WordprocessingML styles and numbering

How the document hub resolves formatting and list labels. References are to ECMA-376 Part 1 (5th edition) unless noted. Where Word's behaviour is not settled by the text, the rule below is what the hub does today and the item is marked to check against Word.

Resolved properties (§17.7.2)

Layers, lowest first. Each property keeps the layer (and style id) that set it.

• A property is an element. spacing, ind, rFonts and lang merge attribute by attribute; a directly written ascii replaces an inherited asciiTheme (likewise hAnsi, eastAsia, cs), firstLine replaces an inherited hanging and the reverse, left/start and right/end are one edge. Everything else is replaced whole.
• Borders (pBdr) merge per side, tab stops (tabs) per position (a clear removes the stop), the list reference (numPr) per child.
• Toggle properties (§17.7.3) b bCs i iCs caps smallCaps strike dstrike outline shadow emboss imprint vanish: direct formatting sets the value outright; otherwise the values the table style, paragraph style and character style levels set are XORed (inside one level a basedOn chain overrides normally); with none, the document default stands. To check against Word: the XOR runs over the three style levels only, and the document default is not part of it.
• A document without w:pPrDefault reads as 8 pt (160) space after when nothing else sets it (ResolvedParagraphProperties.SpaceAfter); observed in Word 365 (16.0.20527). Word's answers for the precedence case (document defaults, basedOn chains, the toggle XOR, direct formatting over styles, character style over paragraph style) and for the numbering label cases all match the resolver. Line spacing without w:pPrDefault is not settled: Word reported a multiple of about 1.16 lines.
• A style chain follows w:basedOn. A missing base, a cycle and an unknown style id are defects (docx.style-*) and never exceptions.
• Table style regions apply in the order wholeTable, band1Vert, band2Vert, band1Horz, band2Horz, firstCol, lastCol, firstRow, lastRow, nwCell, neCell, swCell, seCell (§17.7.6). w:tblLook comes from its attributes or its hex mask; absent means no region flags. The header row is not banded and banding counts from the first row after it. w:cnfStyle caches are ignored.
• Theme fonts and colours resolve from the theme part with the default colour map. A colour's tint and shade are not applied (the raw attributes stay reachable) — needs Word output.
• Numbering level versus paragraph style (to check against Word): when the style supplies numId the level's w:pPr sits below the paragraph style; when the paragraph names the list directly it sits above it.

Numbering (§17.9)

• A paragraph's list is its direct numId, else the nearest style in its chain with one; numId 0 turns numbering off. The level is the direct ilvl, else the style's, else the level whose w:pStyle names the paragraph's style, else 0.
• Counters belong to the abstract definition (after w:numStyleLink), so instances of one definition continue each other. An instance with a w:startOverride restarts that level the first time the instance is used. A w:lvlOverride/w:lvl replaces the level for that instance. LibreOffice's text export agrees on every generated case.
• The first number of a level is the override, else w:start, else 0.
• After a paragraph at level L, level j > L starts again when L < lvlRestart (one-based w:lvlRestart; default j zero-based, i.e. after any higher level). lvlRestart 0 never restarts. To check against Word: LibreOffice ignores lvlRestart 0 (it restarts); the hub follows the specification.
• Label text fills %1..%9 with the counter of that level in that level's format; legal numbering (w:isLgl) shows the other levels in decimal. A level that was never used shows its start value.
• Formats produced exactly: `decimal decimalZero upperRoman lowerRoman upperLetter lowerLetter ordinal bullet none decimalEnclosedCircle (1-20) decimalFullWidth decimalHalfWidth. Letters repeat (z,aa,bb`). Text forms (cardinalText, ordinalText), chicago, hex and every script-specific format are produced as a best guess and every label that uses one says NeedsWordOutput.
• Defects: docx.num-missing, docx.num-abstract-missing, docx.num-level-missing, docx.num-link-broken.

Editing

Style and numbering edits change only styles.xml, numbering.xml and document.xml: a part is rewritten only when its tree was edited, and missing parts are created with their relationship. New elements use the part's own prefix and respect the schema's sequence (abstract definitions before numbering instances).