(format-spec): Propagate text properties of % spec.

1 files changed, 11 insertions, 3 deletions

diff --git a/lisp/gnus/format-spec.el b/lisp/gnus/format-spec.el
index fc34b50bc11..b2fde53b3f1 100644
--- a/lisp/gnus/format-spec.el
+++ b/lisp/gnus/format-spec.el
@@ -33,7 +33,8 @@
   "Return a string based on FORMAT and SPECIFICATION.
 FORMAT is a string containing `format'-like specs like \"bash %u %k\",
 while SPECIFICATION is an alist mapping from format spec characters
-to values."
+to values.  Any text properties on a %-spec itself are propagated to
+the text that it generates."
   (with-temp-buffer
     (insert format)
     (goto-char (point-min))
@@ -47,10 +48,17 @@ to values."
         (let* ((num (match-string 1))
                (spec (string-to-char (match-string 2)))
                (val (cdr (assq spec specification))))
-          (delete-region (1- (match-beginning 0)) (match-end 0))
           (unless val
             (error "Invalid format character: %s" spec))
-          (insert (format (concat "%" num "s") val))))
+          ;; Pad result to desired length.
+          (let ((text (format (concat "%" num "s") val)))
+            ;; Insert first, to preserve text properties.
+            (insert-and-inherit text)
+            ;; Delete the specifier body.
+            (delete-region (+ (match-beginning 0) (length text))
+                           (+ (match-end 0) (length text)))
+            ;; Delete the percent sign.
+            (delete-region (1- (match-beginning 0)) (match-beginning 0)))))
        ;; Signal an error on bogus format strings.
        (t
         (error "Invalid format string"))))