Talk:Gtk2Hs/Tutorials/TreeView

I don't know if any of these comments have anything to do with what these commands really do. Is it okay if I ask for review? What else can we add?

 {- an example how to select from a list
   not satisfactory yet:
       - there should be a simpler way to render a simple list
       - i could not convert the model i got back to a list 
           from which to get the value
       
       - the interface offers a great number of functions 
           and it is very difficult to find which ones are 
           really needed for simple tasks
  -}
import Graphics.UI.Gtk
import Graphics.UI.Gtk.ModelView as Model
main :: IO ()
main = do
   initGUI       -- is start
   window <- windowNew -- make a new window to throw things into
   list <- listStoreNew ["Vince", "Jhen", "Chris", "Sharon"] --store this
   -- the statements inside the {- -} pair is equivalent to the statement after it.
   -- it'll create a treeview widget and put the list into it.
   {- treeview <- Model.treeViewNew
   treeViewSetModel treeview list -}
   treeview <- Model.treeViewNewWithModel list
   -- will make the columns' headers visible
   Model.treeViewSetHeadersVisible treeview True
           -- there should be a simpler way to render a list as the following!
   col <- Model.treeViewColumnNew -- new column that'll show our list
   Model.treeViewColumnSetTitle col "colTitle" -- pretty much describes it, eh?
   renderer <- Model.cellRendererTextNew -- i guess that'll render the text inside the column's cells?
   Model.cellLayoutPackStart col renderer False -- i have no idea
   -- Model.cellLayoutPackStart col renderer True -- NO IDEA
   --
   -- i guess this function says that "col" will be displayed using "renderer"
   -- and for each item in the list it runs that nameless function which changes the cellText attribute
   -- of that particular cell in the column
   Model.cellLayoutSetAttributes col renderer list
           $ \ind -> [Model.cellText := ind]
   -- kinda clear, appends the "col" into the "treeview"
   Model.treeViewAppendColumn treeview col
   -- get currently selected node in the tree
   tree <- Model.treeViewGetSelection treeview
   -- oh, i'm not sure what this one does because when it runs we can select several items.
   Model.treeSelectionSetMode tree  SelectionSingle
   -- well, see explanation below
   Model.onSelectionChanged tree (oneSelection list tree)
   -- setting a few attributes in "window" - size and the widget inside of it, which is our "treeview"
   set window [ windowDefaultWidth := 100
               , windowDefaultHeight := 200
               , containerChild := treeview
              ]
   -- self explanatory, isn't it? when window is destroyed for whatever reason, the program will quit
   onDestroy window mainQuit
   -- blah
   widgetShowAll window
   -- blah
   mainGUI
   return ()

-- 
oneSelection :: ListStore String -> Model.TreeSelection ->  IO ()
oneSelection list tree = do
   -- this creates a list of paths of all selected rows
   sel <- Model.treeSelectionGetSelectedRows tree
   -- sel is [[a]] so now s is a
   let s = head (head sel)
   -- get the s item's value out of the list?
   v <- Model.listStoreGetValue list s
   putStrLn $ "selected " ++ v