Add tagged PDF infrastructure for Section 508 accessibility#67
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craigmcnamara wants to merge 4 commits into
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Add tagged PDF infrastructure for Section 508 accessibility#67craigmcnamara wants to merge 4 commits into
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Adds marked content operators (BMC/BDC/EMC) and structure tree support to pdf-core, enabling accessible/tagged PDF generation. This is the foundation layer that Prawn and Prawn::Table will build on. New modules: - PDF::Core::MarkedContent — emits BMC/BDC/EMC operators in content streams - PDF::Core::StructureTree — manages StructTreeRoot, structure elements, ParentTree, and MCID allocation Modified: - ObjectStore: accepts marked: true, sets /MarkInfo on Catalog - DocumentState: threads marked option through to ObjectStore - Renderer: includes MarkedContent, creates StructureTree when marked, registers before_render callback for structure tree finalization Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Allows setting /ActualText on structure elements so screen readers announce replacement text instead of reading visual characters literally (e.g., "required" instead of "asterisk" for *, "selected" for X). Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This was referenced Mar 26, 2026
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Repackage the stalled upstream Section 508 / tagged-PDF pull requests (prawnpdf/pdf-core#67, prawnpdf/prawn#1391, prawnpdf/prawn-table#164) as a standalone gem that layers onto the published prawn, pdf-core, and (optionally) prawn-table gems via prepend + additive re-opens — no forking. - pdf-core layer: PDF::Core::MarkedContent (BMC/BDC/EMC) and PDF::Core::StructureTree, plus prepends on DocumentState#initialize and Renderer#initialize and an additive ObjectStore#marked?. - prawn layer: Prawn::Accessibility::DocumentExtensions mixin (tagged?, structure, structure_container, artifact, heading, paragraph, figure) and the marked:/language: document options. - prawn-table layer (optional, auto-applied when loaded): Table/TR/TH/TD tagging with header detection and /Scope. Every modified method delegates to super and only diverges when marked: true, so untagged output is unchanged (guarded by regression_spec). 62 specs pass against prawn 2.5.0 / pdf-core 0.10.0 / prawn-table 0.2.2; rubocop clean. Includes GitHub Actions CI (Ruby 3.1-3.4) and a status badge. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Summary
Adds the low-level foundation for generating tagged (accessible) PDFs compliant with GSA Section 508 guidelines.
PDF::Core::MarkedContentmodule — emits BMC/BDC/EMC operators in content streams for marking content sequencesPDF::Core::StructureTreeclass — manages the StructTreeRoot, structure elements (/StructElem), ParentTree (number tree), and per-page MCID allocation. Finalizes automatically viabefore_rendercallback.ObjectStore— acceptsmarked: trueoption, sets/MarkInfo << /Marked true >>on the CatalogDocumentState— threads themarkedoption through to ObjectStoreRenderer— includesMarkedContent, createsStructureTreewhen marked, sets minimum PDF version to 1.7, exposesstructure_treeandmarked?accessors/Alt,/ActualText,/Lang, and/Scopeattributes on structure elementsThis is the foundation layer that prawnpdf/prawn and prawnpdf/prawn-table build on for high-level accessibility APIs. See companion PRs there.
Addresses prawnpdf/prawn-table#78
Test plan
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