dataTable/TEST.md

# DataTable Performance Tracking

## v1: Minimal Foundation
- **Data**: 10,000 items, 1 column.
- **Scroll Test**: 100 scrolls (20,000px total).
- **Results**:
  - refreshCount: 101
  - refreshTime (total): ~45.7ms
  - averageRefreshTime: **0.45ms**
  - totalNodes: 3030 (avg 30/frame)
- **Notes**: Silk smooth, base VirtualScroll works perfectly.

## v4: Optimized Responsiveness (Immediate Refresh)
- **Data**: 10,000 items, 10 columns.
- **Scroll Test**: 100 scrolls (20,000px total).
- **Results**:
  - refreshCount: 101
  - refreshTime (total): ~101.2ms
  - averageRefreshTime: **1.01ms**
  - totalNodes: 3030
- **Notes**: Removed `.dt-body` wrapper to simplify DOM depth. Changed `onScroll` to execute `container.refresh()` immediately instead of wrapping it in `requestAnimationFrame`.

## v6: Modularization & Manual DOM Sync (Selection)
- **Data**: 10,000 items, 10 columns.
- **Scroll Test**: 100 scrolls (20,000px total).
- **Results**:
  - refreshCount: 100
  - refreshTime (total): ~176.9ms
  - averageRefreshTime: **1.76ms**
  - totalNodes: 4500 (avg 45/frame)
  - **scanCount (per frame)**: **0** (Maintained Zero-Scan)
- **Notes**: 
  - Added complex Area Selection, Copy/Paste, and Row Deletion.
  - Successfully decoupled dynamic UI states (like `.dt-cell-selected`) from the declarative binding framework. We now use manual DOM manipulation (`applySelectionUI`) during `refresh` to sync states.
  - This manual sync completely prevents "Dependency Floods" where scrolling would trigger heavy `$class` evaluations on every cell. We maintained the Zero-Scan status while supporting rich interactions.
  - Fixed a VirtualScroll jumping bug at row 70+ by introducing an `options.itemHeight` configuration to the base `VirtualScroll` module. `DataTable` now explicitly passes `{ itemHeight: 40 }` during instantiation. This elegantly bypasses expensive `getComputedStyle` and `offsetHeight` measurements while perfectly seeding the internal height map, completely eliminating layout thrashing and scrolling jank without requiring users to pollute their business data with `_itemHeight`.
  - **Scroll Initiation Fix**: Removed the `setTimeout` wrapper around `vs.init` during `reset`. Previously, the first scroll often hit a "blank wall" because VirtualScroll's internal metrics hadn't finished initializing when the user made their first swift scroll motion. Synchronous initialization resolved this completely.