Remove record from the Group in reversed order

This limit the number of cursor changes on large list as the changes are that
the cursor is still on the top.

issue6741
review39661002

tryton/gui/window/view_form/model/group.py

@@ -124,10 +124,12 @@ class Group(SignalEvent, list):
         del self.__id2record[record.id]
 
     def clear(self):
-        for record in self[:]:
+        # Use reversed order to minimize the cursor reposition as the cursor
+        # has more chances to be on top of the list.
+        for record in reversed(self[:]):
             self.signal('group-list-changed', ('record-removed', record))
             record.destroy()
-            self.pop(0)
+            self.pop()
         self.__id2record = {}
         self.record_removed, self.record_deleted = [], []