# Rendering support

The viewer uses published docx2html 0.7.0, mbtexcel 0.3.0, and pagelayout 0.8.0.
The viewer provides browser freeze handling, a full-workbook virtual Excel grid,
and visible DOCX diagnostics using those published APIs. It does not require
unreleased upstream HTML attributes: frozen pane settings come from the parsed
workbook in a separate inert JSON block.

The accompanying office.mbt changes improve linear gradient fills, borders,
theme/indexed colors, and DOCX body inline pictures. They must be merged and
released upstream, followed by a viewer dependency update, before a registry
build contains those engine fixes. A local MoonBit workspace can exercise the
viewer with the upstream source modules without changing release pins.

## Known limits

- DOCX floating drawing anchors and text wrapping, nested tables, paragraph
  section geometry, footnotes/endnotes, equations, and text boxes need additional
  layout support. Diagnostics report detected omissions; they do not render them.
- Upstream body inline pictures participate in text wrapping, baseline placement,
  line height and pagination. Table-cell and DOCX header/footer picture reading
  remain follow-up work.
- Linear Excel gradients with two colors are supported by the upstream patch.
  Path gradients and full conditional formatting remain incomplete. CSS preserves
  border weights and approximates dash-dot variants as dashed lines.
- The viewer's frozen rows/columns operate within each worksheet scroll area.
  Excel's separately scrollable split-pane UI is not implemented.
- Large Excel worksheets are virtualized across their full used bounds. The
  initial-window arguments select the rendering strategy rather than dropping
  rows or columns. Stored-cell data backs search and range materialization;
  inactive worksheets and offscreen cells do not accumulate DOM nodes.
- XLSX reading and display-value preparation are still synchronous and bounded
  by the reader's resource policy. This is not a streaming XLSX parser.


## Verification

Run `moon test --target js`, `npm run test:browser`, and `npm run build:pages`.
Browser tests use Playwright Chromium; `CHROME_EXECUTABLE` can select an installed
Chrome, and `PLAYWRIGHT_MODULE` can select an externally supplied Playwright module.