ScrollablePane & GridLayoutContainer in CEGUI 0.7.9

[silentyears]

I want to know something about control ScrollablePane & GridLayoutContainer in CEGUI 0.7.9 as follows,
1.First i write xml Statement to create ScrollablePane in .layout file , then i call GetChildCount(sorry，i can't remember the Specific method name) to see how many child windows the ScrollablePane have , and the result is 3 but i don't add any child windows yet. so what do the 3 child windows are?
2. Because there is no widget named GridLayoutContainer in .looknfeel file, so i use "GridLayoutContainer * gird = new GridLayoutContainer ("DefaultWindow", "Grid")" statement to create GridLayoutContainer , but why i can't get the GridLayoutContainer handle with the method "winMgr.Getwindows("Grid")" , so how could i get it like other window type?
3. Is there something useful demo to study? i'll appreciate it!

I have read the .doc but still can't figure it out...

It's difficult for me to upload the code ,so i'm sorry but could master help me? Thanks a lot!!!