getSlideDeltaNid method
Slide delta for the live nid (paint-only FLIP offset), or 0.0 when
the node is not currently sliding. Hot-path equivalent of
getSlideDelta — read every paint, hit-test, and transform call
for visible rows, so saving the TKey→nid hash matters.
Implementation
double getSlideDeltaNid(int nid) => _slide.deltaForNid(nid);