Re: can't tell if one is searching with appended whitespace

[Juri Linkov <juri@jurta.org>]

Kevin Rodgers <ihs_4664@yahoo.com> writes in bug-gnu-emacs:
> Dan Jacobson wrote:
>  > Gentlemen, looking in the minibuffer, how can you tell the difference between
>  > I-search: bla
>  > and
>  > I-search: bla 
>  > Therefore, something must be done about it.
>  > Why, one could miss important stuff if one doesn't realize he is
>  > carrying around an appended blank in his search string!
>  > Perhaps do something with color, or a " $" appearing, or turn on
>  > show-trailing-whitespace in the minibuffer by default.
>  > (setq-default show-trailing-whitespace t in .emacs isn't good enough.)
>
> That may be because trailing whitespace is not highlighted when point is
> at the end of a line in any buffer, even if the line is terminated by a
> newline (and thus there is at least 1 [possibly empty] subsequent line).
>
> Or perhaps that point is moot, because isearch.el displays the search
> string in the echo area, not in the minibuffer (if so, perhaps the
> message function should be changed to respect show-trailing-whitespace).

I suspect it would be very annoying when trailing whitespace will be
highlighted in all messages.  But highlighting it only in failed
isearch (i.e. in the message "Failing I-search: ...") may be good.
Or another solution is to add explicit text about whitespace as the
suffix of the failed string.  I included both solutions below:

Index: lisp/isearch.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/isearch.el,v
retrieving revision 1.228
diff -u -r1.228 isearch.el
--- lisp/isearch.el	6 Jun 2004 13:57:39 -0000	1.228
+++ lisp/isearch.el	7 Jun 2004 00:29:14 -0000
@@ -1764,7 +1786,13 @@
   (let ((cursor-in-echo-area ellipsis)
 	(m (concat
 	    (isearch-message-prefix c-q-hack ellipsis isearch-nonincremental)
-	    isearch-message
+	    (if (and (not isearch-success)
+                     (string-match " +$" isearch-message))
+                (concat
+                 (substring isearch-message 0 (match-beginning 0))
+                 (propertize (substring isearch-message (match-beginning 0))
+                             'face 'trailing-whitespace))
+              isearch-message)
 	    (isearch-message-suffix c-q-hack ellipsis)
 	    )))
     (if c-q-hack
@@ -1806,7 +1834,10 @@
   (concat (if c-q-hack "^Q" "")
 	  (if isearch-invalid-regexp
 	      (concat " [" isearch-invalid-regexp "]")
-	    "")))
+	    "")
+          (if (and (not isearch-success)
+                   (string-match " $" isearch-message))
+              "[whitespace]")))
 
 \f
 ;; Searching

-- 
Juri Linkov
http://www.jurta.org/emacs/