mu4e: honor truncate-string-ellipsis

Use truncate-string-to-width and thus honor truncate-string-ellipsis; so
to get 'fancy' ellipsis, one can set:
   (setq truncate-string-ellipsis "…")

NEWS.org

@@ -1,6 +1,14 @@
 #+STARTUP:showall
 * NEWS (user visible changes)
 
+* 1.5.x (unreleased, development version)
+
+*** mu4e
+
+    - Honor ~truncate-string-ellipsis~ so you can now use 'fancy' ellipses for
+      truncated strings with ~(setq truncate-string-ellipsis "…")~
+
+
 * 1.4 (released, as of April 18 2020)
 
 *** mu

mu4e/mu4e-utils.el

@@ -1221,17 +1221,9 @@ the view and compose modes and will color each signature in digest messages adhe
   "Quote a string to be used literally in the modeline. The
 string will be shortened to fit if its length exceeds
 `mu4e-modeline-max-width'."
-  (let* (;; Adjust the max-width to include the length of the " ..." string
-         (width (let ((w (- mu4e-modeline-max-width 4)))
-                  (if (> w 0) w 0)))
-         (str (let* ((l (length str))
-                     ;; If the input str is longer than the max-width, then will shorten
-                     (w (if (> l width) width l))
-                     ;; If the input str is longer than the max-width, then append " ..."
-                     (a (if (> l width) " ..." "")))
-                (concat (substring str 0 w) a))))
-    ;; Escape the % character
-    (replace-regexp-in-string "%" "%%" str t t)))
+  (replace-regexp-in-string
+   "%" "%%"
+   (truncate-string-to-width str mu4e-modeline-max-width 0 nil t)))
 
 (defun mu4e~active-composition-buffers ()
   "Return all active mu4e composition buffers"

mu4e/mu4e-view.el

@@ -536,7 +536,7 @@ add text-properties to VAL."
       "")))
 
 (defun mu4e~view-header-field-fold ()
-  "Fold/unfold headers' value if there are more than one line."
+  "Fold/unfold headers' value if there is more than one line."
   (interactive)
   (let ((name-pos (field-beginning))
         (value-pos (1+ (field-end))))
@@ -554,7 +554,8 @@ add text-properties to VAL."
                      (vals (split-string (field-string value-pos) "\n" t))
                      (val (if (= (length vals) 1)
                               (car vals)
-                            (concat (substring (car vals) 0 -3) "..."))))
+                            (truncate-string-to-width (car vals)
+                                                      (- (length (car vals)) 1) 0 nil t))))
                 (overlay-put o 'mu4e~view-header-field-folded t)
                 (overlay-put o 'display val))))))))