If parsed data has shortened, overwrite end of line with spaces (#1201)

* If parsed data has shortened, overwrite end of line with spaces

This bug could easily be replicated by running:
  `python can_viewer.py -c vcan0 -i socketcan -d "123:>BB"`
In another terminal send:
  `cansend vcan0 123#FFFF`
Followed by:
  `cansend vcan0 123#0001`

* Fill until end of available line after parsed data
as suggedted by @zariiii9003

Author: simonkerscher

can/viewer.py

@@ -302,6 +302,9 @@ def draw_can_bus_message(self, msg, sorting=False):
                     else:
                         values_list.append(str(x))
                 values_string = " ".join(values_list)
+                self.ids[key]["values_string_length"] = len(values_string)
+                values_string += " " * (self.x - len(values_string))
+
                 self.draw_line(self.ids[key]["row"], 77, values_string, color)
             except (ValueError, struct.error):
                 pass

test/test_viewer.py

@@ -188,6 +188,16 @@ def test_send(self):
         msg = can.Message(arbitration_id=0x101, data=data, is_extended_id=False)
         self.can_viewer.bus.send(msg)
 
+        # Send non-CANopen message with long parsed data length
+        data = [255, 255]
+        msg = can.Message(arbitration_id=0x102, data=data, is_extended_id=False)
+        self.can_viewer.bus.send(msg)
+
+        # Send the same command, but with shorter parsed data length
+        data = [0, 0]
+        msg = can.Message(arbitration_id=0x102, data=data, is_extended_id=False)
+        self.can_viewer.bus.send(msg)
+
         # Message with extended id
         data = [1, 2, 3, 4, 5, 6, 7, 8]
         msg = can.Message(arbitration_id=0x123456, data=data, is_extended_id=True)
@@ -210,6 +220,8 @@ def test_receive(self):
             # For converting the EMCY and HEARTBEAT messages
             0x080 + 0x01: struct.Struct("<HBLB"),
             0x700 + 0x7F: struct.Struct("<B"),
+            # Shorter parsed data length
+            0x102: struct.Struct("<BB"),
             # Big-endian and float test
             0x123456: struct.Struct(">ff"),
         }
@@ -229,6 +241,11 @@ def test_receive(self):
                     for col, v in self.stdscr_dummy.draw_buffer[_id["row"]].items():
                         if col >= 52 + _id["msg"].dlc * 3:
                             self.assertEqual(v, " ")
+                elif _id["msg"].arbitration_id == 0x102:
+                    # Make sure the parsed values have been cleared after the shorted message was send
+                    for col, v in self.stdscr_dummy.draw_buffer[_id["row"]].items():
+                        if col >= 77 + _id["values_string_length"]:
+                            self.assertEqual(v, " ")
                 elif _id["msg"].arbitration_id == 0x123456:
                     # Check if the counter is incremented
                     if _id["dt"] == 0: