(describe-register-1): Use window-width

to truncate string in a register.  Check whether the string
in a register is an empty string or a sequence of white spaces.

1 files changed, 12 insertions, 3 deletions

diff --git a/lisp/register.el b/lisp/register.el
index d149dee200e..ad65d4b7401 100644
--- a/lisp/register.el
+++ b/lisp/register.el
@@ -233,9 +233,18 @@ The Lisp value REGISTER is a character."
           (progn
             (princ "the text:\n")
             (princ val))
-        (princ "text starting with\n    ")
-        (string-match "[^ \t\n].\\{,20\\}" val)
-        (princ (match-string 0 val))))
+        (cond 
+         ;; Extract first N characters starting with first non-whitespace.
+         ((string-match (format "[^ \t\n].\\{,%d\\}"
+                                ;; Deduct 6 for the spaces inserted below.
+                                (min 20 (max 0 (- (window-width) 6))))
+                        val)
+          (princ "text starting with\n    ")
+          (princ (match-string 0 val)))
+         ((string-match "^[ \t\n]+$" val)
+          (princ "whitespace"))
+         (t
+          (princ "the empty string")))))
      (t
       (princ "Garbage:\n")
       (if verbose (prin1 val))))))