Display bug when moving cursor

[fx-carton]

When using the arrow keys to move the cursor, the cursor is not displayed at the good location. Editing further the line leads to more garbage. It is only a display problem, because the message send is correct. Also, moving to another window and back to the original one fixes the display.

To reproduce the bug:

• Type 012345678 in a window (the main one or a chat window)
• Press the left key
• The cursor is displayed at the '4' character, not '7'