Avoid comparison between tuple and int in one2many position

Such comparison is no more supported on Python 3.

issue7998
review46801002

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

@@ -433,8 +433,8 @@ class Screen(SignalEvent):
                 # XXX offset?
                 pos = record.get_index_path()
         else:
-            pos = None
-        self.signal('record-message', (pos or 0, len(self.group) + self.offset,
+            pos = 0
+        self.signal('record-message', (pos, len(self.group) + self.offset,
             self.search_count, record and record.id))
         attachment_count = 0
         if record and record.attachment_count > 0:

tryton/gui/window/view_form/view/form_gtk/one2many.py

@@ -257,6 +257,11 @@ class One2Many(Widget):
             o2m_size = None
             size_limit = False
 
+        first = last = False
+        if isinstance(self._position, int):
+            first = self._position <= 1
+            last = self._position >= self._length
+
         self.but_new.set_sensitive(bool(
                 not self._readonly
                 and self.attrs.get('create', True)
@@ -276,10 +281,10 @@ class One2Many(Widget):
                 and access['read']))
         self.but_next.set_sensitive(bool(
                 self._position
-                and self._position < self._length))
+                and not last))
         self.but_pre.set_sensitive(bool(
                 self._position
-                and self._position > 1))
+                and not first))
         if self.attrs.get('add_remove'):
             self.but_add.set_sensitive(bool(
                     not self._readonly
@@ -481,7 +486,7 @@ class One2Many(Widget):
     def _sig_label(self, screen, signal_data):
         self._position = signal_data[0]
         self._length = signal_data[1]
-        if self._position >= 1:
+        if self._position:
             name = str(self._position)
         else:
             name = '_'