Fix text align for buffer-face-mode (#20)

* Fix text align for buffer-face-mode

* Use sideline--str-len instead of length

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Co-authored-by: Jen-Chieh Shen <jcs090218@gmail.com>

sideline.el

@@ -298,20 +298,22 @@
   "Align sideline STR from the right of the window.
 
 Argument OFFSET is additional calculation from the right alignment."
-  (list (+
-         ;; If the sideline text is displayed without at least 1 pixel gap from the right fringe and
-         ;; overflow-newline-into-fringe is not true, emacs will line wrap it.
-         (if (and (display-graphic-p)
-                  (> (nth 1 (window-fringes)) 0)
-                  (not overflow-newline-into-fringe))
-             1
-           0)
-         (* (window-font-width)
-            (+ offset (if (display-graphic-p)
-                          ;; If right fringe deactivated add 1 offset
-                          (if (= 0 (nth 1 (window-fringes))) 1 0)
-                        1)))
-         (sideline--string-pixel-width str))))
+  (let ((graphic-p (display-graphic-p))
+        (fringes (window-fringes)))
+    (list (+
+           ;; If the sideline text is displayed without at least 1 pixel gap from the right fringe and
+           ;; overflow-newline-into-fringe is not true, emacs will line wrap it.
+           (if (and graphic-p
+                    (> (nth 1 fringes) 0)
+                    (not overflow-newline-into-fringe))
+               1
+             0)
+           (* (window-font-width)
+              (+ offset (if graphic-p
+                            ;; If right fringe deactivated add 1 offset
+                            (if (= 0 (nth 1 fringes)) 1 0)
+                          1)
+                 (sideline--str-len str)))))))
 
 (defun sideline--get-line ()
   "Return current line."