43d31f8dfc
Re-verified per-page Resource dictionary inheritance implementation: - All 33 tests pass (resources + pages) - Arc sharing optimization confirmed (Arc::ptr_eq test) - INV-8 maintained (proptests pass) Acceptance criteria: - ✅ 3-level resource inheritance - ✅ Per-key override semantics - ✅ Arc sharing when no merge needed - ✅ ColorSpace inline arrays preserved - ✅ Empty root /Resources propagation Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
68 lines
3.1 KiB
Markdown
68 lines
3.1 KiB
Markdown
# pdftract-dejqs: Per-page Resource Dictionary Inheritance
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## Summary
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Implemented per-page Resource dictionary inheritance as specified in PDF 1.7 Section 7.7.3.3. The implementation was already complete in `resources.rs` and `pages.rs`; this task verified the implementation and added missing test coverage for Arc sharing.
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## Changes Made
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1. **Added Arc sharing test** (`test_resource_inheritance_page_without_resources`):
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- Modified existing test to verify that when multiple pages have no `/Resources`, they share the same `Arc<ResourceDict>` instance
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- Uses `Arc::ptr_eq` to verify pointer equality (memory efficiency)
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2. **Added public API exports** in `parser/mod.rs`:
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- `pub use resources::{ResourceDict, merge_resources, extract_resources};`
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- `pub use pages::{PageDict, flatten_page_tree, DEFAULT_MEDIABOX};`
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## Acceptance Criteria Status
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| Criterion | Status | Test |
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|-----------|--------|------|
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| 3-level resource inheritance | ✅ PASS | `test_resource_inheritance_three_level` |
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| Per-key override (page's /F1 wins) | ✅ PASS | `test_merge_fonts_last_write_wins` |
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| Arc sharing when /Resources missing | ✅ PASS | `test_resource_inheritance_page_without_resources` (new `Arc::ptr_eq` check) |
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| ColorSpace inline array preserved | ✅ PASS | `test_merge_colorspace_inline_array` |
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| Empty root /Resources propagates | ✅ PASS | `test_resource_inheritance_empty_root` |
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| INV-8 maintained (no panics) | ✅ PASS | `proptests::fuzz_*` tests verify no panics on arbitrary input |
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## Implementation Details
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The `merge_resources` function in `resources.rs` implements per-namespace merging:
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- **Font namespace**: IndexMap<Arc<str>, ObjRef> - per-key last-write-wins
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- **XObject namespace**: IndexMap<Arc<str>, ObjRef>
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- **ExtGState namespace**: IndexMap<Arc<str>, ObjRef>
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- **ColorSpace namespace**: IndexMap<Arc<str>, PdfObject> - preserves inline arrays
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- **Shading namespace**: IndexMap<Arc<str>, ObjRef>
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- **Pattern namespace**: IndexMap<Arc<str>, ObjRef>
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- **Properties namespace**: IndexMap<Arc<str>, ObjRef>
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- **ProcSet**: Vec<Arc<str>> - deprecated, informational only
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The `flatten_page_tree` function in `pages.rs` calls `merge_resources` during traversal:
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- Ancestor resources are accumulated in `InheritedAttrs.resources`
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- Each leaf page merges its own `/Resources` with inherited resources
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- When a page has no `/Resources`, it directly clones the Arc (pointer-sharing, not deep copy)
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## Files Modified
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- `crates/pdftract-core/src/parser/pages.rs`: Enhanced Arc sharing test
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- `crates/pdftract-core/src/parser/mod.rs`: Added public API exports
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- `notes/pdftract-dejqs.md`: This verification note
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## Test Results (2026-05-22 verification)
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All tests pass:
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```
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cargo test --lib -- parser::resources parser::pages
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test result: ok. 33 passed; 0 failed; 0 ignored
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```
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Breakdown:
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- 9 tests in `parser::resources::tests`
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- 20 tests in `parser::pages::tests` (excluding 4 proptests)
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- 4 proptests for INV-8 compliance (no panics on arbitrary input)
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## No Breaking Changes
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The implementation was already complete and tested. This task only added:
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1. One additional test assertion for Arc sharing
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2. Public API exports that were previously internal
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