fix(xlsx): seat a bar chart's Excel category label sheet-space-correctly

[developer0hye]

Summary

Excel right-aligns a worksheet horizontal-bar chart's category label a further EXCEL_BAR_CATEGORY_LABEL_X_SHIFT_EM * size_pt sheet points right of the PowerPoint-calibrated box chart_category_label_box_w shares across every chart host. Measured by patching tests/fixtures/xlsx/issue_1181_fit_to_height.xlsx's category-axis size to 8, 10, 14 and 18pt (assets/validation/issue-1620/category-size-probe.json, native Excel via --backend office) and comparing fresh native exports against the shared box.

The correction is added to plot.dx inside the fitted sheet's own #scale(print_scale) wrapper (write_placed_sheet_anchor in typst_gen.rs), so it has to be calibrated in sheet points, not printed points. An earlier draft of this fix (from a prior session on this branch) calibrated the constant directly against mutool-traced printed points (0.0262), which under-applies by exactly this sheet's own 0.78 print scale once rendered — converting with that constant and remeasuring showed the applied page effect was 0.2044pt at 10pt, not the 0.2610pt printed gap it was meant to close (0.262 x 0.78 = 0.2044, confirmed to 4 significant figures against a fresh before/after isolation diff). Dividing each printed measurement by 0.78 before deriving the ratio gives the corrected constant, 0.0336. Full derivation and the arithmetic check in assets/validation/issue-1620/README.md.

After this fix, the five affected category labels (other, from savings, financial aid, other expenses, discretionary) land within 0.008 printed points of native — essentially exact — down from -0.254 to -0.266pt before it. (#1620's own filed numbers were -0.729 to -0.741pt against an older main; commit 082fa901, #1272, merged one day after this issue was filed, independently closed most of that gap by pulling an overrunning c:manualLayout plot rectangle back inside its chart area. Both corrections are real and independently measured — see the README for the full reconciliation.)

Comparing office2pdf's own output before vs. after this fix in isolation (--fine-shift 0.01): exactly the 11 category labels across both bar charts move, each dx +0.26pt, dy +0.00pt; rectangle census is bit-identical (738/738, 0 geometry deviations). Nothing else on the page moves.

While auditing this fixture's full page 2 for the required visual-evidence contract, three unrelated residuals were found and filed separately rather than bundled here: #1759 (bar-fill vertical seat/width), #1760 (a differ line-grouping classification artifact, not a converter defect), #1761 (a repeated %INC header's horizontal position). #1757 (a form-control label row's -2.16pt outlier) was already filed during an earlier pass of this same audit.

File submission policy

• The fixture (tests/fixtures/xlsx/issue_1181_fit_to_height.xlsx) and its native-export evidence derive from the existing public Gift Budget and Tracker1.xlsx misc issues #982 attachment via XLSX: fitToHeight is not modelled, so a sheet Excel fits on one A3 page prints on two #1181's own tracked fixture; no new organizational file is submitted.

Related issue

Related: #1620

Testing

• Red/green: an_excel_bar_category_label_sits_the_measured_offset_right_of_powerpoints (8pt and 18pt, sheet-space-converted literals) and an_excel_bar_category_label_with_no_declared_size_keeps_powerpoints_box (the no-native-probe guard branch, mirroring excel_category_label_y_shift_pt) fail without the fix.
• cargo test --locked -p office2pdf --lib: 3091 passed.
• cargo test --locked --workspace: all suites green.
• cargo fmt --all --check: clean.
• compare_text_layer.py on a fresh native GT vs. this fix's output: unchanged from before this fix (2 extra spaces, a pre-existing reading-order difference, not touched by this change).
• Required delegated read-only documentation freshness audit: PASS (three passes; the second and third caught a numeric reconciliation gap and the sheet-space/printed-space unit bug this PR now fixes).
• Probe spec, native measurements, and the sheet-space-vs-printed-space derivation: validation.

Visual impact

• No rendered PDF change
• Rendered PDF change or visual evidence added

Visual audit

• Issue: XLSX: horizontal bar-chart category labels remain about 0.74pt left of native #1620
• Fixture: tests/fixtures/xlsx/issue_1181_fit_to_height.xlsx (unmodified; SHA-256 2b4a2d8dceda58758593c88409875efbda05780559154c02bd13fef4f7a1c65b)
• Page(s): 2
• Renderer and DPI: Microsoft Excel for Mac 16.112 native reference; pdftoppm, 300 DPI
• Evidence mode: fix
• Layout audit report: assets/bugfixes/issue-1620/layout-audit.json
• Render cluster reports: assets/bugfixes/issue-1620/render-clusters-page-2.json
• Reference exporter differences: None
• Fine-detail threshold: 0.5pt
• Layout audit page count: Pass
• Layout audit text flow: XLSX: title+header-row text on one native baseline reports as a 1-into-2 line reflow #1760
• Layout audit visible fills: Pass
• Layout audit rectangle geometry: XLSX: fitted worksheet cell fills sit one sheet point above Excel's #1632, XLSX: horizontal bar-chart value-bar fills sit ~0.544pt above native, widest bar 11pt narrow #1759
• Layout audit large shifts: Pass
• Layout audit fine shifts: XLSX: fitted worksheet text keeps the physical margin origin while its paint layer snaps to Excel's sheet-space origin #1719, XLSX: right-aligned cells on the fitted budget sheet land 0.9pt left to 2.2pt right of Excel by number format #1631, XLSX: horizontal bar-chart category baselines deviate from native row placement #1621, XLSX: fitted horizontal bar-chart value labels sit about 0.61pt too high #1622, XLSX: large left-aligned Cambria title starts 1.255pt left of native #1623, XLSX: a form-control label row sits 2.16pt above Excel where the rest of the fitted sheet sits ~0.6-0.8pt off #1757, XLSX: repeated %INC column-header text sits 0.39pt right of native #1761
• New follow-up issues found in this audit: XLSX: horizontal bar-chart value-bar fills sit ~0.544pt above native, widest bar 11pt narrow #1759, XLSX: title+header-row text on one native baseline reports as a 1-into-2 line reflow #1760, XLSX: repeated %INC column-header text sits 0.39pt right of native #1761 (a fourth, XLSX: a form-control label row sits 2.16pt above Excel where the rest of the fitted sheet sits ~0.6-0.8pt off #1757, was filed during an earlier pass of this same audit, before this session)
• Model vision findings: Full GT/output page-2 crops and the 5% diff were inspected at 300 DPI. The category-label crop (gt.jpg/before.jpg/after.jpg, both bar charts' label column) shows no visible difference at this scale — the fix moves text by 0.26 printed points, under one 300-DPI pixel — consistent with the near-zero measured residual. All 394 material render-diff clusters on the page were classified: 380 reused, by exact bbox match, from the committed assets/bugfixes/issue-1564/render-clusters-page-2.json baseline (185 to XLSX: right-aligned cells on the fitted budget sheet land 0.9pt left to 2.2pt right of Excel by number format #1631's number-format-dependent cell dx, 137 to XLSX: fitted worksheet cell fills sit one sheet point above Excel's #1632's one-sheet-point-high fills, 43 to XLSX: large left-aligned Cambria title starts 1.255pt left of native #1623's title dx, 16 to XLSX: a 14-15pt bottom-aligned cell in a 19.5pt fixed row is centred as a tight row where Excel bottom-seats it #1721's tight-row centring); the remaining 14 were freshly inspected this session. Nine are thin (0.72pt-high) bar-fill edge strips at the income and expense charts' own plot value-zero columns (x=152.64 and x=419.28) — cropped and viewed as green rectangle edges sitting a fraction of a point off native, filed as XLSX: horizontal bar-chart value-bar fills sit ~0.544pt above native, widest bar 11pt narrow #1759. One is the "Monthly Scroll" spinner's own selector band containing the bold white "JAN" label, in the same form-control region XLSX: a form-control label row sits 2.16pt above Excel where the rest of the fitted sheet sits ~0.6-0.8pt off #1757 already tracks. Three are a repeated "%INC" column header sitting +0.39pt right of native, a distinct sign and magnitude from the general fitted-text band (XLSX: fitted worksheet text keeps the physical margin origin while its paint layer snaps to Excel's sheet-space origin #1719, -0.475pt) and the number-format cell family (XLSX: right-aligned cells on the fitted budget sheet land 0.9pt left to 2.2pt right of Excel by number format #1631) — filed as XLSX: repeated %INC column-header text sits 0.39pt right of native #1761. None of the 394 clusters fall in the category-label region this fix touches; the five affected labels' own pixel difference at 10pt declared size is below the 20pt² material-cluster floor after this fix.
• GT: assets/bugfixes/issue-1620/gt.jpg
• Before: assets/bugfixes/issue-1620/before.jpg
• After: assets/bugfixes/issue-1620/after.jpg
• Native: None
• Compare: assets/bugfixes/issue-1620/compare.jpg (filed with the original issue)

Visual comparison

GT	Before	After

Required inspection

• Rendered all evidence at 150 DPI or higher
• Stored progressive JPEG quality 86 assets with metadata stripped
• Used Codex/Claude vision to inspect the full GT/output pages, diff, and matched crops
• Inspected matched region crops at full resolution
• Ran compare_layout.py --audit --fine-shift PT and dispositioned every fine/large text-instance shift, rectangle geometry deviation, painted-text visibility mismatch, and visible-fill occlusion
• Ran compare_render.py --cluster-report PATH --strict-clusters and dispositioned every material 5% fuzz diff cluster by explicit ID
• Inventoried hairlines and border dash styles
• Inventoried font weight, italic, and underline emphasis

Deviation audit

Check	Result
Page count/order	Matches GT
Element presence	Matches GT
Position/size	Remaining: #1631, #1621, #1622, #1623, #1721, #1757, #1759, #1761; the two bar charts' category-label horizontal position is fixed by this PR (#1620).
Rotation/flip	No deviation observed
Fill	Remaining: #1632, #1759
Stroke/border	No deviation observed
Shape outline geometry	No deviation observed
Text content	No deviation observed (a pre-existing 2-space/reading-order text-layer difference is unchanged before and after this fix; not touched by this change)
Font family/weight/style	Matches GT
Text color	Matches GT
Alignment	Remaining: #1631, #1621, #1622, #1623, #1719, #1761; the category-label right-alignment box position is fixed by this PR (#1620).
Line/paragraph spacing	Remaining: #1719, #1760
Clipping/overflow	No deviation observed

Checklist

• Commits include a Signed-off-by line
• PR scope contains one root cause
• Remaining converter or harness deviations each reference an open issue

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