Fix sideline for variable pitch mode

cats/+sideline.el

@@ -4,7 +4,44 @@
   :delight
   :hook (after-init . global-sideline-mode)
   :custom
-  (sideline-display-backend-name t))
+  (sideline-display-backend-name t)
+  :config
+  (defun sideline--string-pixel-width (string)
+    "Return the width of STRING in pixels.
+
+Sideline's own version of `string-pixel-width'
+which respect the `face-remapping-alist'."
+    (if (zerop (length string))
+        0
+      (let ((remapping-alist face-remapping-alist))
+        ;; Prevent use original buffer name for minimal side-effects
+        (with-current-buffer (get-buffer-create " *sideline-string-pixel-width*")
+          (setq-local display-line-numbers nil)
+          (delete-region (point-min) (point-max))
+          (setq-local face-remapping-alist remapping-alist)
+          (insert string)
+          (car (buffer-text-pixel-size nil nil t))))))
+
+  (defun sideline--align-right (str offset)
+    "Align sideline STR from the right of the window.
+
+Argument OFFSET is additional calculation from the right alignment."
+    (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--string-pixel-width str))))))
 
 (use-package sideline-flycheck
   :hook (flycheck-mode . sideline-flycheck-setup)
@@ -23,4 +60,4 @@
   :custom
   (sideline-blame-commit-format " %s")
   :config
-  (add-to-list 'sideline-backends-left #'sideline-blame))
+  (add-to-list 'sideline-backends-right #'sideline-blame))