Direct legacy Word paragraph alignment

The typed model exposes a logical direct formatting exception on each stable paragraph handle:

import { parseDoc } from '@christophervr/ole2';

const doc = parseDoc(bytes);
const paragraph = doc.paragraphs[1]!;
console.log(paragraph.directAlignment); // undefined when inherited or undecoded
paragraph.directAlignment = 'justify';
const saved = doc.serialize();

DocParagraphAlignment is 'start' | 'center' | 'end' | 'justify'. Start/end describe logical paragraph direction, without resolving inherited bidi styles or claiming physical left/right positioning. The optional property on the original DocParagraph interface retains compatibility with caller-created paragraph objects; ParsedDocParagraph always has the accessor.

The setter replaces an existing unique sprmPJc (0x2461) operand in an exclusive PAPX formatting run. Native Word also writes a preceding physical sprmPJc80 (0x2403) compatibility operand. When both unique values match, this implementation updates both only for direction-independent center and justify. Mirrored start/end writes throw UnsupportedOle2EditError with reason: 'direction-dependent-alignment'; no inherited direction is guessed. A sole modern slot supports all four logical values. Legacy-only, mismatched, reversed, duplicate, missing or unrecognized formatting remains undefined or refuses mutation. No formatting records are inserted.

See the official MS-DOC paragraph properties and PapxInFkp definitions for physical/logical operand semantics and binary layout.

The writer checks piece PRMs, paragraph/run exclusivity, shared PAPX blobs, other-story piece aliases, text and CHPX overlap, FIB-prefix overlap and section exception overlap. Tables, fields/control characters in the target, external huge PAPX and opaque/reset/style modifiers refuse. Default text/piece budgets apply; paragraph formatting is bounded to 65,536 pages, physical runs and paragraph records, and 262,144 SPRM records before allocation. Invalid values are rejected without object coercion.

Paragraph handles read current bytes after text, run or alignment edits. A successful edit increments the document revision and invalidates old character run handles. Eligible no-op alignment assignments leave bytes, revision and dirty unchanged. Refused edits commit nothing. Bytes outside the one modern operand, or the two mirrored operands, remain identical.

Owned native validation case

test/fixtures/doc/paragraph-alignment.doc is a neutral Word 16 derivative of the owned rich-run fixture. Only the middle paragraph is directly centered; neighbors inherit their alignment. Its generator and SHA-256 are retained in the fixture provenance manifest. Native comparison covers center to justify and exact center restoration, with captured paragraph formatting, text, character fonts, styles, stories and counts checked independently. Sole-modern start/end cases are synthetic codec regressions, not native fidelity evidence. These checks do not establish rendering, pagination, every font/style, or full legacy DOC fidelity.

After building, reproduce the consumer inputs without launching Word:

node scripts/prepare-native-doc-alignment-edits.mjs

The generator pins the source hash, checks exact changed-byte counts and emits an explicit nativeValidatedByThisRun: false manifest. Native Word opening, saving and reopening belongs to the independent corpus validation workflow.