Fix cursor location on changing Text values

Conflicts:
	tests/test_widgets.py

asciimatics/screen.py

@@ -2302,3 +2302,4 @@ def restore(self):
             for signalnum, handler in self._old_signal_states:
                 signal.signal(signalnum, handler)
             self._old_signal_states = []
+

asciimatics/widgets.py

@@ -1620,17 +1620,14 @@ def process_event(self, event):
         if isinstance(event, KeyboardEvent):
             if event.key_code == Screen.KEY_BACK:
                 if self._column > 0:
-                    # Delete character in front of cursor - use value to trigger
-                    # events.
-                    self.value = "".join([
-                        self._value[:self._column - 1],
-                        self._value[self._column:]])
+                    # Delete character in front of cursor.
+                    self._set_and_check_value("".join([self._value[:self._column - 1],
+                                                       self._value[self._column:]]))
                     self._column -= 1
             if event.key_code == Screen.KEY_DELETE:
                 if self._column < len(self._value):
-                    self.value = "".join([
-                        self._value[:self._column],
-                        self._value[self._column + 1:]])
+                    self._set_and_check_value("".join([self._value[:self._column],
+                                                       self._value[self._column + 1:]]))
             elif event.key_code == Screen.KEY_LEFT:
                 self._column -= 1
                 self._column = max(self._column, 0)
@@ -1643,9 +1640,8 @@ def process_event(self, event):
                 self._column = len(self._value)
             elif event.key_code >= 32:
                 # Insert any visible text at the current cursor position.
-                self.value = chr(event.key_code).join([
-                    self._value[:self._column],
-                    self._value[self._column:]])
+                self._set_and_check_value(chr(event.key_code).join([self._value[:self._column],
+                                                                    self._value[self._column:]]))
                 self._column += 1
             else:
                 # Ignore any other key press.
@@ -1670,20 +1666,25 @@ def process_event(self, event):
     def required_height(self, offset, width):
         return 1
 
-    @property
-    def value(self):
-        return self._value
-
     @property
     def frame_update_count(self):
         # Force refresh for cursor if needed.
         return 5 if self._has_focus and not self._frame.reduce_cpu else 0
 
+    @property
+    def value(self):
+        return self._value
+
     @value.setter
     def value(self, new_value):
+        self._set_and_check_value(new_value, reset=True)
+
+    def _set_and_check_value(self, new_value, reset=False):
         # Only trigger the notification after we've changed the value.
         old_value = self._value
         self._value = new_value if new_value else ""
+        if reset:
+            self.reset()
         if old_value != self._value and self._on_change:
             self._on_change()
         if self._validator:
@@ -2074,6 +2075,7 @@ def value(self, new_value):
             self._value = new_value.split("\n")
         else:
             self._value = new_value
+        self.reset()
         if old_value != self._value and self._on_change:
             self._on_change()
 

tests/test_widgets.py

@@ -1716,12 +1716,43 @@ def test_password(self):
         form.save()
         self.assertEqual(text.value, "1234")
 
-        # Check that it is drawn with the obscuring charav=cter, though.
+        # Check that it is drawn with the obscuring character, though.
         form.update(0)
         self.assert_canvas_equals(
             canvas,
             "Password ****                           \n" +
             "                                        \n")
 
+    def test_change_values(self):
+        """
+        Check changing Text values resets cursor position.
+        """
+        # Create a dummy screen.
+        screen = MagicMock(spec=Screen, colours=8, unicode_aware=False)
+        scene = MagicMock(spec=Scene)
+        canvas = Canvas(screen, 10, 40, 0, 0)
+
+        # Create the form we want to test.
+        form = Frame(canvas, canvas.height, canvas.width, has_border=False)
+        layout = Layout([100], fill_frame=True)
+        form.add_layout(layout)
+        text = Text()
+        layout.add_widget(text)
+        form.fix()
+        form.register_scene(scene)
+        form.reset()
+
+        # Check that input is put at the end of the new text
+        text.value = "A test"
+        self.process_keys(form, ["A"])
+        form.save()
+        self.assertEqual(text.value, "A testA")
+
+        # Check that growing longer still puts it at the end.
+        text.value = "A longer test"
+        self.process_keys(form, ["A"])
+        form.save()
+        self.assertEqual(text.value, "A longer testA")
+
 if __name__ == '__main__':
     unittest.main()