paragraphAtGlobalY method

({String id, RenderFluentParagraph render})? paragraphAtGlobalY(double globalY)

Finds the rendered paragraph whose global bounds vertically contain globalY; if none contains it, returns the vertically nearest one.

Iterates only the currently rendered paragraphs (bounded by the viewport

• ListView cache), so it is O(visible) — used by drag selection to do precise hit testing without an O(n) scan over the whole document.

Implementation

({String id, RenderFluentParagraph render})? paragraphAtGlobalY(double globalY) {
  RenderFluentParagraph? best;
  String? bestId;
  double bestDist = double.infinity;

  for (final entry in _renders.entries) {
    final render = entry.value;
    if (!render.attached || !render.hasSize) continue;
    final top = render.localToGlobal(Offset.zero).dy;
    final bottom = top + render.size.height;

    final double dist;
    if (globalY >= top && globalY <= bottom) {
      dist = 0.0;
    } else if (globalY < top) {
      dist = top - globalY;
    } else {
      dist = globalY - bottom;
    }

    if (dist < bestDist) {
      bestDist = dist;
      best = render;
      bestId = entry.key;
      if (dist == 0.0) break; // exact vertical hit, cannot do better
    }
  }

  if (best == null || bestId == null) return null;
  return (id: bestId, render: best);
}