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From: Stalkern 2 <stalkern2 at tin.it>
Reply-To: stalkern2 at tin.it
To: lablgtk at kaba.or.jp
Subject: Rebuilding trees with selected items gives a reselection error 
Date: Mon, 3 Feb 2003 11:27:44 +0100
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Message-Id: <200302031127.44932.stalkern2 at tin.it>

I've also found a nice posting on a "Gtk-CRITICAL **: file gtkwidget.c: line 
3246 (gtk_widget_set_state): assertion `widget != NULL' failed." when 
regenerating a tree that has something selected. The posting is at 
http://mail.gnome.org/archives/gtk-list/1999-August/msg00333.html and the 
clue is to build a function deselecting tree children recursively, and use it 
before deleting the main tree (this does not require a recursive function, 
just a call to
	theMainTree #clear_items )

I add a snippet of code for beginners like me:

==============================
let rec unselect_treeChildren (aTree:GTree.tree) =
  let childrenOfTree = aTree #children
  in 
  let numberOfTreeChildren = (List.length childrenOfTree)
  in
  let rec unselect_firstGenerationOfTree_using_childrenList (aTree:GTree.tree) 
overallListLenght listPositionNow = 
    (
     if ( not(listPositionNow > overallListLenght)) then
       (
	let () = aTree #unselect_item listPositionNow 
	in
	unselect_firstGenerationOfTree_using_childrenList aTree overallListLenght 
(listPositionNow + 1)
       )
     else ()
    )
  in 
    (* let's start deselecting the first generation*)
  let () = unselect_firstGenerationOfTree_using_childrenList aTree 
numberOfTreeChildren 0
  in
(*let's apply the same to every tree at lower level*)
  let apply_unselection_to_childrenList aTreeItem =	
    match (aTreeItem #subtree) with
      None -> () (*this is a leaf: so it's just a child and it has already 
been unselected by its parent tree*)
    | Some t -> (*this is a tree!*)
	unselect_treeChildren t
  in
  List.iter (apply_unselection_to_childrenList) childrenOfTree;;


let callback_remove_rootTree (aTreeToRefresh:GTree.tree) () =
  (*In this case the rootTree has exactly ONE child, so we know when to stop*)
  (* first deselect everything that is selected so to avoid errors if we 
rebuild this tree and then we select an item of it and then GTK attempts to 
unselect what was selected before... but what was selected before was 
destroyed together with the *old* tree, so we'd get a Gtk-CRITICAL error*)
  
  let () = unselect_treeChildren aTreeToRefresh
  in
  let () = aTreeToRefresh #clear_items ~start:0 ~stop:1 
  in
  ();;
==============================

Ciao
Ernesto