pb with widget and overlay

[abel elenas]

i try to write some emacs-lisp code who use "dynamic widget" to make a 
syntaxique editor.

I have some trouble with the field-overlay properties of my widget, when
one of my widget change (deleted) or when a new one appears. The value 
of this properties change in a curious fashion. I can't put here all my 
test but let's see a few of them.
1   5    10    15    20    25    30
<editable-field><push_button_widget>
^              ^                                overlay for the first           
                                                        widget
               ^                  ^              overlay for the 2

if u activate the push_button_widget he is deleted and a second 
editable-field is inserted BUT
1   5    10    15    20    25    30
<editable-field><editable-field-nb2>
^                                  ^ the overlay length of the first
                                        widget change as a side effect
                                        and i dono why
                ^                  ^ the second one is good


other probleme

when i use a editable field after a read-only char the first char
of my widget is read-only as well and i don't understand why.

the 2 file i have write are on the web at

http://inferno.cs.univ-paris8.fr/~alderick/lexico_display.el
http://inferno.cs.univ-paris8.fr/~alderick/ada_syntaxe.el

the line i have write to correct the overlay bug are commented in
a special fashioned : ; *** my_commment ***

If a emacs lisp guru can have a look on that and tell my why i need
all this line and how i can avoid it...
thanks