Module: Pdfrb::Conformance::StructureElements

Defined in:
lib/pdfrb/conformance/structure_elements.rb

Overview

Per-structure-element validation rules derived from the PDF Association's "Tagged PDF Best Practice Guide: Syntax" (BPG).

Each standard structure type has expected children and attributes. This module provides a registry of structure-type validators (OCP: add a validator = register, no switch edits).

Constant Summary collapse

TABLE_CHILDREN =

Standard PDF structure types (ISO 32000-2 §14.8.4).

%i[TR THead TBody TFoot].freeze
STANDARD_TYPES = 
%i[
  Document Part Art Sect Div BlockQuote Caption
  TOC TOCI Index NonStruct Private
  H H1 H2 H3 H4 H5 H6
  P L LI Lbl LBody
  Table TR TH TD THead TBody TFoot
  Span Quote Note Reference BibEntry Code
  Figure Formula Form
  Ruby RB RT RP
  Warichu WT WP
  Annot
].freeze
EXPECTED_CHILDREN =

Map of structure type → expected child types (nil = any).

{
  L: [:LI],
  LI: [:Lbl, :LBody],
  Table: [:THead, :TBody, :TFoot, :TR],
  TR: [:TH, :TD],
  Ruby: [:RB, :RT, :RP],
  Warichu: [:WT, :WP],
  TOC: [:TOCI],
}.freeze
REQUIRED_ATTRIBUTES =

Map of structure type → required attributes (besides /S).

{
  Figure: [:Alt, :ActualText], # at least one required
  Formula: [:Alt, :ActualText], # at least one required
}.freeze

Class Method Summary collapse

Class Method Details

.expected_children(type) ⇒ Object 



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# File 'lib/pdfrb/conformance/structure_elements.rb', line 49

def expected_children(type)
  EXPECTED_CHILDREN[type]
end

.required_attributes(type) ⇒ Object 



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# File 'lib/pdfrb/conformance/structure_elements.rb', line 53

def required_attributes(type)
  REQUIRED_ATTRIBUTES[type]
end

.standard?(type) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/pdfrb/conformance/structure_elements.rb', line 57

def standard?(type)
  STANDARD_TYPES.include?(type.to_sym)
end

.standard_types ⇒ Object 



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# File 'lib/pdfrb/conformance/structure_elements.rb', line 45

def standard_types
  STANDARD_TYPES
end

.validate(document) ⇒ Object 



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# File 'lib/pdfrb/conformance/structure_elements.rb', line 61

def validate(document)
  violations = []

  root_ref = document.catalog[:StructTreeRoot]
  return ValidationResult.new(profile: "structure-elements", violations: []) unless root_ref

  root = if root_ref.is_a?(Pdfrb::Model::Reference)
           document.object(root_ref)
         else
           root_ref
         end
  return ValidationResult.new(profile: "structure-elements", violations: []) unless root

  check_structure(document, root, violations)

  ValidationResult.new(profile: "structure-elements", violations: violations)
end