After modifying the contents of ScreenLines and ScreenLinesUC (actually after modifying its 'off' and 'off-1' positions), how do I tell VIM to redisplay those two characters ? If I do a CTRL-L (ie. redraw) then I get the affect I want, but how to do it systematically ? Is there a refresh call on a per position basis ? In other words, if I modify a character's encoding in position 30, how do I tell VIM that I've done so, and for it to re-display that position again ?