shr.el: add linebreaks to mouse-over tooltips (title attributes)

[asjo@koldfront.dk (Adam Sjøgren)]

When reading nntp+news.gwene.org:gwene.com.xkcd there are often long
title attributes on the comic image, and when shown on one line, the
text does not fit on my tiny screen.

I guess the correct solution would be for Emacs to wrap the "help-echo"
to fit the screen automatically.

The second best thing would be if shr.el wrapped the text to fit the
screen.

And here is what I crudely whipped up, a regex to sort-of-wrap at 72
chars:

--- shr.el.orig	2014-12-12 22:21:34.271477782 +0100
+++ shr.el	2014-12-12 22:20:44.652962400 +0100
@@ -1248,10 +1248,13 @@
 	  (put-text-property start (point) 'image-displayer
 			     (shr-image-displayer shr-content-function))
 	  (put-text-property start (point) 'help-echo
-			     (or (cdr (assq :title cont))
-				 alt)))
+			     (shr-linebreak (or (cdr (assq :title cont))
+				 alt))))
 	(setq shr-state 'image)))))
 
+(defun shr-linebreak (line)
+  (replace-regexp-in-string "\\(.\\{72\\}\s\\)" "\\1\n" line))
+
 (defun shr-tag-pre (cont)
   (let ((shr-folding-mode 'none))
     (shr-ensure-newline)

-- 
 "If you don't run, you rust."                                Adam Sjøgren
                                                         asjo@koldfront.dk