public final void invalidateLine(int line){
  repaint(0,textArea.lineToY(line) + fm.getMaxDescent() + fm.getLeading(),getWidth(),fm.getHeight());
}

public final void invalidateLine ( int line ) { repaint ( 0 , textArea . lineToY ( line ) + fm . getMaxDescent ( ) + fm . getLeading ( ) , getWidth ( ) , fm . getHeight ( ) ) ; }
marks a line as needing a repaint .
