code: func (t *TreeView) SetCurrentNode(node *TreeNode) *TreeView {
  	t.currentNode = node
  	return t
  }
docs: // SetCurrentNode sets the currently selected node. Provide nil to clear all
  // selections. Selected nodes must be visible and selectable, or else the
  // selection will be changed to the top-most selectable and visible node.
  //
  // This function does NOT trigger the "changed" callback.