Partial highlighting of wrapped overlay

[Ralf Angeli]

If you put

(let* ((length (+ (- (window-width) (current-column)) 40))
       (start (point))
       (end (+ (point) length))
       (string (make-string length ?x))
       ov)
  (insert string)
  (setq ov (make-overlay start end))
  (overlay-put ov 'mouse-face 'highlight)
  (overlay-put ov 'display string))

into the *scratch* buffer and type `C-x C-e' with point at the last
parenthesis, you will get a string which does not fit into the line
and has to be wrapped.  If you move over it with your mouse, you
should see that only the part on the second line is being highlighted.
The full string is highlighted only if the 'display property is not
set.

-- 
Ralf