code: protected void blockFinished (SceneBlock block)
      {
          --_pendingBlocks;
  
          // once all the visible pending blocks have completed their
          // resolution, recompute our visible object set and show ourselves
          if (_visiBlocks.remove(block) && _visiBlocks.size() == 0) {
              allBlocksFinished();
          }
      }
docs: Called whenever a block is done resolving, whether it was successfully resolved or if it
  was abandoned.