# UnifiedSpread dev-20.7.0 Spreadsheet Basic UX

## Purpose

dev-20.7.0 improves everyday spreadsheet operations that users expect before moving to deeper formula, chart, image and pivot features.

## Implemented areas

- Fill Handle from the selected range bottom-right corner.
- Auto-fill preview layer during mouse drag.
- Auto-fill commit through CommandRegistry / WorkbookService / EngineAdapter / NativeGridEngine.
- Fill Down and Fill Right commands.
- Ctrl+D and Ctrl+R shortcuts.
- Tab / Shift+Tab and Enter / Shift+Enter cell navigation.
- F2 in-cell edit.
- Ctrl+A select all.
- Structured copy/paste with style preservation.
- TSV paste from external applications.
- Larger selected paste target repeats/tile source data.
- Formula references are adjusted for copy/paste/fill while absolute axes are preserved.

## Architecture notes

The renderer owns pointer gestures and preview classes because those depend on DOM hit testing and viewport scrolling. It does not modify workbook data for fill handle operations. On mouseup it emits `spread.edit.fillHandle` with `sourceRange` and `targetRange`.

The model owns workbook mutations such as `fillDown`, `fillRight`, and `applyAutoFill`. This keeps the same operations available from toolbar, context menu, keyboard shortcuts and Host `exec()` calls.

The clipboard keeps both text and structured cell/style matrices. Browser clipboard compatibility is preserved through tab-delimited text, while internal NativeGrid paste can also keep formulas and styles.

## Current limits

- Auto-fill currently supports copy/tile, formula reference adjustment, and simple numeric series.
- Date series, custom lists, month names and advanced pattern detection are future work.
- Large-data virtualization is still a later performance phase.