protected void renderBookmarkTree(BookmarkData bookmarks) {
assert this.bookmarkTree == null;
if (!hasDocumentNavigation()) {
return;
}
this.bookmarkTree = new BookmarkTree();
for (int i = 0; i < bookmarks.getCount(); i++) {
BookmarkData ext = bookmarks.getSubData(i);
Bookmark b = renderBookmarkItem(ext);
bookmarkTree.addBookmark(b);
}