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Grzegorz MartensandClaude Opus 5.5
b16f0c0a77
An operator takes its operands from the end, and the renderer ignores a surplus before them: `(x) /OC /MC0 BDC` marks a layer's block, and `(x) /GS1 gs` selects `/GS1`. Redaction read some of them from the front, so a surplus stood in for them and what they named went unseen. Found in review of #6882, where Remove Hidden Information left the text of a hidden layer in `(x) /OC /MC0 BDC (LAYERSECRET) Tj EMC`, which both the app's renderer and Poppler hide. In what Apply Redactions and Remove Hidden Information decide: - the layers walk read a block's tag and property list from the front, and kept a hidden layer's block; - the cleanup of `/ActualText`, `/Alt`, `/E` and `/T` in a block whose paint was removed read (and wrote) the property list from the front, and kept the name that still read the removed word; - the tags cleanup read a block's `MCID` from the front, and left the removed text in its structure element's `/ActualText` and `/Alt`; and a `TJ`'s array, so a block that still drew was taken for empty and its structure element lost the content the page still shows; - the property cleanups read the name of a `BDC` or `DP` property list from the front, and retired a property list the page still draws with; - the walk read the ExtGState a `gs` selects from the front, so a font set only that way was not set, and `cs`/`CS` the same for a pattern space; - the Type 3 cleanup's reads of `cs`, `gs`, `Tf`, `BDC` and `DP`, which decide which resources and fonts are still used. The redaction proof read `Tc`, `Tw`, `Tz`, `TL`, `Ts`, `Tf`, `"`, `TJ` and `Do` from the front too. `pdfcraft_content::Op` gains `back`, `name_back` and `num_back`: operand `k` counted from the end. Tests (`crates/redact/src/tests/operands_from_the_end.rs`): a hidden layer's block, `/ActualText` on removed paint, a tag's `MCID`, a tagged `TJ` that still draws, a property list still drawn with, a font from an ExtGState, the pattern a `/Pattern cs` keeps, and a Type 3 font with the ExtGState, colour space, property list and font its glyph uses, each after a surplus operand. In `tests_verify.rs`, `the_proof_reads_operands_from_the_end` (`Tf`, `TJ`, and `Do` of a form and of images), `the_proof_reads_the_text_states_operands_from_the_end` (`Tc`, `Tw`, `Tz`, `TL`, `Ts` and `"`) and `an_image_a_type3_glyph_draws_after_a_surplus_operand_is_found`. And `operands_are_counted_from_the_end` in the content crate. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01AmsdeUCdTaD72jkDw2pJKY