Use group-changed to update wizard buttons states

record-modified is often call earlier because the listener is not supposed to
use the values. But group-changed is triggered by record-changed which is
called when all the fields are really changed included from on_change calls.

issue6576
review43421002

tryton/gui/window/view_form/screen/screen.py

@@ -390,6 +390,7 @@ class Screen(SignalEvent):
     def _group_changed(self, group, record):
         if not self.parent:
             self.display()
+        self.signal('group-changed', record)
 
     def __get_current_record(self):
         if (self.__current_record is not None

tryton/gui/window/wizard.py

@@ -169,7 +169,7 @@ class Wizard(InfoBar):
         button.show()
         return button
 
-    def _record_modified(self, screen, record):
+    def _record_changed(self, screen, record):
         self.update_buttons(record)
 
     def update_buttons(self, record):
@@ -184,8 +184,8 @@ class Wizard(InfoBar):
         self.screen.add_view(view)
         self.screen.switch_view()
         self.screen.widget.show()
-        self.screen.signal_connect(self, 'record-modified',
-            self._record_modified)
+        self.screen.signal_connect(self, 'group-changed',
+            self._record_changed)
 
         title = gtk.Label()
         title.modify_font(pango.FontDescription("bold 14"))