XLSX: worksheet drawing anchors use undersized row and column metrics

[developer0hye]

Summary

Worksheet xdr:twoCellAnchor geometry is rendered smaller than Microsoft Excel even after print scaling is removed from the comparison. The error accumulates across columns, shifting later drawings left.

Found while re-auditing the regression fixture in #434 at 150 DPI against a native Microsoft Excel export.

Reproduction

Convert tests/fixtures/xlsx/theme_color_drawing.xlsx from PR #434 after its print layout is updated to A4 landscape at 100% zoom, then render the Excel GT and office2pdf PDFs with pdftoppm -r 150.

The sheet uses explicit width 6.7109375 for columns A:M, default row height 18pt, and three two-cell anchors spanning three columns and six rows.

Expected

Drawing bounds match the worksheet row/column geometry used by Excel.

Actual

Pixel-exact fill bounds at 150 DPI:

Shape	Excel GT bounds	office2pdf bounds
accent1	294x225+202+188	283x213+199+246
accent1 lighter 60	294x225+594+188	283x213+577+486
accent6 shade 75	294x225+985+188	283x213+954+726

The vertical stacking is tracked separately. This issue is specifically the per-shape size and cumulative horizontal-coordinate error:

• width is 11 px too small;
• height is 12 px too small;
• the third shape starts 31 px too far left.

Root-cause evidence

anchored_image, which also sizes SheetTextBox, resolves DrawingML anchors through the table print metrics (column_width_to_pt and native_excel_pdf_row_height). The resulting drawing bounds do not match Excel's two-cell anchor geometry. This is an implementation-based inference to verify in the fix.

Visual checklist

• Element presence/content/order: preserved.
• Position/size: incorrect as measured above.
• Fill: all three post-XLSX: worksheet-drawing scheme colors ignore the workbook theme #430 RGB values match Excel exactly.
• Rotation/flip/stroke/clipping: no deviation.
• Font mismatch and same-row stacking are tracked separately.

Related: #235, #240, #430, #434