multiple extents with a mouse-face property to run together.
(make-overlay beg end buffer))
(defun set-extent-property (extent prop value)
+ ;; Make sure that separate adjacent extents
+ ;; with the same mouse-face value
+ ;; do not run together as one extent.
+ (and (eq prop 'mouse-face)
+ (symbolp value)
+ (setq value (list value)))
(if (eq prop 'duplicable)
(cond ((and value (not (overlay-get extent prop)))
;; If becoming duplicable, copy all overlayprops to text props.