validation, 'name', severity: :error do |table|
      table.valid_version? &&
        table.valid_encoding_heuristics? &&
        table.family_name_present? &&
        table.postscript_name_valid?
    end

    # Check head table
    check_table :head_validation, 'head', severity: :error do |table|
      table.valid_magic? &&
        table.valid_version? &&
        table.valid_units_per_em?
    end

    # Check structure
    check_structure :required_tables, severity: :error do |font|
      %w[name head maxp hhea].all? { |tag| !font.table(tag).nil? }
    end
  end
end

# Use the validator
font = Fontisan::FontLoader.load('font.ttf')
validator = MyFontValidator.new
report = validator.validate(font)

puts report.valid?                           # => true/false
puts report.summary.errors                   # => number of errors
puts report.summary.warnings                 # => number of warnings

== Validation helpers

The validation framework provides 56 helper methods across 8 core OpenType tables. Each helper returns a boolean indicating whether the validation passed.

class MyValidator < Fontisan::Validators::Validator
  private

  def define_checks
    check_table :name_validation, 'name', severity: :error do |table|
      table.valid_version? &&
        table.valid_encoding_heuristics? &&
        table.family_name_present? &&
        table.postscript_name_valid?
    end
  end
end
class MyValidator < Fontisan::Validators::Validator
  private

  def define_checks
    check_table :head_validation, 'head', severity: :error do |table|
      table.valid_magic? &&
        table.valid_version? &&
        table.valid_units_per_em? &&
        table.valid_bounding_box? &&
        table.valid_index_to_loc_format? &&
        table.valid_glyph_data_format?
    end
  end
end