XLSX: drawing anchors honour the declared defaultRowHeight where Excel recomputes it from the Normal font, so pictures over default rows are 12% short

[developer0hye]

Summary

Drawing anchors on a sheet resolve row extents from the declared
sheetFormatPr defaultRowHeight (anchored_image::row_height_at,
crates/office2pdf/src/parser/xlsx.rs:197-206: row dimension → sheetFormatPr default →
15.0). Excel for Mac does not honour that declared default when laying out rows that carry
no explicit height: it recomputes the default row height from the workbook Normal font and
lays the rows out at 17pt where WithDrawing.xlsx declares defaultRowHeight="15". Every
drawing anchored across default rows is therefore ~2pt/row short in height and its
from_row offset drifts accordingly.

Measured

WithDrawing.xlsx sheet 1 (Calibri 11 Normal font, defaultRowHeight="15"), local
Excel-for-Mac GT export vs the #620 fix build:

	GT (Excel)	office2pdf
clock.jpg height (rows 0→8 + 12pt rowOff)	148pt (8 × 17 + 12)	132pt (8 × 15 + 12)
tomcat.png height	79pt	69pt
clock.jpg aspect	1.074	1.150

The 17pt/row hypothesis reconciles both heights exactly (8 rows × 2pt = 16pt = 148 − 132;
tomcat's rows likewise). The independent cols probe (openpyxl, Calibri 11,
defaultRowHeight 15) reproduces the same 17pt GT rows with no <cols> involvement.

Reproduction

cargo run -p office2pdf-cli -- tests/fixtures/xlsx/poi/WithDrawing.xlsx -o out.pdf
mutool draw -F trace -o - out.pdf 1 | grep fill_image   # clock 151.74 x 132; GT 159 x 148

Expected

Row extents under drawing anchors match Excel's printed default row height for the
workbook's Normal font (17pt for Calibri 11 on the Mac export path), not the stored
defaultRowHeight hint.

Actual

Rows resolve at the declared 15pt, so pictures anchored across default rows are ~12% short
and aspect-distorted even after the #620 column-metric fix.

Related: #620 #658 #710

Found in: the #620 fix-PR visual audit (WithDrawing.xlsx sheet 1, local Excel-for-Mac GT, 150 DPI, 2026-07-30). Visual comparison below.

Visual comparison

Compare

GT left, office2pdf right, 150 DPI, page 1.

[developer0hye]

Confirmed the file's side of this, and one caution about the 17pt figure.

What the fixture declares

tests/fixtures/xlsx/WithDrawing.xlsx sheet 1:

<sheetFormatPr defaultRowHeight="15"/>

and the workbook's Normal font is Calibri 11:

<font><sz val="11"/><color theme="1"/><name val="Calibri"/><family val="2"/><scheme val="minor"/>

So the premise is exactly as stated — a declared 15pt default with a Calibri 11
Normal font — and row_height_at honouring the declared 15 is confirmed by
inspection.

The caution

The proposed rule is "Excel recomputes the default row height from the Normal
font", with 17pt as the value for Calibri 11. That figure does not match
what Excel is normally documented to use: Calibri 11's default row height is
14.4pt (19 px at 96 dpi) on Windows, and 15pt is the value this and most
generated workbooks declare precisely because it is the common default.

17pt may well be right for Excel for Mac specifically — this issue's
reconciliation is arithmetically clean, since 8 rows x 2pt accounts for the
148 − 132 exactly, and the same 2pt/row reconciles the second image — but it is
a platform-specific number, not "the Normal font's height" in general.

That distinction matters for the fix's shape. If the rule is implemented as
"recompute the default from the Normal font", it needs a font-to-height function
that returns 17 for Calibri 11, which will be wrong for any host or reader
expecting 14.4 or 15. If the rule is "Excel for Mac uses 17pt for Calibri 11",
that is a lookup fitted to one exporter, and hard-coding it would move every
drawing on every workbook that declares a default — including the ones currently
correct.

What would settle it

A one-factor probe of the kind #698 proposes: the same workbook exported with
the Normal font changed to two or three other faces and sizes, with the drawing
anchor unchanged, measuring the implied row height each time. Two points from
one font cannot distinguish "recomputed from the font" from "a fixed 17pt that
happens to fit Calibri 11", and those two rules diverge on every other workbook.

Until then I would not change row_height_at: honouring the declared value is
at least what the file says, and a wrong recomputation would silently move
drawings on workbooks that are correct today.

Related: #713, which is on the same fixture — note that sheet declares no
pageSetup at all, so the two sides also disagree about paper size. Worth
knowing before any measurement on this file is compared against that GT.

No change made.

[developer0hye]

Resolved by #1048: drawing anchors' dimension-less rows now take the default row height Excel recomputes from the workbook's Normal font (measured Calibri 11 → 17pt), gated on the sheet not marking customHeight. WithDrawing.xlsx's clock prints 148.0pt and the tomcat 79.0pt — both byte-matching the native export's traces. Whether the printed table grid recomputes the same way is split into #1047 (probe pending the Excel export automation fix).