Calculate the widths of non-Latin characters correctly.

* modeline.el (modeline-format-main): Now use the following function
to calculate the correct widths.

(modeline-length): Use the name and the decomposition of a character
to determine if a character should take 1.7 columns instead of 1
column.

1 files changed, 23 insertions, 2 deletions

diff --git a/modeline.el b/modeline.el
index b93b833..cb06b0d 100644
--- a/modeline.el
+++ b/modeline.el
@@ -5,8 +5,8 @@
   "The main mode line format."
   (let* ((left (modeline-format-left))
          (right (modeline-format-right))
-         (left-len (length left))
-         (right-len (length right))
+         (left-len (modeline-length left))
+         (right-len (modeline-length right))
          (middle (propertize " " 'display
                              (make-string
                               (max (- (window-total-width)
@@ -78,6 +78,27 @@
    (modeline-format-major-mode)
    (modeline-format-vc-mode)))
 
+;;; Calculate the correct lengths of characters
+
+;;;###autoload
+(defun modeline-length (str)
+  "Return the length of STR.
+Characters that take up more than one column will be counted with
+1.7 columns."
+  (declare (side-effect-free t) (pure t))
+  (let ((len 0))
+    (mapc (lambda (char)
+            (let ((name (get-char-code-property char 'name))
+                  (decomposition (get-char-code-property char 'decomposition)))
+              (cond
+               ((or (string-match (rx-to-string '(seq bos "CJK"))
+                                  name)
+                    (eq (car decomposition) 'wide))
+                (setq len (+ len 1.7)))
+               ((setq len (1+ len))))))
+          str)
+    (floor len)))
+
 ;;; Conveniently add text properties
 
 ;;;###autoload