renderObjectFor method

RenderObject? renderObjectFor(String id)

The render object id names, or null when this tree has no such node.

The expensive direction, and deliberately not offered as something to call often: it costs a whole summary-tree walk, because an id is a position in the summary tree and nothing cheaper knows where that is. GuestWatch calls it once when the selection changes and holds the result — which is only safe because it also drops it whenever the shape moves.

The map is keyed the other way round because the hit test needs it that way, and inverting a few dozen entries here beats building both.

Implementation

RenderObject? renderObjectFor(String id) {
  var (:tree, :byRenderObject) = _build();
  if (tree.root == null) return null;
  for (var entry in byRenderObject.entries) {
    if (entry.value == id) return entry.key;
  }
  return null;
}