dataView.virtual

Pure virtualization window math for Z.dataView — given a scroll position and geometry, compute the inclusive range of row indices that are visible.

Exports

• M.windowFor(scrollTop, viewportH, rowH, count, overscan) -> { first, last } — 1-based inclusive; last < first when the dataset is empty. overscan extends the window above and below the visible band.

Notes

• Pure functions, no engine calls — unit-tested in the editor_dataview suite.
• Backs the row-window rendering; the same math would drive a future construction-virtualization provider.