Function buildPreviewRects

src/hooks/usePanelDrag.ts:230–251

(
  metrics: ContainerMetrics,
  items: LayoutItem[],
  dragItem: LayoutItem,
  cols: number,
)

}

function buildPreviewRects(
  metrics: ContainerMetrics,
  items: LayoutItem[],
  dragItem: LayoutItem,
  cols: number,
) : PreviewCandidate[] {
  return Array.from({ length: items.length + 1 }, (_, insertIndex) => {
    const nextItems = [...items];
    nextItems.splice(insertIndex, 0, dragItem);
    const simulated = simulatePanels(metrics, nextItems, cols);
    const placement = simulated[insertIndex];
    if (!placement) return null;
    return {
      insertIndex,
      previewRect: placement.rect,
      row: placement.row,
      col: placement.col,
      colSpan: placement.colSpan,
      rowSpan: placement.rowSpan,
    };
  }).filter((candidate): candidate is PreviewCandidate => Boolean(candidate));
}

function distanceToRect(clientX: number, clientY: number, rect: DOMRect) {
  const dx = clientX < rect.left ? rect.left - clientX : clientX > rect.right ? clientX - rect.right : 0;