bug#10978: `calendar-string-spread' loses with double-width characters

[Glenn Morris <rgm@gnu.org>]

Eli Zaretskii wrote:

> But it looks like calendar-insert-at-column and calendar-string-spread
> also need similar changes.

ACK on calendar-insert-at-column, but calendar-string-spread is the
function already being discussed - was there a third?

> Sorry, I don't follow.  Could you elaborate on what you had in mind?

I meant, don't do this:

(calendar-string-spread '("a" "b" "c") ?矢 10)

 ie, a restriction similar to that of truncate-string-to-width:

   The optional 4th arg PADDING, if non-nil, specifies a padding
   character (which should have a display width of 1)

But, it can be handled a bit better with:

*** lisp/calendar/calendar.el	2012-03-06 02:18:29 +0000
--- lisp/calendar/calendar.el	2012-03-12 20:23:23 +0000
***************
*** 1756,1763 ****
                            (if (< (length strings) 2)
                                (append (list "") strings (list ""))
                              strings)))
!          (n (- length (length (apply 'concat strings))))
!          (m (1- (length strings)))
           (s (car strings))
           (strings (cdr strings))
           (i 0))
--- 1756,1763 ----
                            (if (< (length strings) 2)
                                (append (list "") strings (list ""))
                              strings)))
!          (n (- length (string-width (apply 'concat strings))))
!          (m (* (1- (length strings)) (char-width char)))
           (s (car strings))
           (strings (cdr strings))
           (i 0))
***************
*** 1766,1772 ****
                        (make-string (max 0 (/ (+ n i) m)) char)
                        string)
              i (1+ i)))
!     (substring s 0 length)))
  
  (defun calendar-update-mode-line ()
    "Update the calendar mode line with the current date and date style."
--- 1766,1772 ----
                        (make-string (max 0 (/ (+ n i) m)) char)
                        string)
              i (1+ i)))
!     (truncate-string-to-width s length)))
  
  (defun calendar-update-mode-line ()
    "Update the calendar mode line with the current date and date style."