pdfThumbnailDropIndexAt function

int? pdfThumbnailDropIndexAt({ required BuildContext? panelContext, required Map<int, GlobalKey<State<StatefulWidget>>> tileKeys, required int pageCount, required Axis axis, required Offset globalPosition, bool reversed = false, })

The insertion index a drop at globalPosition lands on for a panel whose tiles are laid out along axis, or null when the point is outside the panel.

panelContext bounds the hit to the panel's own box; tileKeys holds the panel's per-page tile keys (only the built ones answer - a scrolled-away tile has no render object, and the nearest built tile then wins). The result is a slot: 0..pageCount, the position the dropped pages would take.

Implementation

int? pdfThumbnailDropIndexAt({
  required BuildContext? panelContext,
  required Map<int, GlobalKey> tileKeys,
  required int pageCount,
  required Axis axis,
  required Offset globalPosition,
  bool reversed = false,
}) {
  final panel = panelContext?.findRenderObject();
  if (panel is! RenderBox || !panel.hasSize || !panel.attached) return null;
  final local = panel.globalToLocal(globalPosition);
  if (!(Offset.zero & panel.size).contains(local)) return null;
  if (pageCount <= 0) return 0;

  int? nearest;
  Rect? nearestRect;
  var nearestDistance = double.infinity;
  for (final entry in tileKeys.entries) {
    if (entry.key >= pageCount) continue;
    final box = entry.value.currentContext?.findRenderObject();
    if (box is! RenderBox || !box.hasSize || !box.attached) continue;
    final rect = box.localToGlobal(Offset.zero) & box.size;
    final distance = _distanceTo(rect, globalPosition);
    if (distance < nearestDistance) {
      nearest = entry.key;
      nearestRect = rect;
      nearestDistance = distance;
    }
  }
  if (nearest == null || nearestRect == null) return null;

  final centre = nearestRect.center;
  var after = axis == Axis.vertical
      ? globalPosition.dy > centre.dy
      : globalPosition.dx > centre.dx;
  if (reversed) after = !after;
  return (nearest + (after ? 1 : 0)).clamp(0, pageCount);
}