Steps to Reproduce

1. run the attached code

Current Result

Object childNode = _model.getChild(node, i); in Tree.renderChildren() is always called during rendering. So the number of node a Tree get will actually larger than initRodSize (50). If getChild() costs heavily, e.g. getChild() retrieves data from a database, then initRodSize doesn't save the cost.

Proposed Solution

• getChild() later
• compute path based on the parent and current child index

      private void renderChildren(Renderer renderer, Treechildren parent, Object node) throws Throwable {
          final int initSize = initRodSize();
          for (int i = 0, j = _model.getChildCount(node); i < j; i++) {
              Treeitem ti = newUnloadedItem();
              ti.setParent(parent);
              // Bug ZK-1696: must render all opened node to have correct page count
              TreeOpenableModel model = (TreeOpenableModel) _model;
              // render nodes when no ROD or within ROD range or opened node
              if (initSize < 0 || i < initSize || model.isPathOpened(toChildPath(node, i))) {
                  Object childNode = _model.getChild(node, i);
                  renderChildren0(renderer, parent, ti, childNode, i);
              } else { //render empty row
                  ti.appendChild(new Treerow());
                  ti.getTreerow().appendChild(new Treecell());
              }
          }
      }
  
      private int[] toChildPath(Object parentNode, int childIndex) {
          int[] parentPath = _model.getPath(parentNode);
          int[] path = Arrays.copyOf(parentPath, 3);
          path[parentPath.length] = childIndex;
          return path;
      }